A chemorheological model for the cure of unsaturated polyester resin

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Abstract
A chemorheological model is developed, using the free volume concept, for the prediction of viscosity during the cure of unsaturated polyester resin. We have incorporated into the development of the chemorheological model a mechanistic kinetic model of curing kinetics that predicts the degree of cure as a function of cure time. The mechanistic kinetic model uses an approach of free‐radical polymerization that takes into account diffusion‐controlled curing reactions, In order to test the usefulness of the chemorheological model developed, we have conducted cure experiments and measured viscosities of partially cured resin samples, using a general‐purpose unsaturated polyester resin. Specifically, the following measurements were taken: (1) the quantity of ethylenic double bonds in the resin system before and after the cure reaction by infrared spectroscopy, (2) the glass transition temperature by differential scanning calorimetry (DSC) and (3) the viscosity as a function of shear rate, at several temperatures, using a cone‐and‐plate rheometer. It is concluded that the chemorheological model developed is very useful for predicting the variation of viscosity during the cure of unsaturated polyester resin.