Sustainable polylactide/polycaprolactone based polyurethane blends fabricated via reactive compatibilization

A series of polylactide (PLA)/polycaprolactone-based polyurethane (PCLU) blends were prepared by reactive blending of PLA with polycaprolactone diol (PCL diol) and hexamethylene diisocyanate (HDI). The reaction mechanism, compatibility, crystallization behavior and the mechanical properties of the PLA/PCLU blends were investigated. It was demonstrated that the hydroxyl group of PCL diol or PLA could react with the isocyanate (NCO) group of HDI to form PCLU or PLA-co-PCLU in situ, thereby improving the interfacial compatibility between PLA and PCLU phases. Phase-separated morphology with the PCLU dispersed in the PLA matrix was observed for the PLA blends with an obscure interphase. The thermal and cold crystallization ability of PLA were retarded. PLA/PCLU blend showed higher impact strength and elongation at break compared with pure PLA. Specifically, at a 40 wt% feed ratio of PCL diol, the impact strength reached an impressive 28 kJ m-2. Notably, the shape memory performance of the blend showed a substantial improvement, achieving a remarkable shape recovery rate of 96.3% at the same 40 wt% PCL diol feed ratio. The mechanisms governing both toughening and shape memory enhancement in the blend were thoroughly elucidated.