Influence of processing conditions on shrinkage behavior of low profile unsaturated polyester resins. I: Systems without fillers

Abstract

Abstract Blends of unsaturated polyester resin and polyvinylacetate (PVAc) were molded with a new instrument called the Plastoreactomat (PRM). The shrinkage and exothermic peak of polymerization were recorded during moding, and the influence of the processing conditions (pressure and temperature) on these phenomena and on the morphology was investigated for various PVAc contents. Within the limits of this study, it was found that shrinkage increases as the temperature and pressure increase. These results are discussed in terms of a competition between the phase separation and the reaction rates. In addition, it was verified that a co‐continuous two‐phase system consisting of the PVAc and the polyester network enhances the low‐profile behavior.