Odor Evaluation of Polyolefin Material used for Food Plastic
Containers
Patrícia Lalíssuc Chaves
Thesis to obtain the Master of Science Degree in
Chemical Engineering
Supervisors:
Prof. Doctor Carlos Manuel Faria de Barros Henriques
R&D Raw Material Engineer Inge Welkenhuysen
Examination Committee
Chairperson: Prof. Doctor João Carlos Moura Bordado
Supervisor: Prof. Doctor Carlos Manuel Faria de Barros Henriques
Member of the Committee: Prof. Doctor Maria do Rosário Ribeiro
November 2019
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ACKNOWLEDGMENTS
Foremost, I would like to thank all Tupperware for making this opportunity possible, believing in my
knowledge and that I could be successful. It was truly a pleasure to spend these months in a company that
believes in people, innovative ideas and concepts. All the kind words, especially during my last days, will stay
with me.
A special thanks to Inge Welkenhuysen for all the shared knowledge and with whom I have learned so
much, not only about this industry but also about the Flemish culture. Her patience in answering all my questions
have kept my curiosity alive throughout this master thesis.
To Emil Cupsa and Laurent Tabey for the guidance and knowledgeable advices. Since the beginning,
their motivation have always challenged me to become better and to achieve more.
I would like to thank Professor Carlos Henriques for accepting my invitation to be my coordinator in
such short period and defending this project and its potential. Without his support, my journey at Tupperware
would have not happened.
Also, I ought a thank to Patrícia and Pedro for staying by my side and caring for me during these months.
Their kindness and support made Belgium feel like home.
This master thesis marks the end of a phase. To Bernardo and Catarina that, above anyone else, have
been with me in the good and troubled moments.
Dirijo um agradecimento especial a toda a minha família por toda a amizade e apoio durante estes
últimos anos. À minha Mãe por ser tudo o que a palavra indica, a expressão mais alta de aconchego, de porto
seguro. Ao meu Pai por acreditar em mim e por ajudar a tornar este percurso possível. À minha irmã Nicole pelas
gargalhadas e por tornar a minha vida mais leve. Ao meu tio Avelino por todos os conselhos e palavras honestas.
Por último, um obrigada à minha avó Carmina que me ensinou que “é bom bonito saber ler, muito mais
ser educado”. Uma lição para a vida.
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ABSTRACT
Polypropylene is a thermoplastic polymer known for its mechanical, thermal and chemical properties
that makes it useful in a wide range of applications including in the food packaging industry. In spite of its
importance, the explanation of its odor generation is far from being fully understood.
The identification and characterization of odor-active compounds in this plastic material were
investigated by regulatory odor tests and analytical techniques such as gas chromatography/ time-of-flight mass
spectrometry (GC-TofMS) as well as gas chromatography - olfactometry (GC-O) where the human nose acts as
the detector. Statistical tools were applied to analyze and validate data.
Results proved that the generation of odor-active compounds in polypropylene is strongly influenced
by different processing stages as Injection Molding and Blow Molding. Additives are also responsible for the odor.
It was verified that the nucleating agent present in the studied polypropylene degrades and releases, at least
one, odor-active compound.
GC-TofMS and GC-O detected and characterized aldehydes (acetaldehyde, butanal, hexanal,
benzaldehyde), terpenes (a-Pinene, C10H16 terpene, D-limonene) and organic acid (acetic acid) as odor-active
compounds. Other candidates are ketone (2,3-butanedione), mercaptan (methanethiol) and organic acid
(butanoic acid).
Two state-of-art treatment processes were tested for odor removal using vacuum and heated desiccant
air dryers. The heated desiccant air dryer with a regeneration system proved to be efficient in volatile organic
compounds removal and the reduction of the overall odor intensity in polypropylene end-products.
Keywords:
Polypropylene, Volatile organic compounds, Odor-active compounds, Food packaging, Additives,
Heated desiccant air dryer
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RESUMO
O polipropileno é um termoplástico conhecido pelas suas propriedades mecânicas, térmicas e químicas,
sendo utilizado numa ampla gama de aplicações, inclusive na indústria de embalagem de alimentos. Apesar da
sua importância, a explicação da origem do seu odor está longe de ser totalmente compreendida.
A identificação e caracterização de compostos odoríferos neste tipo de plástico foi investigada
recorrendo a testes regulatórios de odores e a técnicas analíticas como a cromatografia gasosa/ espectrometria
de massa pela análise do tempo-de-voo (GC-TofMS) e a cromatografia gasosa - olfatometria (GC-O), onde o nariz
humano atua como detetor. Ferramentas estatísticas foram aplicadas para análise e validação de dados.
Os resultados provam que a formação de compostos odoríferos em polipropileno é fortemente
influenciada por diferentes etapas do processamento tais como a moldagem por injeção e moldagem por sopro.
Os aditivos também são responsáveis pelo odor, tendo sido sendo verificado que o agente nucleante em estudo
degrada-se e liberta, pelo menos, um composto odorífero.
As técnicas analíticas GC-TofMS e GC-O permitiram detetar e caracterizar aldeídos (acetaldeído,
butanal, hexanal, benzaldeído), terpenos (a-Pineno, terpeno C10H16, D-limoneno) e o ácido orgânico (ácido
acético) como compostos odoríferos. Outros candidatos são a cetona (2,3-butanodiona), o mercaptano
(metanotiol) e o ácido orgânico (ácido butanoico).
Dois tratamentos para remoção de odor foram testados recorrendo a equipamentos de secagem a
vácuo e de ar comprimido dessecante. O secador de ar comprimido dessecante mostrou-se eficiente na remoção
de compostos orgânicos voláteis e na redução da intensidade geral de odores nos produtos finais de
polipropileno.
Palavras-chave:
Polipropileno, Compostos orgânicos voltáteis, Compostos odoríferos, Embalagem de alimentos,
Additivos, Secadores de ar comprimido dessecante
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TABLE OF CONTENTS
1.
TUPPERWARE .......................................................................................................................................... 1
2.
INTRODUCTION ........................................................................................................................................ 3
3.
LITERATURE REVIEW ................................................................................................................................ 5
3.1. POLYMERS ................................................................................................................................................. 5
3.1.1. Polypropylene ................................................................................................................................ 6
3.2. PROCESSING .............................................................................................................................................. 7
3.2.1. Injection Molding ........................................................................................................................... 7
3.2.2. Injection Stretch Blow Molding ...................................................................................................... 8
3.3. POLYMER ADDITIVES ................................................................................................................................. 8
3.3.1. Stabilizers ....................................................................................................................................... 9
3.3.2. Antistatics ...................................................................................................................................... 9
3.3.3. Nucleating agents / Clarifiers ........................................................................................................ 9
3.3.4. Lubricants / Slip agents .................................................................................................................. 9
3.3.5. Fillers / Reinforcements ............................................................................................................... 10
3.3.6. Organic Peroxides ........................................................................................................................ 10
4.
PROBLEM STATEMENT ........................................................................................................................... 11
4.1. ODOR AND ODOR PERCEPTION ............................................................................................................... 11
4.1.1. Odor Causes ................................................................................................................................. 13
4.1.2. Odor diffusion and permeability .................................................................................................. 15
4.1.3. Odor analysis ............................................................................................................................... 17
5.
MAIN DRIVERS FOR ODOR AND TASTE IN POLYOLEFINS ........................................................................ 19
5.1. POLYPROPYLENE DEGRADATION ............................................................................................................ 19
5.1.1. Thermal degradation ................................................................................................................... 19
5.1.2. Weathering degradation ............................................................................................................. 21
5.1.3. Degradation of Additives ............................................................................................................. 21
6.
POLYMER TREATMENT ........................................................................................................................... 25
6.1. VACUUM DRYER ...................................................................................................................................... 26
6.2. HEATED DESICCANT AIR DRYER ............................................................................................................... 27
7.
ODOR-ACTIVE COMPOUNDS IDENTIFIED IN POLYPROPYLENE ................................................................ 29
8.
MATERIALS AND METHODS ................................................................................................................... 33
8.1. POLYPROPYLENE SAMPLES ..................................................................................................................... 33
8.2. PRODUCTION SAMPLES........................................................................................................................... 36
8.2.1. Production 1 - Modular Container Oval #3 .................................................................................. 36
8.2.2. Production 2 - Bottle 750 ml Round ............................................................................................. 36
8.2.3. Production 3 - Bottle 500 ml Round ............................................................................................. 37
8.3. SENSORY ANALYSIS ................................................................................................................................. 38
8.3.1. DIN 10954 Paired Comparison/Multicomparison Test ................................................................ 38
8.4. ANALYTICAL ANALYSIS ............................................................................................................................ 38
8.4.1. Gas Chromatography/Time-Of-Flight Mass Spectrometry (GC-TofMS) and GC-O ..................... 39
8.4.2. High Temperature Gel Permeation Chromatography (HT-GPC) .................................................. 39
8.5. DATA ANALYSIS ....................................................................................................................................... 40
8.5.1. Kruskal-Wallis Test ....................................................................................................................... 40
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9.
RESULTS AND DISCUSSION ..................................................................................................................... 43
9.1. RESULTS PRODUCTION 1 ......................................................................................................................... 43
9.1.1. Sensory and Data Analysis ........................................................................................................... 43
9.2. RESULTS PRODUCTION 2 ......................................................................................................................... 47
9.2.1. Sensory and Data Analysis ........................................................................................................... 47
9.2.2. GC-TofMS results ......................................................................................................................... 50
9.2.3. GC-O results and correlation to identification ............................................................................. 53
9.2.4. HT-GPC results ............................................................................................................................. 59
9.3. RESULTS PRODUCTION 3 ......................................................................................................................... 60
9.3.1. Sensory and Data Analysis ........................................................................................................... 60
9.3.2. GC-TofMS results ......................................................................................................................... 60
10. CONCLUSIONS AND FUTURE WORK ....................................................................................................... 63
11. REFERENCES ........................................................................................................................................... 65
12. ANNEXES ................................................................................................................................................ 67
I.
II.
III.
IV.
V.
POLYPROPYLENE PROPERTIES .......................................................................................................................... 67
ODOR PERMEABILITY OF POLYPROPYLENE PACKAGING FILM. ................................................................................. 67
PRODUCTION 1............................................................................................................................................ 68
III.1 Odor tests results ......................................................................................................................... 68
PRODUCTION 2............................................................................................................................................ 70
IV.1 Odor tests results ......................................................................................................................... 70
IV.2 GC-TofMS results ......................................................................................................................... 73
IV.3 GC-TofMS chromatograms .......................................................................................................... 79
IV.4 HT-GPC chromatograms .............................................................................................................. 80
PRODUCTION 3............................................................................................................................................ 81
V.1
Odor tests results ......................................................................................................................... 81
V.2
GC-TofMS results ......................................................................................................................... 81
V.3
GC-TofMS chromatograms .......................................................................................................... 83
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LIST OF FIGURES
Figure 1. Classification of polymers based on their structure. From left to right: linear, branch chain and
cross-linked polymer. .............................................................................................................................................. 5
Figure 2. Structures of Polypropylene: atactic (aPP), isotactic (iPP) and syndiotactic (sPP). [4] ................. 7
Figure 3. Schematic representation of an Injection Molding machine. [9]................................................. 8
Figure 4. Schematic representation of the Blow Molding process. 1-injection molded preform heated, 2preform secured into blow mold, 3-preform stretched with core rod, 4-compressed air is blown in and the
preform inflates to mold, 5-final product is removed from the mold. [12] ............................................................... 8
Figure 5. Human olfactory system representation. ................................................................................ 11
Figure 6. Human odor threshold in air.[20] ............................................................................................... 12
Figure 7. Tris (2, 4-di-tert-butylphenol) phosphite chemical structure. .................................................. 21
Figure 8. Pentaerythritol tetrakis (3, 5-di-ter-butyl-4-hydroxyhydrocinnamate) chemical structure.[39] 22
Figure 9. Glycerol monostearate chemical structure. ............................................................................. 22
Figure 10. Schematic representation of the polymer treatment process................................................ 25
Figure 11. Semi-continuous vacuum dryer configuration.[44] .................................................................. 26
Figure 12. Regeneration system in a heated desiccant air dryer. [46] ....................................................... 27
Figure 13. Images of Tupperware products studied. (a) Bottle Round, (b) Modular Container Oval #3. 33
Figure 14. Image of two types of pellets used. (a) PP3, (b) PP6. ............................................................. 34
Figure 15. LDP 200 Maguire, on the left, and Motan Luxor 80 Heated Desiccant Air Dryer, on the right.
.............................................................................................................................................................................. 37
Figure 16. Example of Multi Comparisons chart. On the left, the Boxplots with Sign Confidence Intervals
chart and, on the right, the Pairwise Comparison chart. [50] .................................................................................. 40
Figure 17. Comparison of odor intensity of Conditions A, B, C and D in PP2 containers represented in a
Multiple Comparison chart.................................................................................................................................... 44
Figure 18. Comparison of odor intensity of Conditions A, B, C and D in PP6 containers represented in a
Multiple Comparison chart.................................................................................................................................... 44
Figure 19. Comparison of odor intensity of Conditions A, B, C and D in PP7 containers represented in a
Multiple Comparison chart.................................................................................................................................... 44
Figure 20. Comparison of odor intensities of PP1, PP2, PP6 and PP7 grades represented in a Multiple
Comparison chart. ................................................................................................................................................. 45
Figure 21. Comparison of odor intensity of pellets, preforms and bottles of PP2 grade represented in a
Multiple Comparison chart.................................................................................................................................... 47
Figure 22. Comparison of odor intensity of pellets, preforms and bottles of PP3 grade represented in a
Multiple Comparison chart.................................................................................................................................... 47
Figure 23. Comparison of odor intensity of pellets, preforms and bottles of PP4 grade represented in a
Multiple Comparison chart.................................................................................................................................... 48
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Figure 24. Comparison of odor intensity of pellets, preforms and bottles of PP5 grade represented in a
Multiple Comparison chart.................................................................................................................................... 48
Figure 25. Comparison of odor intensity of Conditions A, B, C and D in PP3 preforms represented in a
Multiple Comparison chart.................................................................................................................................... 49
Figure 26. Design of Experiment of grade PP3 represented in a Pareto Chart of Standardized Effects. 49
Figure 27. Comparison of odor intensities of PP2, PP4, PP5 and PP6 grades represented in a Multiple
Comparison chart. ................................................................................................................................................. 50
Figure 28. Total concentrations of the main chemical families identified. ............................................. 53
Figure 29. Overview of the sensory perception of the smells described by panelists. ............................ 56
Figure 30. Comparison of odor intensity of PP5, PP5-A and PP5-B bottles represented in a Multiple
Comparison chart. ................................................................................................................................................. 60
Figure 31. Permeability coefficient for VOC versus molecular weight.[28] ............................................... 67
Figure 32. Comparison of odor intensity of Conditions A, B, C and D in PP2 preforms represented in a
Multiple Comparison chart.................................................................................................................................... 72
Figure 33. Comparison of odor intensity of Conditions A, B, C and D in PP4 preforms represented in a
Multiple Comparison chart.................................................................................................................................... 72
Figure 34. Comparison of odor intensity of Conditions A, B, C and D in PP5 preforms represented in a
Multiple Comparison chart.................................................................................................................................... 72
Figure 35. GC-TofMS chromatogram of PP2 bottle. ............................................................................... 79
Figure 36. GC-TofMS chromatogram of PP4 bottle. ............................................................................... 79
Figure 37. GC-TofMS chromatogram of PP5 bottle. ............................................................................... 79
Figure 38. HT-GPC chromatograms of PP2 pellets. ................................................................................. 80
Figure 39. HT-GPC chromatograms of PP4 pellets. ................................................................................. 80
Figure 40. HT-GPC chromatograms of PP5 pellets. ................................................................................. 80
Figure 41. GC-TofMS chromatogram of PP5 bottle. ............................................................................... 83
Figure 42. GC-TofMS chromatogram of PP5-A bottle. ............................................................................ 84
Figure 43. GC-TofMS chromatogram of PP5-B bottle. ............................................................................ 84
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LIST OF TABLES
Table 1. List of identified odor-active compounds in polypropylene found in several books and articles.
.............................................................................................................................................................................. 29
Table 2. Identified compounds of polypropylene decomposition. [47] ...................................................... 31
Table 3. Proposed impurities/ reaction products/ breakdown products for some additives present in
polypropylene grades in study.[38] ......................................................................................................................... 31
Table 4. List of polypropylene grades in study. ....................................................................................... 33
Table 5. Overall migration values in different simulants for the grades in study. .................................. 34
Table 6. Polymers’ additives composition and their respective maximum weight percent value in each
grade. .................................................................................................................................................................... 35
Table 7. Processing conditions applied in Production 1. ......................................................................... 36
Table 8. Processing conditions applied in Production 2. ......................................................................... 36
Table 9. LDP 200 Maguire test conditions. ............................................................................................. 37
Table 10. Motan Luxor 80 Heated desiccant air dryer test conditions. .................................................. 37
Table 11. Odor intensity scale in DIN 10954 Paired Comparison/Multicomparison test. ....................... 38
Table 12. Color code applied in GC-TofMS results. ................................................................................. 50
Table 13. GC-TofMS results of PP2, PP4 and PP5. Concentrations in bold and red exceed the odor
threshold value (OTV) and concentrations in bold and green don´t exceed 0,1 µg/m 3. ....................................... 51
Table 14. GC-O results of PP2, PP4 and PP5 and correlation to the compounds identified by GC-TofMS.
.............................................................................................................................................................................. 54
Table 15. Summary of the correlation between GC-O compounds odor intensities and concentrations
measured in GC-TofMS. N/D means not detected in GC-TofMS. .......................................................................... 55
Table 16. Dispersity of PP2, PP4 and PP5 samples.................................................................................. 59
Table 17. GC-TofMS results of PP5, PP5 treated with vacuum dryer (PP5-A) and PP5 (PP5-B) treated
with heated desiccant air dryer. Concentration of compounds marked with (*) cannot be determined accurately;
concentrations in bold and red exceed the odor threshold value (OTV) and concentrations in bold and green
don´t exceed 0,1 µg/m3. ....................................................................................................................................... 61
Table 18. Polypropylene structural and physical properties. .................................................................. 67
Table 19. Tests comparing two process stages (pellets and injection molded containers at conditions B)
and studying the impact of temperature (60°C and 160°C) and time (15 min and 180 min) in pellets’ sample
preparation for test TQA-009-041-I, in different polypropylene grades (PP1, PP2, PP6 and PP7). ....................... 68
Table 20. Tests studying the impact of temperature (60°C and 120°C) and time (15 min and 180 min) in
pellets’ sample preparation for test TQA-009-041-I. ............................................................................................ 68
Table 21. Tests comparing different processing conditions (A, B, C and D) in different polypropylene
grades (PP2, PP6 and PP7). ................................................................................................................................... 69
Table 22. Test comparing different polypropylene grades (PP1, PP2, PP6 and PP7) injection molded at
condition B. ........................................................................................................................................................... 69
xi
Table 23. Tests comparing three process stages (pellets, preforms and injection molded bottles at
condition D) and studying the impact of temperature (60°C and 160°C), in different polypropylene grades (PP2,
PP3, PP4 and PP5). Reference samples are PP2 preforms injection molded using Tupperware standard
parameters. ........................................................................................................................................................... 70
Table 24. Tests comparing different processing conditions (A, B, C and D) in different polypropylene
grades (PP2, PP3, PP4 and PP5). Reference samples are PP2 preforms injection molded using Tupperware
standard parameters. ........................................................................................................................................... 70
Table 25. Tests comparing different bottles of polypropylene grades (PP2, PP3, PP4 and PP5) injection
molded at condition D. Reference samples is a PP2 bottle blow-molded using Tupperware standard parameters.
.............................................................................................................................................................................. 71
Table 26. GC-TofMS results of PP2, PP4 and PP5. Concentration of compounds marked with (*) cannot
be determined accurately, concentrations in bold and red exceed the odor threshold value (OTV) and
concentrations in bold and green don´t exceed 0,1 ug/m 3. .................................................................................. 73
Table 27. Production 3 odor test results- test comparing PP5 bottles, PP5-A and PP5-B. Reference
samples are PP2 bottles blow-molded using Tupperware standard parameters. ................................................ 81
Table 28. GC-TofMS results of PP5, PP5 treated with vacuum dryer (PP5-A) and PP5 treated with
heated desiccant air dryer (PP5-B). Concentration of compounds marked with (*) cannot be determined
accurately; concentrations in bold and red exceed the odor threshold value (OTV) and concentrations in bold
and green don´t exceed 0,1 µg/m3. ....................................................................................................................... 81
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ABBREVIATIONS
AO – Antioxidant(s)
AO1 – Primary Antioxidant
AO2 – Secondary Antioxidant
aPP – Atactic Polypropylene
CMB – Color masterbatch
E-nose – Electronic Nose
GC – Gas Chromatography
HALS – Hindered amine light stabilizers
iPP – Isotactic Polypropylene
ISBM – Injection Stretch Blow Molding
MS – Mass Spectroscopy
MWD – Molecular Weight Distribution
OR – Odorant Receptor(s)
OTV – Odor Threshold Value(s)
PE – Polyethylene
PET – Polyethylene Terephthalate
PP – Polypropylene
PPB – Polypropylene Block Copolymer
PPH – Polypropylene Homopolymer
PPRC – Polypropylene Random Copolymer
PS – Polystyrene
PVC – Polyvinyl chloride
sPP – Syndiotactic Polypropylene
VOC – Volatile Organic Compound(s)
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1. TUPPERWARE
The successful story of Tupperware started in 1944 when Earl Tupper founded Tupperware Plastics
Company. This American chemist was a pioneer in the use of polyethylene for household use. Two years later,
he launched his famous "Wonderful Bowl", a revolutionary closing bowl, hermetic, much lighter and stronger
than traditional materials. During the first years of marketing, these products could be found in supermarkets,
hardware stores and other businesses establishments. The disadvantage of this type of sale was that users did
not receive specific explanations of the advantages of Tupperware products.
In 1948, Vice President Brownie Wise introduced Tupperware Home Party, a new sales strategy where
products were demonstrated and the consumer could also test them extensively. By 1951, the "Home Party"
system was so successful that the products were removed from the store sale. Since then, products can only be
purchased through these workshops under the guidance of specially trained counselors. Few exceptions are
made in certain countries, where it is possible to buy Tupperware products online.
Tupperware Belgium NV, located in Aalst, is a central part of Tupperware’s representation in Europe.
The Belgian plant is now the center of design specialization and development of new products for the company.
Furthermore, not only the production of some of the most complex Tupperware products is held there, but it is
also the logistics center for the distribution of products to Belgium distributors and other European countries.
Nowadays, Tupperware products seek to improve quality of life by offering high quality and innovative
designs. As the world changes, Tupperware follows this change, seeking to create solutions that keep up with
modernity and the demands of domestic tasks.
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2. INTRODUCTION
In today’s world, plastic is an integrant part of society lifestyle as it is used in numerous products that
provide comfort, convenience and safety. Plastic is used in food packaging, maintaining food’s fresh attributes,
nutritional quality and, consequently, reducing the amount of food wasted and decreasing the use of
preservative food additives needed. As consumers’ sensitivity and awareness increase, complex issues such as
odor and taste in final products have been becoming major causes of consumer complaints worldwide, as the
presence of these may be directly related to product quality and the impact that may have on health. For this
reason, low or no odor and taste properties are now requirements, not only for the end consumer but also in
the context of food safety, leading to a need for deeper understanding and characterization of odor and taste.
The odor is caused by odor-active compounds, i.e., substances presented at concentrations that can be
perceived by the human nose. On the other hand, the taste is a gustatory perception which is a combination of
taste, odor and nervous systems that are dependents of one another. Therefore, odor perception presents a
higher interest as its study can be, in some extension, applied to taste understanding.
