Procedures Conditioning the Absorption/Desorption Behavior of Cold-Cured Epoxy Resins

The absorption/desorption behavior of a commercial cold-cured bisphenolic epoxy resin, subjected to different treatments prior to exposure to water, was analyzed. The epoxy system has been already used as both matrix and adhesive for the manufacture and application, respectively, of fiber reinforced polymers composites employed for rehabilitation procedures. The effects of different curing, conditioning, and storing conditions on the water absorption/desorption process taking place in the cured resin were evaluated. The different conditioning procedures used to dry the specimens before their exposure to water caused a different extent of physical aging and of curing on each system, influencing the amount and the rate of diffusion of the water molecules inside the specimens. Moreover, if the specimens are subjected to thermohygrometric cycles prior to immersion in water, the rate of diffusion and the amount of water also depends on the presence of water molecules inside the cured resins not easy to remove by any drying treatment. During all the hygrometric treatments performed, a deaging process took place. The kinetic of this deaging process for the not-fully cured systems depends on the additional crosslinking taking place in the samples. The different procedures used to condition the specimens also affect the variations in glass transition temperature (Tg) of the cured systems during and after immersion in water. Finally, the different drying procedures employed proved to be not equally appropriate for cold-cured epoxy resins.