Effect of curing temperature on the morphology of unsaturated polyester resin blended with poly(vinyl acetate)

Phase separation of unsaturated polyester/styrene (UPE/styrene) resin blended with 5 and 10 wt% of poly(vinyl acetate) (PVAc) cured at various temperatures ranging from 75degreesC to 150degreesC was studied using low angle laser light scattering (LALS) and scanning electron microscopy (SEM). For UPE/styrene resin blended with 5 wt% PVAc cured at a temperature below 90degreesC, a discrete phase-separated structure was observed. As curing temperature was raised above 90degreesC, SEM micrographs revealed that more and more cured UPE globules fused together with increasing curing temperature. The LALS intensity profile became broader with increasing curing temperature, indicating a less discrete phase-separated structure at a higher curing temperature. As PVAc content was increased to 10 wt%, SEM micrographs revealed a co-continuous phase-separated structure. The LALS intensity decayed slowly from the center of the scattering pattern to a high scattering angle without the appearance of maximum scattering peak intensity. The morphology of the cured sample did not change too much with curing temperature for UPE/styrene resin blended with 10 wt% of PVAc.