Gel time prediction of polyester resin for lamination of polymer composites

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. DOI: https://dx.doi.org/10.4314/bcse.v34i1.1

Electrical resistivity measurements of carbonized cattle bone/epoxy composite for electrical insulation

This research was focused on determining the electrical resistivity of composite materials developed from carbonized and uncarbonized animal cattle bone (CB). The cattle bone was carbonized at 750°C in the absence of oxygen using a heat treatment furnace; after which they were milled into powder and sieved into 150μm, 300μm and 600μm. The epoxy resin used varied from 10wt% to 60wt%. The effect of carbonization on the resistivity properties was studied and used as criteria for the evaluation of the composites. Better enhancement of property was obtained for the composites with lower wt% and smaller particle sizes. Higher resistivity was evident in the uncarbonized samples. The Cube and 3D graphs show the estimated response surface for the composite properties as a function of sample condition, wt%, and particle size. It is also evident from the results that the actual experimental values are in close proximity with the predicted values.Keywords: carbonization, composite, cow bone, electrical resistivity, electrical insulatio