Curing studies of unsaturated polyester resin used in FRP products

Fiber reinforced plastics (FRP) products being strong and light in weight, find extensive applications in automobiles, marine, structural and household components. Unsaturated polyester (UP) resin is a principle binder material used in FRP products. Curing of UP resin is a key for successful FRP processing. Gel time (tgel) and peak exothermic temperature (θpeak) are critical measures of curing of resin. tgel indicates commencement of polymer cross-linking (setting) while θpeak controls shrinkage and cracking of polymer. This paper aims to predict the tgel and θpeak during cure of UP resin. The weight percent of methyl ethyl ketone peroxide (MEKP) as catalyst, cobalt octoate (Coct) as an accelerator, calcium carbonate (CaCO3) as filler and glass fibers as reinforcements are used as process variables. The variations in tgel and θpeak are approximated by regression equations. Strong interactions are found between the process variables. The process optimization is made to achieve a desired combination of tgel and θpeak within the regime of experimentation. Confirmatory experiments are performed to validate the predicted results.