Application of macromolecular chain extender and contribution to the toughening of poly(ethylene terephthalate)

Abstract

An epoxy macromolecular chain extender, polymethyl methacrylate- co-glycidyl methacrylate (PMMA- co-GMA), was synthesized by continuous random free radical polymerization, which was introduced into poly(ethylene terephthalate) (PET) and PET blends. The modified PET blends exhibited higher torque with increasing the content and the polymerization degree of PMMA- co-GMA. The rise of torque after initial melting period was observed, which indicated the occurrence of reaction between the epoxy group of PMMA-co-GMA and hydroxyl or carboxyl end groups of PET. The melting temperature, crystallization temperature, and crystallization degree of PET blends decreased. The chain extender was introduced in PET/ethylene–propylene–diene monomer (EPDM)-graft-GMA (EPDM- g-GMA) blends with the composition of 85/15, which exhibited brittle fracture behavior. The blends, in which the chain extender content in PET was over 8 wt%, exhibited ductile fracture behavior. EPDM- g-GMA was used to toughen PET with 8 wt% chain extender. The brittle–ductile transition took place between the rubber content of 10 wt% and 15 wt%. The transition was in advance when compared with PET/EPDM- g-GMA blends. The content of chain extender in PET showed little influence on the compatibility of PET blends. The macromolecular chain extender was an effective extender for PET. The introduction of macromolecular chain extender showed contribution for the toughening PET.