Curing behaviour of unsaturated polyester resins based on recycled poly(ethylene terephthalate) (RPET): effects of RPET content and glycol type

Abstract

Curing behaviour of unsaturated polyester (UPE) resins based on recycled poly(ethylene terephthalate) (RPET) was investigated by measuring exotherms during cure employing differential scanning calorimetry. The UPE resins were prepared by glycolysis of RPET and polycondensation of the glycolysis product with maleic anhydride. In the preparation of the UPE resins, RPET content and glycol type were varied. The curing behaviour of the UPE resins based on RPET was similar to that of conventional UPE resins. The rate of cure increased with increasing RPET content of the UPE resin based on propylene glycol (PG) and RPET. It decreased with increasing RPET content of the UPE resin based on dipropylene glycol (DPG) and RPET. The final degree of isothermal cure increased with increasing RPET content, or changing the glycol type from PG to DPG, in the UPE resins. The curing behaviour was interpreted from the viewpoints of change in double bond concentration, inherent reactivity, and styrene/fumarate ratio of the UPE resins. ©1997 SCI