Preparation and Characterization of High-Melt-Strength Polylactide with Long-Chain Branched Structure through γ-Radiation-Induced Chemical Reactions

Abstract

An easy procedure was applied to prepare high-melt-strength polylactide (PLA) that involves γ-radiation-induced free-radical reactions to introduce a long-chain branched structure onto a linear PLA precursor with addition of a trifunctional monomer, trimethylolpropane triacrylate (TMPTA). The results from size-exclusion chromatography coupled with multiangle laser light scattering (SEC-MALLS) detection indicate that the resultant long-chain branched PLA (LCB PLA) samples have an increased molecular mass and an elevated branching degree with increasing amount of TMPTA incorporated during the irradiation process. Various rheological plots including viscosity, storage modulus, loss tangent, Cole–Cole plots, and weighted relaxation spectra were used to distinguish the improved melt strength for LCB PLA samples. The effect of LCB structure on elongational rheological properties was further investigated. The LCB PLA samples exhibited an enhancement of strain-hardening under elongational flow. The enhanced melt ...