Effect of ultraviolet irradiation on strength and toughness of composites of poly(lactic acid) and poly(butylene adipate-co-terephthalate) with different mass ratio

Composites of poly(lactic acid) (PLA) and poly(butylene adipate-co-terephthalate) (PBAT) with different mass ratio, containing nano-sized calcium carbonate, benzophenone and triallyl isocyanurate, were prepared by using a double screw extruder, and blown into films by extrusion blow molding. After ultraviolet (UV) exposure at irradiation doses (ID) of 20 J/cm2 and 40 J/cm2, the mechanical, dynamic mechanical and thermal properties of the radiated films were tested and compared with that of the unradiated. The tensile strength of the PLA/PBAT (100/0) film with single PLA phase increased after exposure to UV light, but its fracture energy decreased. In contrast, both the tensile strength and fracture energy of PLA/PBAT (70/30) film with PLA and PBAT co-continuous phases increased after exposure, but both the tensile strength and fracture energy of PLA/PBAT (50/50) film with PBAT continuous phase decreased. The glass transition temperature (Tg) of PLA/PBAT (100/0) film increased after exposure to UV light, but the Tg of both PLA/PBAT (70/30) and (50/50) films unchanged or varied within the error range. The crystallization temperature (Tc) of all the films did not changed after UV exposure, but the crystallizability significantly decreased. It suggested that UV irradiation was a simple and effective technique to simultaneously improve the strength and toughness of the film with PLA and PBAT co-continuous phases.