Thermal property and curing behavior of unsaturated polyester resins based on recycled poly(ethylene terephthalate)

Abstract

Unsaturated polyester (UPE) resins of different molecular weight or different degree of unsaturation were prepared from recycled poly(ethylene terephthalate) (RPET). The thermal properties and curing behaviour of the UPE resins based on RPET were studied by employing differential scanning calorimeter. Glass transition temperature (Tg) of the cured UPE resin was dependent on Tg of the uncured resin and molecular weight between the crosslink points. The rate of cure was not changed much while final degree of cure during isothermal cure decreased with increasing molecular weight of the UPE resin. It was also observed that the rate of cure of the UPE resin decreased with decreasing degree of unsaturation of the UPE resin. It is postulated that curing behaviour of the UPE resins based on RPET depends on thermal properties and degree of unsaturation as the curing is a diffusion controlled free radical polymerization. The curing behaviour of the UPE resins based on RPET was analyzed by employing the diffusion controlled free radical polymerization scheme and was found to be similar to the curing behaviour of conventional UPE resins.