Abstract
The influence of styrene contents on the hardening reaction of unsaturated polyester resins was studied. The degree of cross-linking in the resins with different styrene contents was estimated by solid-NMR analysis, laser Raman analysis and quantitative analysis of organic acid by sub-critical water hydrolysis method. We also measured the density and glass transition point of the resins. The degree of cross-linking in the resins estimated by these methods was nearly the same. Although the cross-linking reaction increased with an increase in styrene contents, the hardening reaction didn't proceed at the styrene content above about 70%. Moreover, the molecular weight of the styrene-fumaric acid copolymer that was produced by sub-critical water hydrolysis, increased with an increase in styrene contents, suggesting that the sequence length of the styrene residues in the cross-linking of the resins also increased with increasing styrene contents. The decreases in the density and glass transition temperature of the resins with an increase in styrene contents are correlated to the decrease in the cross-link density of the resins, namely the increase in the average distance between the cross-linking points.
