Zinc‐Catalysed Depolymerization of Poly(Butylene Succinate) and Poly(Butylene Adipate‐ <i>co</i> ‐Terephthalate) and Enhanced Degradation of Catalyst‐Polymer Composite Films

The depolymerization of poly(butylene succinate) (PBS) and poly(butylene adipate-co-terephthalate) (PBAT) with a highly active zinc catalyst was investigated. The methanolysis of PBS in solution was optimised by varying temperature, catalyst loading, and methanol equivalents, giving a maximum conversion of 98% after 48 h with a dimethyl succinate yield of 62%. Solvent-free methanolysis of PBS and PBAT was shown to reach high conversion after 1 h, although increased temperature was required (100-130°C). When the catalyst was embedded into thin films of PBS and PBAT, a significant loss of mass and a reduction in molecular weight was observed after incubation at 50°C in methanol, comparing favorably with samples of pure polymer. Some increase in degradation activity was also observed in deionized water. This work demonstrates the application of common chemical recycling techniques to increasingly relevant bio-derived polyesters as well as the potential for embedded zinc catalysts to promote degradation.