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MECHANICAL PROPERTIES AND MORPHOLOGY OF POLY (LACTIC ACID) (PLA) WITH DIFFERENT FLEXIBLE COPOLYMERS

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International Journal of Mechanical Engineering and Technology (IJMET)
Volume 10, Issue 01, January 2019, pp. 745–754, Article ID: IJMET_10_01_076
Available online at http://www.iaeme.com/ijmet/issues.asp?JType=IJMET&VType=10&IType=01
ISSN Print: 0976-6340 and ISSN Online: 0976-6359
© IAEME Publication
Scopus Indexed
MECHANICAL PROPERTIES AND MORPHOLOGY OF POLY
(LACTIC ACID) (PLA) WITH DIFFERENT FLEXIBLE
COPOLYMERS
B Ramanjaneyulu
Research scholar, Department of mechanical engineering, Jawaharlal Nehru technological
university ananthapur, A.P. India
N.Venkatachalapathi
Department of mechanical engineering, Annamacharya institute of technology and sciences
(Autonomous) Rajampet, A.P. Kadapa
G.Prasanthi
Department of mechanical engineering, Jawaharlal Nehru technological university ananthapur,
A.P. India
ABSTRACT
Poly (lactic acid) (PLA) blended with acrylonitrile-butadiene styrene (ABS) and
natural biodegradable tapioca cassava starch powder (NBTCSP) the weight ratios on the
properties of blends, the blends films were prepared by using a twin-screw extruder and
semi-automatic compression molding machine. The mechanical and morphological
properties of samples were investigated by tensile test, flexural, compressive , impact test
and scanning electron microscope (SEM), respectively.it was found that the tensile
strength of PLA/ABS (45/45/ wt %) blend composite was about 31.50 MPa the in the
absence of natural biodegradable tapioca cassava starch (NBTCSP), and it increased to
28.66 –32.90 MPa in presence of natural biodegradable tapioca cassava starch powder
(NBTCSP) at 10 wt% .The flexural value of PLA/ABS (45/45/ wt %) blend composite was
about 31.50 MPa the in the absence of natural biodegradable tapioca cassava starch
Powder (NBTCSP), and it increased to 28.66 –32.90 MPa in presence of natural
biodegradable tapioca cassava starch powder (NBTCSP) at 10 wt% . The SEM images
showed good interface and distribution for PLA containing 47.5 wt% ABS, 5 wt%
(NBTCSP) and 45 wt% ABS 10 wt% (NBTCSP)
KEY WORDS: Poly (lactic acid) (PLA) blended with acrylonitrile-butadiene styrene
(ABS) and natural biodegradable tapioca cassava starch powder (NBTCSP) and SEM
analysis.
Cite this Article: B Ramanjaneyulu N.Venkatachalapathi and G.Prasanthi, Mechanical
Properties and Morphology of Poly (Lactic Acid) (Pla) with Different Flexible Copolymers,
International Journal of Mechanical Engineering and Technology, 10(01), 2019, pp.745–
754
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B Ramanjaneyulu N.Venkatachalapathi and G.Prasanthi
1. INTRODUCTION
The word composite can be defined as a material composed of two or more different materials,
with the properties of the resultant material being superior to the properties of the individual
materials that make up the composite. Composite material is a lightweight, strong, and low
thermal expansion material used in different application due to their good properties. The raw
materials are much less expensive. Its bulk strength and weight properties are very favorable
when compared to metals, and it can be easily formed using molding processes. Now a day’s
natural and partial biodegradable polymer blend composites materials are replacing the plastics
and this natural and partial biodegradable polymer composites doesn’t create any environmental
issues. By using natural biodegradable blend polymer materials, and partial and natural
biodegradable blend polymer composites is improved remarkably due to the fact that the field of
application is improved day by day in different field of applications 1-2. Several researches have
been taken place in this direction. Most of the studies on natural biodegradable polymer
composites are concerned with and without reinforcement and the addition of biodegradable
polymer matrix material to the ABS can make the composite hybrid which is comparatively
cheaper and easy to use. In the present study the mechanical properties PLA matrix composite
materials is studied. The PLA matrix composite materials are manufactured by semi-automatic
compression molding process. The properties such as tensile, compression, flexural and impact
are studied and presented in detail. The results indicated that the addition of PLA and NBTCSP
material makes the composite hybrid and it improves the properties
2. MATERIALS AND METHODS
2.1. Materials
Poly 3052D (lactic acid) (PLA) (NATURE TECTMA-1001) [density =1.25g/cm3 (21.5˚C),
MFI=g/10min (210˚C/2.16kg)] was supplied by India Industrial Company. Pvt.Ltd. (Chennai,
India), the selected grade is an extrusion material; it was must be driedat60˚Cfor6hours before
using. Acrylonitrile-butadiene styrene (ABS) (AADILAKSHMI PLASTIC TRDERS-ABS)
[density =1.05 g/cm3, MFI= 21.3g/10 min (220˚C/10 kg, MFR= 50 g/10min (200˚C/21.6
kg)].Was supplied by AADILAKSHMI PLASTIC TRDERS Pvt.Ltd (Hyderabad India) the
selected grade is extrusion material Acrylonitrile-butadiene-Styrene; it was must be driedat8085˚Cfor2-5hours before using. TAPIOCA CASAVA STRACH extracted from cassava tubers
(TAPIOCA CASSAVA STRACH FOOD GRADE) which was purchase from ANGEL
STARCH&FOOD Pvt.Ltd (Chennai INDIA).It has a particle size of 0.075mm.
