Investigation of Conversion of Styrene and Fumarate Double Bonds in Unsaturated Polyester Resins

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Abstract
The conversion of styrene and fumarate double bonds in the copolymerization of unsaturated polyesters and styrene was investigated. Several commercial polyester resins including Bisphenol-type, Iso-type and G-type resins were used. The initial fumarate double bond, the equivalent double bond per 100 g of the polyesters, was determined by the hydrogenation procedure which was developed for the present study. Using palladium-carbon catalyst and benzene-acetone (1:1) mixture, polyester resin can be hydrogenated satisfactorily. The cured resin was extracted with chloroform. The styrene in the chloroform was determined by ASTM D-1159, bromine index method. The conversion of the fumarate double bond was calculated from the soluble part of polyester resin using the theoretical equations which were derived from the basic theory of Flory. The validity of the equations was examined by application of Funke et al.'s experimental results and found to be satisfactory. With the confidence of these results, commercial polyester resins were investigated to determine the effect of the condition of polymerization on the conversion of styrene and fumarate double bonds. For all the polyesters the conversion of styrene was at least over 80% after a room temperature cure of 24 hr with a dimethyl anilin-cobalt naphthenate-methyl ethyl ketone peroxide three component catalyst system, and it reached approximately 100% after postcure of 100[ddot]C for 2 hr. On the other hand, the conversion of the fumarate double bond depended greatly upon the type of the resin. Bisphenol-type resin gave the highest conversion, and the conversion for Iso-type resin was higher than that for G-type resin. In the case of Bisphenol-type resin, there was no difference in the conversion of fumarate double bond between the room temperature cure and the postcure, but the conversions of fumarate double bond for G- and Iso-type resins were increased remarkably by postcure. The Barcol hardness is applicable to determine the conversion of styrene for the specified polyesters based on the relationship between the conversion of styrene and the Barcol hardness.