Tupperware is a renowned company specialized in plastic food packaging for multiple uses. It is known
for its products that present high quality and durability. One of the most used plastic by the brand is
polypropylene, a polyolefin used in the production of containers and bottles sold all over the world, generating
millions of revenues. Over time, one of the challenges regarding polypropylene products at Tupperware in quality
approval is the odor, making the pursuit for polymers with good organoleptic properties incessant. Currently,
sensory quality tests are performed by panelists that evaluate products’ odor quality and intensity. Although
these tests are always necessary and useful for quality approval, other tests have to be performed to avoid the
creation of odor. Besides, current odor tests are performed in final products, meaning that injected and blowmolded pieces have to be produced. For this reason, there is also a will of performing tests with raw materials,
i.e., polymer pellets, by creating a quick and easy pellets’ evaluation to be carried out when polymer batches
arrive at Tupperware. Polymers would be then selected without the expenses of production. In this context, the
objective of this thesis can be divided into different specific goals:
i.
Study the parameters needed to recreate the final products’ odor in pellets (simplification of the current
Tupperware odor test);
ii.
Study the influence of processing in the creation of odor-active compounds, especially, Injection
Molding and Blow Molding;
iii.
Study the influence of polymers additives in the creation of odor-active compounds;
iv.
Identification and characterization of odor-active compounds present in selected polypropylene grades;
v.
Improvement of Tupperware products’ odor level.
In this thesis, in general, the rules for the nomenclature from the International Union of Pure and
Applied Chemistry (IUPAC) have been followed. A number of names not following the IUPAC nomenclature are
included as the external laboratory preferred to used other nomenclatures when presenting the analyses results.
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4
3. LITERATURE REVIEW
3.1. POLYMERS
Polymers are long-chain molecules composed of many repeating units of identical structures, chemically
linked denominated monomers. Monomers can be simple structures, made of a few atoms or, complex ringshaped structures with dozens of atoms that contribute to the structure of a macromolecule. Strong covalent
bonds link atoms to one another to form individual molecules and then intermolecular forces join different
molecules towards each other to form polymers. Therefore, polymers can be divided into four groups according
to their molecular forces: elastomers, thermoplastics, thermosetting plastics and fibers. [1]
In thermoplastic polymers, chains are held by intermolecular Van der Waal’s forces. These polymers are
in a viscous liquid state at high temperatures because the intermolecular forces easily weaken with increased
temperatures and then solidify upon cooling, forming a hard mass. They do not contain cross bonds. Polystyrene
(PS) used to produce disposable plastic cutlery, for instance, and Polyvinyl chloride (PVC) which is used to make
pipes are two examples of this type of material.
Another way of classifying polymers is based on their structure into linear, branch chain and cross-linked
polymers. In linear polymers, repeated monomeric units are linked by covalent carbon-carbon bonds to form a
single continuous chain and, therefore, have high densities, tensile strength and melting points. Branch chain
polymers are formed when branches of monomers with different lengths are originated at random points along
the polymer chain. As a result, polymer molecules are not packed in a regular way. Crystallization is not only
dependent on polymer regularity but also on the length of the branches because short branches reduce the
amount of crystallinity, while long branches can form lamellar crystals of their own. At last, in cross-linked
polymers, monomers are linked to form three-dimensional networks which make them more rigid. These linking
bonds may take the form of covalent or ionic bonds. [1]
Figure 1. Classification of polymers based on their structure. From left to right: linear, branch chain and cross-linked
polymer.
Nowadays, one of the most important commercial plastic groups are the polyolefins used for food
plastic containers. Polyolefins are non-aromatic high molecular weight thermoplastics which are obtained by
polymerizing olefins. Olefins are unsaturated hydrocarbons, in this case, alkenes (CnH2n) that contain, at least,
one carbon-carbon bond. They usually derive from natural gas or low molecular weight compounds of
petroleum.[2]
5
Polyolefins are usually processed by extrusion, injection, blow and rotational molding. Polyethylene (PE)
and polypropylene (PP) are two of the most used types of polyolefins worldwide due to their low cost and wide
range of applications. Although both PP and PE materials are important for food storage purposes, Tupperware
processes a higher volume of containers made of polypropylene, which led to a bigger demand for a deeper
understanding of this material.
3.1.1. Polypropylene
Polypropylene (PP) is a rigid translucent to transparent thermoplastic polyolefin (C 3H6)n with a glossy
surface. It presents good resistance to acids, alkalis, organic and inorganic chemicals except for hydrocarbons
and chlorinated compounds. In comparison with other polyolefins, it has improved impact strength, a higher
softening point, lower density, better stress cracking and more scratch resistance. One disadvantage of this
polymer is its brittleness at low temperatures.[3] At last, PP is a non-hygroscopic resin, hence, it does not adsorb
moisture because the space between molecular chains is smaller than the size of a single water molecule. Some
polypropylene properties are presented in Annex I - Table 18.
Polypropylene plays a key role in various industries such as packaging, consumer goods, automotive,
medical material, fibers and fabrics, as it exhibits an excellent cost-performance ratio.[4] Good barrier properties,
high strength, durability, structural integrity and good surface finish make polypropylene ideal for packaging
applications, either for flexible or rigid packaging. [4] Besides, PP presents a versatile temperature range, making
it suitable for microwave and freezer use.[5] In the automotive industry, PP is used to produce automotive parts
such as battery cases, instrumental panels, door trims, fender liners, etc. Other market segments are fabrics and
fibers and medical equipment where PP is used to make continuous filaments and disposable syringes,
respectively.
There are two general types of PP: Polypropylene Homopolymer (PPH) and Polypropylene Copolymer
which is divided into Polypropylene Block Copolymer (PPB) and Polypropylene Random Copolymer (PPRC). PPH
is the most used polymer and it only contains propylene monomers in a semi-crystalline solid form. Comonomer
of PP is ethylene which is used to control the degree of short-chain branches and to retard the growth of large
crystal structures.[6] PPRC presents comonomers arranged in irregular patterns and contains 1-7% of ethylene,
being a flexible material. On the other hand, PPB has comonomer units arranged in blocks, i.e., in regular
patterns, and contains between 5-15% of ethylene. The addition of ethylene enhances impact resistance and the
regular pattern makes the copolymer tougher and less brittle than PPRC, more suitable for industrial use where
high strength is required. [7] When comparing Homopolymer PP and Copolymer PP, PPH tends to have higher
crystallinity levels and, consequently, a higher strength to weight ratio and higher temperature resistance than
Copolymer. Besides, its good chemical resistance makes it a better option for many corrosion resistant
structures. Copolymer PP is a bit softer but has better impact strength, is tougher and more durable than PPH.[4]
As mentioned previously, PP is produced by the polymerization of propylene. Nowadays, there are two
main polymerization processes where the differentiation is in the type of catalyst used: Ziegler-Natta (ZN) or
metallocene. All the polymers used in this study were polymerized using ZN catalyst. Upon polymerization, PP
6
can form three basic chain structures depending on the position of the pendant methyl groups attached to
alternate carbon atoms: Atactic (aPP) - irregular methyl group arrangement, isotactic (iPP) – methyl groups
arranged on one side of the carbon chain and syndiotactic (sPP) - alternating methyl group arrangement.[4] The
amount of isotactic, syndiotactic and atactic polymer depends on the catalyst used and polymerization
conditions, being isotactic polymers with small amounts of atactic polymer the most common type. iPP presents
high crystallinity, stiffness and tensile strength due to its regular structure. On the other hand, aPP has low
crystallinity resulting in amorphous material with good impact resistance and stretchability, but low stiffness,
haze and color quality. sPP material presents intermediate properties, being less stiff than iPP, however, it
presents better clarity and stronger impact resistance. [8]
Figure 2. Structures of Polypropylene: atactic (aPP), isotactic (iPP) and syndiotactic (sPP).[4]
3.2. PROCESSING
3.2.1. Injection Molding
Injection Molding is a molding technique suitable for thermoplastics and thermosets. The process cycle
for Injection Molding consists of four stages: clamping, injection, cooling and ejection. In Figure 3, there is a
schematic representation of an Injection Molding machine. [9]
Firstly, the two halves of the mold must first be securely closed by the clamping unit. After that, the
granulate or powder is fed through the hopper and advanced towards the mold by the injection unit. During this
process, the material is melted by heat and pressure while it is transported and homogenized by the screw inside
the barrel. The molten plastic is then injected into the mold very quickly and the build-up of pressure packs and
holds the material. In the third processing stage, the molten plastic inside the mold begins to cool as soon as it
contacts the interior mold surfaces. Once the entire cavity is filled, cooling is continued until the product reaches
the discharge temperature. This is the temperature at which the product retains its shape. Finally, the cooled
part is ejected from the mold by the ejection system, which is attached to the rear half of the mold. When the
mold is opened, a mechanism is used to push the part out of the mold. Once the part is ejected, the mold can be
clamped shut for the next shot to be injected. [10]
7
Figure 3. Schematic representation of an Injection Molding machine. [9]
3.2.2. Injection Stretch Blow Molding
At Tupperware, the production of bottles is done by the Injection Stretch Blow Molding (ISBM) process.
Firstly, the plastic is molded into preforms using an Injection Molding machine separated from the blow molder.
These are produced with the necks of the bottles, including threads on one end. After, preforms are cooled,
stored, and fed later into a re-heat stretch Blow Molding machine. In the Two-Step Reheat Blow process, the
preforms are heated, typically using infrared heaters, then stretched and blown in length as well as radially using
high-pressure air in the blow molds. Stretching of the material introduces some crystallinity. This type of
processing allows PP improved strength and barrier properties at much lighter weights.[11]
Figure 4. Schematic representation of the Blow Molding process. 1-injection molded preform heated, 2-preform
secured into blow mold, 3-preform stretched with core rod, 4-compressed air is blown in and the preform inflates to mold,
5-final product is removed from the mold. [12]
3.3. POLYMER ADDITIVES
Polymers’ properties can be “tailored” through the incorporation of additives in their matrix to enhance
the processability, end-use of the polymer product or to suit a special requirement. Polymer packaging uses
functional additives including clarifiers, nucleating agents, stabilizers, antioxidants (AO), lubricants/ slip agents,
fillers/ reinforcements and organic peroxides.
8
3.3.1. Stabilizers
Stabilizers are organic and inorganic additives which are compounded into polymeric materials,
inhibiting degradation from the environmental exposure such as heat, light and weathering.
Ultraviolet stabilizers protect polymers exposed to strong sunlight and prevents discoloration, cracking
and loss of physical properties. The most commercially used are hindered amine light stabilizers (HALS).[13]
Antioxidants (AO) are stabilizers that inhibit oxidation. According to their mechanism in interrupting the
degradation process, there are chain-terminating primary antioxidants and hydroperoxide decomposing
secondary antioxidants. Primary antioxidants (AO1) react rapidly and are termed radical scavengers in the
oxidation process. The most important are sterically hindered phenolics and secondary aromatic amines.
Phenolic compounds consist of a hydroxyl group directly bonded to an aromatic hydrocarbon group that provides
melt processing stability as a hydrogen donor. They protect plastics against thermal oxidation, especially during
processing and long-term storage of polyolefins.
Secondary antioxidants (AO2) are phosphorus-based melt processing stabilizers that react with
hydroperoxides to produce non-radical products and thus remove radical intermediates, being an important
property to avoid chain scission as explained in Chapter 5.1.[13] After reaction with hydroperoxides, these
antioxidants decompose. They are particularly useful in synergistic combinations with primary antioxidants.
3.3.2. Antistatics
Antistatic additives are added to plastics to reduce or eliminate a static build-up. They work by lowering
the resistivity of material so that charges are mobile and, therefore, will not cause static issues such as dust
attraction or electrostatic discharge. The limited compatibility forces the antistatic to migrate to the free surface
of a polymeric material. The polar groups react with water on the surface to produce a weakly conductive surface
film. These materials are used in very low bulk concentration in most polymer applications to create an
homogenous adsorption and avoid bulk adsorption into polymers.
3.3.3. Nucleating agents / Clarifiers
Polypropylene normally crystallizes slowly into relatively large crystals known as spherulites which are
larger than the wavelength of visible light and thus they reflect it, reducing clarity and increasing haze in the
material. One typical group within nucleating agents are clarifiers that increase the rate of crystal initiation and
decrease the size of the crystals, giving high levels of clarity and gloss. The improvement of processing
characteristics is a side effect of the use of these additives. The use of nucleating agents in plastic packaging
materials is claimed to have eliminated taste and odor in some liquids and foods. [13], which may be a result of its
moisture barrier properties.
3.3.4. Lubricants / Slip agents
Lubricants reduce the shear rate during processing, especially when an inorganic material is being
added. Typical lubricants suitable for films and moldings are primary amides that modify the surface of
9
polyolefins, reducing friction and tendency towards blocking. After processing, depending on the surface
properties of the polymer, amides might migrate to the surface. They are often used in conjunction with antiblocking agents such as silica or talc. [13]
3.3.5. Fillers / Reinforcements
There are many types of inorganic reinforcements, since natural and synthetic minerals to specialized
materials. The basic purpose is to fill a compound, i.e., increase its bulk at low cost. Fillers may also improve
mechanical properties when they are homogeneous and present good polymer adhesion. Talc is a very pure
white magnesium silicate compound which is mainly used as reinforcement, giving good stiffness and
dimensional stability to crystalline thermoplastics as polypropylene. [13],[14]
3.3.6. Organic Peroxides
Organic peroxides are organic compounds containing the peroxide functional group (ROOR′) where R
and R’ are the organic radicals. They are useful in chemical synthesis due to their tendency to decompose,
generating radicals that help the polymerization initiation. Besides, they can also be integrated into polymers to
adjust the melt flow and to narrow the molecular weight distribution, in an operation called “visbreaking” or “PP
controlled rheology” to improve its properties, resulting in a uniform shrinkage.[15],[16]
10
4. PROBLEM STATEMENT
4.1. ODOR AND ODOR PERCEPTION
Odor perception is influenced by external environmental factors as well as many factors unique to each
individual. Mood effects, perception effects and scent preferences influence the experiences and emotions
associated with these sensations.
Odors are caused by one or more volatile organic compounds (VOC) that humans and animals can perceive
by their sense of smell. VOC present high vapor pressure at ordinary room temperature due to their low boiling
point, being volatile at atmospheric pressure and, consequently, detected by the human olfactory system.
The human olfactory system is very complex. VOC
must penetrate the mucus of the nasal cavity to be
detected by odorant receptors (OR) which are localized
on olfactory sensory neurons, in the olfactory bulb.
Humans have around 400 different types of OR. Each OR
binds to several odorants, and each odorant is detected
by a specific combination of OR. The brain then translates
this specific ‘receptor code’ into a distinct smell. [17]
Compounds with a molecular mass over 300 g/mol do not
show odor activity as they are not able to bind to odor
receptor cells. [6]
Figure 5. Human olfactory system representation.
According to Hopfer[6], odorants can be perceived by nasal and retronasal impression. Nasal impression
happens when there is a direct passage of the VOC from the nose to the OR while retronasal occurs when odoractive compounds are released in the mouth by chewing, warming and/or contact with the salvia and get to the
olfactory bulb passing through the palate.
Each VOC is a different odorant, which can be recognized at a specific concentration according to their
odor threshold value (OTV). Two types of OTV can be distinguished, detection and recognition thresholds.
Detection is the minimum concentration that can be detected by the human nose without any requirements to
identify or recognize the stimulus, while recognition is the minimum concentration at which a stimulus can be
identified or recognized by some specified percentage of the population.[18] In this thesis, the values presented
are detection limits. Some chemical compounds are recognized at very low concentrations (0,00001 µg/m3 = 10
ppt). Odor emissions depend on the sample surface rather than on the sample mass.[19]
In Figure 6 is possible to see typical levels of odor detection concentrations for some chemical groups.
It is important to observe that these levels are approximately 100 times lower than common food approval
specification limits.
11
Figure 6. Human odor threshold in air.[20]
The sense directly related to odor is taste. Taste is the sensation produced when a substance in the
mouth is distinguished by the brain, based on information provided by the taste buds, mostly on the tongue. [21]
Recognition of flavors is a result of taste, olfaction and somatosensory system. Apple flavor is a collection of
different inputs, such as tastes (sweet, sour), textures (crispy, juicy), and odor (lemony, acetone-like, honey). The
somatosensory system is a complex system of sensory neurons and pathways that responds to changes at the
surface or inside the body, giving the faculty of bodily perception. This way, examples of somatic senses are touch
(including the texture of food), temperature, proprioception (body position), and nociception (pain). These three
systems are not completely independent as they can increase or decrease the signal of individual systems.[22]
Our gustatory system allows the perception of different food constituents as alkali metallic salts (salty),
acids (sour), sugars (sweet), and bitter compounds. Umami is a different taste, arising from the perception of
amino acids, such as l-glutamate, and 5’-ribonucleotides.[23] Many researchers have been indorsing that eighty
to ninety percent of what is perceived as taste is smell. Reciprocal effects of odors on tastes are known, for
instance, the sweet taste is enhanced in the presence of a congruent odorant as strawberry. [22]
Due to all the reasons mentioned above, it is difficult to make conclusions about taste from flavors.
More than the smell and its intensity, taste is a subjective, individualized sense that proves to be very hard to
describe and quantify and, consequently, it will not be studied in this thesis.
12
4.1.1. Odor Causes
Odor generation comes along the whole product process chain at Tupperware. Odor problems in
polymers mainly arise from:[24]
i.
Release of residual monomers, process solvents, chain transfer agents1 and/or low molecular
weight oligomers, oils and waxes trapped in the polymer;
ii.
Thermal degradation of the polymer during polymerization process, end-product production
process and use;
iii.
Additives with high vapor pressure and/or degradation or interaction of additives in the
polymer formulation;
iv.
Chemical reactions with the environment like hydrolysis and oxidation;
v.
Heat, sun/light, humidity conditions and dishwasher use during the end-product use;
One possible cause of the odor is also the use of 𝛾-irradiation sterilization treatment commonly done in
packaging materials to kill microorganisms. Odor creation from this sterilization treatment will not be studied in
this thesis as Tupperware does not perform it in their products.
Regarding the odor potential of monomers, opinions differ. While some researches present outgassing
of residual monomers as a source of odor[24], according to Hopfer[6] it is not clear yet. In fact, in her research
monomers appear in the final polyolefins. Although that indicates that residual monomers are a valid cause of
the odor, experiments showed that not many or strong odor-active compounds could be detected.[6]
INFLUENCE OF RAW MATERIALS PRODUCTION PROCESS
VOC are formed during the production of raw materials which is mainly divided into two processes,
polymerization followed by extrusion into granules. Odor creation in the polymerization process can occur due
to several parameters of the process such as temperature, pressure, type of catalyst used and the use of
additives. Besides the process, the polymer itself can release odor-active compounds depending on its rheology,
molecular weight distribution and structure, for instance, the existence of branching. In polypropylene, shortchain hydrocarbons like alkanes, alkenes, and dialkenes were found in the emitted compounds which
participated in odor generation when chains were shorter than 16 carbon atoms. [22]
INFLUENCE OF ADDITIVATION
In a study, PP containing numerous additives was analyzed for odor-active compounds. Results showed
that talc, UV stabilizer and color masterbatch (CMB) released VOC during processing, showing a massive impact
on the generation of odor-active compounds by the formation of new odor-active species.[6] CMB was confirmed
to affect polymer thermal stability and to react with several species in the grades. Also, talc and sterically
hindered phenols (AO1) combined increased the odor, as it is believed that talc degrades and absorbs the
antioxidant to its surface. The same situation happens with HALS that consume sterically hindered phenols that
1 Chain transfer agents, also called modifiers or regulators, have at least one weak chemical bond, which therefore
facilitates the chain transfer reaction, i.e., polymerization reaction. Common chain transfer agents include thiols
and halocarbons.
13
are no longer available to catch radicals during polymer degradation.[6] Experiments revealed that despite the
fact these additives prevent degradation, they do not prevent odor creation by oxidation reaction during
processing.[6]
Organic peroxides are useful because they can generate radicals for the polymerization process.
However, the formation of radicals in polymer degradation is a major cause of odor creation. This way, visbreaking reagents, i.e., organic peroxides have a high impact in releasing odor-active compounds as grades that
did not present organic peroxides in their composition showed the lowest odor values.[6]
INFLUENCE OF PROCESSING
Experiments done with PPB and PPRC showed that the number of odor-active compounds increase after
Injection Molding processes, such as aldehydes, ketones and carbonyls.[6] In these experiments, all investigations
where pellets and injection molded plaques were analyzed, a higher number of and more intense odor-active
compounds were detected in the processed samples. Other compounds such as 2-acetyl-1-pyrroline and one
unknown substance from additives were found in higher amounts after Injection Molding indicating a
temperature-driven reaction in PP grade used.[6]
Therefore, Injection Molding is a big cause of the generation of odor-actives compounds. For this reason,
Injection Molding parameters such as melt temperature, cooling time and plasticizing time, dosing speed and
back pressure, are studied as they are believed to have the most influence in the creation of shear and,
consequently, odor during processing. For instance, the shear caused by the injection pressure, called back
pressure, inside the barrel changes the molecular weight distribution of the polymer, increasing the VOC realized,
as explained in Chapter 5.1.1.
Melt temperature is the temperature of the polymer as it exits the nozzle and enters the mold. Cooling
time is the time before the molding has cooled and become sufficiently rigid to allow it to be demolded and
usually takes up over 50% of cycle time. The dosing speed is the rate at which an amount of material from the
hopper is transferred to the processing machine. Finally, plasticizing time is the time that pellets are being heated
and homogenized inside the barrel.
14
4.1.2. Odor diffusion and permeability
Transport of gases through polymer films happens initially with the condensation and solution of the
gas to the polymer surface, followed by the diffusion through the polymer and evaporation at the other
surface.[25]
Diffusion in solids is very different from the physical process which occurs in liquids and gases.[25]
Diffusion is usually described using Fick’s first law that relates the diffusive flux to the concentration under the
assumption of steady-state, i.e., where concentration is not varying with time. It states that the flux going
through the x-direction (𝐹𝑥 ) is proportional to the concentration gradient which is the driving force of the
diffusion process, as represented in Equation 1.
Equation 1. Fick’s first law of diffusion.
𝑭𝒙 = −𝑫
𝝏𝑪
𝝏𝒙
Flux is the amount of substance diffusing across a unit area in unit time, 𝐷 is the diffusion coefficient
which depends on the temperature, 𝐶 is the concentration of the diffusant, 𝑥 the depth of penetration and 𝑡 is
the time.
In majority of real situations, the concentration gradient is not constant but changes with time. This
way, Fick’s second law describes non-steady state diffusion, i.e., the concentration changes as a function of time
to the change in flux concerning the position. Its formula is presented in Equation 2.
Equation 2. Fick’s second law of diffusion.
𝝏𝑪
𝝏𝟐 𝑪
= −𝑫 𝟐
𝝏𝒕
𝝏𝒙
While diffusion describes the movement of the penetrant molecules inside the bulk of the polymer, the
term permeation refers to the overall mass transport of the penetrant gas or liquid across the membrane.
Permeability is important in food packaging applications as polymers with low permeability, i.e., higher barrier
properties are required with the view of preventing odor, color or flavor release.[26] Permeability coefficient (P)
represents the permeability of the membrane and is the product of the diffusion coefficient (𝐷) and the solubility
coefficient (𝑆).
Equation 3. Permeability coefficient.
𝑷 = 𝑫𝑺
Three assumptions are made in the simple treatment of permeation. These are that diffusion is in a
steady-state condition, the concentration-distance relationship through the polymer is linear, and diffusion takes
place in one direction only.[27]
In general, permeability and solubility at a given temperature depend on the degree of crystallinity
(morphology), the molecular weight, the type of permeant and its concentration or pressure, and in the case of
copolymers, also on the composition. The crystalline form is more stable than the amorphous form and has lower
energy at the molecular level with stronger bonding between molecules that require higher energy to break. This
way, the higher the crystallinity, the lower the solubility and, consequently, the permeability.
15
Permeability and solubility of vapor are low for nonpolar polymers such as PE and PP, whereas the
opposite trend is observed for oxygen. The density of the polymer is also an important factor as lower the density,
higher the polymer permeability to oxygen. Crystalline structures have a greater degree of molecular packing
and the individual lamellae crystals may be considered as almost impermeable to a diffusing molecule. This way,
diffusion can only occur in the amorphous zones or at regions of imperfection in the crystal structure. Therefore,
semi-crystalline polymers tend to be less permeable than amorphous polymers.[26]
As the permeability of packaging materials to organic vapor is of considerable interest, some
experiments were already done to analyze if simple relationships exist between permeability coefficient and
permeant molecular structure for coextruded PP packaging. Results showed that the permeation coefficient
decreases with increasing molecular weight only for the smallest molecules. On the other hand, above a
molecular weight of 60 g/mol, including most odorous materials, the permeation coefficient rises with the
increase in molecular weight, at low odorants concentrations (Annex I - Figure 31).[28]
Migration, leaching, and partitioning are considered in the diffusion transportation of odors inside the
product.
