Morphology and mechanical properties of poly(lactic acid) with a core-shell impact modifier
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Date
2016-06
Authors
Lee Chee Keong
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Abstract
Poly(lactic acid) (PLA)/core-shell impact modifier (CSIM) blends were prepared via melt mixing with different amount of CSIM (1-20 wt %) using a single screw extruder followed by injection molding and compression molding. The objective of this research was to study the effects of CSIM on the morphological and mechanical properties of PLA. The PLA/CSIM blends were characterized impact, tensile tests and field emission scanning electron microscopy (FESEM). FESEM micrograph of cryogenically fractured samples showed that CSIM domains were uniformly dispersed. Average diameter of CSIM domain (3-20 wt %) were measured and the range was 358 nm-475 nm. The PLA/CSIM blends did not contain significant CSIM agglomerates. The CSIM domains also adhered well to PLA matrix. Notched and unnotched Izod impact strength increased as the content (wt %) of CSIM increased. For unnotched Izod impact strength, incorporation of just 5 wt % CSIM had increased the impact strength of neat PLA by almost 200%. Morphology of Izod impact fractured surface of the blends showed the characteristics of ductile fracture when the content of CSIM increased included formation of fibrils and stress whitening zone. Meanwhile, the tensile modulus and yield strength of PLA/CSIM blends decreased as the loading of CSIM increased. Besides that, elongation at break for the PLA/CSIM blends also showed decrement as the content of CSIM increased. However, the decrement was only 1% almost insignificant. Morphological of tensile fractured surface showed energy absorption-related deformation and existence of air bubbles.