Acetophenone-Assisted Main-Chain Photocrosslinking of Poly(ethylene terephthalate)

Abstract

Maximum gel fraction of 99.1% was obtained under continuous UV irradiation of a UV energy of 200 J cm(-2) on poly(ethylene terephthalate) (PET) containing only in presence of 2.9%(w/w) acetophenone (AP). The fragmented AP radicals abstract the hydrogen atoms of methylene units in PET, producing secondary methine radicals which couples to main-chain crosslinks. The crystal structure of the crosslinked PET became disordered remarkably. The glass transition temperature disappeared and the peak thermal decomposition temperature was significantly retarded as much as 85 degrees C. The crosslinking density and molecular weight between crosslinks reaches up to 0.129 mol g(-1) and 7.7 g mol(-1), respectively. Also tensile modulus and strength increased by 200 and 72% compared with those of the pristine PET respectively, resulting in more toughened PET. The solid-state photocrosslinking may extend high-temperature applications of PET with enhanced thermal and mechanical properties. (C) 2013 Wiley Periodicals, Inc.