MIGRATION
Odor generation in materials, either on gaseous, liquid or solid phase occurs when components from
the plastics or compounds formed by the degradation of polymers or their additives migrate. [22]
Migration is the diffusion of an additive from plastic to other contacting material. In some plastics, some
compounds are already known for migrating into food, like acetaldehyde, for example. Acetaldehyde is a
common degradation product PET formed during the melt condensation reaction and melt processing of PET.[22]
When plasticizers, which increase the plasticity or decrease the viscosity of a material, and other additives
migrate to the interface, diffusion can be a complex parameter. In this case, the diffusion coefficient is a function
of position, and when the solute is highly soluble in the polymer (strong plasticizer), the diffusion coefficient is
also a function of time and exposure history (non-Fick diffusion). [26]
In a previous Tupperware study[29], it was possible to observe that with an increased rate of amorphous
phase in PP, higher the tendency to migration, agreeing with the permeation behavior described previously. As
the additives cannot enter the crystalline phase, they go to the amorphous phase, easily migrating inside the
polymer structure.[29]
LEACHING
Leaching is the process of extracting substances from a solid by dissolving them in a liquid, naturally. It
occurs when components are soluble in a solvent, for instance in water, being extracted and deposited in enough
concentration on the surface of the material. Leaching has a bigger impact in taste sense and it is not a probable
cause for odor in PP due to its high heat tolerance, being unlikely to leach even when in contact with hot water. [30]
In a recent research, additives and residual monomers from PP were extracted by shaking in n-hexane,
a non-polar organic solvent, for 24h. The results suggested the presence of extractable residual monomers,
however, no aliphatic compound could be detected in the PP leachate.[31]
16
PARTITIONING
Partitioning occurs when a substance is in contact with two different phases and presents different
affinity for each phase. Partitioning of odor compounds can happen between polymer-polymer, polymer-liquid
(leaching), polymer-gas or gas-liquid.[22] A part of the substance will be absorbed or dissolved by one phase and
the other part by another, depending on the dissolved amounts of the relative affinities for each phase. There
are few literature references regarding these systems.[22]
Partition coefficients, Kij, reflect the concentration ration of a solute in phases i (𝐶𝑖 ) and j (𝐶𝑗 ), which are
in equilibrium, presented in Equation 4.
Equation 4. Partition coefficient.
𝑲𝒊𝒋 =
𝑪𝒊
𝑪𝒋
This coefficient describe how a solute is distributed between two immiscible solvents. When one solvent
is water (leaching), partition of each VOC will depend of its hydrophilicity. Polymer-based partition coefficients
can be found mostly for environmental sampling phases like air, but for a single compound of one given polymer,
these coefficients present wide ranges of magnitude.[32] No literature regarding partition coefficients that could
be important for this odor study was found.
4.1.3. Odor analysis
Odor characterization and measurement present several difficulties as mentioned below[24]
i.
Extremely low odor thresholds;
ii.
Same odor for numerous substances;
iii.
Different odor depending on concentration;
iv.
Very slow formation of off-odors;
v.
Unexpected reactions (oxidation, condensation, dehydration, etc.);
vi.
Extensive time required for diffusion through packaging materials;
vii.
Overlapping of odor-active substances;
Currently, odor analysis can be performed using sensory and analytical evaluation. Sensory odor
analysis, which was initially used in the food-processing industry, has been widely applied in different fields,
especially for quality inspection, product design and marketing. It can be described as the use of a group of
people, the panel, to evaluate the odor of products and their intensity. This type of analysis requires a certain
amount of people to have a statistically significant result, training of perception and recognition of odors and
only gives the overall odor of a product and no further information about the composition or concentration of
the VOC sniffed.[6] The appropriate test method selection (e.g., paired comparison, triangle test, simple
descriptive, ranking, etc.) is important to get the right information from the evaluation.
17
Hedonic evaluation is a specificity of the human nose that it is related to subjective opinions.
Nevertheless, in most situations, this type of analysis is not accurate enough, and quantitative and qualitative
techniques for identification and characterization of single odor compounds are necessary for the understanding
of odor generation and its causes. For this reason, analytical methods are performed.
Regarding analytical analysis, Gas Chromatography (GC) coupled to Mass Spectroscopy (MS) has been
the preferred technique for separation and identification of odors. However, when it is necessary to know if a
compound is odor-active or not, only humans can use their sense of smell to know it and, for that reason, human
noses are used as a detector. In these cases, panelists detect compounds after the separation in GC, as explained
in Chapter 8.4.1.
Over the past decades, progress in sensor technology has enabled the development of instruments that
replicate human olfactory to predict the human perceptions of smell, odor recognition and odor hedonics, with
the ultimate goal of replacing human sensory evaluation.
Electronic noses (e-noses) consist of a headspace sampling, sensor array, and pattern recognition
modules to generate a signal pattern that is used for qualitative or quantitative analysis of odors. E-noses cannot
identify the chemical compounds responsible for the odor, instead, they can compare and categorize samples,
after proper training with qualified samples to build a database of reference. Then the instrument can recognize
new samples by comparing a VOC “fingerprint”, i.e., chemical structures, to those contained in its database. They
can thus be used as quick screening tools reducing the amount of human sensory and advanced chemical testing
needed. Despite the developments done, e-noses still cannot completely replace the human senses for
sensitivity, selectivity and speed. For instance, many odors are made up of multiple different molecules, which
may be wrongly interpreted by the device as it registers them as different compounds, resulting in incorrect or
inaccurate results.
Recently, biosensor systems that present olfactory receptors have been introduced. Bioelectronic noses
(bio-e-noses) are constructed using biological materials and nanomaterials such as carbon nanotube, conducting
polymer, and graphene. Besides, they use olfactory receptors, proteins cloned from biological organisms, e.g.
humans that bind to specific odor molecules. OR improved the selectivity of the sensor allowing the
discrimination of differences between single carbon atoms, and the use of nanomaterials enhanced the
sensitivity, presenting an OTV of 0,02 ppt, lower than normal human perception value of 10 ppt. [33]
18
5. MAIN DRIVERS FOR ODOR AND TASTE IN POLYOLEFINS
5.1. POLYPROPYLENE DEGRADATION
PP product deterioration can occur by direct or indirect agency. Direct agency can be physical,
biochemical or microbiological while indirect agents can be time, temperature, moisture, light, gases or pressure,
as mentioned previously. Typically alkanes, alkenes, and dialkenes dominate the volatiles obtained from
polypropylene degradation. [19] PP is mostly vulnerable to chain degradation ate temperatures above 100 ⁰C.
5.1.1. Thermal degradation
PP oxidation occurs in the amorphous region of the polymer. Polypropylene structure highly influences
its preponderance to oxidation. PP presents tertiary hydrogen on the carbon atom bonded to the pendant methyl
group, being susceptible to oxidation through free radical chain reactions as seen in Equation 5 where there is a
homolytic cleavage of carbon-hydrogen bond resulting in two radicals. The cleavage is due to mechanical stress,
heat, presence of a metal catalyst residue or oxygen.[8]
Equation 5. Carbon hydrogen homolytic cleavage.
𝑷𝑯 → 𝑷∗ + 𝑯∗
However, initiation by direct interaction of molecular oxygen with the polymer can be portrayed as the
bimolecular interaction of oxygen with the monomer units of the polymer.
Equation 6. Chain initiation reaction in the presence of oxygen.
𝑷𝑯 + 𝑶𝟐 → 𝑷∗ + 𝑯𝑶𝟐 ∗
𝑃𝐻 are the monomers units of polypropylene. The chain propagation occurs by an alternation of two
reactions, the formation of peroxide radicals (𝑃𝑂2 ∗ ) and hydroperoxide (𝑃𝑂𝑂𝐻). Macro radicals, 𝑃 ∗ , which
appeared in chain initiation can easily react with oxygen molecules to give peroxide radicals. Peroxides radical
then pull hydrogen from another polypropylene molecules to form polymeric hydroperoxides (𝑃𝑂𝑂𝐻).[34]
Equation 7. Chain propagation - formation of a peroxide-free radical.
𝑷∗ + 𝑶𝟐 →
𝒇𝒂𝒔𝒕
𝑷𝑶𝟐 ∗
Equation 8. Chain propagation - formation of hydroperoxide.
𝑷𝑶𝟐 ∗ + 𝑷𝑯 →
𝒔𝒍𝒐𝒘
𝑷𝑶𝑶𝑯 + 𝑷∗
The slow step determines the rate of this oxidation reaction. As previously mentioned, the presence of
tertiary hydrogen atoms in the chain increases the susceptibility of PP to oxidation because it forms a more stable
free radical (𝑃∗ ) than the abstraction of any other hydrogen-bonded to the primary and secondary carbons. This
occurs because hydrogens are stabilized by adjacent atoms that can donate electron density, in this case, alkyl
groups (𝑃 ∗ ). This means free radicals increase stability as the number of carbon substituents increases, from
primary to tertiary carbon.
19
Branching of the chain occurs, i.e., chain reactions in which the number of free radicals increases in
each propagation, in the decay of polymer hydroperoxides by metal catalyst residues or heat. Some basic
mechanisms of decomposition of hydroperoxides are presented below:
Equation 9. Chain branching - Decomposition of hydroxides (mechanism 1).
𝑷𝑶𝑶𝑯 + 𝑷𝑯 → 𝑷𝑶∗ + 𝑶𝑯∗
Equation 10. Chain branching - Decomposition of hydroxides (mechanism 2).
𝟐 𝑷𝑶𝑶𝑯 → 𝑷𝑶∗ + 𝑯𝟐 𝑶 + 𝑷𝑶∗𝟐
At high concentrations of hydroperoxides, mechanism 2 dominates, while mechanism 1 is predominant
in small quantities and in polymers containing weak hydrogen bonds.
These reactions led to the formation of alkoxy radicals (𝑃𝑂 ∗ ) that disintegrate and are believed to cause
chain scission, as in Equation11. Chain termination occurs when two free radical species react with each other
to form a stable, non-radical product.
Equation 11. Oxidation reaction for main chain scission.
𝑷𝑶∗ + 𝑶𝑯∗ → 𝑷(𝟏) 𝑶 + 𝑷(𝟐)∗
Chain scission causes loss of molecular weight of the polymer, changing its structure and properties. All
in all, oxidation reactions cause polymer degradation and may influence its molecular weight distribution (MWD),
for instance. Polypropylene resins with regular chain length present narrow MWD while those with wide
variations have broader MWD. Polypropylene with broad MWD is more shear sensitive than a narrow MWD
formulation, so it is more prone to VOC generation.
A polymer material is denoted by the term disperse when it presents varying chain lengths over a wide
range of molecular masses. This way, one way of defining the molecular weight distribution is using dispersity
(Đ) as presented in Equation 12.
Equation 12. Dispersity.
Đ=
𝑴𝒘
𝑴𝒏
Where 𝑀𝑤 is the mass-average molar mass (or molecular weight) and 𝑀𝑛 is the number-average molar
mass (or molecular weight). 𝑀𝑛 is more sensitive to molecules of low molecular mass, while 𝑀𝑤 is more sensitive
to molecules of high molecular mass.
Studies not only showed that the majority of odor-active compounds in polyolefins are oxidation
products including highly odor-active carbonyls, but also that the formation of products such as aldehydes,
ketones, lactones, alcohols, carboxylic acids and esters is also possible during oxidation reaction. Finally, it was
concluded that oxidation occurs before even processing and it can happen anytime: before and after
polymerization. This way, it is not dependent on the polymerization process, but the time of the sample (time
since it was molded).[35]
20
5.1.2. Weathering degradation
Weathering or photodegradation of polypropylene only occurs when the polymer is partially oxidized.
This happens since PP does not absorb UV light, i.e., wavelengths between 290-400 nm, and only when
degradation is intensified by heat, moisture or oxidative conditions. In those cases, groups capable of absorbing
UV radiation are formed and photodegrading reactions take place. [36]
Photochemical degradation is a radical chain process where due to the poor penetrating capacity of UV
light, the surface layers of the polymer are mainly attacked. It does not depend on the temperature, instead, it
depends on the quantum energy of UV that must exceed the energy of the carbon-carbon bond. Different groups
of atoms such as C=O, C-C, C=C-C=C, etc. which contain chromophore atoms degrade faster. [36]
Other processes cause degradation of polymers such as the chemical attack of thermoplastics which
involves specific chemical reactions with the fluids, as hydrolysis by water. Hydrolysis results in the reduction of
the molecular weight, increasing the chain scission process.[37]
5.1.3. Degradation of Additives
Stabilizers
Some organic stabilizers can react with molecular oxygen to form alkyl radicals, causing polymer
degradation, resulting in embrittlement, melt flow instability, loss of tensile properties, and discoloration. In
these cases, primary and secondary antioxidants should be added to reduce the rate of propagation or to prevent
the initial formation of free radicals, respectively.[37]
An example of secondary antioxidant is tris (2, 4-di-tert-butylphenol) phosphite - CAS number 3157004-4. Organic compounds of trivalent phosphorus are excellent processing stabilizers for polyolefins because
they act as hydroperoxide-decomposing AO and also block polyvalent metal ions, preventing chain initiation. [38]
Figure 7. Tris (2, 4-di-tert-butylphenol) phosphite chemical structure.
The reaction of this AO with hydroperoxide forms alcohols and phosphates that usually found in
migration extracts. Common degradation products of this primary antioxidant are present in Chapter 7 - Table 3.
A primary AO is pentaerythritol tetrakis (3, 5-di-ter-butyl-4-hydroxyhydrocinnamate) - CAS number
6683-19-8. Hydrolysis of the ester bonds is the preferred degradation mechanism, which is an unwanted side
reaction as it reduces the antioxidant efficiency without adding to the protection of the polymer as already
indicated above, being an AO1 less suitable for materials intended for water. This is aggravated by the fact that
the formed products with free hydroxyl groups show an increased solubility in water. Even though subsequent
21
transformation products still have the antioxidant capacity, they are rendered useless as they are easily leached
out from the polymeric material when in contact with water.[39]
Figure 8. Pentaerythritol tetrakis (3, 5-di-ter-butyl-4-hydroxyhydrocinnamate) chemical structure.[39]
In several studies, degradation products of hindered phenol-type antioxidants have been analyzed.
Several degradation products have been detected as migrants from polyolefins, for instance, 2,6-di-tert-butylbenzoquinone, 7,6-di-tert-butyl-1-oxaspiro[4,5]deca-6,9-diene-2,8-dione.[38] More degradation products of this
primary antioxidant are present in Chapter 7 - Table 3.
Other primary antioxidants are also commonly use as 1,3,5-tris(3,5-di-tert-butyl-4-hydroxybenzyl)-striazine-2,4,6(1H,3H,5H) trione. However, experiments have shown that comparing to pentaerythritol tetrakis
(3, 5-di-ter-butyl-4-hydroxyhydrocinnamate), this additive is less thermally stable, being more easily degraded
by oxidation.[39]
In some cases, primary antioxidants are significantly more effective when combined with secondary
oxidants. It is the case of pentaerythritol tetrakis (3, 5-di-ter-butyl-4-hydroxyhydrocinnamate) used in
combination with tris (2, 4-di-tert-butylphenol) phosphite, often applied in polyolefins where the secondary AO
is used as a short-term stabilizer, reducing the consumption of the primary AO during melt processing, being the
last one more effective in the final product.[39]
Lubricants/ slip agents
Thermal degradation which occurs during film processing is known to harm the properties of slip agents.
This can cause slip additives to become ineffective, especially for slip additives with low thermal stability.
Odorous and colored compounds are amongst the products that are formed from the degradation of slip
additives. Highly colored fatty acid nitriles have been isolated as by-products during the synthesis and isolation
of fatty acid amides. These nitriles are formed by dehydration of fatty acid amides. [37]
Figure 9. Glycerol monostearate chemical structure.
Glycerol monostearate - CAS number 31566-31-1 is synthesized by the reaction of triglycerides with an
excess of glycerol. Therefore, the impurities are mainly diglycerides, unreacted triglycerides, glycerol and fatty
acids like stearic acid, tetradecanoic acid, hexadecanoic acid and their esters. Thermal decomposition products
22
include oxides of carbon and no literature was found specifically on the degradation during processing and use
in polymers.[37] All proposed impurities/ reaction products/ breakdown products of glycerol monostearate are
present in Chapter 7 - Table 3.
Nucleating agents
Diparamethylenedibenzylidene sorbitol or its derivatives are common nucleating agents used in
polypropylene grades. These additives suffer partial decomposition before, during and after processing,
especially at temperatures higher than 200°C. The hydrolysis of its acetylic structure is the probable cause for
the partial cleavage of the molecule and responsible for the odor problems. Possible products of this reaction
are acetaldehyde, 3,4-dimethyl-benzaldehyde and sorbitol.[38] Possible impurities and products for
Diparamethylenedibenzylidene sorbitol or its derivatives degradation are present in Chapter 7 - Table 3.
23
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24
6. POLYMER TREATMENT
There are several methods for odor removal that may be applied during different stages of the product
production, i.e., pre-processing, processing, post-processing and packaging treatments. This may include the use
of compounds that remove odor such as additives and scavengers, for instance. Also, odor-absorbing layers in
packaging and polymer filters treated by plasma-assisted graft polymerization and/or non-thermal plasma, are
possible solutions that have been already applied in some cases in the plastic industry. However, they present
disadvantages that make them not suitable for application at Tupperware as the fact that most of these solutions
contain substances that are not food contact approved and/or are solutions highly selective for some groups of
chemical compounds and not for VOC in general.
VOC removal by conventional means as ozone oxidation, photocatalytic oxidation, condensation and air
ionization at very low concentrations is not efficient.[40]
For this reason, one specific method was considered to be of interest to this study as it might be
economically viable and can be adjustable in production. The separation of VOC from the particulate polymer as
pellets was studied and applied according to patent number US 7,790,842 B2.[41]
This patent consists of three main steps:
i.
Feed the pellets into a purge vessel and let them move through it in plug-flow mode.
ii.
Heat the pellets inside the purge vessel above 30°C, but not sufficient to cause agglomeration.
iii.
Feed gas through the purge vessel to remove volatiles, followed by the removal of the polymer
from the purge vessel.
Figure 10. Schematic representation of the polymer treatment process.
Initially, as seen in Figure 10, pellets are fed into the purge vessel in a continuous stream 3 via pipe. In
this case, the feed, stream 1, comes from an extruder and the excess is transferred to a buffer silo through stream
2. For this patent, the feed flow rate is 6 ton/h and the purge vessel presents a diameter of 4,5 m and an internal
volume of 150 m3. Then, the air coming from stream 5 is heated with steam from stream 4 and introduced by
stream 6 into the purge vessel. The hot air is responsible for maintaining the temperature of 90°C inside the
25
purge vessel. The air flows upwards through the pellets in plug flow, countercurrent mode and goes to the
atmosphere through stream 7. The plug flow mode is ensured by one discharge valve which opens and closes
two minutes at a time.
The treated pellets are discharged through stream 8 to a hopper and then to a cooling vessel which
cools the stream to 40-60°C to form a condensed portion enriched in monomers and an uncondensed portion
enriched in the purge gas. The vessel is cooled with water that gets in through stream 9 and goes out through
stream 10. Finally, the cooled pellets are discharged into a conveyor line 11.
Other patents[42],[43] show similar processes, but with the use of inert gases instead of air to reduce
oxidative reactions. In those cases, vent recovery units, which comprise refrigeration, compression and
purification stages, are added to separate and recycle the stripping gas which consists of a mixture of inert gas
and monomer gas that did not condensate. On the other hand, it is believed that for better results, the air used
to dry the material should have a certain level of humidity, as it leads to better VOC removal.
One type of equipment that can mimic the process described above are dryers. Two types of dryers are
specifically interesting for this type of application, vacuum and heated desiccant air dryers, that do not require
the use of inert gases which increase the treatment cost.
6.1. VACUUM DRYER
Low-pressure dryers, also called vacuum dryers, are known for being batch dryers, but recently, some
semi-continuous systems were introduced into the industry. These dryers are already used in the plastic industry
to eliminate moisture in hygroscopic polymers. They consist of three containers in a carousel configuration as
seen in Figure 11.
Figure 11. Semi-continuous vacuum dryer configuration.[44]
Firstly, pellets are uploaded in the material inlet chamber and then are heated by hot air. The carousel
is then rotated and the chamber with the heated pellets is set to another position and under vacuum. Finally,
the carousel is rotated again and the dried pellets are evacuated through the third chamber. This process can be
performed in a semi-continuous way as one chamber can be continuously filled in the first position while the
other pellets are being put under vacuum and discharged in second and third positions, respectively. All in all,
26
this process can be used to simulate the previous patent as the material is initially heated, leading to the creation
and release of VOC. The vacuum can then be used to remove the VOC from the heated headspace inside the
chamber.[44]
6.2. HEATED DESICCANT AIR DRYER
Recently, sorption filtration using desiccants has been reported as the most effective way of removing
VOC. Desiccant materials such as silica gel, zeolites or activated carbon, for instance, are very hygroscopic.
Although polypropylene is a non-hygroscopic material, the use of desiccants allows the simultaneous removal of
VOC and superficial moisture, being an energy-efficient process for any kind of plastic, in a process called cosorption.[45]
In this case, the sorption process that occurs by using the desiccants is adsorption where gases are taken
out from the gas phase and accumulated into a solid surface. Although adsorption involves competition by
adsorbing molecules for binding sites on the adsorbent surface, i.e., competition between water and VOC on
desiccants, it has been reported that VOC and moisture removal is barely affected by the phenomena,
maintaining process effectiveness.[45]
Instead of using ambient air, heated desiccant air dryers use dry air to dry pellets in the hopper. The
process air in the desiccant drying system circulates in a closed-loop, passing through a regeneration system,
presented in Figure 12.
In a regeneration system, in one tower there is the removal of moisture from ambient air to dry it. Part
of the dried air goes to the hopper to remove the moisture and VOC from the pellets. The remaining of the air
that exists the drying tower, about 8%, is sent to the heater. After that, the heated and dried air is sent to the
desiccant in the regenerating tower, freeing the previously captured moisture when the desiccant is saturated.
Humidity is then discharged into the atmosphere.
Figure 12. Regeneration system in a heated desiccant air dryer.[46]
27
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28
7. ODOR-ACTIVE COMPOUNDS IDENTIFIED IN POLYPROPYLENE
Table 1 presents chemical substances that were identified as odor-active compounds in polypropylene
in the literature studied. When available, the sensory threshold values in air for each compound are presented,
as well as, the headwords that better describe the odor quality. It is common to see ranges of OTV values with
different magnitudes, as the data found is from different sources, experimental methodologies and was
performed by different panelists with a different olfactory response. This way, the concentration range that is
thought to include the OTV was selected.
Table 1. List of identified odor-active compounds in polypropylene found in several books and articles.
