Preparation of High-Molecular-Weight Polylactic Acid Based on Melt Polycondensation and Chain Extension Technology

This study employed a two-step approach involving melt polycondensation and chain extension to synthesize high-molecular-weight PLA. Initially, the mechanism of ring-forming side reactions during polycondensation was systematically investigated using MALDI-TOF-MS. The results demonstrated that the SnCl 2 /TSA composite catalyst effectively suppressed the formation of cyclic oligomers, and the optimal reaction conditions were determined as 180°C for 8 h. Based on these findings, HDI was chosen as an efficient chain extender. By optimizing both the molecular weight of PLA during polycondensation and the HDI content, chain-extended PLA with a molecular weight of 1.48 × 10 5 g/mol was successfully obtained. The results showed that the chain-extended product exhibited excellent overall performance. Its tensile strength (75.5 MPa) was comparable to that of commercial PLA 4032D (75.3 MPa), while its elongation at break (12.21%) slightly exceeded that of the commercial sample (11.1%). This work provides a novel strategy for the industrial production of high-performance PLA.