Tailoring mechanical performance and biodegradability of poly(lactic acid) using renewable additives

Poly(lactic acid) (PLA) has gained substantial attention in the bioplastic industry. However, its practical application is hindered by inherent brittleness and slow biodegradability. This research purposes to simultaneously enhance the toughness and biodegradation rate of PLA through melt blending with 1-5 wt% of epoxidized soybean oil (ESO) and epoxidized natural rubbers (ENRs) with molecular weights of ∼70,000 g/mol (ENR-70k) and ∼250,000 g/mol (ENR-250k). The incorporation of these additives significantly improved the mechanical properties of PLA, increasing elongation by 26-30 times and impact strength by 2.0-3.2 times at 5 wt% loading compared to neat PLA. ESO provided the greatest enhancement in stretchability, whereas ENR-250k led to the highest impact strength. These improvements are attributed to enhanced interfacial adhesion between the dispersed phase and PLA matrix, evidenced by downward shifts in glass transition temperature and the formation of yielding and microfibrils on impact-fractured surfaces. Moreover, PLA/ENR-250k blends exhibited maximum biodegradation of ∼74 % compared to neat PLA (∼38 %) at 90 days, measured from CO₂ evolution, which correlates with increased chain mobility and elastomer compatibility. The results highlight the effectiveness of tailored elastomers in promoting the environmental decomposition of PLA, offering a promising pathway for expanding its applicability in sustainable materials design, particularly where accelerated biodegradability is essential.