Effect of Accelerators on the Curing of Unsaturated Polyester Resins: Kinetic Model for Room Temperature Curing

Several iron and vanadium compounds were evaluated as accelerators for curing of unsaturated polyester resins, serving as alternatives to toxic cobalt(II) carboxylates currently in widespread use in the composite industry. The catalytic power of the given metal-based compounds has been verified by gelation time measurements on a multipurpose unsaturated polyester/styrene/methyl ethyl ketone peroxide system. Due to different demands of the application sphere, our detailed investigation of the curing process has covered two extreme situations: the behaviors of the accelerators under adiabatic and isothermal conditions. Exothermic behavior in the thermally isolated system, followed by a K-type thermocouple, enabled recognition of the inhibition of the curing process at high concentration of the accelerator and verification of its thermal stability. At isothermal conditions, a radical copolymerization process has been followed by real-time near-infrared spectroscopy, which enabled the establishment of a kinetic model for precise quantification of the catalytic effect for given accelerators.