Compound
OTV in air
(µg/m3) [18]
Odor quality
References
-
[6]
ALCOHOLS
1-decanol
1-dodecanol
tetradecanol
hexadecanol
octadecanol
hexanal
heptanal
octanal
nonanal
decanal
undecanal
dodecanal
tetradecanal
(E)-2-nonenal
(Z)-2-nonenal
(Z)-4-nonenal
(E)-2-decenal
(Z)-2-decenal
(Z)-3-hexenal
(E)-2-heptanal
(E,Z)-2,6-nonadienal
(E)-4,5-epoxy-(E)-2-decenal
4-methylphenol (p-cresol)
3-ethylphenol
benzene
ethylbenzene
2-/3-/4-dimethylbenzene (o/m-/p-xylene)
2-acetyl-1-pyrroline
ethenylbenzene
isopropylbenzene
propylbenzene
ethylmethylbenzene
1,3,5-trimethylbenzene
1,2,4-trimethylbenzene
isopropyltoluene
naphthene
5,0 - 440
1200
-
ALDEHYDES
1,4 - 230
Grassy, green
0,9 - 260
Green, soapy, fatty, fresh, stink bug
0,88 - 170
Green, soapy, fatty, cardboard, metallic
Soapy, cardboard, dusty, fatty
2,6 - 63
Soapy, plastic, green, fatty
0,54 - 140
20 - 33
0,09 - 1,1
Card board, rancid, fatty
0,022 - 0,039
Fatty (waxy, putty)
4,5
Fatty (waxy, putty)
2,7 - 77
Plastic, pungent, rancid, fatty
2,2 - 3,1
Plastic
1,2 - 2,7
Grassy
Green, fatty, nuts, pungent
0,11 - 0,2
Cucumber
AROMATIC COMPOUNDS
0,24 - 10
Animal, horse
1-2
Leather
8600
26 - 730
0,02 - 0,04
150 - 26400
41 - 5300
19
830 - 10700
140 - 590
-
-
[6]
[6]
[6]
[6]
[6], [22]
[6], [35]
[6], [22] , [35]
[6], [22]
[6]
[6]
[6]
[6]
[6], [22] , [35]
[6], [22]
[6], [22]
[6], [22] , [35]
[22]
[22]
[35]
[6], [22]
[6]
[6], [22]
[6], [22]
[6]
[6]
[6]
[6]
-
[6]
[6]
[6]
[6]
[6]
[6]
[6]
[6]
29
vanillin
ethylvanillin
2,6-di-tert-butylquinone
2,6-di-tert-butylphenol
2,6-di-ter-butyl-4ethylphenol
2,6-di-tert-butyl-4propylphenol
0,6 - 1,2
0,007 - 0,027
-
Vanilla
Vanilla
-
[6], [22]
-
-
[6], [19]
-
-
[6], [19]
4-methyl-2-heptanone
unknown methyl ketone
1-octen-3-one
1-nonen-3-one
1-hexen-3-one
1-hept-3-one
1-nonen-3-one
3-hepten-2-one
3-octen-2-one
2,3-butadione
2,3-pentadione
-undecalactone
-dodecalactone
0,03 - 0,12
0,01
0,01 - 0,1
0,01
60
6.7
-
[6], [22]
[6]
[6], [19]
KETONES
Ƴ-octalactone
Ƴ-nonalactone
Ƴ-decalactone
Ƴ-undecalactone
Ƴ-dodecalactone
acetic acid
butanoic acid
pentanoic acid
hexanoic acid
octanoic acid
tetradecanoic acid
pentanoic acid
hexadecanoic acid
2/3-methylbutanoic acid
2- methylpropanoic acid
2-methylpentanoic acid
4-methylpentanoic acid
phenyltacetic acid
Mushroom, forest soil–earthy, green
Mushroom
Sweet (peach like)
Sweet (peach like)
LACTONES
1,8
0,8 - 60
Coconut
Peach
Peach
Peach
ORGANIC ACIDS
15 - 150
Sour, acrid, vinegar
0,86 - 20
Cheesy, buttery
0,16 - 0,26
4,8 - 10
Smoky (burnt), moldy (musty)
5,1 - 18
0,16 - 0,26
Cheesy/buttery
20/ 0,33 - 1,8
Sour, acrid, fruity
Cheesy/buttery
Cheesy/buttery
1,9 - 37
Cheesy/buttery
Bee wax
[6]
[6]
[6], [22] , [35]
[6]
[6]
[6]
[6], [22]
[6]
[6]
[6]
[6]
[22]
[22]
[6]
[6], [22]
[6], [22]
[6], [22]
[6], [22]
[6], [22]
[6], [22]
[6]
[6], [22]
[6]
[6]
[22]
[6]
[6], [22]
[22]
[22]
[22]
[6], [22]
Other compounds can still be a cause of odor in polypropylene. These may be products of the
decomposition of the polypropylene molecule itself or a result of additives breakdown products, reaction
products or even impurities. In Table 2 are some decomposition products of PP that may be released and cause
odor, and sensory threshold values in air for each compound, when possible. In Table 3 possible chemical
substances resultant of some additives degradation are presented together with their molecular weight. As
previously mentioned, this is of relevance as compounds with a molecular mass over 300 g/mol do not bind to
odor receptor cells and, therefore, they do not show odor activity.
30
Table 2. Identified compounds of polypropylene decomposition.[47]
Compound
undecane
dodecane
tridecane
hexadecane
heptadecane
octadecane
5,5-diethylpentadecane
phenanthrene
di-tert-butylphenol-p-cresol
di-tert-butyl-benzoquinzene
OTV in air (µg/m3) [18]
5600 - 9600
770 - 11800
42000
500
20
55 - 60
-
Table 3. Proposed impurities/ reaction products/ breakdown products for some additives present in polypropylene
grades in study.[38]
OTV in air
Molecular
Molecular
Polymer additive
(µg/m3) [18]
formula
weight (g/mol)
DIPARAMETHYLDIBENZYLIDENE SORBITOL AND DERIVATIVES
C22H26O6
386
acetaldehyde
2,7 - 90
C2H4O
44
3,4-dimethylbenzaldehyde
C9H10O
134
sorbitol
C6H14O6
182
3,4-dimethylbenzylidene sorbitol
C15H20O6
260
TRIS(2,4-DI-TERT-BUTYLPHENYL)PHOSPHITE
C24H63PO3
430
2,4-di-tert-butylphenol
C14H22O
206
1,3-di-tert-butyl-benzene
C14H22
190
2,4-di-tert-butylphenylphosphate
C14H23PO3
271
phosphoric acid
H3PO4
99
tert-butylphenol
C10H14O
150
tert-butylbenzene
C10H14
134
phenol
21 - 46
C6H6O
94
benzene
8600
C6H6
78
PENTAERYTHRITOL TETRAKIS(3,5-DI-TERT-BUTYL-4C73H108O12
1177
HYDROXYHYDROCINNAMATE)
2,6-di-tert-butylbenzoquinone; 2,6-di-tertbutyl-2,5-cyclohexadieneC14H20O2
220
1,4-dione
7,6-di-tert-butyl-1-oxaspiro[4.5]deca-6,9-diene-2,8-dione
C17H24O3
276
2,6-di-tert-butylphenol
C14H22O
206
p-benzoquinone
C6H4O2
108
methyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate
C18H28O3
292
3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid*
C17H26O3
278
2-ethylhexyl-p-methoxycinnamate
C18H26O3
290
3,5-di-tert-butyl-4-hydroxystyrene
C16H24O
232
3,5-di-tert-butyl-4-hydroxybenzaldehyde
C15H22O2
234
3,5-di-tert-butyl-4-hydroxyacetophenone
C16H24O2
248
quinone methide, {2,6-di-tert-butyl-4-(propen-1-oic)- 2,5cyclohexadien-1-one}acid, cyclohexa-1,4-diene-1,5-bis-tert-butyl-6C17H24O3
276
on-4-(2-carboxy-ethylidene)
1,3-di-tert-butylbenzene
C14H22
190
quinone methide methyl ester, cyclohexa-1,4-diene-1,5-bis-tertC18H26O3
290
butyl-6-on-4-(2-carboxy-ethylidene) methyl ester
tert-butylphenol
C10H14O
150
phenol
21 - 46
C6H6O
94
di-isopropyl-benzene
C12H18
162
GLYCEROL MONOSTEARATE (GMS)
C21H42O4
358
stearic acid
C18H36O2
248
octadecanoic acid
C18H36O2
284
tetradecanoic acid
C14H28O2
228
hexadecanoic acid
C16H32O2
256
glycerol
C3H8O
92
31
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32
8. MATERIALS AND METHODS
In this study, some decisions were made to focus on what would be simultaneously beneficial for
Tupperware and the overall odor study. This way, the experiment scope is described below.
i.
Polypropylene: PPRC, PPB and PPH;
ii.
No addition of color masterbatch;
iii.
Three Tupperware products: Bottle 500 ml Round, Bottle 750 ml Round and Modular Container
Oval #3 (not including their caps);
iv.
Study of different process stages;
a. Pellets and final containers for the Modular Container Oval #3;
b. Pellets, preforms and final bottles for Bottle 500 ml Round and Bottle 750 ml Round;
(a)
(b)
Figure 13. Images of Tupperware products studied. (a) Bottle Round, (b) Modular Container Oval #3.
8.1. POLYPROPYLENE SAMPLES
The materials used for the study of polyolefin odor were different PP polymers from different well
known large chemical suppliers as LyondellBasell, INEOS, Sabic and Braskem. The pellets were ordered by
Tupperware and delivered in Portugal and Belgium production sites, depending on where the sample production
would take place. Some physical and chemical properties of the grades are listed in Table 4. Although information
about polymer granulometry was not given by the suppliers, in Figure 14 is possible to observe that the grain size
is regular, even between different grades. These values were observed for all the pellets used.
Table 4. List of polypropylene grades in study.
Number
Type
PP1
PP2
PP3
PP4
PP5
PP6
PP7
PPRC
PPRC
PPRC
PPRC
PPRC
PPH
PPB
Density (g/cm3)
at 23 ⁰C
0,9
n/a
0,9
0,9
0,9
0,9
n/a
MFI2
(g/10 min)
40
25
40
45
40
7,5
40
Tensile modulus
(MPa)
1100
n/a
1150
n/a
1150
1500
n/a
Flexural
modulus (MPa)
n/a
1100
n/a
1150
n/a
n/a
1350
2 Melt flow index (MFI) (230 ⁰C/2.16 kg)
33
(a)
(b)
Figure 14. Image of two types of pellets used. (a) PP3, (b) PP6.
Overall Migration values obtained from previous Overall Migration Limit (OML) tests performed at
Tupperware for the different polymers in study were requested. In food science, OML is the maximum total
amount of non-volatile substances permitted that can migrate from a food container into food. The overall
migration is determined by exposing the item to a chemical food simulant for a specified and appropriate length
of time, after which the extracted residue is dried and weighed. The results are important to observe if the
migration of non-volatile substances is correlated with the release of VOC. The combination of the simulants in
Table 5 covers all type of food, including aqueous foodstuff according to European directives. [48] Tests were
performed on injection molded containers.
Table 5. Overall migration values in different simulants for the grades in study.
Overall migration (µg/dm²)
Food simulant
Acetic acid 3%
Ethanol 95%
Iso-octane
Olive oil
Time (days)
10
10
2
10
Temperature (⁰C)
40
40
20
40
PP1
0,8
2,8
n/a
5,2
PP2
0,5
3
8,9
6,3
PP3
0
1,2
2,4
0,4
PP4
0,5
2,4
8,3
-
PP5
0,45
2,2
n/a
n/a
PP6
0,2
1,1
1,3
0
PP7
0,1
0,5
4,8
0,1
Finally, the additives presented in each polymer are described in Table 6. The values presented are the
maximum additive weight percent (% wt) that might be in polymer’s composition and not the exact weight
percent value of the additives in the different grades.
34
Table 6. Polymers’ additives composition and their respective maximum weight percent value in each grade.
Additives
Maximum weight percent (% wt)
PP1
PP2
PP3
PP4
PP5
PP6
PP7
Nucleating agent
0,205
0,198
0,198
0,210
0,249
-
-
Primary Antioxidant - AO1.1
0,061
-
-
0,050
-
-
-
Nucleating agent
-
-
-
-
-
-
0,025
0,002
-
-
-
-
UV stabilizer
Secondary Antioxidant- AO2
0,135
0,080
0,100
0,050
0,052
0,050
0,080
Primary Antioxidant - AO1.2
-
0,040
0,050
-
0,052
0,050
0,040
Lubricant, Slip agent
0,150
-
-
-
-
-
-
Lubricant
0,037
-
-
-
-
0,045
-
Lubricants, Slip Agent, Heat
Stabilizer
0,037
0,050
0,050
0,050
0,083
0,045
0,040
Lubricant
-
0,030
-
0,100
0,103
-
0,360
Primary Antioxidant- AO1.3
-
-
-
-
-
0,015
-
Organic peroxide
-
-
-
-
-
0,035
-
35
8.2. PRODUCTION SAMPLES
8.2.1. Production 1 - Modular Container Oval #3
Modular Container Oval #3 samples were injected molded at Tupperware Belgium. The grades used
were PP1 (PPRC), PP2 (PPRC), PP6 (PPH) and PP7 (PPB).
With the view of studying the influence of processing conditions in odor creation in polypropylene,
three parameters were looked up in deeper detail. Samples were processed at different melt temperatures
(190⁰C and 220⁰C), dosing speed (45% and 100%) and back pressure (0 bar and 25 bar). The conditions were
chosen to get extreme processing conditions in comparison to Tupperware standard values but also to
maintain the feasibility of the process. This way, using the Fractional Factorial Design, the obtained
experimental design is described in Table 7. This design was chosen with the view of studying the effect of
these three parameters in odor while performing the minimum amount of experiments.
Also in this stage of the project, grades were compared to one another with the purpose of
understanding the effect of polymer structure and the percentage of ethylene on the creation and release of
VOC.
Table 7. Processing conditions applied in Production 1.
Conditions
Melt T (⁰C)
Dosing speed (%)
Back pressure (bar)
A
B
C
D
190
190
220
220
45
100
45
100
25
0
0
25
Tupperware standard
200
100
5
8.2.2. Production 2 - Bottle 750 ml Round
750 ml Round Bottles were produced at Tupperware Portugal. Firstly, pellets were injection molded
into preforms and, one day after injection the preforms were blow-molded into bottles through the ISBM
process. Bottles were produced using PP1, PP2, PP3, PP4 and PP5 as raw materials, i.e., only PPRC grades
were processed. After careful consideration, it was decided that the melt temperature, cooling time and
plasticizing time would be the most probable causes for odor during preform injection. Samples were
processed at different melt temperatures (190 ⁰C and 220 ⁰C), cooling time (8s and 12s) and plasticizing time
(12s and 18s). The obtained experimental design using the Fractional Factorial Design is described in Table 8.
The Blow Molding process was performed according to Tupperware’s standard parameters.
Table 8. Processing conditions applied in Production 2.
Conditions
Melt T (⁰C)
Cooling time (s)
Plasticizing time (s)
A
B
C
D
Tupperware standard
190
190
220
220
210
8
12
8
12
10
18
12
12
18
16
36
8.2.3. Production 3 - Bottle 500 ml Round
The third production set had the aim of testing experimental odor removal treatments. Based on
patents and research, two different experiments were performed using different dryer equipment in the
attempt of removing odor from pellets. Although the experiments were performed with dryers, this
equipment was not used to dry material, i.e., to remove the superficial humidity of PP. Instead, its purpose is
to partly degrade pellets by thermal degradation and remove the VOC created during that process, as
explained in Chapter 6. Therefore, PP5 was the grade chose to perform the tests, using Low-pressure Dryer
(LDP) 200 Maguire (PP5-A) and Heated Desiccant Air Dryer Motan Luxor 80 (PP5-B), seen in Figure 15. In Table
9 and Table 10 are presented the test conditions for the vacuum and heated desiccant air dryer, respectively.
Figure 15. LDP 200 Maguire, on the left, and Motan Luxor 80 Heated Desiccant Air Dryer, on the right.
Table 9. LDP 200 Maguire test conditions.
Parameter
Value
Dryer volume (L)
Compressed air pressure (bar)
Residence time (min)
Pellets mass (kg)
Temperature (⁰C)
Air flow (m3/h)
57
6-8
45
≈ 34
90
80
Table 10. Motan Luxor 80 Heated desiccant air dryer test conditions.
Parameter
Value
Dryer volume (L)
Dry air flow rate (m3/h)
Max heating power (kW)
Residence time (h)
Pellets mass (kg)
Temperature (⁰C)
150
80
6,5
≈ 15
≈ 90
90
After these experiments were performed, Bottles 500 ml Round using the treated pellets were
produced. This way, PP2, PP5, PP5-A and PP5-B were injection molded using Tupperware standard conditions:
melt temperature of 210⁰C, cooling time of 10s and plasticizing time of 16s. As previously done in Production
2, the Blow Molding process was also performed according to Tupperware’s standard parameters.
37
8.3. SENSORY ANALYSIS
The sensory analysis was performed based on an internal Tupperware test TQA-009-041-I, from the
Tupperware World Wide Quality Manual. The odor test presented can be performed either in raw material
pellets or in injection molded samples.
8.3.1. DIN 10954 Paired Comparison/Multicomparison Test
Sample preparation
For raw material pellets, using Sartorius AG Germany LA 6200 scale, 30 g of material were measured
in glass containers and then sealed with aluminum foil. In injection molded pieces testing, samples were
cooled down for at least 24h after processing and then covered with aluminum foil. For both tests, samples
were placed in a hot air oven at 60 ⁰C for 3 hours. After 3 hours, samples were taken out and let cool down,
minimum 1h and maximum 2,5h until they reached ambient temperature. The samples were then organized
and presented to the panel. The panelists were non-smokers and did not drink coffee at least 3 hours
previously to test. As advised, each panelist sniffed a maximum of eight samples per day.
Test procedure
A certain number of generally different samples are presented. The test can also be performed as a
multicomparison test in which a standard is compared with several samples. In Production 2 and 3, PP2
preforms were injection molded using Tupperware standard conditions to be used as a reference in these
tests to help the panel during evaluation. The samples shall be detected and given an odor intensity rate that
is quantified according to the numeric scale presented in Table 11. For intensity of 2 or more, the difference
in odor should be described using headwords.
Table 11. Odor intensity scale in DIN 10954 Paired Comparison/Multicomparison test.
Neutral
Very slight odor
Slight odor
Noticeable odor
Strong odor
0
1
2
3
4
Very strong odor
5
The final odor intensity is then the median of odor intensity values given by all the panelists. The use
of the median allows the elimination of outliner values and reduces the test subjectivity. Internally, for a
product to be acceptable to sell, its odor value can go to a maximum of 2-2,5.
8.4. ANALYTICAL ANALYSIS
The analytical analysis was performed in PP2, PP4 and PP5 Bottles 750 ml Round (Production 2) and
PP5, PP5-A and PP5-B Bottles 500 ml Round (Production 3).
38
8.4.1. Gas Chromatography/Time-Of-Flight Mass Spectrometry (GC-TofMS) and
GC-O
Sample preparation
Three bottles of each polypropylene grade were introduced into Nalophan bags of 40 L, filled with
synthetic air and stored for 3 days at room temperature (18 ± 2°C) to generate enough headspace. Then, 500
mL of the headspace generated in each Nalophan bag were extracted and pumped on a Tenax tube. For each
PP bottle grade, three Tenax tubes were prepared to pump from the same bag to obtain robust and accurate
results. The Tenax tubes content was finally analyzed by GC-TofMS and GC-O.
Test procedure
GC-O combines high-end separation techniques with the human nose as a detector. GC-O added a
sensory dimension to GC-TofMS: the odor description of simple components of a complex mixture. Once the
compounds of one sample were separated by the chromatographic column, a portion of the eluate flowed
to the detector MS while the other part flowed to the sniffing module, allowing the operator to smell the
compounds coming out of the column.
Once the panelist sniffed an odorous compound, he/she described the character and intensity of the
smell. As the two detectors are used simultaneously, the compounds were perceived at the exact moment
when they were detected by the detector MS, which facilitated the identification of individual compounds in
complex mixtures. The identification of the compounds was done using sophisticated molecular identification
tools coupled with standard molecular libraries and based on data acquired by the Odournet group.[49] Two
trained operators performed the olfactory analysis in the sniffing port. During the analysis, each participant
provided a description of the compounds for 15 minutes before handing over to the other panelist to cover
approximately 45 minutes of the complete chromatographic process. Therefore, the analysis was divided into
3 periods. Each panelist covered all chromatographic cycles twice, so each panelist covered the entire
chromatogram, to confirm perceived odors and/or to try to find other undetected odors on the first pass.
Equipment
The apparatus used was Agilent 7890A Gas Chromatograph coupled with BenchTOF-dx mass
spectrometer, manufactured by ALMSCO, which can measure compounds at concentrations of about 10 to
100 times less than conventional GC-MS systems. The mass measurement system allowed the quantification
of compounds with a high level of accuracy.
8.4.2. High Temperature Gel Permeation Chromatography (HT-GPC)
Sample preparation
The polymer was weighted in a 40 ml glass vial with a screw top and phenolic open top cab and a
PTFE/silicon septum. The concentration of the polymer solution was preferentially in the range of 1-10 µg/ml.
The polymer sample was dissolved in 1,2,4-trichlorobenzene (TCB) stabilized with 500 ppm of 3,5-di-tertbutyl-4-hydroxytoluene (BHT) and a steering bar was added. The vial was placed in the autosampler which
39
was heated at 120°C for 1 hour before injection to dissolve the polymer. There was a 20 min waiting time
before injection. The sample volume was 200 µl and was injected at a flow rate of 1 ml/min while the systems
were at 145°C during measurement,. Two injections were done for each sample.
Equipment
Molecular weights of polymers were characterized by HT-GPC using a Malvern Viscotek 350A HTGPC system with a Refractive Index Detector, a Viscotek 2600 Photodiode Array Detector and a Viscometry
Detector. Manual filtration is not required as the system is included with filters. The separation was done on
two Malvern columns T6000, ORG GPC/SEC Col 300x8 mm and correspondent guard column. All data analysis
was done on the Omnisec 4.7 software. The GPC values were obtained by absolute values using universal
calibration based on a combination of the refractive index detector and the viscosity detector.
8.5. DATA ANALYSIS
The results from sensory tests were analyzed using nonparametric tests. As the sample distribution
does not follow a Normal Distribution, the results are better represented by the population median and not
the mean used in parametric tests. Besides, odor tests results depend on the size of the panel, usually made
of 5 to 8 panelists, resulting in a small sample size for the statistical analysis. For these two main reasons,
nonparametric tests were applied.
8.5.1. Kruskal-Wallis Test
This test is used to determine if there are “significant” differences among the population medians.
The hypotheses tested in our results are the null hypothesis where all medians are equal and the alternative
hypothesis where, at least, one median is different. The results of this test are presented in the form of the
charts below.
Figure 16. Example of Multi Comparisons chart. On the left, the Boxplots with Sign Confidence Intervals chart
and, on the right, the Pairwise Comparison chart.[50]
40
In Figure 16 there are two graphs displayed. The Boxplots of the groups with their sign confidence
intervals for the medians is an important chart as it allows the comparison of groups to each other. The
confidence level is presented above the chart, in this case, it is 86,761%, meaning that it is 86,761% certain
that the obtained range of values contains the true mean of the population. On the right, the Pairwise
Comparison chart allows the understanding of the magnitude of the group differences as well as their
direction. In addition, it is possible to see if a certain difference between the group is statically “significant”,
i.e., if it rejects the null hypothesis, as it presents positive and negative z-values. This way, in this example,
Group 3 and 4 are statistically different since Group 4 distance goes beyond the z-value when compared to
Group 3.[50]
Equipment
All data analysis was done using Minitab 19, the recent version of the statistical and qualitative data
analysis software.
41
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42
9. RESULTS AND DISCUSSION
9.1. RESULTS PRODUCTION 1
9.1.1. Sensory and Data Analysis
Simplification of current Tupperware odor test
Odor tests in pellets were performed by changing the samples preparation conditions of TQA-009041-I. This way, the heating temperature and residence time of the test were studied. Extreme heating
temperatures were chosen (60°C and 160°C) to see the polymer odor behavior when it’s heated to
temperatures similar to its melting point ≈ 160°C. Pellets heated to 60°C stayed in the oven for 3 hours, while
those who were heated to 160°C, their residence time was 15 minutes. Also, to verify if the final product
presented an odor intensity similar to pellets, modular containers were tested at 60°C for 3 hours. These
experiments were performed using grades PP1, PP2, PP6 and PP7. The odor tests results can be seen in Annex
III.1 - Table 19.
From the results, it is possible to observe that for all grades, pellets heated at a higher temperature
during less time have a higher odor intensity, showing that in these grades, higher heating temperature
created a more intense odor in pellets.
By comparison of experiments performed during 3 hours, it is easily seen that for all grades, the
containers have always a higher smell intensity than pellets, showing that for the same odor test’s
preparation conditions, containers present a higher odor intensity than before processing. It is interesting to
notice that odor intensities for the containers were always higher than for pellets heated at 60°C for 3 hours
and lower than for pellets heated at 160°C for 15 minutes.
