Optimization of Postcure Conditions and Heat Sag Resistance of a Polyurea-Polyurethane

A model polyurea-polyurethane elastomer was used to demonstrate the mor phology desired to minimize heat sag of a urethane elastomer. The morphology of the elastomer could be widely varied by minor changes in the catalyst con tent. An oscillating disk rheometer was used to optimize the time and tempera ture of the postcure conditions. The rheometer was also used to demonstrate the importance to minimize the time between demolding and postcure. The adverse effect of humidity on heat sag resistance was also demonstrated.