COMPETITION BETWEEN CURE AND THERMAL-DEGRADATION IN A HIGH TG EPOXY SYSTEM - EFFECT OF TIME AND TEMPERATURE OF ISOTHERMAL CURE ON THE GLASS-TRANSITION TEMPERATURE

The isothermal cure of a diglycidyl ether of bisphenol A with a tetrafunctional aromatic diamine has been studied in an attempt to achieve full cure (maximum glass transition temperature, Tg∞, ca. 170°C). Since high temperatures of cure are necessary for high Tg∞ systems (because of low reaction rates after vitrification), cure and thermal degradation reactions often compete. In this work Tg is used as a direct measure of conversion. An approach leading to a series of iso‐Tg contours in a temperature vs. time transformation (TTT) diagram, which can be used to design time‐temperature cure paths leading to particular values of Tg, is discussed. Copyright © 1990 John Wiley & Sons, Inc.