With the view of achieving pellets’ test conditions that give the real value of the odor intensity of
the samples after Injection Molding, new parameters for samples’ preparation conditions of TQA-009-041-I
where chosen. Pellets were then heated at 120°C for 15 minutes and 30 minutes. The results for these extra
tests can be seen in Annex III.1 - Table 20.
For these conditions, the odor intensity for both containers was higher than for pellets heated at
120°C for 15 minutes and lower than for pellets heated at 120°C for 30 minutes. Although none of the test
conditions recreated the final product real odor, the odor values for these tests were closer to the real value.
These conditions tested in bottles in Production 2 and the results were the same, i.e., the final products
presented an odor intensity between the two different conditions applied in pellets.
Influence of processing conditions in the creation of odor-active compounds
Another set of experiments was done to compare different processing conditions (A, B, C and D)
described previously in three different grades, PP2, PP6 and PP7. The odor results present in the Annex III.1
- Table 21 were then analyzed using Minitab 19 and the results obtained from the Kruskal-Wallis test are
presented below in Figure 17, Figure 18 and Figure 19.
43
Figure 17. Comparison of odor intensity of Conditions A, B, C and D in PP2 containers represented in a Multiple
Comparison chart.
Figure 18. Comparison of odor intensity of Conditions A, B, C and D in PP6 containers represented in a Multiple
Comparison chart.
Figure 19. Comparison of odor intensity of Conditions A, B, C and D in PP7 containers represented in a Multiple
Comparison chart.
44
From the graphics above is possible to conclude that for the three grades, there is no significant
difference between the different process conditions. This means that melt temperature, dosing speed and
back pressure do not have a significant impact on odor creation on these containers. These results are only
applied to the range of values tested: melt temperature (190-220°C), dosing speed (45-100%) and back
pressure (0-25 bar).
In Table 22 - Annex III.1 is presented the odor test results comparing different grades, PP1, PP2, PP6
and PP7. From the median values, it is possible to visualize that PP1 presents the lowest odor intensity when
compared to grade PP2, PP6 and PP7 where panelists mainly scored 3 or 4 in the odor intensity scale. As the
values given by the panel were in agreement, the test was only performed once.
The results were then analyzed using Minitab 19 and the results obtained from the Kruskal-Wallis
test are presented in Figure 20.
Figure 20. Comparison of odor intensities of PP1, PP2, PP6 and PP7 grades represented in a Multiple
Comparison chart.
From the Pairwise Comparisons chart is possible to conclude that there are significant differences
between grade PP1 and PP2, PP1 and PP6, and PP1 and PP7. These results are interesting as they show a
difference between PPRC grade (PP1) with both PPH grade (PP6) and PPB grade (PP7).
Initially, it was thought that polymer structure and the percentage of ethylene presented in the
grade would have a big impact on odor creation. However, the results did not show a linear correlation
between these properties and odor formation. Also, the significant differences were not observed for PPRC
grade (PP2), reinforcing that no comparison can be done between these four grades as they present different
additives and properties, making them more or less suitable for production and, consequently, more or less
prone to creation of VOC.
Considering this, these results mainly show the good organoleptic properties of PP1 as it presents a
lower odor intensity when compared to other grades, being the best grade, in an organoleptic point of view,
to use in the production of Modular Containers #3.
45
One possible reason for the significant difference between PPRC grades, PP1 and PP2, might be the
melt flow rate (MFI) for each grade presented in Table 4 as PP1 has a higher MFI than PP2. Melt flow index is
a measure of the ease of the melt of a thermoplastic polymer under a give temperature and pressure and it
is inversely proportional to viscosity for Non-Newtonian fluids, as is the case of polyolefins. Polypropylene
with lower viscosity at processing shear rates, independently of having a narrow MWD or a broad MDW, flow
easier, having fewer molded-in stresses and, consequently, less prone to the formation of VOC and odor
release.[51] In addition, as mentioned previously, other parameters have to be taken into account, as well as,
the polymer’s formulation.
46
9.2. RESULTS PRODUCTION 2
9.2.1. Sensory and Data Analysis
Influence of processing in the creation of odor-active compounds
In Production 2, the effect of Blow Molding and Injection Molding on odor creation was also studied.
The odor results for the odor tests are in Annex IV.1 -Table 23 and the respective statistical analysis charts
are presented in the figures below.
Figure 21. Comparison of odor intensity of pellets, preforms and bottles of PP2 grade represented in a Multiple
Comparison chart.
Figure 22. Comparison of odor intensity of pellets, preforms and bottles of PP3 grade represented in a Multiple
Comparison chart.
47
Figure 23. Comparison of odor intensity of pellets, preforms and bottles of PP4 grade represented in a Multiple
Comparison chart.
Figure 24. Comparison of odor intensity of pellets, preforms and bottles of PP5 grade represented in a Multiple
Comparison chart.
It is possible to observe that for the four grades tested, all showed a significant difference between
odor intensity in pellets and their respective bottles. It is then evident that bottles processing, more
particularly, the combination of Injection Molding followed by preforms Blow Molding has a strong impact in
odor creation. In PP4 the difference between pellets and preforms is already significant, showing the impact
of Injection Molding in this grade. On the other hand, in PP5 there is a significant difference between preforms
and bottles odor values, having Blow Molding a higher impact than Injection Molding.
Influence of processing conditions in the creation of odor-active compounds
Four different conditions were applied during preforms Injection Molding, condition A, B, C and D in
which the parameters melt temperature, cooling time and plasticizing time varied. The results of the odor
tests performed in the preforms comparing the different conditions are in Annex IV.1 - Table 24. As it is
difficult to make conclusions based on the odor test results, Kruskal-Wallis nonparametric tests were
performed. PP3 results are presented in Figure 25, while the others three charts of PP2, PP4 and PP5 grades
can be seen in Annex IV.1 - Figure 32, Figure 33 and Figure 34, respectively.
48
Figure 25. Comparison of odor intensity of Conditions A, B, C and D in PP3 preforms represented in a Multiple
Comparison chart.
Results obtained showed that only for grade PP3 was a significant difference when different
conditions were applied. Conditions B and D are significantly different as well as conditions C and D. By
observing the Fractional Factorial Design applied in this experiment, it is possible to realize that the
parameters values that differ conditions B and D are the melting temperature and the plasticizing time, while
for conditions C and D are the cooling time and the plasticizing time. However, it is not possible to conclude
on the effect of an individualized parameter as they depend from each other. For this reason, a Design of
Experiment (DOE) was performed, which is a statistical design capable of explore multiple process parameters
simultaneously to determine the relationship between factors affecting a process and the output of that
process.
A DOE is a parametric method and, consequently, analyze means and not medians as in
nonparametric tests. Intending to understand the effect of these processing parameters as they are essential
in odor generation, it was assumed in that means≈medians in order to apply the Design of Experiment. The
result is presented in Figure 26.
Figure 26. Design of Experiment of grade PP3 represented in a Pareto Chart of Standardized Effects.
From the figure above is possible to observe that plasticizing time affected the odor intensity of the
preform, while the variation of melt temperature and cooling time did not show significant differences. As
49
the highest odor intensity was given to preforms produced in condition D, it is possible to conclude that a
melt temperature of 220 ⁰C, cooling time of 12s and plasticizing time of 18s combined lead to polymer
degradation, hence, releasing VOC during Injection Molding and cause intense odor not only in preforms, but
also in the final bottles.
Comparison of polypropylene random copolymer grades
At last, bottles using different PPRC grades produced in the same conditions were compared. The
results of the odor tests performed are in Annex IV.1 - Table 25.
Figure 27. Comparison of odor intensities of PP2, PP4, PP5 and PP6 grades represented in a Multiple
Comparison chart.
The analysis showed significant differences between PP2 and PP4 as well as between PP4 and PP5.
With the purpose of understanding these differences, some PP2, PP4 and PP5 bottles were sent to an external
laboratory to further analysis using GC-TofMS and GC-O analytical techniques.
9.2.2. GC-TofMS results
To understand the potential participation of the individual chemical compounds to the overall
product odor, color code for the comparison of the measured concentrations with the olfactory thresholds
values (OTV) of the compounds was applied. This way, an order of the number of times by which the
measured concentration is greater than the theoretical olfactory threshold is indicated in Table 12.
Table 12. Color code applied in GC-TofMS results.
<1 × OTV
1 - 10 × OTV
10 - 50 × OTV
50 - 100 ×OTV
100 - 1000 × OTV
> 1000 × OTV
50
The table below presents the main results of the analyses by GC-TofMS that identified and quantified
the volatile organic compounds presented in PP2, PP4 and PP5 grades. Compounds present in quantities
greater than their theoretical olfactory threshold or in notable concentrations as well as the totals of all
chemical families are summarized in Table 13. Full details are provided in the Annex IV.2 - Table 26.
Table 13. GC-TofMS results of PP2, PP4 and PP5. Concentrations in bold and red exceed the odor threshold
value (OTV) and concentrations in bold and green don´t exceed 0,1 µg/m3.
Concentration (µg/m3)
Compound
Isopropyl Alcohol
2-Propanol, 2-methyl1-Propanol, 2-methyl1-Nonanol
Total Alcohols
Acetaldehyde (*)
Methacrolein
Butanal
Hexanal
Benzaldehyde
Total Aldehydes
Pentane, 2-methylHeptane, 2-methylHeptane, 2,4-dimethyl2,4-Dimethyl-1-heptene
Octane, 4-methylNonane, 2,6-dimethylUndecane
Total Aliphatic Hydrocarbons
Benzene
Total Aromatic compounds
Cyclopropane, 1-ethyl-1-methylTotal Cyclic Hydrocarbons
Total Esters
Total Ethers
Total Furans
CAS No.
ALCOHOLS
67-63-0
75-65-0
78-83-1
143-08-8
ALDEHYDES
75-07-0
78-85-3
123-72-8
66-25-1
100-52-7
ALIPHATIC HYDROCARBONS
107-83-5
592-27-8
2213-23-2
19549-87-2
2216-34-4
17302-28-2
1120-21-4
AROMATIC COMPOUNDS
71-43-2
CYCLIC HYDROCARBONS
53778-43-1
PP2
PP4
PP5
1,9
0,0
0,0
0,0
35,3
9,8
861,5
1,7
4,8
1075,6
251,4
0,0
46,3
0,0
364,9
Yes
Yes
Yes
Yes
2,7
0,0
3,6
0,0
0,0
11,7
3,8
30,0
16,4
3,2
3,8
66,8
3,4
0,0
7,8
15,3
0,0
34,9
Yes
Yes
Yes
Yes
Yes
1107,9
257,5
706,9
48,0
527,9
123,0
316,5
4795,2
62,0
90,2
1053,8
1045,0
695,9
466,6
994,5
10434,9
2497,8
1579,5
2925,0
123,9
1029,2
1061,5
1659,9
22777,8
Yes
Yes
No
No
No
No
Yes
0,0
15,3
0,2
17,3
4,1
32,8
Yes
26,2
42,1
3,0
14,6
0,1
770,0
826,7
5,9
166,1
10,6
285,7
367,0
55,5
21,5
1,6
No
0,5
3,5
7,4
21,3
Yes
1600,4
1882,7
0,0
13,6
65,6
83,2
29,3
60,3
Yes
19,2
19,2
3,1
1,8
0,0
0,0
5,3
0,0
Yes
0,0
7,3
Yes
HALOGEN-CONTAINING COMPOUNDS
67-66-3
2,0
8,5
KETONES
Acetone
67-64-1
30,0
Total Ketones
32,7
Total Mercaptans
0,0
Total Nitrogen-containing compounds
2,2
ORGANIC ACIDS
Acetic acid
64-19-7
0,0
Total Organic acids
0,0
Total Oxygen-containing compounds
0,0
Total Sulfur-containing compounds
1,6
TERPENES
a-Pinene
80-56-8
6,0
Trichloromethane
Total Halogen-containing compounds
OTV
available
51
C10H16
D-Limonene
Total Terpenes
Total Heterogroups
TOTAL VOC
5989-27-5
3,9
0,0
10,0
19,7
4992,0
2,1
2,3
11,6
22,2
14561,6
9,6
5,7
30,4
17,1
23902,8
No
Yes
In total 273 chemical compounds were identified by GC-TofMS. Most compounds are presented at
concentrations not perceived by the human nose, being some alcohols, aldehydes, aliphatic hydrocarbons
and organic acids families an exception as many compounds exceed their OTV.
The total alcohols concentration in sample PP4 (1075,6 μg/m3) is nearly 3 times more than in sample
PP5 (364,9 μg/m3) and 30 times more than in sample PP2 (35,3 μg/m3). PP4 contains 2-methyl-2-propanol at
861,5 μg/m3, below its theoretical OTV (14000 μg/m3)[18], whereas this compound was not
chromatographically detected in the 2 other samples. Instead, PP5 contains 2-methyl-1-propanol at 46,3
μg/m3, 1 to 10 times above its theoretical OTV (33 μg/m3)[18]. This compound is not present in the 2 other
samples. PP5 contains a higher concentration of isopropyl alcohol.
In total 145 different aliphatic hydrocarbons were identified as expected because these molecules
are characteristics of plastic materials. The total aliphatic hydrocarbons concentration in sample PP5 (22777,8
μg/m3) is 2 times more than in PP4 (10434,9 μg/m3) and 4,7 times more than in PP2 (4795,2 μg/m3). The main
compounds identified are 2-methyl-pentane, 2-methyl-heptane, 2,4-dimethyl-heptane, 2,4-dimethyl-1heptene, 4-methyl-octane, 2,6-dimethyl-nonane and undecane. Few theoretical OTV values are available for
this chemical family. It is thus difficult to conclude whether those compounds could participate or not to the
global product odor. Only 2-methyl-heptane in sample PP5 (1579,5 μg/m3) presents a concentration 1 to 10
times higher than its theoretical OTV (Odournet database).
The main cyclic hydrocarbon identified is the 1-ethyl-1-methyl cyclopropane. PP4 is the sample
containing the higher concentration of this compound (770 μg/m3). Samples PP5 and PP2 contain 285,7 μg/m3
and 26,2 μg/m3, respectively.
Sample PP5 contains higher trichloromethane concentration (7,4 μg/m3) compared to the 2 other
samples (2,0 μg/m3 for PP2 and 0,5 μg/m3 for PP4). Sample PP4 contains higher quantities of acetone
compared to others (1600,4 μg/m3), 24 times more than PP5 and 53 times more than PP2. This former sample
also contains acetic acid at 19,2 μg/m3; whereas it was not identified in samples PP2 and PP5. The
concentration of acetic acid in sample PP4 is 1 to 10 times greater than its theoretical OTV (15-150 μg/m3)[18].
The sample containing the higher concentration of volatile organic compounds, VOC, is sample PP5
(23 902,8 μg/ m3). Sample PP5 contains 1,64 times more VOC than PP4 and, in turn, 4,8 times more than PP2.
This difference is mainly explained by the aliphatic hydrocarbons total concentration measured in this sample.
Figure 28 below gives an overview of total VOC concentrations in the samples as well as the details
of total concentrations for alcohols, aliphatic hydrocarbons, cyclic hydrocarbons and others.
52
PP5
PP4
PP2
0,0
5000,0
10000,0
15000,0
20000,0
25000,0
Concentration (ug/m3)
Alcohols
Aliphatic Hydrocarbons
Cyclic Hydrocarbons
Others
Figure 28. Total concentrations of the main chemical families identified.
9.2.3. GC-O results and correlation to identification
Table 14 presents the odor-active compounds detected and described by the panel, and the
correlation to the compounds identified by GC-TofMS, when possible. The objective of this analysis was to
identify the molecules present in the sample which participate in its odor. As the human nose remains the
most sensitive detector to sniff, some odors were detected by the panelists but were chromatographically
undetectable, so their origin compound are unknown. Also, marked in bold green, candidates are the
compounds that were identified in this test, but there are no guarantees that are responsible for the smell.
Odors that were chemically characterized with a high probability are in bold black. All the odors detected are
characterized by their retention time (RT) in the GC column.
As previously explained, the olfactory descriptors listed below were given by 2 panelists. Those
descriptors refer to the odors of the molecules perceived individually, not to the overall product odor. The
odor scale used was the odor intensity scale of DIN 10954 Paired Comparison/ Multicomparison test.
53
Table 14. GC-O results of PP2, PP4 and PP5 and correlation to the compounds identified by GC-TofMS.
RT
(min)
Descriptor
Compound
46,4
aromatic
Unknown
5,9
solvent, sweet
Acetaldehyde
41,8
chemical, plastic
Unknown
31,2
citrus
D-Limonene
37,9
citrus, green
Unknown
30,2
mushroom
Unknown
Candidates
CAS
75-07-0
5989-27-5
2,3-butanedione
123-72-8/
431-03-8
Intensity
PP2
PP4
PP5
2
2
3
3
3
3
2
2
3
3
3
2
3
4
3
4
3
2
13,4
butter
Butanal
18,8
fatty, green
Unknown
2
38,8
fatty, oily
Unknown
3
39,0
fatty, oily
Unknown
23,1
green, grass
Hexanal
26,6
vegetal, plastic
Unknown
27,6
vegetal, green
a-Pinene
33,6
vegetal, earthy
Unknown
4
43,3
green, chemical
Unknown
3
3
28,5
organic, baked
Unknown
2
2
28,8
organic, salty
Unknown
25,6
plastic, medicine
Unknown
2
28,3
synthetic, leather
Unknown
2
30,6
plastic, synthetic
C10H16 terpene
36,4
plastic, synthetic
Unknown
39,3
plastic, chemical
Unknown
40,1
plastic, toasted
40,8
42,9
2
66-25-1
80-56-8
2
2
3
2
3
4
2
3
2
2
3
3
2
2
2
3
Unknown
2
2
2
plastic, synthetic
Unknown
3
3
2
plastic, synthetic
Unknown
2
2
44,7
plastic, synthetic
Unknown
2
3
6,4
putrid, organic
3
2
putrid, rancid
24,1
cheesy, putrid
26,3
putrid, rancid
35,7
45,5
Methanethiol
74-93-1
Butanoic acid
107-92-7
Unknown
3
3
3
4
3
Unknown
3
3
3
putrid, synthetic
Unknown
2
3
3
putrid, humid
Unknown
3
3
39,4
spicy, synthetic
Unknown
3
41,2
smoked, toxic
Unknown
34,1
sweet, toasted
Unknown
34,2
sweet, toasted
Unknown
3
3
44,5
sweet, synthetic
Unknown
3
2
48,4
sweet, aromatic
Unknown
2
2
30,8
roasted, meaty
Benzaldehyde
39,7
toasted, nutty
Unknown
16,3
vinegar, sour
Acetic acid
Total
3
citrus
earthy
green/
vegetal
organic
3
3
2
chemical
2
3
23,5
-
aromatic
fatty
3
3
Category
3
3
plastic/
synthetic
putrid
spicy
3
2
100-52-7
64-19-7
3
2
2
2
2
3
2
51
112
86
sweet
toasted
vinegar
54
Various descriptors were used by the panelists to describe the odor of the 41 odor-active chemical
compounds sniffed during the GC-O analysis. Those descriptors were then classified in 13 families:
“aromatic”, “chemical”, “citrus”, “earthy”, “fatty”, “green/vegetal”, “organic”, “plastic/synthetic”, “putrid”,
“spicy”, “sweet”, “toasted” and “vinegar”.
The sum of odorous compounds intensities ranking obtained by GC-O is PP2 << PP5 < PP4. The results
are in agreement with the DIN 10954 Paired Comparison/Multicomparison Tests performed internally at
Tupperware confirming the importance of these tests for quality assurance. Table 15 summarizes the
correlation between GC-O compounds odor intensities and concentrations measured in GC-TofMS.
Table 15. Summary of the correlation between GC-O compounds odor intensities and concentrations measured
in GC-TofMS. N/D means not detected in GC-TofMS.
Descriptors Category
Acetaldehyde
D-Limonene
Butanal
2,3Butadione
Hexanal
solvent,
sweet
citrus
PP2
PP4
PP5
Concentration
Concentration
Concentration
Odor
Odor
Odor
measured by
measured by
measured by
intensity
intensity
intensity
GC-TofMS
GC-TofMS
GC-TofMS
GC-O
GC-O
GC-O
(μg/m3)
(μg/m3)
(μg/m3)
chemical
2
2,7
3
citrus
2
0,0
2
3,6
butter
fatty
green, grass
green/
vegetal,
vegetal
α-Pinene
green
C10H16
plastic,
plastic,
terpene
synthetic synthetic
putrid,
Methanethiol
organic
putrid
cheesy,
Butanoic acid
putrid
roasted,
Benzaldehyde
toasted
meaty
vinegar,
Acetic acid
vinegar
sour
3
N/D
3,4
3
3,4
2,3
2
5,7
16,4
4
N/D
7,8
3
N/D
N/D
0,0
2
3,2
3
15,3
2
6,0
3
0,0
2
7,3
N/D
3,9
3
2,1
3
9,6
N/D
N/D
3
N/D
2
N/D
3
N/D
4
N/D
3
N/D
N/D
0,0
3
3,8
N/D
0,0
2
0,0
3
19,2
2
0,0
Sum of VOC in GC-TofMS (ug/m3)
4992,0
14561,6
23902,8
Sum of odor intensities in GC-O
510
112
86
Important to notice that, even though sample PP5 is the one containing the highest quantity of VOC,
sample PP4 is the one that emits the highest overall odor intensity. This may because many VOC released are
presented in concentrations lower than their sensory odor threshold, therefore, they are not detected by the
human nose. Also, some chemical compounds present high OTV, being only detected by humans when their
concentration in the samples is very high.
Only 10 out of 41 compounds detected by GC-O were characterized. For this reason, although
conclusions were made regarding the identified compounds, a big part of the overall odor origin is still
unknown.
55
Acetaldehyde was detected and characterized as a “solvent, sweet” odor. The intensity of the odor
of this compound was higher in samples PP4 and PP5 compared to sample PP2, agreeing with the higher
concentration of acetaldehyde measured in PP4 and PP5 samples where the concentration was identified as
superior to the theoretical OTV (2,7-90 μg/m3)[18]. D-Limonene was detected and characterized as a “citrus”
odor. The odor intensity related to this compound is higher in sample PP5 compared to the 2 others, being in
line with the higher concentration of D-Limonene measured by GCTof-MS in this sample. Important to
observe that although D-limonene was not detected chromatographically in sample PP2, it was sniffed by the
panel. Both butanal and 2,3-butanedione were characterized as a “butter” and “fatty” odor. 2,3-butanedione
was not detected chromatographically but due to its retention time and typical odor description, it was
considered a candidate. Hexanal and α-pinene were characterized as having a “green and vegetal” odor. The
“green, grass” odor related to hexanal has been evaluated with a higher intensity in PP5 compared to PP4,
while in PP2 was not detected. The results are in agreement with the molecular analysis.
As for α-pinene, the odor intensity of sample PP4 was higher compared to the 2 others even if it was
not detected by the Mass Spectrometry in this sample. C10H16 terpene was described as a “plastic and
synthetic” odor, being rated with an intensity of 3 for both PP4 and PP5 samples and was not sniffed by the
panel in sample PP2. Methanethiol was associated with a “putrid, organic” odor and butanoic acid with a
“cheesy and putrid” odor. None of those compounds was detected in GC-TofMS, however, both compounds
were sniffed in sample PP4 and PP5, being odor intensity higher for PP4 in both cases. Benzaldehyde was
described as “roasted and meaty” and was only detected in sample PP4, being in line with the concentrations
detected during GC-TofMS analysis. Acetic acid was characterized as a compound with “vinegar, sour” odor.
Again, PP4 is the sample with the higher intensity for this descriptor.
Figure 29 provides an overview of the sensory perception of the six main smells described by the
panelists, according to the sum of their intensities.
Chemical
25
20
Sweet
15
Putrid
10
PP2
PP4
PP5
5
0
Green/vegetal
Plastic/synthetic
Fatty
Figure 29. Overview of the sensory perception of the smells described by panelists.
