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Gel time prediction of polyester resin for lamination of polymer composites

C.O. Ujah
A.P.I. Popoola
I.C. Ezema


Lamination of fibre reinforced plastics (FRP) and catalytic curing of unsaturated polyester (UP) resin were the major focus of this study. The polyester resin was cured at ambient temperature with methyl ethyl ketone peroxide (MEKP) catalyst, cobalt octoate accelerator and phenol inhibitor. This was used to generate model equations that can predict the gel time of polyester resin when curing additives are added. The gelation was obtained by stirring 20 g of catalysed UP resin weighed into a plastic container until the viscosity suddenly increased. Gel times obtained were subjected to regression analysis and analysis of variance (ANOVA) so as to obtain the best predictive model. The ANOVA result showed that the gel time (Ti) in terms of inhibitor concentration, Ti = 2820i – 6 was the best predictive equation of the gel time with a degree of accuracy of 98.89%; where i is the inhibitor concentration. In the model, catalyst and accelerator are at constant concentrations of 1% and 0.5%, respectively. The model was validated by laminating pilot components using hand lay-up technique. Thereafter, a laminating template was developed that would aid in reducing material wastes and lengthy down time during FRP lamination. This will be useful in increasing productivity and profitability in FRP small scale industry.


Bull. Chem. Soc. Ethiop. 2020, 34(1), 163-174.