Rheological study of the copolymerization reaction of acrylate-terminated unsaturated copolyesters with styrene

The free radical copolymerization reaction of three series of acrylate-term inated unsaturated polyesters with styrene, using benzoyl peroxide/N,N-dime thylaniline as the redox initiator system, was followed by dynamic mechanic al analysis. The presence of double bonds at both chain ends allows the for mation of a regular network during the crosslinking copolymerization with s tyrene. The evolution of the rheological parameters, such as storage modulu s G' and loss modulus G ", was recorded. The polymerization reaction, leadi ng to the formation of a crosslinked structure, is described by a second or der phenomenological equation, which takes into account a self-acceleration effect, as a consequence of not only the chemical reaction of crosslinking after the gel point but also phase segregation. This rheokinetic model of curing acrylate-terminated polyesters permits the determination of the nume rical values of the kinetic equation constants and the degree of rheologica l conversion as a function of cure time. The influence of the terminal doub le bonds as well as of the cis-trans configuration on the curing kinetics o f the unsaturated copolyesters was evaluated.