Influence of Crosslinking Agent and Chain Extender on Properties of Gamma-Irradiated PLA

Abstract

The reactive process in the presence of a multifunctional monomer was performed to recover the molecular weight and improve the properties of gamma irradiated PLA. The effects of two multifunctional monomers, crosslinking agent (CA) and chain extender (CE), were comparatively evaluated. The effects of multifunctional monomers concentration and the irradiation dose on molecular architecture and molar mass distribution were studied. The properties of modified samples were monitored in terms of rheological, thermal, mechanical and optical properties. The results showed that the addition of CA and CE enhanced the average molar mass (M w and M n ) of irradiated PLA, resulting in an increase in shear viscosity, crystallization process, tensile and optical properties. For PLA/CE samples, the irradiation still caused chain scission degradation, which is similar to that of irradiated PLA. Although the average molar mass was reduced by the irradiation, it was much improved compared with that of irradiated PLA. The irradiation had a complicated effect on the PLA/CA samples. The development of long-chain branches with a relatively long arm or star-like structure was observed for PLA/CA irradiated at the irradiation dose of 10 kGy, whereas the crosslinking was observed at the irradiation dose of 20 kGy. This chain branching and crosslinking were also responsible for the improved rheological, tensile and optical properties of irradiated samples. Nevertheless, the presence of these structures retarded the crystallization process.