WATER SORPTION IN TETRAFUNCTIONAL PHENOL NOVOLAC EPOXY MIXTURES CUREDWITH A DIAMINE

The diffusive and dynamic mechanical behaviour of an epoxy system cont aining tetraglycidyl-4,4'-diaminodiphenylmethane and a multifunctional Novolac glycidyl ether cured with 4,4'-diaminodiphenylsulfone was stu died after water sorption. The diffusion of water was performed at 100 % relative humidity, by immersion of specimens in water at 20, 40, 70 and 100 degrees C. In all sorption experiments, the water diffusion fo llowed Fick's law. Diffusion coefficients and saturated water concentr ations were estimated for these temperatures. The activation energy fo r diffusion was determined from the relationship linking the diffusion coefficient and the reciprocal of the absolute temperature. The value obtained was 45.7 kJ mol(-1). Dynamic mechanical analysis of samples immersed in water at 25 and 100 degrees C, and with various water cont ents, showed a shift in T-g (defined by the tan delta peak) to lower t emperatures over the glass transition region, and a slight decrease in the dynamic storage modulus in the presence of water as a result of a plasticization effect.