Supertough poly(lactic acid)/bio-polyurethane blends fabricated by dynamic self-vulcanization of dual difunctional monomers.

In this work, a facile and efficient strategy known as 'dynamic self-vulcanization of dual difunctional monomers' was reported to toughen poly(lactic acid) (PLA) with in-situ formed crosslinked bio-polyurethane (PCPUE) phase from plant oil-derived hydrogenated dimer diol (Pripol) and hexamethylene diisocyanate (HDI). By simply adjusting equivalent ratios (n/n) of complementary functional groups between these two difunctional toughening monomers from 1.0 to 2.2 while fixing their total feeding content at 20 wt%, the notched impact strength (IS) and phase morphologies of PLA blends can be tailored in a broad range. When the ratio reached 1.6, the maximum IS value up to 87.1 kJ/m (about 28 times that of neat PLA) was achieved with an elongation-at-break of ~223 %. Based on the analysis on reaction mechanism and phase morphologies, the optimum interfacial compatibility between PLA and PCPUE phases in junction with the proper crosslinking density of rubbery PCPUE phase was considered to be responsible for such a remarkable improvement in impact toughness.