Compatibilization of poly(butylene adipate-co-terephthalate)/polylactic acid blends by gamma radiation

Abstract

Polylactic acid (PLA) is a widely used biopolymer and is currently produced on a global scale. However, PLA has low melt strength, which limits its application. Poly(butylene adipate-co-terephthalate) (PBAT) is a fully biodegradable polymer and one of the most attractive polymers for hardening PLA. As PLA and PBAT are immiscible, they need to be compatibilized to improve the properties of the blend. In this context, the compatibilization of PLA/PBAT blends was investigated through an irradiation process. PLA was previously irradiated, at different absorbed doses, in a cobalt-60 source to assess the compatibility of its blends with PBAT. Differential scanning calorimetry showed a reduction in the glass transition, cold crystallization and melting temperatures, and a second melting peak was observed after polymer irradiation. Also, X-ray diffraction analyses revealed a slight increase in the crystalline fraction. Thermogravimetric analysis showed that as the absorbed dose increased, the thermal stability of PLA decreased. Fourier-transform infrared spectroscopy shows bands attributed to oxidized terminations of polymer chains with carbonyls attributed to the effect of irradiation exposure. For samples irradiated above 100 kGy, an increase in tensile strength and tensile modulus can be observed as the dose increases. Rheological measurements showed a decrease in the complex viscosity of irradiated PLA with increasing absorbed dose. The surface of the polymer blend with PLA irradiated with gamma rays at 150 kGy appears to be more homogeneous according to scanning electron analysis. The polymer blend with 150 kGy irradiated PLA showed improved interaction between the components.