Polyester-based polyurethanes derived from alcoholysis of polylactide as toughening agents for blends with shape-memory properties

A process for sizing down and functionalizing commercial polylactide (PLA) resin is developed by alcoholysis with 1,4-butanediol (BDO) and propylene glycol (PG) to medium-sized PLA-based diols, with lower cost than a bottom-up synthesis process. These are subsequently used as polyols in preparing polyurethanes (PU) by reacting with 1,6-diisocyanatohexane (HDI). The PLA-based PU has an excellent elongation at break of 487%. The products are suitable as toughening agents for brittle PLA resin due to their highly elastic properties and high compatibility with PLA. The PU products are blended with PLA resin at various compositions, and their physical and mechanical properties and shape recovery are examined. The tensile tests showed enhancements in elongation at break up to 160% with low modulus. The fracture morphology and FTIR results confirm that the blends show strong interfacial interaction and adhesion between the PLA-based PU disperse phase and the PLA matrix. The PLA/PU blends exhibit a high shape recovery efficiency, and their recovery mechanisms are identified. These flexible PLA/PU blends are promising for various applications where bio-compatibility/degradability and high ductility are required, especially as filaments for 3D bio-printing.