Low temperature cure of unsaturated polyester resins with thermoplastic additives I. Dilatometry and morphology study

A dilatometry and morphological study of the effect of the various thermopl astic additives on shrinkage control of unsaturated polyester (UP) resins c ured at low temperatures is presented in this article. It was found that sh rinkage control is closely related to the morphological changes during curi ng. There are two major transitions in the relationship of shrinkage and ad ditive concentration that can be explained by the sample morphology. The ad ditive starts to be effective on shrinkage control at the first transition, when a co-continuous phase structure exists in the sample at a certain add itive concentration. The shrinkage control effect vanishes at the second tr ansition, when severe particle fusion is observed in the sample because of too high an additive concentration. The effective additive concentration ra nge does not change much for various thermoplastics, but the two transition s occur at different concentrations for each thermoplastic. (C) 1999 Elsevi er Science Ltd. All rights reserved.