Preparation of Natural Rubber-graft-Poly(lactic acid) Used as a Compatibilizer for Poly(lactic acid)/NR Blends

Poly(lactic acid) (PLA) is a biodegradable plastic with good properties in terms of high tensile strength and high tensile modulus, but the brittleness and low impact strength behavior limit its applications. To enhance the impact strength of PLA, natural rubber (NR) with excellent elastic property should be applied to PLA. However, the polarity difference of these constituents leads the incompatibility resulting in poor mechanical properties of PLA/NR blends. Thus, the chemical modification of NR to increase its polarity is required. This research aimed to synthesize NR-graft-PLA (NR-PLA) as a compatibilizer for PLA/NR blends. There were 2 steps to prepare NR-PLA compatibilizer. Firstly, NR was functionalized by various maleic anhydride (MAH) contents (5-20 phr) to produce NR-MAH having higher polarity than NR. Then, NR-MAH was grafted with PLA via esterification using 4-dimethyaminopyridine (DMAP) as a catalyst. The structural characterization of the NR-MAH and NR-PLA was conducted by FT-IR and H-1 NMR spectrooscopy. This was observed that the increase in the MAH contents increased the amount of grafted MAH in the NR-MAH structure. The higher grafted MAH content induced the greater efficiency for grafting PLA in preparation of NR-PLA. The effects of DMAP, NR/PLA wt ratio and temperature in the esterification step on the grafted PLA were investigated.