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.