Effect of temperature gradients on cure and stress gradients in thick thermoset castings

The temperature gradient developed during casting of an unsaturated polyester for which the kinetics of reaction and the heat capacities, thermal conductivities, and densities were known from earlier work was measured experimentally as a function of time in a thick casting and compared with predicted values calculated from a mathematical model. Agreement was excellent. The castings were sectioned and the sections were examined by birefringence. These examinations show good agreement between the temperature gradient developed during cure and the residual stress gradient. This work demonstrates that the extent of cure as a function of position can be predicted from heat transfer calculations if the reaction kinetics and thermal properties are known and that the residual stress gradient is dependent upon the temperature gradient developed.