Synthesis of a multi-armed bio-based cardanol ester plasticizer for efficient plasticization of PLA

Polylactic acid (PLA) suffers from inherent brittleness, while the high migration tendency of conventional plasticizers further limits its practical application in flexible materials. In this study, a multi-armed bio-based plasticizer (LST) was synthesized from cardanol through a two-step process: cardanol was first esterified with succinic anhydride to yield a linear intermediate (LS), which then reacted with triglycidyl isocyanurate (TGIC) to form the branched plasticizer LST. Owing to its branched molecular architecture, LST exhibited significantly reduced migration compared to LS, the linear intermediate formed in the first reaction step. At an addition level of 20 wt%, the migration rate of LST was 0.19 %, markedly lower than that of LS (0.48 %). Simultaneously, LST improved the elongation at break of PLA to 276 % and increased the impact strength to 25.3 kJ/m². Furthermore, a one-pot melt blending strategy involving PLA, LS, and TGIC was investigated. At an optimal epoxy-to-carboxyl molar ratio (R = 0.20), this method yielded PLA with a tensile strength of 32.05 MPa and an elongation at break of 321 %. These findings demonstrate that the multi-armed architecture of LST not only enhances mechanical performance but also effectively suppresses migration, providing a sustainable and efficient approach for the development of high-performance PLA-based materials.