International Journal of Mechanical Engineering and Technology (IJMET)
Volume 9, Issue 11, November 2018, pp. 779–788, Article ID: IJMET_09_11_079
Available online at http://www.iaeme.com/ijmet/issues.asp?JType=IJMET&VType=9&IType=11
ISSN Print: 0976-6340 and ISSN Online: 0976-6359
© IAEME Publication
Scopus Indexed
MECHANICAL AND WATER ABSORPTION OF
INJECTION MOULDED PINEAPPLE LEAF
FIBER REINFORCED POLYLACTIC ACID
COMPOSITES
Darsan R S*
Department of Mechanical Engineering, Noorul Islam Centre for Higher Education,
Kumaracoil -629 180, Tamil Nadu, India
B. Stanly Jones Retnam
Department of Automobile Engineering, Noorul Islam Centre for Higher Education,
Kumaracoil -629 180, Tamil Nadu, India
M.Sivapragash,
PSN College of Engineering and Technology,
Melathediyoor, Tirunelveli 627152, Tamil Nadu, India.
*corresponding author
ABSTRACT
The short natural fiber reinforced polylactic acid (PLA) composites were prepared by
injection moulding for different fiber loading. Alkali treated pineapple leaf fiber (PALF)
is used reinforcement in the composite. The biocomposites made out of PLA up to 20%
fiber loading of untreated and treated PAF. The mechanical (tensile, flexural and impact
strength) and water absorption characterizations were performed on the PAF reinforced
polylactic acid composite with different percentage loading of untreated and treated PAF
fibers. Tensile modulus of the composite has improved 42.99% and 52.77% for untreated
and treated fiber reinforced composite respectively. Similar properties were observed for
flexural modulus and impact strength of the prepared composites. The work absorption
of the composite shows hydrophilic nature. The fracture behaviour observed from the
SEM images shows better interfacial interaction for untreated fiber reinforced composites
than treated fiber reinforced composites.
Keywords: Polylactic acid, pineapple leaf fiber (PLF), untreated & treated fiber,
mechanical and water absorption property.
Cite this Article Darsan R S, B. Stanly Jones Retnam and M Sivapragash, Mechanical and
Water Absorption of Injection Moulded Pineapple Leaf Fiber Reinforced Polylactic Acid
Composites, International Journal of Mechanical Engineering and Technology, 9(11),
2018, pp. 779–788.
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Darsan R S, B. Stanly Jones Retnam and M Sivapragash
1. INTRODUCTION
The polymer composites are widely used in countless applications in our daily life such as
food processing, packaging, health and hygiene, transportation, medical product etc. Among all
the applications the thermoplastic based polymers composites contribute to 80% of the
application due to ease of recycling [1]. Over the years these composites made from
nondegradable, nonrenewable petroleum-based polymers which are depleting in nature as time
pass by. The degradation of such polymers-based products after use causes large scale
environmental issues. The degradation process faces two major concerns for the currently used
polymers. First one is the long degradation time for the polymers to naturally decay into the soil,
causing huge pile up of waste in landfill sites [2]. Second is the emission of toxic gases during
recycling process, which lead to higher risk to health[3]. Forcing the researches come up with
polymers which are degradable with lower levels of rate of emissions and can be produced from
renewable sources.
The natural biodegradable polymers are produced either from agricultural crops or by
synthesis of bio monomers from the agricultural resources[4]. Some of the degradable
biopolymers like polylactic acid (PLA), poly(glycolic acid) (PGA), and poly(e-caprolactone)
(PCL) are produced by syntheses of bio monomers and they belong to polyester family [5].
Polylactic acid being the finest degradable polymer among the polyesters, is a linear aliphatic
thermoplastic produced from renewable agro sources6. The large molecular weight polymers are
made by condensation reaction or ring polymerization of lactide monomer, which is prepared
from the fermentation of corn or sugar [5,6]. Polylactic acid composites have attained higher
degree of biodegradability and mechanical properties after synthesis [1]. They have lower
processability and brittleness which make it difficult for usage in commercial applications [7].
