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, T g ∞ , ca. 170°C). Since high temperatures of cure are necessary for high T g ∞ systems (because of low reaction rates after vitrification), cure and thermal degradation reactions often compete. In this work T g is used as a direct measure of conversion. An approach leading to a series of iso‐ T g contours in a temperature vs. time transformation (TTT) diagram, which can be used to design time‐temperature cure paths leading to particular values of T g , is discussed.