The Evaluation of Low Profile Additives on the Shrinkage Control of Unsaturated Polyester Resin Cured at Room Temperature
The unsaturated polyester (UP) resins have the largest consumption of thermoset resins in the composite industry. The copolymerization of alkyd oligomer with styrene monomer at low temperature condition leads to 5-10% volume shrinkage which may cause problems in the surface quality and dimensional control of produced parts. One effective way for the reduction or elimination of the shrinkage is adding a thermoplastic polymer called low profile additive (LPA). The effect of poly(vinyl toluene) (PVT) and poly(ethyl methacrylate) (PEMA), as two new LPAs have been compared to three types of poly(vinyl acetate) (PVAc) and polystyrene (PS) which are used as conventional LPAs. The phase separation results and morphology of samples containing PEMA showed that this LPA enable to reduce the volume shrinkage. It reduced the volume shrinkage of neat UP from 8.3% to 5.4%. The cure kinetics behaviour of the samples containing PVT and PVAc was completely different from that of the neat UP resin.