Thermogravimetric Study of Tetrafunctional /Phenol Novolac Epoxy Mixtures Cured with a Diamine

Abstract

The degradation behaviour of an epoxy system containing both tetraglycidyl-4-4′-diami-nodiphenylmethane (TGDDM) and a multifunctional novolac glycidyl ether resins, which are cured with 4,4′-diaminodiphenylsulphone (DDS) has been studied using thermogravimetric technique (TG).

Isothermal and non-isothermal (dynamic) methods were used to determine the kinetic parameters of this system. An isothermal method and five dynamic methods reported in the literature were used to determine the activation energies of the system. Kissinger’s method only requires knowledge of the temperature at which the rate of weight loss is at maximum to calculate the activation energy. The Flynn-Wall-Ozawa method provides the activation energy without any assumption about the reaction order while the other three methods (Coats and Redfern, Horowitz and Metzger and Van Krevelen et al.) require a prior knowledge of the mechanism of degradation for this system to calculate the kinetic parameters.

The results obtained by applying these different methods agreed well. In fact, the values of the activation energies provided by the six methods have shown excellent agreement when the degradation behaviour of this system was assumed to be of the deceleratory rate type. The kinetic parameters have been used to estimate the half-life of this system in two different ways.