56
From the GC-O results, sample PP2 contains the lower odorous compounds quantity, as the sum of
intensities is much lower than for the two other samples. However, the odor of this grade is still perceptive
and not always acceptable. Butanal and 2,3-butanedione, as a candidate, were ranged with an intensity of 3,
being butanal the major responsible for the odor in this grade and 2,3-butanedione a possible cause. The
same occurs with butanoic acid that was considered an odor candidate with an intensity of 3, despite not
being chromatography detected, confirming its high odor impact at really low concentrations.
For PP4, some compounds from different chemical families were classified with an odor intensity of
3 or more such as acetaldehyde, benzaldehyde and butanal (aldehydes), α-Pinene and C10H16 terpenes
(terpenes), and acetic acid (organic acids). 2,3-butanedione, methanethiol and butanoic acid were classified
as possible candidates for odor-active compounds in this grade. Important to refer that butanoic acid and
acetic acid were already identified as odor-active compounds in other publications - Table 1.
PP5 also presented compounds that were ranged with an odor intensity of 3 or more. Acetaldehyde,
butanal and hexanal (aldehydes) and D-limonene (terpenes) were confirmed as odor-active compounds and
2,3-butanedione and butanoic acid as candidates. Also, butanal, 2,3-butanedione and butanoic acid were
identified/classified as candidates for the three grades, increasing the possibility of being present in general
polypropylene grades.
Finally, even though that aldehydes (acetaldehyde, butanal, hexanal, benzaldehyde) and terpenes
(α-pinene, D-Limonene and C10H16) were present in low concentrations according to GC-TofMS analyses,
they were detected during the sniffing analysis. It can be concluded that these two chemical families have a
big influence on the overall odor intensity of a polypropylene grade.
Correlation of GC-TofMS and GC-O results with literature
As presented in Table 3, acetaldehyde is a degradation product of the nucleating agent
Diparamethyldibenzylidene sorbitol, commonly used in the plastic industry. This nucleating agent is present
in PP2, PP4 and PP5 grades composition as seen in Table 6. From the GC-TofMS analysis of these three grades
is possible to observe that acetaldehyde was presented in the headspace generated by the bottles. More
specifically, the concentration of acetaldehyde is 2,7 µg/m3 in PP2, 3,8 µg/m3 in PP4 and 3,4 µg/m3 in PP5,
being in the last two samples in higher concentration than acetaldehyde OTV (2,7-90 μg/m3)[18]. In the GC-O
analysis, acetaldehyde was detected and characterized, presenting an odor intensity of 2, 3 and 3 for PP2,
PP4 and PP5 samples, respectively. Based on the information presented above, it can be concluded that
nucleating agent Diparamethyldibenzylidene sorbitol degrades and generates acetaldehyde that gives a
strong odor to the final bottle.
No conclusions can be made between the mass percentage of this additive in one grade and the final
odor intensity as grades in study present different additives formulations that may have different interactions
with this nucleating agent. However, it is possible to confirm that for grades with mass percentages of
Diparamethyldibenzylidene sorbitol higher than 0,21 wt%, acetaldehyde was detected as a chemical odor by
the human nose.
57
As previously seen in Table 3, benzene is a degradation product of secondary antioxidant Tris (2,4di-ter-butylphenyl) phosphite (AO2). This compound was chromatographically detected by GC-TofMS in PP4
(0,2 µg/m3) and PP5 (4,1 µg/m3), in concentrations lower than benzene OTV (8600 μg/m3)[18]. The results are
in line with the polymers’ composition as both grades present this secondary antioxidant in their formulation.
PP2 also has AO2 in its formulation, however, in GC-TofMS results, benzene does not appear as a VOC of this
grade. As expected, benzene was not detected by GC-O due to its low concentration in samples and high OTV.
This way, although secondary antioxidant Tris (2,4-di-ter-butylphenyl) phosphite (AO2) degrades and releases
benzene, it is not an odor-active compound and, consequently, it is not responsible for the overall odor
intensity of grade PP4 and PP5.
In Table 6 is possible to observe that PP4 and PP5 have similar formulations. Despite not knowing
the exact concentration of each additive in both grades, internal sources confirm that these two materials
are from the same supplier and their differences rely on the primary antioxidant used. While in PP4 the
primary antioxidant present is 1,3,5-tris(3,5-di-tert-butyl-4-hydroxybenzyl)-s-triazine-2,4,6(1H,3H,5H) trione
(AO1.1), in PP5 is Pentaerythritol tetratkis (3-(3,5-di-tert-butyl-4-hydroxylphenyl) propionate) (AO1.2). With this
in mind, it would be expected that these PPRC grades would present a similar concentration of VOC, as well
as, overall odor intensity. However, that is not verified.
As mentioned in Chapter 5.1.3, primary antioxidant AO1.1 is less thermally stable than AO1.2 being
more prone to oxidation and/or degradation during the process. In addition, when AO1.2 is in combination
with AO2, the consumption of the primary antioxidant is reduced while melt processing, being more effective
in the final productions and, consequently, a possible reason for the lower odor intensity in PP5 when
compared to PP4.
Correlation of GC-TofMS with Overall migration
When comparing overall migration values presented in Table 5Overall Migration values obtained
from previous Overall Migration Limit (OML) tests performed at Tupperware for the different polymers in
study were requested. In food science, OML is the maximum total amount of non-volatile substances
permitted that can migrate from a food container into food. The overall migration is determined by exposing
the item to a chemical food simulant for a specified and appropriate length of time, after which the extracted
residue is dried and weighed. The results are important to observe if the migration of non-volatile substances
is correlated with the release of VOC. The combination of the simulants in Table 5 covers all type of food,
including aqueous foodstuff according to European directives. [48] Tests were performed on injection molded
containers.
Table 5 with the concentration of VOC detected by GC-TofMS for grades PP2, PP4 and PP5, it is
possible to observe that even though, PP5 presents the lower overall migration value in acetic acid 3% and
ethanol 95%, it is the grade that released a higher VOC concentration.
The opposite occurs with PP2, that presents the highest overall migration for the different simulants
and the lowest concentration of VOC. For the reasons mention, diffusion of volatile and non-volatile
58
compounds cannot be compared and correlated, meaning that additives migration test will not give a right
perception of the odor of one grade.
9.2.4. HT-GPC results
Results obtained from Gel Permeation Chromatography are presented in Table 16. The
chromatograms are present in Annex IV.4 - Figure 38. HT-GPC chromatograms of PP2 pellets. 38, Figure 39 and
Figure 40.
Table 16. Dispersity of PP2, PP4 and PP5 samples.
Sample
Mw
Mn
Đ
PP2
PP2
PP4
PP4
PP5
PP5
421600
422700
364700
381300
380800
379600
279000
267000
107700
115900
76000
82100
1,5
1,6
3,4
3,5
4,8
4,6
Concentration
of VOC (ug/m3)
Intensity in
GC-O
4992,0
51
14561,6
112
23902,8
86
As it is possible to see in the table above, the results are in agreement with the literature research.
It was verified that with an increasing dispersity, the concentration of VOC released is higher, as expected.
This is due to the fact that a big dispersity contributes to the polymer shear sensitivity as it presents chains
with different lengths, making the structure less compact and more sensible when put under pressure in an
Injection Molding machine or stretched during Blow Molding process, for instance.
This way, to ensure low VOC release, it is recommended that the polypropylene material presents
low dispersity. On the other hand, materials with broad MWD, i.e., high dispersity present better self-support
during blow molding, while solidifying.[51]
59
9.3. RESULTS PRODUCTION 3
9.3.1. Sensory and Data Analysis
In Production 3, the effect of the treatments applied using different dryer equipment was studied.
The odor results for the odor tests are in Annex V.1 - Table 27 and the respective statistical analysis chart is
presented in the Figure 30.
Figure 30. Comparison of odor intensity of PP5, PP5-A and PP5-B bottles represented in a Multiple Comparison
chart.
In the figure presented above is possible to observe that there was a decrease in the odor intensity
of the bottles for both dryer treatments when compared to the original grade (PP5). Although, it is also
possible to see that only for the treatment using the heated desiccant air dryer there was a significant
difference. To better understand the results, some PP5, PP5-A and PP5-B bottles were sent to an external lab
to be analyzed by GC-TofMS.
9.3.2. GC-TofMS results
The table below presents the main results of the analyses by GC-TofMS which identified and
quantified the volatile organic compounds presented in PP5, PP5-A and PP5-B bottles. Compounds present
in quantities greater than their theoretical olfactory threshold (OTV) or in notable concentrations, as well as,
the totals of all chemical families are summarized in Table 17. Full details are provided in the Annex V.2 - Table
28.
60
Table 17. GC-TofMS results of PP5, PP5 treated with vacuum dryer (PP5-A) and PP5 treated with heated
desiccant air dryer (PP5-B). Concentration of compounds marked with (*) cannot be determined accurately;
concentrations in bold and red exceed the odor threshold value (OTV) and concentrations in bold and green don´t exceed
0,1 µg/m3.
Compound
CAS No.
Concentration (µg/m3)
OTV
available
PP5
PP5-A
PP6-B
8,7
9,6
1,0
1,4
1,3
0,0
2,7
2,0
0,0
3,6
5,7
Yes
Yes
Yes
2,4
19,6
1,7
6,0
296,8
10,2
32,4
14,8
36,8
8,5
2,9
142,5
448,8
67,4
65,6
82,1
213,1
1800,4
11,8
10,5
0,0
0,0
0,0
0,0
58,7
0,0
2,0
1,1
11,3
3,2
0,0
34,8
184,5
17,0
12,8
28,2
90,1
559,4
9,9
0,0
No
Yes
Yes
No
Yes
No
Yes
Yes
No
No
No
Yes
No
No
No
No
No
4,3
4,3
11,1
3,5
3,7
3,7
1,8
0,0
No
760,4
92,1
5,8
557,3
1415,6
0,0
0,0
0,0
0,0
0,0
Yes
Yes
Yes
Yes
12,6
12,6
0,0
0,0
Yes
0,0
0,0
3282,0
1,9
1,9
583,4
Yes
ALCOHOLS
Total Alcohols
Acetaldehyde (*)
Propanal
Nonanal
Total Aldehydes
ALDEHYDES
75-07-0
123-38-6
124-19-6
1,4
0,0
0,0
1,5
ALIPHATIC HYDROCARBONS
1-Butene, 3-methyl563-45-1
2,8
Butane, 2-methyl78-78-4
22,1
Pentane
109-66-0
9,0
1-Pentene, 4-methyl691-37-2
7,0
Pentane, 2-methyl107-83-5
350,4
1-Pentene, 2-methyl763-29-1
11,8
n-Hexane
110-54-3
40,0
Heptane
142-82-5
17,7
Hexane, 2,5-dimethyl592-13-2
43,9
Hexane, 2,4-dimethyl589-43-5
10,0
1-Hexene, 2,5-dimethyl6975-92-4
3,5
Heptane, 2-methyl592-27-8
165,3
Heptane, 2,4-dimethyl2213-23-2
505,7
Octane, 4-methyl2216-34-4
66,3
Nonane, 2-methyl871-83-0
49,4
Nonane, 2,6-dimethyl17302-28-2
83,3
Decane, 2,4,6-trimethyl62108-27-4
213,4
Total Aliphatic Hydrocarbons
1944,4
Total Aromatic compounds
7,4
Total Cyclic Hydrocarbons
2,7
ETHERS
1,3-Dioxolane, 2-methyl497-26-7
0,0
Total Ethers
0,0
Total Ketones
6,7
Total Nitrogen-containing compounds
1,4
ORGANIC ACIDS
Acetic acid
64-19-7
0,0
Propanoic acid
79-09-4
0,0
Propanoic acid, 2-methyl79-31-2
0,0
Butanoic acid
107-92-6
0,0
Total Organic Acids
0,0
SULFUR-CONTAINING COMPOUNDS
Disulfide, dimethyl
624-92-0
0,0
Total Sulfur-containing compounds
0,0
TERPENES
a-Pinene
80-56-8
0,0
Total Terpenes
0,0
TOTAL VOC
1972,8
From the results above is possible to observe that there was an approximately 66% increase of VOC
concentration in PP5-A bottle when compared to the PP5 bottle. The increase was verified for all chemical
families except for aliphatic hydrocarbons where a small decrease was observed.
61
The major difference was observed in the organic acids family. The total organic acids concentration
in sample PP5 (< 0,1 µg/m3) increased to 1415,6 µg/m3 in sample PP5-A, where acetic acid is present at a
concentration (760 µg/m3) 10 to 50 times higher than its OTV (15-150 μg/m3)[18], propanoic acid and 2-methylpropanoic acid at concentrations (92,1 µg/m3and 5,8 µg/m3, respectively) 1 to 10 times higher than its OTV
(Odournet database) and butanoic acid at a concentration (557,3 µg/m3) 50-100 times higher than its OTV
(0,86-20 µg/m3)[18].
These results are in disagreement with the odor tests as in Figure 30 where PP5-A presents an odor
intensity lower than PP5. Interesting to notice the results of odor tests for this experiment are in Annex V Table 27 where it is possible to realize that for the first test, odor intensity in PP5-A was considered lower
than PP5, while when the test was redone, the opposite was verified.
Different results were observed for PP5-B where was an approximately 70% decrease of VOC
concentration in PP5-B bottle when compared to PP5 bottle. In Table 17 is possible to see that the
concentration of VOC decrease in aliphatic hydrocarbons, cyclic hydrocarbons, ketones and nitrogencontaining compounds and an increase in aldehydes, aromatic hydrocarbons, terpenes and ethers
concentrations. No changes in concentrations were observed for organic acids and sulfur-containing
compounds chemical families.
The main reduction was observed in the concentration of aliphatic hydrocarbons which was high in
the PP5 bottle (1944,4 µg/m3). When the PP5 pellets were treated using a heated desiccant air dryer, it
decreased to 559,4 µg/m3. As many OTV for aliphatic compounds are unknown, it is not possible to
understand if this is the main reason for odor removal. In PP5-B bottles, the only compound in which
concentration (3,6 µg/m3) was 1 to 10 times higher than its OTV (Odournet database) was nonanal. For this
reason, this aldehyde is a probably odor-active compound in the PP5-B bottle.
Although GC-O was not performed, some conclusions can be taken from GC-O results of Production
2 as both Production 2 and 3 present PP5 as sample grade, even if the produced bottles were not the same,
but 750 ml and 500 ml, respectively. Important to notice that for PP5 750 ml Round Bottles, panelists in GCO detected and characterized acetic acid, and considered butanoic acid an odor-active compound candidate,
although these compounds were not chromatography detected by GCTof-MS. This way, even though
acetaldehyde, a-Pinene, butanoic acid and acetic acid are presented at low concentrations in PP5-B, lower
than their OTV, these may be odor-active compounds.
Several assumptions regarding polymer treatments can be made based on these results,. One of the
reasons why the vacuum dryer was not efficient might be due to the fact that the air which was heated to
treat the pellets was not filtered. The air was directly taken from atmospheric air at the portuguese
production site which may be already contaminated from the production that was occurring simultaneously.
Another reason may have been the short residence time applied, showing that 45 minutes is not enough time
for efficient VOC release and extraction.
62
10. CONCLUSIONS AND FUTURE WORK
The work developed allows a number of conclusions and remarks.
Odor tests in pellets by changing the samples preparation conditions of TQA-009-041-I were
performed. A comparison was done between pellets heated at 60°C for 3 hours, pellets heated at 160°C for
15 minutes and containers heated at 60°C for 3 hours. Odor intensities for the containers were always higher
than pellets heated at 60°C for 3 hours and lower pellets heated at 160°C for 15 minutes, never giving the
real odor value of the final product. For this reason, tests where pellets heated at 120°C for 15 minutes and
30 minutes were performed. For these conditions, the odor intensity for both containers was higher than
pellets heated at 120°C for 15 minutes and lower than pellets heated at 120°C for 30 minutes.
Based on the results, it can be concluded that performing odor tests with raw material to substitute
the current procedure on injected molded pieces is not yet feasible as optimum conditions were not achieved.
Nevertheless, it is possible to heat pellets at 120°C for 15 minutes and at 120°C for 30 minutes and know that
the real odor product will be between the obtained values. Thus, it is advisable to perform more tests to
sustain these results in other injection molded pieces as the shape and processing have a big impact on endproduct odor.
The influence of processing in the creation of odor-active compounds was studied in Production 2.
In all grades tested, all presented a significant difference between the odor intensity in pellets and their
respective bottles, confirming the impact of the Injection Molding and Blow Molding combined. Tupperware
bottles’ production increases significantly the odor released by the material.
In Production 2, GC-TofMS was performed in PP2, PP4 and PP5 polypropylene grades. In total 273
chemical compounds were identified. Aliphatic hydrocarbons were released in higher concentrations,
followed by alcohols.
GC-TofMS and GC-O detected and characterized aldehydes (acetaldehyde, butanal, hexanal and
benzaldehyde), terpenes (a-Pinene, C10H16 terpene and D-limonene) and organic acid (acetic acid) as odoractive compounds. Other candidates are ketone (2,3-butanedione), mercaptan (methanethiol) and organic
acid (butanoic acid).
GC-O results are in line with the DIN 10954 Paired Comparison/Multicomparison Tests performed
internally at Tupperware, where the order of the grades by increasing intensity is PP2 << PP5 < PP4.
From the results, it was possible to conclude that nucleating agent Diparamethyldibenzylidene
sorbitol degrades and generates acetaldehyde that gives a strong odor to the final bottle. Secondary
antioxidant Tris (2,4-di-ter-butylphenyl) phosphite (AO2) also was proved to degrade and release benzene,
but as its concentration in samples is lower than its OTV, benzene is not responsible for the overall odor
intensity of grade PP4 and PP5.
No correlation was possible to make between the overall migration of non-volatile compounds and
the concentration of organic volatile compounds released by the same grades.
63
As it was expected from the literature, it was possible to confirm that with an increasing dispersity,
the concentration of VOC released is higher because the polymer presents more shear sensibility, degrading
more easily when compared to a polymer with low dispersity.
Production 3 had the aim of testing experimental odor removal treatments. Two different
experiments were performed using different dryer equipment, a vacuum and a heated desiccant air dryers.
In the odor tests, the panel sniffed a decrease in the odor intensity of the bottles for both dryer treatments
when compared to the original grade (PP5). To confirm this, GC-TofMS was performed in PP5, PP5-A and PP5B bottles. There was an approximately 66% increase of VOC concentration in PP5-A bottle when compared
to the PP5 bottle. Different results were observed for PP5-B where there was an approximately 70% decrease
of VOC concentration in PP5-B bottle when compared to PP5 bottle.
In PP5-B, the main decrease was observed in the concentration of aliphatic hydrocarbons. In these
bottles, the only compound in which concentration was 1 to 10 times higher than its OTV was nonanal. Except
for aldehydes, aromatic compounds and terpenes, where small concentration increases were observed,
heated air heated desiccant air dryer proved to be efficient in the removal of VOC from pellets.
Regarding future work, much research is needed to fully understand the sense of smell, as many
questions in this field are still to answer. For Tupperware, it will be interesting to study parameters to optimize
the use of the heated desiccant air dryer that already proved to be efficient in reducing VOC concentration in
polypropylene products. Especially, reducing the residence time to less than fifteen hours is important to
make the process viable in a product line. Finally, this treatment can be combined with additives able to
remove specific problematic compounds, as nonanal, which concentration increased during the process.
64
11. REFERENCES
[1]
[2]
[3]
[4]
[5]
[6]
[7]
[8]
[9]
[10]
[11]
[12]
[13]
[14]
[15]
[16]
[17]
[18]
[19]
[20]
[21]
[22]
[23]
[24]
[25]
[26]
[27]
“Classification of Polymers: Source, Structure, Polymerisation, Examples.” [Online]. Available:
https://www.toppr.com/guides/chemistry/polymers/classification-of-polymers/. [Accessed: 16-Jul2019].
“What Is an Olefin in Chemistry?” [Online]. Available: https://sciencing.com/olefin-chemistry6716429.html. [Accessed: 16-Jul-2019].
“Polypropylene | PP price reports | forecasts and margin analysis | ICIS.com.” [Online]. Available:
https://www.icis.com/explore/commodities/chemicals/polypropylene/#about-polypropylene.
[Accessed: 16-Jul-2019].
“Polypropylene (PP) Plastic: Types, Properties, Uses & Structure Info.” [Online]. Available:
https://omnexus.specialchem.com/selection-guide/polypropylene-pp-plastic. [Accessed: 16-Jul2019].
“10 Reasons To Use Polypropylene For Your Next Food Packaging Project.” [Online]. Available:
http://blog.impactplastics-ct.com/blog/10-reasons-to-use-polypropylene-for-your-next-foodpackaging-project. [Accessed: 16-Jul-2019].
H. Hopfer, “Identification of odour-active compounds in polyolefins,” Technischen Universitat Graz,
2010.
“Everything You Need To Know About Polypropylene (PP) Plastic.” [Online]. Available:
https://www.creativemechanisms.com/blog/all-about-polypropylene-pp-plastic. [Accessed: 16-Jul2019].
S. Arjmand, “Investigation of spatial configuration of Polypropylene and the influence of Molecular
Weight Distribution, Catalyst type and Tacticity on mechanical, Thermal and optical properties of
polymers.,” IOSR J. Polym. Text. Eng., vol. 1, no. 3, pp. 37–45, 2014.
“What Is Plastic Injection Molding? | Vision Plastics, Inc.” [Online]. Available:
https://visionplastics.net/resources/what-is-plastic-injection-molding/. [Accessed: 17-Jul-2019].
“Injection
Molding
Process,
Defects,
Plastic.”
[Online].
Available:
https://www.custompartnet.com/wu/InjectionMolding. [Accessed: 18-Jul-2019].
“What
is
blow
molding?
|
Milacron
Blog.”
[Online].
Available:
https://www.milacron.com/mblog/2018/02/28/what-is-blow-molding/. [Accessed: 23-Jul-2019].
“Robinson Packaging | Injection Stretch Blow Moulding.” [Online]. Available:
https://robinsonpackaging.com/plastics/injection-stretch-blow-moulding/. [Accessed: 23-Jul-2019].
J. Murphy, Additives for Plastics Handbooks. Elsevier Science Ltd, 2001.
M. Bolgar, J. Hubball, J. Groeger, and S. Meronek, Handbook for the Chemical Analysis of Plastic and
Polymer Additives, 2nd ed. Florida: CRC Press, 2016.
“Luperox® peroxides for polymer initiation - polypropylene (PP).” [Online]. Available:
https://www.luperox.com/en/product-ranges/pp-modification/. [Accessed: 11-Aug-2019].
“SAFETY AND HANDLING OF ORGANIC PEROXIDES: A Guide Prepared by the Organic Peroxide
Producers Safety Division of Plastics Industry Association,” 2018.
A. Rinaldi, “The scent of life. The exquisite complexity of the sense of smell in animals and humans,”
EMBO Rep., vol. 8, no. 7, pp. 629–633, Jul. 2007.
L. J. van Gemert, Odour Thresholds. Oliemans Punter & Partners BV, 2011.
E. Reingruber, J. Reussner, C. Sauer, A. Standler, and W. Buchberger, “Studies on the emission
behavior of polypropylene by gas chromatography/mass spectrometry with static headspace or
thermodesorption,” J. Chromatogr. A, vol. 1218, no. 21, pp. 3326–3331, May 2011.
“Your partner in CAPS & CLOSURES Polyolefins-the material of choice.”
J. Bradbury, “Taste Perception: Cracking the Code,” PLoS Biol., vol. 2, no. 3, p. e64, Mar. 2004.
G. Wypych, Handbook of odors in plastic materials. Chemtec, 2013.
L. Briand and C. Salles, “Taste perception and integration,” in Flavor, Elsevier, 2016, pp. 101–119.
J. C. J. Bart, Polymer additive analytics : industrial practice and case studies. Firenze University Press,
2006.
J. A. Horas and M. G. Rizzotto, “Gas diffusion in and through polypropylene,” Springer, Dordrecht,
1999, pp. 273–276.
“Permeability of Polymers.” [Online]. Available: https://polymerdatabase.com/polymer
physics/Permeability.html. [Accessed: 29-Jul-2019].
J. Comyn, Polymer permeability. Chapman & Hall, 1985.
65
[28]
[29]
[30]
[31]
[32]
[33]
[34]
[35]
[36]
[37]
[38]
[39]
[40]
[41]
[42]
[43]
[44]
[45]
[46]
[47]
[48]
[49]
[50]
[51]
M. G. R. Zobel, “The odour permeability of polypropylene packaging film,” Polym. Test., vol. 5, no. 2,
pp. 153–165, Jan. 1985.
