Plasticization of Poly (lactic acid) Using Epoxidized Palm Stearin

Abstract

Polylactic acid (PLA) is a promising biodegradable alternative to petroleum-based polymers, yet its industrial applications are hindered by inherent brittleness and low elongation at break. This study aims to enhance PLA’s mechanical performance by investigating the effects of epoxidized palm stearin (EPS) as a bio-based plasticizer and starch as a reinforcing filler. EPS was selected as a sustainable, reactive additive because its epoxy groups interact with PLA, thereby improving chain mobility and flexibility. Starch was incorporated as a natural filler because it is cost-effective, renewable, and can act as a reinforcing agent to mitigate the loss of stiffness and toughness often caused by excessive plasticization. The primary objective of the study was to evaluate the thermal and mechanical properties of these blends to determine the optimal composition for balanced flexibility and strength. Blends containing 5–20 wt.% EPS and a fixed 5 wt.% starch were prepared via melt blending. Thermal analysis via DSC revealed that increasing EPS content successfully reduced the glass transition temperature (Tg) and cold crystallization temperature (Tcc), confirming improved molecular mobility. Mechanically, the PLA/EPS20/St5 blend achieved the highest elongation at break at 15.65%, while the addition of starch consistently improved impact strength across all EPS-containing blends. Although excessive EPS loading eventually reduced tensile strength, the results demonstrate that the combination of EPS and starch offers a viable, eco-friendly strategy to tailor PLA properties for industrial use.