2.2. Blending
The blends were processed in a Twin-screw extruder (ZV20-High Torque, L/D= 40, NEO
PLAST) at 1960c (die) and 300 rpm. The extrusion rate was 10kg / hr. And the accumulation time
was approximately 2 min. Seven hundred and fifty six gram PLA and 313 g ABS were mixed in
a 1-l beaker and then 62.5 g NBTCSP was added. In the same manner other blends were prepared
with different proportion as show in table .1 the mixed pellets were collected from the granulator
and dried for 6 h at 600c in a hot air oven. Twin-screw extruder and hot air oven shown in fig.1
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Mechanical Properties and Morphology of Poly (Lactic Acid) (Pla) with Different Flexible Copolymers
A
b
Figure1. (a) Twin Screw Extruder Machine NEOPLAST (b) Hot air Oven with Dimensions Model
HOS-5 605 mm X 605 mm X 605 mm
2.2. Samples Preparation
Table1. PLA formulations and blend compositions.
Samples formulation
neat PLA
neat ABS
PLA70/ABS30
PLA50/ABS 50
PLA30/ABS70
PLA47.5/ABS47.5/NBTCSP5
PLA45/ABS45 / NBTCSP10
PLA25/ABS60/ NBTCSP15
PLA60/ABS25/ NBTCSP15
PLA (wt %)
(g)
100
70
50
30
47.5
45
25
60
ABS (wt %)
(g)
NBTCSP (wt %)
(g)
100
30
50
70
47.5
45
60
25
5
10
15
15
The prepared granules were Compression molded at 190˚C- 210˚C using NEO PLAST
ENGINEERING (NP30) Compression machine (NEOPLAST ENGINEERING PVT.LTD,
GUJARATH (INDIA)). The tensile samples were prepared according to the following
Compression conditions, cooling time in the mold was15sec, the mold temperature was room
temperature with water-cooling (25˚C) and injection pressure was 9MPa.Themoldedsamples
were dog bone-shaped sampleswithathicknessandwidthof4mmand10mm respectively. The gauge
length ofthesamplewas80mm (Fig 2).The obtained products were immediately packed in plastics
bags and stored in a dark cool surrounding.
2.3 Experimental test specimens
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Figure. 2: Tensile test specimens type 1A and 1B
3 MECHANICAL AND MORPHOLOGICAL TEST
3.1. Tensile test
The polymer composite material fabricated is cut into required dimension using a CNC contour
cutting and the edges finished by using emery paper for mechanical testing. The tensile test
specimen is prepared according to the ASTM D 638standard. The dimensions, gauge length and
cross-head speeds are 50 mm and 5mm/min respectively. The tests are conducted on four
identical specimens for each type of compounded separately. The Universal Testing Machine
with Flexural and Compression Set-Up are shown in Fig. 3 and Fig. 4, respectively. The testing
process involves placing the test specimen in the testing machine and applying tension to it until
it fractures. The tensile force is recorded as a function of the increase in gauge length. During the
application of tension, the elongation of the gauge section is recorded against the applied force.
Experimental tests to sort out the tensile strength of partial biodegradable polymer prepared
blends material were conducted in Static Mechanical Properties Testing Laboratory of
G.Pullareddy Engineering College Autonomous by using Universal Testing machine INSTRON
3969 USA (Fig3). Group is the world’s leading supplier of static materials testing machines,
developed by experts for use in demanding testing situations and in a wide range of applications.
Their static testing machines have been specially designed for tensile, compression and flexure
tests, as well as shear and torsion tests, making them ideal for the most rigorous materials and
component testing requirements. Max. Test load 10kN, work space height 1050mm, work space
width 440mm, Max. Crosshead speed 1000 mm/min
Figure 3.Universal Testing Machine model (INSTRON -3369)
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Mechanical Properties and Morphology of Poly (Lactic Acid) (Pla) with Different Flexible Copolymers
3.2. Compression test
The compressive test specimen is prepared according to the ASTM D638 standard. The
dimensions, width, height, and Length and cross-head speeds are 13 mmx13 mmx10 mm and
5mm/min respectively.
