Effects of Styrene Evaporation on the Cure Kinetics Behaviour of a Vinylester Resin System Suitable for Composite Pultrusion

The paper describes the effects of styrene evaporation on the curing reactions of a vinylester resin, explored by the use of differential scanning calorimetry. The thermosetting system under study is characterized by the presence of three distinct exothermic peaks, attributed to different cure reaction mechanisms. A chemical cure kinetics model is presented, incorporating effects of diffusion limitations on the later stages of the cure. Whilst the nature of the curing mechanism is unaffected by the loss of styrene, the expected reductions in the overall heat of reaction from the individual reaction components are noted and quantified. The glass to rubber transition temperature, T_g, of fully cured resin is shown to decrease from 124°C in the initial sample to 121°C in samples in which over 20% of the initial styrene content had evaporated.