Effect of water sorption on the structure and mechanical properties of an epoxy resin system

The characteristics of sorption and diffusion of water in an amine-cured ep oxy system based on tetraglycidyl diaminodiphenylmethane and a novolac glyc idyl ether resin were studied as a function both of the polymer microstruct ure, known from previous works, and the temperature. Water-sorption experim ents and dynamic mechanical analysis (DMA) were performed. Tensile stress-s train and Rockwell hardness tests were conducted to investigate the effects of absorbed water on the mechanical properties of the material. Competing effects of the sorption of water in the free volume and of strong interacti ons between water molecules and polar groups of the network were used to ex plain the diffusional behavior observed, which followed Fick's second law. DMA analysis seemed to be sensitive to the water effects and the viscoelast ic behavior was related both to the water-sorption processes and to the mic rostructure of the system. An important impact of water uptake on the tensi le properties at break was also appreciated. (C) 2001 John Wiley & Sons, In c.