Figure .4. UTM with compressive test set-up
3.4. Flexural test
The flexural specimens are prepared as per the ASTM D790 standard. The 3-point flexural
bending test is the most common flexural test for polymer composite blend materials. Specimen
deflection is measured by the crosshead position. Test results include flexural strength and
displacement. The testing process involves placing the test specimen in the universal testing
machine and applying force to it until it fractures and breaks. The specimen used for conducting
the flexural test. The tests are carried out at a condition of an average relative humidity of 50%.
5 (a) Specimen for under the Flexural bending test condition. 5 (b) Specimens for flexural test
FIGURE 5. Physical appearance of Specimens for flexural 5 (b) (i) neat PLA,( ii) neat ABS (iii)
PLA30/ABS70 wt%, (iv) PLA50/ABS50 wt%, (v)PLA70/ABS30 wt%, (vi)
PLA47.5/ABS47.5/NBTCSP5 wt%, (vii) PLA45/ABS45/NBTCSP10 wt%, (viii)
PLA60/ABS25/NBTCSP15 wt%, (ix) PLA25/ABS60/NBTCSP15 wt%,
3.5. Impact test
The impact test specimens are prepared according to the required dimension following
the ASTM-D-256 standard. During the testing process, the specimen must be loaded in the
testing machine and allows the pendulum until it fractures or breaks. Using the impact test, the
energy needed to break the material can be measured easily and can be used to measure the
toughness of the material and the yield strength
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Figure 6. Impact test rig
4. RESULTS AND DISCUSSION
The use of polymer composite blend materials in the different fields is increasing day by day due
to their improved properties. Engineers and Scientists are working together for number of years
for finding the alternative solution for the high solution materials. In the present study partial
biodegradable composites are added to the thermo plastics, composite materials and their effect
on mechanical properties is evaluated and tensile fractured surfaces morphology properties are
investigated.
4.1. Tensile properties and SEM of Specimens
The modulus, tensile strength and elongation at break were displayed in table 2. The tensile
properties such as tensile strength and modulus increasing with increasing of ABS percentage,
the increases tensile strength resulted from the presence copolymers inserted in PLA matrix [910]. The increase in elongation at break probably resulted from the samples were some ductile
nature. PLA added 60 wt% ABS showed the highest elongation at break value. It also appeared
necking phenomenon which demonstrated the ductile behavior of the polymer blends.
Table 2. Tensile properties of PLA and the blends containing different copolymers.
Sample
neat ABS
neat PLA
PLA70/ABS30
PLA50/ABS 50
PLA30/ABS70
PLA47.5/ABS47.5/NBTCSP5
PLA45/ABS45/NBTCSP10
PLA25/ABS60/NB TCS P15
PLA60/ABS25/NBTCSP15
Modulus
(MPa)
1873.52
1102.56
1315.69
1331.80
1399.96
1707.51
1714.14
1732.17
1512.55
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Tensile Strength(MPa)
Elongation at
break [%]
29.59
56.39
28.66
28.38
31.50
31.05
32.90
31.97
24.03
19.80
19.68
13.37
12.57
13.37
13.04
11.55
14.70
10.98
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Mechanical Properties and Morphology of Poly (Lactic Acid) (Pla) with Different Flexible Copolymers
(a) PLA50/ABS50 wt%,
(b) PLA70/ABS30 wt%
(c) PLA47.5/ABS47.5/NBTCSP5
wt%,
(d) PLA45/ABS45/NBTCSP10 wt%,
(e) PLA60/ABS25/NBTCSP15
wt%,
(f) PLA25/ABS60/NBTCSP15
wt%,
From figure 7, it was demonstrated that complete breakage could be obtained with samples
a), b),c), d), e), and f) Stress whitening near the notched tip was observed due to crazing or micro
cracks, and it showed that the matrix could bear most of the stress [17]. It is common that the
continuous transfer of energy is an important factor for impact resistance. In adding dispersed
phases into the polymer matrix, the good distribution of the dispersed phase, smaller particle sizes
and good interfacial adhesion are key factors to determining the optimum performance of
materials. Fractured surface of impact specimens corresponding to the same concentration of
copolymers are shown in figures 5(a) and 5 (f). The tensile fractured surface micrographs of neat
PLA and PLA/ABS/NBTCSP blends are displayed in Figure7. It can be confirmed from Figure 7 (d)
that PLA45/ABS45/NBTCSP5 undergoes a little brittle failure, whereas the fractured surface of
PLA25/ABS60/NBTCSP15 wt% was smooth and a homogenous microstructure can be seen,
indicating that no phase separation took place. No agglomerates or brittle crack behavior were
observed in Figure 7(f), which evidences good interfacial adhesion between the two phases of PLA
matrix and with copolymers of ABS and NBTCSP. This was indirectly reflected in the more efficient
load transfer under stress conditions, which was apparent from the improved tensile, flexural and
impact properties of the blend [4 and 6].
