Toughening polylactide by reactive blending with poly(4‐hydroxybutyrate)‐based polyurethane prepolymer

Abstract A blend of poly(lactic acid) (PLLA) and poly(4‐hydroxybutyrate)‐based polyurethane prepolymer (P4HBU) was prepared through reactive blending in this study. Thermal properties, mechanical properties, rheological properties, and the degradation behavior of the PLLA/P4HBU blends were investigated as varying the P4HBU content. Dynamic mechanical analysis indicated that the glass transition temperatures of PLLA and P4HBU got closer to each other after melt blending, implying that the compatibility between them was improved. With the increase of P4HBU content increased, the elongation of the PLLA/P4HBU composite enhanced obviously, as well as the notched impact strength. When the P4HBU content reached 20 wt%, the elongation increased to 196.2% and the notched impact strength increased to 8.4 kJ/m 2 , respectively, about 26.2 and 2.4 times those of PLLA homopolymer. Meanwhile, the tensile strength decreased to 30.5 MPa. Scanning electron microscopy results proved that the shear yielding of the PLLA matrix and cavitation were the primary toughening mechanisms, resulting in an enhanced ductility of the PLLA/P4HBU blends. The degradation rate of the PLLA/P4HBU blends was improved for the incorporation of the P4HBU. Highlights P4HBU improved PLLA elongation (196.2%) and impact strength (8.4 kJ/m 2 ). Tensile strength of PLLA/P4HBU was reduced to 30.5 MPa. The compatibility between PLLA and P4HBU was enhanced. Shear yielding and cavitation were the primary toughening mechanisms. The degradation rate of the PLLA/P4HBU blends was improved.