Moisture absorption by cyanate ester modified epoxy resin matrices. Part IV: Effect of curing schedules

The cure schedule (time and temperature) has a profound effect on the physical properties of thermosetting materials. For hydrophilic systems, it can also influence the rate of diffusion of moisture and the equilibrium concentration. The effect of post-cure time and temperature on the moisture sorption behavior and the viscoelastic properties of cyanate ester modified epoxy resin has been investigated. Moisture absorbed at 96% R.H. (relative humidity) and 50degreesC under isothermal conditions was found to increase with post-cure temperature, but the diffusion coefficient decreased in line with the crosslink density. Resins of high crosslink density and high glass transition temperature appeared to exhibit a larger reduction in glass transition temperature on plasticization by moisture in comparison to those with lower crosslink density.