D. Ismailove and T. Martinache, “Blooming and Odour in Polypropylene,” 2017.
“Toxic Plastics and How to Avoid Them | Blog | Little Acorns to Mighty Oaks.” [Online]. Available:
https://www.littleacornstomightyoaks.co.uk/blog/2008/12/01/toxic-plastics-and-how-to-avoidthem. [Accessed: 31-Jul-2019].
M. Björnsdotter and B. Van Bavel, “Leaching of residual monomers, oligomers and additives from
polyethylene, polypropylene, polyvinyl chloride, high---density polyethylene and polystyrene virgin
plastics.”
D. Gilbert, G. Witt, F. Smedes, and P. Mayer, “Polymers as Reference Partitioning Phase: Polymer
Calibration for an Analytically Operational Approach To Quantify Multimedia Phase Partitioning,”
Anal. Chem., vol. 88, no. 11, pp. 5818–5826, Jun. 2016.
H. J. Ko and T. H. Park, “Bioelectronic nose and its application to smell visualization,” J. Biol. Eng., vol.
10, no. 1, p. 17, Dec. 2016.
L. Shibryaeva, “Thermal Oxidation of Polypropylene and Modified Polypropylene-Structure Effects.”
H. Hopfer, N. Haar, W. Stockreiter, C. Sauer, and E. Leitner, “Combining different analytical
approaches to identify odor formation mechanisms in polyethylene and polypropylene,” Anal.
Bioanal. Chem., vol. 402, no. 2, pp. 903–919, Jan. 2012.
I. N. Gogotov and S. K. Barazov, “The Effect of Ultraviolet Light and Temperature on the Degradation
of Composite Polypropylene,” Int. Polym. Sci. Technol., vol. 41, no. 3, pp. 55–58, Mar. 2014.
A. S. Maxwell, W. R. Broughton, G. Dean, and G. D. Sims, “NPL REPORT Review of accelerated ageing
methods and lifetime prediction techniques for polymeric materials,” 2005.
E. Bradley and L. Coulier, “Report FD 07/01: An investigation into the reaction and breakdown
products from starting substances used to produce food contact plastics,” 2007.
S. Beißmann, M. Stiftinger, K. Grabmayer, G. Wallner, D. Nitsche, and W. Buchberger, “Monitoring
the degradation of stabilization systems in polypropylene during accelerated aging tests by liquid
chromatography combined with atmospheric pressure chemical ionization mass spectrometry,”
Polym. Degrad. Stab., vol. 98, no. 9, pp. 1655–1661, Sep. 2013.
M. Ncube and Y. Su, “The removal of volatile organic compounds from supply air using a desiccant
column – A theoretical study,” Int. J. Sustain. Built Environ., vol. 1, no. 2, pp. 259–268, Dec. 2012.
F. Cousin, B. Walworth, and D. Marissal, “Polymer Treatment,” US 7,790,842 B2, 2010.
L. Girardot and J.-L. Chamayou, “Polymer degassing process control,” US9181367B2, 2012.
J.-M. Galewski, H. Goujon, and N. Ville, “Process and apparatus for degassing a polymer,” US
7,268,206 B2, 2003.
“Resin Drying - FarragTech Company,” 2009.
M. Ncube and Y. Su, “The removal of volatile organic compounds from supply air using a desiccant
column – A theoretical study,” Int. J. Sustain. Built Environ., vol. 1, no. 2, pp. 259–268, Dec. 2012.
“Desiccant
Air
Dryer
System
|
Quincy
Compressor.”
[Online].
Available:
https://www.quincycompressor.com/products/desiccant-dryers/. [Accessed: 27-Aug-2019].
“Identification of VOCs generated by natural and synthetic Polymers.” [Online]. Available:
https://www.researchgate.net/publication/325711620_Identification_of_VOCs_generated_by_nat
ural_and_synthetic_Polymers. [Accessed: 09-Oct-2019].
“EUR-Lex
32011R0010
EN
EUR-Lex.”
[Online].
Available:
https://eurlex.europa.eu/eli/reg/2011/10/oj. [Accessed: 19-Aug-2019].
“The
Odournet
group
|
Odournet.”
[Online].
Available:
https://www.odournet.com/company/odournet-group/. [Accessed: 20-Aug-2019].
S. Orlich, “Kruskal-Wallis Multiple Comparisons with a MINITAB Macro Dunn’s Test.” Minitab, Inc.
“Polyolefin Flow Characteristics: More than Just Melt Index or Melt Flow Rate,” LyondellBasell Tech.
Tip.
66
12. ANNEXES
I. Polypropylene properties
Table 18. Polypropylene structural and physical properties.
Parameter
Monomer(s) molecular weight(s) (g/mol)
Monomer(s) expected purity(ies) (%)
Temperature of polymerization (°C)
Mass average molecular weight, Mw (g/mol)
Crystallinity %
Crystallization Temperature (°C)
Melting temperature (°C)
42,08
99,2
70 (bulk); 60-100 (gas-phase)
1,000-5,400,000
3,2-67
116-140
120-176
II. Odor permeability of polypropylene packaging film.
Figure 31. Permeability coefficient for VOC versus molecular weight.[28]
67
III. Production 1
III.1 Odor tests results
Table 19. Tests comparing two process stages (pellets and injection molded containers at conditions B) and
studying the impact of temperature (60°C and 160°C) and time (15 min and 180 min) in pellets’ sample preparation for
test TQA-009-041-I, in different polypropylene grades (PP1, PP2, PP6 and PP7).
PP1
PP2
PP6
PP7
Experiment
Temperature
Polymer state
(°C)
Pellets
160
Pellets
60
Injected molded
60
containers - B
Pellets
160
Pellets
60
Injected molded
60
containers - B
Pellets
160
Pellets
60
Injected molded
60
containers - B
Pellets
160
Pellets
60
Injected molded
60
containers - B
Time
(min)
15
180
Pan.
1
2
1
Panelists (Pan.)
Pan. Pan. Pan. Pan.
2
3
4
5
2
1
2
4
1
0
2
1
180
1
2
0
1
2
2
1,5
15
180
2
1
4
3
4
3
3
2
3
2
4
3
3,5
2,5
180
2
3
3
3
3
4
3,0
15
180
3
1
2
2
5
1
3
1
4
2
3
3
3,0
1,5
180
1
3
1
1
4
4
2,0
15
180
3
3
4
2
4
2
4
3
4
3
4
2
4,0
2,5
180
3
3
1
3
4
3
3,0
Pan.
6
1
1
Median
2,0
1,0
Table 20. Tests studying the impact of temperature (60°C and 120°C) and time (15 min and 180 min) in pellets’
sample preparation for test TQA-009-041-I.
PP2
PP6
Experiment
Temperature
Polymer state
(°C)
Pellets
120
Pellets
120
Injected molded
60
containers - B
Pellets
120
Pellets
120
Injected molded
60
containers - B
Panelists (Pan.)
Pan. Pan. Pan.
3
4
5
2
1
2
3
3
3
Time
(min)
15
30
Pan.
1
2
3
Pan.
2
2
3
Pan.
6
3
3
180
2
2
4
3
2
3
2,5
15
30
2
4
3
4
2
4
3
3
2
2
0
2
2,0
3,5
180
2
2
3
3
1,5
3
2,5
Median
2,0
3,0
68
Table 21. Tests comparing different processing conditions (A, B, C and D) in different polypropylene grades
(PP2, PP6 and PP7).
PP2
PP6
PP7
Conditions
A
B
C
D
A
B
C
D
A
B
C
D
Pan. 1
2
2
2
3
4
4
3
3
2
3
2
1
Pan. 2
4
5
4
5
2
2
3
3
3
2
3
2
Pan. 3
4
4
1
2
3
3
4
3
2
2
1
1
Pan. 4
2
3
3
3
3
2
2
3
3
4
4
3
Pan. 5
5
4
4
4
3
3
3
3
2
3
2
3
Pan. 6
3
3
3
3
3
3
3
3
2
3
3
3
Median
3,5
3,5
3,0
3,0
3,0
3,0
3,0
3,0
2,0
3,0
2,5
2,5
Table 22. Test comparing different polypropylene grades (PP1, PP2, PP6 and PP7) injection molded at condition
B.
Condition B
PP1
PP2
PP6
PP7
Pan. 1
1
2
3
3
Pan. 2
1
3
4
5
Pan. 3
1
4
3
3
Pan. 4
3
3
4
4
Pan. 5
2
4
4
4
Pan. 6
2
3
3
3
Median
1,7
3,2
3,5
3,7
69
IV. Production 2
IV.1 Odor tests results
Table 23. Tests comparing three process stages (pellets, preforms and injection molded bottles at condition D)
and studying the impact of temperature (60°C and 160°C), in different polypropylene grades (PP2, PP3, PP4 and PP5).
Reference samples are PP2 preforms injection molded using Tupperware standard parameters.
Experiment
Temperature
Polymer state
(°C)
Reference Preform
Pellets
60
Preforms - D
Bottles - D
Reference Preform
Pellets
60
Preforms - D
Bottles - D
Reference Preform
Pellets
60
Preforms - D
Bottles - D
Reference Preform
Pellets
60
Preforms - D
Bottles - D
PP2
PP3
PP4
PP5
Time
(min)
180
180
180
180
Pan.
1
Panelists (Pan.)
Pan. Pan. Pan. Pan.
2
3
4
5
Pan.
6
1
3
3
1
2
2
1
3
3
2
3
4
1
2
3
4
3
4
1
2
3
1
2
3
3
3
4
2
2
2
1
2
3
3
2
2
2
3
4
2
4
5
2
3
4
2
1
3
1
3
5
1
3
3
2
1
3
1
2
3
1
1
3
1
0
3
1
1
3
2
2
2
Median
≈ 3,0
1,0
3,0
3,0
≈ 3,0
1,5
2,5
3,0
≈ 3,0
2,0
3,0
4,0
≈ 3,0
1,0
1,0
3,0
Table 24. Tests comparing different processing conditions (A, B, C and D) in different polypropylene grades
(PP2, PP3, PP4 and PP5). Reference samples are PP2 preforms injection molded using Tupperware standard parameters.
PP2
PP2
2nd test
PP3
PP3
2 test
nd
Conditions
Reference Preform
A
B
C
D
Reference Preform
A
B
C
D
Reference Preform
A
B
C
D
Reference Preform
A
B
C
D
Pan. 1
Pan. 2
Pan. 3
Pan. 4
Pan. 5
Pan. 6
3
3
3
2
3
3
3
3
3
3
3
3
2
2
2
2
2
2
2
2
1
3
3
3
3
2
2
2
3
2
3
4
3
3
3
3
3
3
3
3
1
2
2
3
4
3
2
2
2
1
1
3
3
2
2
4
3
2
1
4
3
2
2
4
3
2
2
4
2
2
2
3
2
2
1
3
1
2
2
3
3
2
2
2
2
1
1
2
3
3
3
3
2
3
3
3
Median
≈ 3,0
2,5
3,0
3,0
2,5
≈ 3,0
3,0
2,5
2,5
3,0
≈ 3,0
3,0
2,0
2,0
4,0
≈ 3,0
2,0
2,0
2,0
3,0
70
PP4
PP4
2nd test
PP5
PP5
2nd test
Reference Preform
A
B
C
D
Reference Preform
A
B
C
D
Reference Preform
A
B
C
D
Reference Preform
A
B
C
D
2
2
3
3
4
3
2
2
4
3
2
3
1
2
0
2
4
4
4
4
2
2
3
2
3
2
3
3
4
4
3
4
4
3
3
2
3
3
3
3
5
4
5
4
4
3
2
3
1
1
1
2
1
1
2
2
1
2
2
2
2
3
2
2
2
2
2
1
2
2
2
2
2
3
2
1
2
2
4
2
1
2
3
2
3
2
1
2
4
4
4
4
4
4
2
3
≈ 3,0
3,0
2,5
2,5
2,5
≈ 3,0
4,0
3,0
3,0
3,0
≈ 3,0
1,5
2,0
2,0
2,0
≈ 3,0
2,5
2,5
2,5
2,0
Table 25. Tests comparing different bottles of polypropylene grades (PP2, PP3, PP4 and PP5) injection molded
at condition D. Reference samples is a PP2 bottle blow-molded using Tupperware standard parameters.
Condition D
Reference Bottle
PP2
PP3
PP4
PP5
PP2 2nd test
PP3 2nd test
PP4 2nd test
PP5 2nd test
Pan. 1
Pan. 2
Pan. 3
Pan. 4
Pan. 5
Pan. 6
3
3
4
2
3
3
4
3
2
3
5
4
2
4
5
5
0
3
5
2
3
2
3
2
2
2
3
3
3
3
3
3
3
2
5
3
4
4
5
5
3
5
3
2
2
4
3
3
Median
≈ 3,0
2,5
3,0
4,5
2,5
3,0
3,5
3,5
3,0
71
Figure 32. Comparison of odor intensity of Conditions A, B, C and D in PP2 preforms represented in a Multiple
Comparison chart.
Figure 33. Comparison of odor intensity of Conditions A, B, C and D in PP4 preforms represented in a Multiple
Comparison chart.
Figure 34. Comparison of odor intensity of Conditions A, B, C and D in PP5 preforms represented in a Multiple
Comparison chart.
72
IV.2 GC-TofMS results
In the following tables, for each chemical family, compounds are sorted by retention time in an
ascending order. Retention time values are not presented in these tables.
Table 26. GC-TofMS results of PP2, PP4 and PP5. Concentration of compounds marked with (*) cannot be
determined accurately, concentrations in bold and red exceed the odor threshold value (OTV) and concentrations in bold
and green don´t exceed 0,1 ug/m3.
Concentration (ug/m3)
Compound
Methyl Alcohol (*)
Ethanol
Isopropyl Alcohol
2-Propanol, 2-methyl1-Propanol
3-Buten-2-ol, 2-methyl1-Propanol, 2-methylAmylene hydrate
1-Butanol
2-Pentanol
2-Butanol, 2,3-dimethyl3-Buten-1-ol, 3-methyl2-Butanol, 3,3'-oxybis1-Butanol, 2-ethyl1-Pentanol, 2-ethyl1-Octanol, 3,7-dimethyl1-Octanol, 2-butyl2-Isopropyl-5-methyl-1-heptanol
1-Dodecanol
1-Nonanol
Total Alcohols
Acetaldehyde (*)
2-Propenal
Propanal
Methacrolein
Butanal
Hexanal
Benzaldehyde
Benzaldehyde, 4-propyl3-Fluoro-5-(trifluoromethyl)benzaldehyde
Total Aldehydes
Propene
Propane
Isobutane
1-Propene, 2-methylButane
1-Butene, 3-methylButane, 2-methyl2-Pentene, (E)Pentane
2-Methyl-1-butene
2-Butene, 2-methyl1-Pentene, 4-methylButane, 2,3-dimethyl-
CAS No.
OTV
available
PP2
PP4
PP5
0,0
19,5
1,9
0,0
0,0
0,0
0,0
0,0
0,0
0,0
0,0
0,0
0,0
0,0
0,0
13,7
0,0
0,0
0,0
0,0
35,3
0,0
50,7
9,8
861,5
1,3
3,5
1,7
81,2
2,4
1,9
1,1
21,2
1,0
1,3
7,4
0,0
16,0
8,8
0,0
4,8
1075,6
23,7
30,0
251,4
0,0
1,3
0,0
46,3
0,0
3,8
0,0
0,0
0,0
0,0
0,0
0,0
0,0
0,0
0,0
8,3
0,0
364,9
Yes
Yes
Yes
Yes
Yes
No
Yes
Yes
Yes
No
No
No
No
Yes
No
No
No
No
No
Yes
2,7
4,7
0,6
0,0
3,6
0,0
0,0
0,0
0,0
11,7
3,8
0,0
0,0
30,0
16,4
3,2
3,8
9,6
0,0
66,8
3,4
5,9
1,1
0,0
7,8
15,3
0,0
0,0
1,5
34,9
Yes
Yes
Yes
Yes
Yes
Yes
Yes
No
No
ALIPHATIC HYDROCARBONS
115-07-1
1,0
74-98-6
1,8
75-28-5
0,0
115-11-7
6,7
106-97-8
0,0
563-45-1
0,9
78-78-4
43,4
646-04-8
0,0
109-66-0
0,0
563-46-2
0,0
513-35-9
0,0
691-37-2
8,8
79-29-8
0,0
27,3
10,5
26,5
256,0
0,0
0,0
13,6
0,0
896,7
6,2
4,3
0,0
2,3
0,0
8,1
2,2
5,4
45,3
56,6
461,6
266,2
162,4
2,4
10,0
149,4
314,0
Yes
Yes
Yes
Yes
Yes
No
Yes
No
Yes
No
No
No
Yes
ALCOHOLS
67-56-1
64-17-5
67-63-0
75-65-0
71-23-8
115-18-4
78-83-1
75-85-4
71-36-3
6032-29-7
594-60-5
763-32-6
54305-61-2
97-95-0
27522-11-8
106-21-8
3913-02-8
91337-07-4
112-53-8
143-08-8
ALDEHYDES
75-07-0
107-02-8
123-38-6
78-85-3
123-72-8
66-25-1
100-52-7
28785-06-0
188815-30-7
73
Pentane, 2-methyl2-Pentene, 4-methyl2-Pentene, 4-methyl-, (Z)Pentane, 3-methyln-Hexane
2-Pentene, 2-methyl2-Hexene, (E)1-Butene, 2,3-dimethylPentane, 2,4-dimethyl1-Pentene, 2-methyl2-Butene, 2,3-dimethyl1-Pentene, 2,4-dimethyl2,4-Dimethyl 1,4-pentadiene
1-Pentene, 2,3-dimethylHexane, 2-methyl1-Hexene, 5-methylPentane, 2,3-dimethyl1-Butene, 2-ethyl-3-methylHexane, 3-methyl(Z)-Hex-2-ene, 5-methyl1-Hexene, 2-methyl2,4-Hexadiene, 3-methylHeptane
1,4-Hexadiene, 2-methyl3-Hexene, 2,5-dimethyl-, (E)1-Hexene, 3,5-dimethyl2-Hexene, 2,5-dimethylHexane, 2,5-dimethylPentane, 3-ethyl-2,2-dimethyl2,3-Dimethyl-1-hexene
Hexane, 3,3-dimethyl2-Heptene, 3-methylPentane, 2,3,4-trimethyl1-Hexene, 2,5-dimethyl2,4-Dimethyl-1-hexene
2-Heptene, 4-methyl-, (E)1-Heptene, 4-methyl2-Octyne
Heptane, 2-methylHeptane, 4-methylHeptane, 3-methyl1-Heptene, 2-methyl2,4-Hexadiene, 2,5-dimethylOctane
trans-2-Methyl-3-octene
Hexane, 2,3,5-trimethylHeptane, 2,4-dimethylHeptane, 2,6-dimethylHeptane, 3,5-dimethylHeptane, 3-ethyl-5-methylene2,4-Dimethyl-1-heptene
3-Hexene, 3-ethyl-2,5-dimethyl1-Heptene, 2,6-dimethylHeptane, 2,3-dimethylOctane, 4-methyl3-Heptene, 2,6-dimethylOctane, 3-methylHexane, 3-ethyl-2-methyl2,6-Dimethyl-1,6-heptadiene
1,5-Heptadiene, 2,6-dimethyl-
107-83-5
4461-48-7
691-38-3
96-14-0
110-54-3
625-27-4
4050-45-7
563-78-0
108-08-7
763-29-1
563-79-1
2213-32-3
4161-65-3
3404-72-6
591-76-4
3524-73-0
565-59-3
7357-93-9
589-34-4
13151-17-2
6094-02-6
28823-42-9
142-82-5
1119-14-8
692-70-6
7423-69-0
3404-78-2
592-13-2
16747-32-3
16746-86-4
563-16-6
3404-75-9
565-75-3
6975-92-4
16746-87-5
66225-17-0
13151-05-8
2809-67-8
592-27-8
589-53-7
589-81-1
15870-10-7
764-13-6
111-65-9
52937-36-7
1069-53-0
2213-23-2
1072-05-5
926-82-9
19549-87-2
62338-08-3
3074-78-0
3074-71-3
2216-34-4
2738-18-3
2216-33-3
16789-46-1
51708-83-9
6709-39-3
1107,9
11,4
0,0
6,6
232,2
1,1
0,0
0,0
7,3
0,0
0,0
1,3
1,5
0,0
16,3
5,1
1,8
0,0
0,0
0,0
2,2
0,0
21,6
0,0
0,0
0,0
0,0
76,1
42,3
0,0
0,0
0,0
2,1
0,0
14,5
0,0
13,3
0,0
257,5
50,9
32,0
6,7
0,0
129,1
1,2
47,9
706,9
8,5
0,8
3,6
48,0
8,0
0,0
33,0
527,9
0,0
1,5
6,2
0,0
0,0
62,0
0,0
0,0
0,0
19,2
3,1
0,0
0,0
0,0
5,0
0,0
7,1
0,0
0,0
1,9
0,0
0,0
0,0
5,9
0,0
5,7
0,0
21,6
0,0
0,0
0,0
0,0
7,5
7,8
0,0
0,0
0,0
0,0
0,0
6,5
3,3
16,8
0,0
90,2
712,2
6,8
38,6
0,0
67,1
0,0
63,4
1053,8
9,0
0,0
2,0
1045,0
0,0
0,0
44,0
695,9
0,0
2,8
8,1
0,0
0,0
2497,8
0,0
385,1
10,7
807,3
16,5
3,1
0,9
18,7
0,0
4,1
17,9
27,0
2,6
91,7
0,0
31,7
6,6
0,0
5,6
12,5
4,1
478,8
2,2
6,8
7,0
1,9
790,4
215,9
4,8
1,6
2,1
7,3
83,9
0,0
0,0
0,0
2,1
1579,5
503,9
38,9
35,8
3,8
480,5
33,9
0,0
2925,0
37,9
0,0
24,7
123,9
1,6
33,3
57,8
1029,2
4,7
2,5
16,6
8,8
1,8
Yes
No
No
Yes
Yes
No
No
No
Yes
No
No
No
No
No
Yes
No
Yes
No
Yes
No
No
No
Yes
No
No
No
No
No
No
No
No
No
No
No
No
No
No
Yes
Yes
Yes
Yes
No
No
Yes
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
74
Nonane
Heptane, 2,4,6-trimethylNeopentane
Octane, 2,5-dimethylOctane, 2,7-dimethylOctane, 2,6-dimethyl1-Octene, 2,7-dimethylUndecane, 6-methylHeptane, 3-ethyl-2-methylNonane, 5-methylNonane, 4-methylNonane, 2-methylNonane, 3-methylOctane, 2,4,6-trimethyl2-Methyl-1-nonene
