Influence of water absorption on the mechanical properties of a DGEBA (n = 0)/1, 2 DCH epoxy system

The diffusive, calorimetric, and mechanical behavior of a system composed of a diglycidyl ether of bisphenol-A (DGEBA, n = 0) and 1, 2 diamine cyclohexane (1, 2 DCH) were investigated during water sorption at different temperatures (23, 47, 58, 77, and 100°C). Experimental results showed that the water absorption at these temperatures fitted well to Fick's law. The water moisture content at the equilibrium temperature and the water moisture content at the equilibrium-curing conditions dependences have been checked. The activation energy for diffusion was calculated obtaining a value 26.01 kJ/mol. Dynamic mechanical analysis of several samples immersed in water at 100°C during different periods of time showed no significant changes in the glass transition temperature, and a decrease in the storage modulus at 2% of water content was observed. Storage modulus remained essentialy constant above that water content. Values of glass transition temperature were corroborated by differential scanning calorimetric measurements.