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4.2 Compressive properties
The specimen size for compression test is 13x13x11mm.The results generated directly from the
machine for compression test with respect to load and displacement for partial biodegradable
polymer composites. That the results show that the maximum compressive strength is 84.9MPa
the respective elongation at break is 25.08 %. [7]
Table 3. Compressive properties of PLA and the blend
Sample
neat ABS
neat PLA
PLA70/ABS30
PLA50/ABS 50
PLA30/ABS70
PLA47.5/ABS47.5/NBTCSP 5
PLA45/ABS45 /NBTCSP10
PLA25/ABS60/NBTCSP 15
PLA60/ABS25/NBTCSP 15
Modulus
(MPa)
11246.08
5198.219
4721.231
7088.841
6741.882
11312.91
9051.129
6278.662
10590.88
Compressive
Strength(MPa)
126.4
37.90
89.9
84.80
67.14
28.19
68.33
76.00
67.24
Elongation at
break [%]
5.56
5.28
25.08
8.56
8.99
3.03
4.97
8.75
4.97
4.3. Flexural properties
The flexural specimens Prepared as for ASTMD 638.The results generated directly from the
machine for three point bending test with respect to load and displacement for partial
biodegradable polymer composites. That the results show that the maximum flexural strength is
84.9MPa the respective elongation at break is 25.08 %. [7]
Table 4. Flexural properties of PLA and the blend.
Sample
Modulus(MPa)
neat ABS
neat PLA
PLA70/ABS30
PLA50/ABS 50
PLA30/ABS70
PLA47.5/ABS47.5 /NBTCSP5
PLA45/ABS45 /NBTCSP10
PLA25/ABS60/NBTCSP 15
PLA60/ABS25/NBTCSP15
3790.28
3331.22
3445.92
3032.09
3063.83
2937.09
3537.20
4118.99
2922.86
Flexural Strength(MPa)
98.26
75.48
64.35
51.28
43.63
53.53
62.46
61.89
57.27
Elongation at break
[%]
50.06
50.04
42.26
28.02
26.86
32.81
30.10
25.46
35.27
4.4. Izod Impact properties
The impact test un-necked specimens are prepared according to the required dimension following
the ASTM-D638 standard. The dimension length width and thickness are 67.5mmX 12.75mm X
4mmduring the testing process, the specimen must be loaded in the testing machine and allows
the pendulum until it fractures or breaks. Using the impact test, the energy needed to break the
material can be measured easily and can be used to measure the impact resistance of the material
and the absorbed energy ,the obtain results are shown in the table.5 [5and 7]
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Table 5. Impact properties of PLA and the blend
Izod impact strength (IS) (KJ/m2)
57.74
89.23
68.24
57.74
78.74
68.24
62.99
68.40
62.99
sample
neat ABS
neat PLA
PLA70/ABS30
PLA50/ABS 50
PLA30/ABS70
PLA47.5/ABS47.5 /NBTCSP5
PLA45/ABS45 / NBTCSP10
PLA25/ABS60/ NBTCSP15
PLA60/ABS25/NBTCSP15
5. CONCLUSION
In this study, the partial biodegradable polymer blend composite samples have been fabricated
successfully by the compression molding technique. The tensile strength, impact strength and
flexural strength of the fabricated composite material have been evaluated satisfactorily. The
following conclusions are drawn from this experimental investigation
• The partial biodegradable polymer based polymeric matrix composites has been
fabricated.
• The tensile strength, compressive strength flexural, and impact strength of the
fabricated materials have been found by different tests.
• The average tensile strength of fabricated specimen is 29.26 MPa, which make it
suitable for medium tension applications such as agricultural high tunnel poly house
or green house applications
• In flexural test, the specimens show their higher durability under higher load. The
average flexural strength of fabricated composite laminates is 63.12 MPa.
• The average impact strength of specimens was 68.25K J/m2.
• SEM results evidence good interfacial adhesion between the two phases of the PLA
matrix and their copolymers
ACKNOWLEDGMENTS
The authors would like to gratefully thank institution of engineers, India (IEI) and this work was
supported by a grant from IEI R&D Cell Technical Department The institution of engineers
(India)
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