Decane
Heptane, 2,2,4,6,6-pentamethyl2-Octene, 4-ethylHeptane, 5-ethyl-2-methylDecane, 5-methylNonane, 2,5-dimethyl2-Decene, 5-methyl-, (Z)Nonane, 2,6-dimethyl4-Decene, 7-methyl-, (E)Octane, 3,3-dimethylNonane, 2-methyl-3-methylene2,2,4,4-Tetramethyloctane
Decane, 4-methyleneHeptane, 4-ethylUndecane
Octane, 3,5-dimethylOctane, 2-methyl1-Nonene, 4,6,8-trimethyl5-Ethyl-1-nonene
Octane, 2,3,6,7-tetramethyl2,6-Dimethyldecane
Undecane, 4-methylOctane, 2,6,6-trimethylDecane, 2,9-dimethylPentane, 2,2-dimethyl4,4-Dimethyl octane
Heptane, 4-propylHexane, 3,3,4,4-tetramethylUndecane, 2-methylDecane, 2,6,8-trimethylUndecane, 5,7-dimethylDodecane
Decane, 3,7-dimethylUndecane, 2,4-dimethylUndecane, 2,6-dimethylUndecane, 3,7-dimethylUndecane, 4,8-dimethylDecane, 2,3,5,8-tetramethylTridecane
Dodecane, 4,6-dimethylDecane, 2,4,6-trimethylHeptane, 3-ethyl-5-methylDodecane, 4-methylDodecane, 2,6,11-trimethylDecane, 4-methyl-
111-84-2
2613-61-8
463-82-1
15869-89-3
1072-16-8
2051-30-1
33718-03-5
17302-33-9
14676-29-0
15869-85-9
17301-94-9
871-83-0
5911-04-6
62016-37-9
2980-71-4
124-18-5
13475-82-6
53966-52-2
13475-78-0
13151-35-4
17302-27-1
74645-86-6
17302-28-2
62338-48-1
4110-44-5
55499-08-6
62183-79-3
24949-41-5
2216-32-2
1120-21-4
15869-93-9
3221-61-2
54410-98-9
19780-74-6
52670-34-5
13150-81-7
2980-69-0
54166-32-4
1002-17-1
590-35-2
15869-95-1
3178-29-8
5171-84-6
7045-71-8
62108-26-3
17312-83-3
112-40-3
17312-54-8
17312-80-0
17301-23-4
17301-29-0
17301-33-6
192823-15-7
629-50-5
61141-72-8
62108-27-4
52896-90-9
6117-97-1
31295-56-4
2847-72-5
12,7
6,3
0,7
7,1
15,1
8,5
0,0
0,0
1,4
2,6
16,8
80,6
4,0
71,1
0,0
33,5
10,9
0,0
8,3
60,5
131,2
2,2
123,0
0,0
1,6
0,0
0,0
2,5
59,5
316,5
36,7
0,9
0,0
0,0
170,1
12,2
10,1
0,0
1,4
0,0
0,0
0,0
2,2
6,2
4,4
0,0
7,6
1,1
0,0
11,9
1,7
5,3
0,0
2,2
0,0
11,1
0,0
8,6
17,9
4,9
62,9
9,0
0,0
19,3
70,6
19,9
1,7
2,5
0,0
0,0
129,4
285,1
5,2
264,5
0,0
61,1
75,9
6,7
240,4
442,9
488,2
0,0
466,6
37,0
0,0
7,3
6,3
20,2
131,0
994,5
225,4
2,6
177,1
166,5
257,8
54,5
28,2
0,0
9,6
1,9
0,0
0,0
7,8
26,7
22,5
4,1
10,7
27,9
0,0
26,6
3,7
23,6
9,0
9,5
9,1
10,7
14,5
45,2
105,9
4,5
279,4
24,5
1,2
51,8
252,9
50,4
3,2
4,7
0,0
0,0
262,2
793,2
4,2
711,9
3,4
121,4
14,1
0,0
97,9
984,9
266,6
8,1
1061,5
0,0
0,0
0,0
0,0
17,4
205,3
1659,9
489,6
4,7
0,0
0,0
239,6
44,8
17,6
2,3
28,9
0,0
1,1
12,4
24,3
86,4
60,5
7,0
22,4
87,7
23,2
63,8
4,2
69,2
6,6
56,6
0,0
5,1
45,9
137,9
288,7
14,3
Yes
No
No
No
No
No
No
No
No
No
No
No
No
No
No
Yes
No
No
No
No
No
No
No
No
No
No
No
No
No
Yes
No
No
No
No
No
No
No
No
No
Yes
No
No
No
No
No
No
Yes
No
No
No
No
No
No
Yes
No
No
No
No
No
No
75
Decane, 5-ethyl-5-methylDecane, 2,3,7-trimethylTridecane, 2-methylHexane, 2,4-dimethylTetradecane
Decane, 2,4-dimethylNonadecane
Decane, 2-methylPentadecane
Octadecane
Heptadecane, 2,6,10,15-tetramethylUndecane, 4,7-dimethylTotal Aliphatic Hydrocarbons
Benzene
Toluene
Ethylbenzene
p,m-Xylene
o-Xylene
Benzene, propylTotal Aromatic compounds
Cyclopropane
Cyclopropane, ethylCyclopropane, 1,1-dimethylCyclopropane, ethylideneIsopropenylcyclopropane
Cyclopropane, 1-ethyl-1-methylCyclopentane, methylCyclopropane, 1,1-diethylEthylidenecyclobutane
Cyclopentene, 1-(1-methylethyl)Butane, 2-cyclopropylCyclobutane, ethylCyclohexane, 1,3,5-trimethylTricyclo[2.2.1.0(2,6)]heptane, 1,3,3-trimethylCyclohexane, 1,1-dimethylCyclooctane, 1,4-dimethyl-, cisTotal Cyclic Hydrocarbons
17312-74-2
62238-13-5
1560-96-9
589-43-5
629-59-4
2801-84-5
629-92-5
6975-98-0
629-62-9
593-45-3
54833-48-6
17301-32-5
4,9
10,4
0,8
0,0
9,2
0,0
0,0
3,8
6,9
4,1
0,0
5,1
10434,9
11,2
8,2
4,3
4,1
0,0
1,8
8,2
4,3
0,0
7,2
23,3
3,6
22777,8
No
No
No
No
Yes
No
No
No
No
No
No
No
0,0
11,1
0,8
0,2
8,6
1,2
4,1
19,6
1,9
Yes
Yes
Yes
0,0
4,7
7,3
Yes
3,3
0,0
15,3
0,0
2,6
17,3
0,0
0,0
32,8
Yes
Yes
0,0
0,0
5,8
0,0
0,0
26,2
6,7
0,0
0,0
0,0
3,3
0,0
0,0
0,0
0,0
0,0
42,1
0,0
16,5
0,0
9,7
0,0
770,0
0,0
0,0
3,7
0,0
1,2
1,3
6,3
16,6
1,2
0,0
826,7
3,7
13,5
0,0
0,0
33,3
285,7
7,0
2,1
0,0
2,0
15,8
0,0
0,0
0,0
0,0
3,9
367,0
No
No
No
No
No
No
Yes
No
No
No
No
No
No
No
No
No
ESTERS
141-78-6
616-38-6
553-90-2
14861-06-4
-
1,2
0,0
0,0
1,7
0,0
0,0
0,0
0,6
0,0
0,0
1,3
0,0
2,0
0,0
1,2
0,0
0,0
52,3
Yes
Yes
No
No
No
No
84-69-5
0,0
3,9
0,0
No
3,0
5,9
55,5
0,0
0,0
0,0
0,0
0,0
0,0
10,1
0,0
0,0
1,1
1,0
18,3
99,8
0,0
35,5
0,8
1,6
1,2
0,0
0,0
0,0
0,0
0,9
0,0
19,6
0,0
0,0
AROMATIC COMPOUNDS
71-43-2
108-88-3
100-41-4
108-38-3/10642-3
95-47-6
103-65-1
CYCLIC HYDROCARBONS
75-19-4
1191-96-4
1630-94-0
18631-83-9
4663-22-3
53778-43-1
96-37-7
1003-19-6
1528-21-8
1462-07-3
5750-02-7
4806-61-5
1839-63-0
488-97-1
590-66-9
13151-99-0
Ethyl Acetate
Carbonic acid, dimethyl ester
Ethanedioic acid, dimethyl ester
Formic acid, 2-ethylbutyl ester
Vinyl crotonate
Sulfurous acid, nonyl 2-pentyl ester
1,2-Benzenedicarboxylic acid, bis(2-methylpropyl)
ester
Total Esters
Propanoic acid, 2-propenyl ester
Oxetane, 3-(1-methylethyl)Propane, 2-methoxy-2-methylPropane, 2-ethoxy-2-methyl1,3-Dioxolane
Oxetane, 2,2-dimethyl1,3-Dioxolane, 2-methylOxirane, 2-ethyl-2-methylButane, 2-methoxy-2-methyl-
0,0
4,6
0,0
0,0
0,0
0,0
0,0
0,0
0,0
0,0
0,0
0,0
4795,2
ETHERS
2408-20-0
10317-17-6
1634-04-4
637-92-3
646-06-0
6245-99-4
497-26-7
30095-63-7
994-05-8
No
No
Yes
No
Yes
No
No
No
No
76
1,4-Dioxane
Propane, 1-(1,1-dimethylethoxy)-2-methyl1-Butyne, 3-methyl-3-(1-methylethoxy)Octane, 1,1'-oxybisCyclopenta [g]-2-benzopyran, 1,3,4,6,7,8-hexahydro4,6,6,7,8,8-hexamethylTotal Ethers
123-91-1
33021-02-2
53907-63-4
629-82-3
0,4
0,0
0,0
0,0
0,2
1,7
0,5
4,3
0,8
0,0
0,0
0,0
Yes
No
No
No
1222-05-5
4,0
0,0
0,0
No
14,6
166,1
21,5
Furan
0,1
Furan, 2-methyl0,0
Furan, tetrahydro-2,2,5,5-tetramethyl0,0
5-Methyl-2-(2-methyl-2-tetrahydrofuryl)
0,0
tetrahydrofuran
Total Furans
0,1
HALOGEN-CONTAINING COMPOUNDS
Norflurane
811-97-2
0,6
Propane, 1-chloro-2-methyl513-36-0
2,4
1,3,5-Trifluorobenzene
372-38-3
0,0
Trichloromethane
67-66-3
2,0
2-Norbornyl bromide
29342-65-2
0,0
Butane, 1-chloro-2-methyl-, (S)40560-29-0
2,1
Hexane, 2-iodo18589-27-0
1,3
Octane, 1-iodo629-27-6
0,0
1-Iodo-2-methylundecane
73105-67-6
0,0
Decane, 3-bromo30571-71-2
0,0
Total Halogen-containing compounds
8,5
KETONES
Acetone
67-64-1
30,0
2-Butanone, 3-methyl563-80-4
1,0
2-Butanone
78-93-3
1,6
Cyclohexanone
108-94-1
0,0
1-Propanone, 1-cyclopropyl6704-19-4
0,0
2,3-Pentanedione, 4-methyl7493-58-5
0,0
3-Hexen-2-one, 5-methyl5166-53-0
0,0
3-Pentanone
96-22-0
0,0
Cyclobutanone, 2,2,3-trimethyl1449-49-6
0,0
Methyl Isobutyl Ketone
108-10-1
0,0
2-Hexanone
591-78-6
0,0
2-Hepten-4-one, 2-methyl22319-24-0
0,0
2-Heptanone, 4-methyl6137-06-0
0,0
2-Pentanone, 3-methylene4359-77-7
0,0
4,4-(Ethylenedioxy)-2-pentanone
14255-36-8
0,0
Cyclohexanone, 4-(1,1-dimethylethyl)98-53-3
0,0
3,4-Hexanedione, 2,2,5-trimethyl20633-03-8
0,0
Total Ketones
32,7
MERCAPTANS
2-Undecanethiol, 2-methyl10059-13-9
0,0
Total Mercaptans
0,0
NITROGEN-CONTAINING COMPOUNDS
Acetonitrile
75-05-8
0,7
Diamide
10465-78-8
0,0
Butanenitrile, 2-methyl18936-17-9
0,0
3-(Butylamino)propionitrile
693-51-6
0,0
Pyrrolidine
123-75-1
0,0
Pyridine
110-86-1
0,0
1H-Tetrazole, 5-methyl4076-36-2
0,0
1,2,4-Triazine
290-38-0
0,0
Pyridine, 1,2,3,6-tetrahydro-1,2-dimethyl694-84-8
0,0
4-Aminoquinaldine
6628-04-2
1,4
Total Nitrogen-containing compounds
2,2
0,0
1,6
2,4
1,5
0,0
0,0
Yes
No
No
6,5
0,0
No
10,6
1,6
0,0
0,0
0,0
0,5
0,0
0,0
0,0
0,0
3,0
0,0
3,5
1,3
0,0
0,6
7,4
1,7
0,0
0,0
8,2
0,0
2,0
21,3
No
Yes
No
Yes
No
No
No
No
No
No
1600,4
0,0
222,1
0,0
0,0
14,9
16,8
3,1
0,0
2,4
0,0
3,5
1,3
0,0
2,6
15,6
0,0
1882,7
65,6
0,0
2,7
1,2
0,9
0,0
0,0
0,0
2,8
0,0
0,6
0,0
0,0
7,0
0,0
0,0
2,2
83,2
Yes
Yes
Yes
No
No
No
No
Yes
No
Yes
Yes
No
No
No
No
No
No
0,0
0,0
29,3
29,3
No
1,2
8,3
0,0
0,0
0,0
0,0
0,0
0,0
2,7
1,3
13,6
0,0
0,0
0,3
1,8
41,3
11,9
2,2
1,1
0,0
1,7
60,3
Yes
No
No
No
No
Yes
No
No
No
No
FURANS
110-00-9
534-22-5
15045-43-9
77
Acetic acid
Total Organic acids
ORGANIC ACIDS
64-19-7
0,0
0,0
OXYGEN-CONTAINING COMPOUNDS
1,2,4,5-Tetroxane, 3,3,6,6-tetramethyl1073-91-2
0,0
Ethanol, 2-phenoxy122-99-6
0,0
Total Oxygen-containing compounds
0,0
SULFUR-CONTAINING COMPOUNDS
Carbonyl sulfide (*)
463-58-1
0,1
Methanesulfonic anhydride
7143-01-3
1,4
Total Sulfur-containing compounds
1,6
TERPENES
1-Isopropylcyclohex-1-ene
4292-04-0
0,0
a-Pinene
80-56-8
6,0
ß-Phellandrene
555-10-2
0,0
C10H16
3,9
D-Limonene
5989-27-5
0,0
Total Terpenes
10,0
HETEROGROUPS
Carbamic acid, monoammonium salt
1111-78-0
18,1
Ethane, pentafluoro354-33-6
0,0
Furazan, dimethyl4975-21-7
0,0
Ethaneperoxoic acid, 1-cyano-1-[2-(2-phenyl-1,358422-92-7
1,6
dioxolan-2-yl)ethyl]pentyl ester
Total Heterogroups
19,7
TOTAL VOC
4992,0
19,2
19,2
0,0
0,0
Yes
3,1
0,0
3,1
0,0
5,3
5,3
No
No
0,0
1,7
1,8
0,0
0,0
0,0
Yes
No
0,0
0,0
7,2
2,1
2,3
11,6
7,8
7,3
0,0
9,6
5,7
30,4
No
Yes
No
No
Yes
19,8
0,0
2,4
16,5
0,5
0,0
No
No
No
0,0
0,0
No
22,2
14561,6
17,1
23902,8
78
IV.3 GC-TofMS chromatograms
Figure 35. GC-TofMS chromatogram of PP2 bottle.
Figure 36. GC-TofMS chromatogram of PP4 bottle.
Figure 37. GC-TofMS chromatogram of PP5 bottle.
79
IV.4 HT-GPC chromatograms
Figure 38. HT-GPC chromatograms of PP2 pellets.
Figure 39. HT-GPC chromatograms of PP4 pellets.
Figure 40. HT-GPC chromatograms of PP5 pellets.
80
V. Production 3
V.1 Odor tests results
Table 27. Production 3 odor test results- test comparing PP5 bottles, PP5-A and PP5-B. Reference samples are
PP2 bottles blow-molded using Tupperware standard parameters.
Condition TW standard
Reference Bottle
PP5
PP5 - A
PP5 - B
PP5 2nd test
PP5 - A 2nd test
PP5 - B 2nd test
Pan. 1
Pan. 2
Pan. 3
Pan. 4
Pan. 5
Pan. 6
4
2
1
2
3
1
4
4
3
4
4
3
3
2
1
2
3
1
3
3
2
2
2
2
4
1
0
2
2
2
4
3
3
3
3
2
Median
≈ 3,0
4,0
2,5
1,5
2,0
3,0
2,0
V.2 GC-TofMS results
In the following tables, for each chemical family, compounds are sorted by retention time in an
ascending order. Retention time values are not presented in these tables.
Table 28. GC-TofMS results of PP5, PP5 treated with vacuum dryer (PP5-A) and PP5 treated with heated
desiccant air dryer (PP5-B). Concentration of compounds marked with (*) cannot be determined accurately;
concentrations in bold and red exceed the odor threshold value (OTV) and concentrations in bold and green don´t exceed
0,1 µg/m3.
Concentration (ug/m3)
Compound
Ethanol
Isopropyl Alcohol
1-Propanol, 2-methylTotal Alcohols
Acetaldehyde (*)
Propanal
Nonanal
Total Aldehydes
Propene
1-Propene, 2-methylButane
1-Butene, 3-methylButane, 2-methylPentane
1-Pentene, 4-methylButane, 2,3-dimethylPentane, 2-methyl2-Pentene, 4-methyl-, (Z)1-Pentene, 2-methyln-Hexane
2,4-Dimethyl 1,4-pentadiene
Hexane, 2-methylHeptane
CAS No.
OTV
available
PP5
PP5-A
PP6-B
2,6
6,1
0,0
8,7
2,4
5,8
1,5
9,6
1,0
0,0
0,0
1,0
Yes
Yes
Yes
1,4
0,0
0,0
1,5
ALIPHATIC HYDROCARBONS
115-07-1
0,0
115-11-7
0,0
106-97-8
0,0
563-45-1
2,8
78-78-4
22,1
109-66-0
9,0
691-37-2
7,0
79-29-8
18,8
107-83-5
350,4
691-38-3
22,8
763-29-1
11,8
110-54-3
40,0
4161-65-3
1,2
591-76-4
4,2
142-82-5
17,7
1,4
1,3
0,0
2,7
2,0
0,0
3,6
5,7
Yes
Yes
Yes
12,1
3,1
0,1
2,4
19,6
1,7
6,0
16,3
296,8
19,7
10,2
32,4
1,0
3,8
14,8
0,0
0,0
0,0
0,0
0,0
0,0
0,0
5,7
58,7
4,3
0,0
2,0
0,0
1,3
1,1
No
Yes
Yes
No
Yes
Yes
No
Yes
Yes
No
No
Yes
No
Yes
Yes
ALCOHOLS
64-17-5
67-63-0
78-83-1
ALDEHYDES
75-07-0
123-38-6
124-19-6
81
Hexane, 2,5-dimethylHexane, 2,4-dimethyl1-Hexene, 2,5-dimethylHeptane, 2-methylHeptane, 4-methyl1-Heptene, 2-methylOctane
Hexane, 2,3,5-trimethylHeptane, 2,4-dimethylHeptane, 2,6-dimethyl2,4-Dimethyl-1-heptene
1-Heptene, 2,6-dimethylHeptane, 2,3-dimethylOctane, 4-methylNonane
Octane, 2,5-dimethylOctane, 2,7-dimethylOctane, 2,6-dimethylNonane, 4-methylNonane, 2-methylHeptane, 2,4,6-trimethylDecane
Pentane, 2,2,4,4-tetramethylOctane, 3,3-dimethylDecane, 5-methylNonane, 2,5-dimethylNonane, 2,6-dimethylDecane, 2,4,6-trimethylUndecane
2,6-Dimethyldecane
Octane, 3,5-dimethylDecane, 2,9-dimethylUndecane, 4-methylUndecane, 2-methylDecane, 2,5,9-trimethylDodecane
Undecane, 2,4-dimethylUndecane, 2,6-dimethylDecane, 2,3,4-trimethylTetradecane
Decane, 2,3,5,8-tetramethylDodecane, 4,6-dimethylTridecane
Dodecane, 2,6,11-trimethylPentadecane
Hexadecane
Total Aliphatic Hydrocarbons
592-13-2
589-43-5
6975-92-4
592-27-8
589-53-7
15870-10-7
111-65-9
1069-53-0
2213-23-2
1072-05-5
19549-87-2
3074-78-0
3074-71-3
2216-34-4
111-84-2
15869-89-3
1072-16-8
2051-30-1
17301-94-9
871-83-0
2613-61-8
124-18-5
1070-87-7
4110-44-5
13151-35-4
17302-27-1
17302-28-2
62108-27-4
1120-21-4
13150-81-7
15869-93-9
1002-17-1
2980-69-0
7045-71-8
62108-22-9
112-40-3
17312-80-0
17301-23-4
62238-15-7
629-59-4
192823-15-7
61141-72-8
629-50-5
31295-56-4
629-62-9
544-76-3
43,9
10,0
3,5
165,3
26,8
1,7
21,4
19,9
505,7
1,4
4,0
1,2
2,5
66,3
12,7
2,3
12,7
2,8
12,3
49,4
43,3
6,4
0,0
4,6
54,2
14,3
83,3
213,4
2,7
12,6
2,3
1,3
0,0
4,2
4,6
0,0
0,0
2,8
2,9
0,0
0,0
2,0
0,0
0,0
15,6
0,0
1944,4
AROMATIC COMPOUNDS
Benzene
71-43-2
0,0
Toluene
108-88-3
2,6
108-38-3/106p,m-Xylene
1,6
42-3
o-Xylene
95-47-6
3,2
Total Aromatic compounds
7,4
CYCLIC HYDROCARBONS
Cyclopropane, 1,2-dimethyl-, cis930-18-7
0,0
Isopropenylcyclopropane
4663-22-3
0,0
Cyclopentene, 3-methyl1120-62-3
1,3
Tricyclo[2.2.1.0(2,6)]heptane, 1,3,3-trimethyl488-97-1
1,4
Total Cyclic Hydrocarbons
2,7
36,8
8,5
2,9
142,5
22,9
1,4
19,2
17,6
448,8
0,0
4,1
0,9
0,0
67,4
12,2
2,0
11,7
2,2
13,1
65,6
40,0
6,9
0,0
4,8
53,0
15,0
82,1
213,1
3,6
14,0
2,5
1,7
1,3
5,1
3,6
2,1
1,4
3,7
4,1
3,3
2,3
0,0
0,0
16,8
0,0
0,0
1800,4
11,3
3,2
0,0
34,8
6,4
0,0
4,2
7,9
184,5
0,0
0,0
0,0
0,0
17,0
2,8
0,0
4,0
0,0
3,5
12,8
16,5
2,9
1,2
1,6
18,4
4,8
28,2
90,1
2,4
5,5
0,0
0,0
0,0
0,0
1,9
2,5
0,0
1,3
1,5
0,0
0,0
0,0
4,0
8,9
0,0
2,4
559,4
No
No
No
Yes
Yes
No
Yes
No
No
No
No
No
No
No
Yes
No
No
No
No
No
No
Yes
No
No
No
No
No
No
Yes
No
No
No
No
No
No
Yes
No
No
No
Yes
No
No
Yes
No
No
Yes
1,7
3,9
0,0
6,0
Yes
Yes
2,4
1,8
Yes
3,8
11,8
2,1
9,9
Yes
7,9
1,2
0,0
1,3
10,5
0,0
0,0
0,0
0,0
0,0
No
No
No
No
82
1,3-Dioxolane, 2-methylTotal Ethers
2-Butanone
Acetone
Total Ketones
ETHERS
497-26-7
KETONES
78-93-3
67-64-1
0,0
0,0
3,7
3,0
6,7
NITROGEN-CONTAINING COMPOUNDS
Formamide, N-methyl123-39-7
0,0
Butanenitrile
109-74-0
0,0
Pyrrolidine
123-75-1
1,4
Total Nitrogen-containing compounds
1,4
ORGANIC ACIDS
Acetic acid
64-19-7
0,0
Propanoic acid
79-09-4
0,0
Propanoic acid, 2-methyl79-31-2
0,0
Butanoic acid
107-92-6
0,0
Total Organic Acids
0,0
SULFUR-CONTAINING COMPOUNDS
Disulfide, dimethyl
624-92-0
0,0
Total Sulfur-containing compounds
0,0
TERPENES
a-Pinene
80-56-8
0,0
Total Terpenes
0,0
TOTAL VOC
1972,8
4,3
4,3
3,7
3,7
No
0,0
11,1
11,1
0,0
1,7
1,8
Yes
Yes
1,8
0,3
1,3
3,5
0,0
0,0
0,0
0,0
No
No
No
760,4
92,1
5,8
557,3
1415,6
0,0
0,0
0,0
0,0
0,0
Yes
Yes
Yes
Yes
12,6
12,6
0,0
0,0
Yes
0,0
0,0
3282,0
1,9
1,9
583,4
Yes
V.3 GC-TofMS chromatograms
Figure 41. GC-TofMS chromatogram of PP5 bottle.
83
Figure 42. GC-TofMS chromatogram of PP5-A bottle.
Figure 43. GC-TofMS chromatogram of PP5-B bottle.
84