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

Abstract

The free radical copolymerization reaction of three series of acrylate-terminated unsaturated polyesters with styrene, using benzoyl peroxide/N,N-dimethylaniline as the redox initiator system, was followed by dynamic mechanical analysis. The presence of double bonds at both chain ends allows the formation of a regular network during the crosslinking copolymerization with styrene. The evolution of the rheological parameters, such as storage modulus G' and loss modulus G ", was recorded. The polymerization reaction, leading to the formation of a crosslinked structure, is described by a second order 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 numerical values of the kinetic equation constants and the degree of rheological conversion as a function of cure time. The influence of the terminal double bonds as well as of the cis-trans configuration on the curing kinetics of the unsaturated copolyesters was evaluated.