Green composites made from renewable sources which are biodegradable, biopolymers with
natural fibers as the reinforcement, can be the best replacement candidate for the petroleum-based
composites [8,9]. The byproduct of the agricultural waste can be used for extraction of various
natural fibers. The different natural fibers such as bamboo [10], flax [11], jute [12], kenaf [13],
ramie [14], banana [1] and sisal [15] were explored in numerous researches. Predominant
mechanical properties are exhibited by some of the leaf-based fibers like pineapple leaf due to
the higher cellulose content along with lower microfibril angle [16,17]. The composites with short
pineapple fiber reinforced polyethylene have shown remarkable mechanical characteristics with
polyethylene [17,18]. The surface modification of the pineapple fiber has enhanced the properties
of the composites [16]. Recent studies analyses the mechanical properties of pineapple fiber
reinforced biopolymers, especially to check the compatibility of green composite were carried
out by researches [19]. Found satisfactory when compared with the polypropylene [20].
The present study aims in fabrication, mechanical and water absorption property evaluation
of pineapple leaf fiber reinforced composites by injection moulding. The effects of fiber loading
on the properties of untreated and treated short pineapple leaf fiber loading. Assess the optimum
tensile, flexural and impact strength from different untreated and treated fiber loading of the
composites. Evaluate the water absorption characteristic of the prepared composite. And finally,
to interpret the fracture behavior of the composites using SEM.
2. MATERIALS & EXPERIMENTAL PROCEDURES
2.1. Materials
Polylactic acid (PLA 3052D) was procured from Nature Works LLC, USA. Pineapple leaf
fiber(PLF) were supplied by Vrushacomposites and services,(Chennai, India). Sodium hydroxide
(NaOH) pellets purchased from SRL Pvt., India and Glacial Acetic acid from HIMEDIA, India.
The mechanical and thermal properties of PLF and PLA are shown in table 1.
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Mechanical and Water Absorption of Injection Moulded Pineapple Leaf Fiber Reinforced Polylactic
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Table 1 The Mechanical and thermal properties of PLF [16,18] and PLA 3052D
Properties
Density, g/m3
Tensile strength (MPA)
Tensile Modulus (GPa)
Elongation (%)
Glass transition temperature (oC)
Melting Temperature(oC)
Transition Temperature (oC)
PLF
1.53
287 -800
7.0 -8.0
14.5
PLA 3052D
1.24
62
3.5
55 -60
145 -160
60
2.2. Surface treatment of Pineapple leaf fiber
Pineapple leaf fibers were soaked in mild distilled water of 1% detergent solution for 2 hours at
room temperature. Followed by washing in distilled water to remove any traces of detergent left.
The washed fibers where dipped in 2% NaOH solution for 2hour [18,19] under room condition.
After the alkali treatment the fibers were washed with deionized water followed by immersion in
1% glacial acetic acid to remove any traces of alkali on the fiber. The pH value of the fiber is
brought down to neutral condition and is tested using a pH paper. The fibers are air dried for 24
hours followed by drying under room condition for 3 days, till the entire water vapour content is
removed. After drying the long fibers are chopped into short fiber of 3 -6mm length
2.3. Composite preparation
Prior to processing of composites, the PLA pellets and PALF fibers were dried in hot air oven at
80OC for 3 hours to remove any amount of moisture content left after primary drying. Using twin
screw extruder (M/s. Specific Engineering, ZV 20, Baroda India) the fiber and polymer were melt
blended. Initially. The mix blending is carried out at 175 O C and screw speed of 72 rpm for 15
minutes for different fiber loading 0%, 10%, 15%, 20% of untreated and treated fiber. The
blended materials are water cooled and shredded to smaller size using a shredding machine. The
shredded small size blended materials are dried in hot air oven at 80OC to remove the water
content during cooling in twin screw extruder. The dried blended material is then moulded to
standard specimen sizes using an automatic injection moulding machine (M/S. Feromatic
Milacron, Omega 80Wide, India).
3. CHARACTERIZATION METHODS
3.1. Mechanical Testing
3.2. Tensile testing
The tensile test specimens are prepared based on ASTM D638 standard to find out the tensile
strength, tensile modulus and percentage elongation of various composites which were prepared.
The testing is carried out at cross head speed of 5mm/min, on a gauge length of 50mm using
Universal testing machine (M/s. Tinius Olsen, H 50KL).
