Influence of the styrene-maleate ratio on the structure-property relationships of unsaturated polyester networks

Several structural series of unsaturated polyester networks which had different isophthalic acid-maleic anhydride ratios or different percentage rates of styrene incorporated in the network were studied by means of thermomechanical tests. It was demonstrated that the transition zone (alpha and beta) did not correspond specifically to a polytyrene phase but could be linked to the presence of microdomains of different structures within the polyester network. It is the successive setting in motion of these microdomains, under the effect of a rise in temperature, which creates a broad transition zone. Structural chain formations based on the resin components (prepolymer and styrene) were proposed and linked to the transition temperatures detected. The improved knowledge of the structure and the various microdomains present within the networks will provide a better apprehension of the hydrolytic stability of unsaturated polyester materials.