THERMOGRAVIMETRIC STUDY OF TETRAFUNCTIONAL PHENOL NOVOLAC EPOXY MIXTURES CURED WITH A DIAMINE

The degradation behaviour of an epoxy system containing both tetraglyc idyl-4-4'-diaminodiphenylmethane (TGDDM) and a multifunctional novolac glycidyl ether resins, which are cured with 4,4'-diaminodiphenylsulph one (DDS) has been studied using thermogravimetric technique (TG). Iso thermal and non-isothermal (dynamic) methods were used to determine th e kinetic parameters of this system. An isothermal method and five dyn amic methods reported in the literature were used to determine the act ivation energies of the system. Kissinger's method only requires knowl edge of the temperature at which the rate of weight loss is at maximum to calculate the activation energy. The Flynn-Wall-Ozawa method provi des the activation energy without any assumption about the reaction or der while the other three methods (Coats and Redfern, Horowitz and Met zger and Van Krevelen et al.) require a prior knowledge of the mechani sm 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 me thods have shown excellent agreement when the degradation behaviour of this system was assumed to be of the deceleratory rate type. The kine tic parameters have been used to estimate the half-life of this system in two different ways.