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.