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 (T_g) of PLA/PBAT (100/0) film increased after exposure to UV light, but the T_g of both PLA/PBAT (70/30) and (50/50) films unchanged or varied within the error range. The crystallization temperature (T_c) 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.