3.3. Flexural testing
The flexural test is performed on the same universal testing according to the ASTM D790
standard, to find the flexural strength and flexural modulus.
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3.4. Impact testing
The impact strength is found out according to the ASTM D256 standard. Using
Olsen, Impact 104, machine impact strength of the samples was found out.
M/s. Tinius
3.5. Water Absorption
The percentage of water absorption for the set of samples were prepared and conducted according
to ASTM D570 standard. The specimens are initially dried using hot air oven and cool to room
temperature. The initial weights of the samples are recorded to nearest 0.001 g.
3.6. Morphological characteristics
The morphological characteristics are observed by a Scanning electron microscopy (SEM), M/s.
Jeol, 6390 LV with a resolution of 4nm.
4. RESULTS AND DISCUSSION
4.1. Mechanical properties
4.1.1. Tensile properties on the UPLF/PLA & TPLF/PLA composites
The tensile strength, tensile modulus and percentage elongation of the UPLF/PLA & TPLF/PLA
composites with various fiber loadings are shown in figure 1, 2 & 3 respectively. The tensile
strength shows an increase in 1.51% and 9.58% for 10% and 15 % UPLF/PLA composites
respectively with respect to virgin PLA. But shows a decrease in 23.52% and 14.79% for 10%
and 15 % TPLF/PLA composites respectively with respect to virgin PLA. The tensile modulus
of the UPLF/PLA composites increases on addition of fiber and reaches a maximum value of
42.99% at 20% fiber loading. In the case of TPLF/PLA composites 52.77% increases in modulus
for 15% fiber loading and decreases on more fiber loading. The percentage elongation according
to graph shows a decrease in both UPLF/PLA & TPLF/PLA composites. The fiber agglomeration
at high volume fraction leads to decrease in tensile strength and poor interfacial bonding in treated
PLF gives a decrease in tensile property at higher fiber loading [21]. The increase in tensile
modulus due to the introduction of high stiffness fiber into the matrix and decrease in percentage
elongation shows poor interfacial bonding between fiber and matrix.
Figure 1 Tensile strength of UPLF/PLA and TPLF/PLA composites
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Figure 2 Tensile modulus of UPLF/PLA and TPLF/PLA composites
Figure 3 Percentage elongation of UPLF/PLA and TPLF/PLA composites
4.1.2. Impact strength on the UPLF/PLA & TPLF/PLA composites
The impact strength of UPLF/PLA and TPLF/PLA composites is shown in figure 4. Initially on
increases in fiber loading of untreated fiber up to 15%, the impact strength increases from 13.62%
to 45.91% and followed by decrease in 3.11% on 20% fiber loading. The similar characteristics
is observed for treated fiber as the fiber loading increases from 10% to 15% the impact strength
increases initially to 22.96% to 49.03% and a decline to 3.5% for 20 % fiber loading when
compare with virgin PLA. The increase in impact strength is due to the introduction of higher
stiffness fiber into the matrix. Similar property was observed in tensile modulus results. The
agglomeration at higher volume fraction may be reason for failure at higher volume fractions.
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Figure 4 Impact strength of UPLF/PLA and TPLF/PLA composites
4.1.3. Flexural properties on the UPLF/PLA & TPLF/PLA composites
Figure 5 Flexural strength of UPLF/PLA and TPLF/PLA composites
The flexural strength and modules of UPLF/PLA and TPLF/PLA composites is shown in
figure 5 & 6. The flexural strength of the composites reduces to 28.7%, 23.03%, 35.31% for 10%,
15%, and 15% in fiber loading respectively untreated PLF into the PLA matrix. Similarly, a
reduction of 65.6%, 20.53%, 24.7% for 10%, 15%, and 15% respectively of treated fiber into the
PLA matrix. The flexural strength of the composites increases on higher fiber loading of UPLF
and TPLF fiber into the PLA matrix to form the composite. The best flexural modulus is observed
for 20% fiber loaded UPLF/PLA composite, has 65.22% increases in property when compared
with virgin PLA. An increase of 47.16% for 20% fiber loaded TPLF/PLA composite was
observed from the test results. The decrease in flexural stress may be due to weak interfacial
bonding between fiber and matrix or poor distribution of load between fiber and matrix [17,20].
