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 75°C to 150°C 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 90°C, a discrete phase‐separated structure was observed. As curing temperature was raised above 90°C, 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.