Improvement of Poly(ethylene terephthalate) Melt-Foamability by Long-Chain Branching with the Combination of Pyromellitic Dianhydride and Triglycidyl Isocyanurate

Abstract

Reactive processing on conventional poly(ethylene terephthalate) (PET) with the combination of pyromellitic dianhydride (PMDA) and triglycidyl isocyanurate (TGIC) was used to produce long-chain branched PET (LCB-PET). The branching factors of the PET samples were correlated from their intrinsic viscosity and molar mass results. In all PET samples without a cross-linked structure, PET modified with 0.1 wt % PMDA and 0.5 wt % TGIC (PET-P1T5) had the highest branching degree, with a branching factor of 0.84. The relaxation time spectra of the three modified PET samples with strain-hardening behaviors displayed rubbery states during the relaxation process, which was ascribed to their increased molecular weight or long-chain branched structure. Batch melt-foaming experiments with CO2 were carried out to evaluate the melt-foamability of PET. The results indicated that both a high molecular weight and long-chain branched structure, especially the latter, could efficiently lead to strong molecular entanglements a...