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Figure 6 Flexural modulus of UPLF/PLA and TPLF/PLA composites
4.2. WATER ABSORPTION PROPERTIES
Figure 7 Water absorption of UPLF/PLA and TPLF/PLA composites
The water absorption from figure 7 shows an increase in percentage water absorption for
higher fiber loading for both untreated and treated PLF /PLA composites. A maximum value of
57.24% and 750.70% increase absorption was observed in 20% for both untreated and treated
PLF /PLA composites. The result depicts the hydrophilic nature of the PLF fiber [21,22].
4.3. Morphological properties
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Darsan R S, B. Stanly Jones Retnam and M Sivapragash
Figure 7 Different magnification of SEM images for 10% UPLF/PLA composites
Figure 8 Different magnification of SEM images for 10% TPLF/PLA composites
Figures 7 & 8 shows 500x and 750x magnified SEM images of 10% UPLF/PLA and 10%
TPLF/PLA composites. Ductile fracture is observed for 10% UPLF/PLA composite with large
amount of fiber pullout of the fiber from the matrix. Matrix shows fiber agglomeration, with good
interfacial bonding. But in few areas where the fiber agglomeration doesn’t happen shows poor
interfacial bonding. The SEM images of 10% TPLF/PLA composite shows short length fracture,
this can be attributed to brittle fracture behavior of the composites, with the agglomerated PLF
fiber pullout from the matrix. Considerable number of voids appear over the matrix, along with
matrix breakages. The poor interfacial bonding is evident from the images. These fracture
behaviors might indicate poor mechanical characteristics of the TPLF/PLA composites.
5. CONCLUSION
In this study, the composites are prepared by reinforcing untreated and treated pineapple leaf fiber
into the polylactic acid matrix. The prepared UPLF/PLA and TPLF/PLA composites are
evaluated for mechanical, water absorption and morphological properties.
The following conclusion are made from the study.
• Both UPLF and TPLF are reinforced into the PLA matrix using a twin-screw extruder
followed by injection moulded into standard specimen sizes.
• Tensile strength results from the UPLF/PLA composites gives an initial increase and
a decrease in values were noted in the case of TPLF/PLA composites shows. The
tensile modulus of TPLF/PLA composites is higher than the UPLF/PLA composites.
The percentage of elongation decreases on addition of fiber loading for both the types
of composites. The percentage of elongation results for UPLF/PLA composites
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•
•
•
•
•
demonstrates higher values than TPLF/PLA composites. This implies that, the
increase in fiber loading on the composites are becoming more and more brittle due
to the introduction of stiff fiber into PLA matrix.
Flexural strength of both the composites are lower than the virgin PLA. Poor
interfacial interaction and low load sharing between the fiber and matrix causes
decrement in flexural property. But the flexural modulus increases on addition of fiber
into the matrix. The incorporation of stiffer fiber helps increase in modulus of the
composite.
Impact strength of the UPLF/PLA and TPLF/PLA composites increases on increase
in fiber loading up to 15% and decreases there on. The reduction in impact strength
arisen due to the agglomeration of the fiber at higher volume faction.
Percentage of water absorption increases on addition of fiber, is evident that
hydrophilic nature of the fiber absorbs more water than virgin PLA.
The ductile fracture behavior depicted from the SEM images of UPLF/PLA
composites with fiber being pulled from the matrix, with fiber agglomeration and
large amount of fiber pull out from the PLA matrix. Brittle fracture with short fiber
projecting out from the TPLF/PLA composite on loading. The presence of numerous
voids, matrix breakage and poor interfacial bonding of the fiber with the matrix was
seen from the SEM images. This may be attributed to decrement in mechanical
strengths compared with the untreated fiber composites.
Over all, the study of reinforcement of untreated and treated fiber on PLA matrix
shows that untreated fiber composites have much better properties than treated fiber
composites.
ACKNOWLEDGEMENT
The authors are thankful to CIPET: Institute of Plastics Technology (IPT), Kochi, Sophisticated
Analytical Instrument Facility (SAIF) at STIC, Kochi and J J Murphy Research Centre, Rubber
Park, Kochi in conducting different characterizations.
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