Polylactic Acid (PLA)-Natural Rubber (NR) and Polylactic Acid (PLA)- Styrene Butadiene Rubber (SBR) blends- processability, mechanical properties, morphology and thermal properties
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Date
2016-06
Authors
Lim Yu Hsien
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Abstract
This thesis includes the processing torque, mechanical, morphological, thermal properties and crystallinity of PLA/NR and PLA/SBR blends, which were made by blending polylactic acid (PLA) blend with natural rubber (NR) and styrene butadiene rubber (SBR) at various ratios from 100/0 to 80/20. It was found that increasing of rubber content in both PLA/NR and PLA/SBR blends had increased the impact strength, elongation at break and degree of crystallinity but decreased in stabilization torque, tensile strength, Young’s modulus and thermal stability of the blends. The impact strength of PLA/NR blend is better than PLA/SBR blend because NR has superior resilience properties. PLA/NR blends performed better tensile strength and elongation at break than PLA/SBR blends due to strain induced crystallization. PLA/SBR blends performed better Young’s modulus due to its bulky styrene pendant group. SEM micrographs of the impact fracture surfaces of PLA/NR blends showed more rupture lines and matrix tearing when compared with PLA/SBR blends, it indicated that a higher energy is required to cause catastrophic failure. On the other hand, SEM micrographs of tensile fracture surface of PLA/SBR blends showed larger holes and more voids formation, suggesting that the detachment of SBR from the blend occurredwhich results in lower tensile strength.. Thermal stabilities of PLA/NR and PLA/SBR blends were found to decrease with increased of rubber content. Increment in degree of crystallinity was found in both PLA/NR and PLA/SBR blends with increased of rubber content. This could be due to the nucleating effects of NR and SBR over PLA.