Epoxy Resins under Repeated Hygrothermal Conditions

In this paper, the effects of repeated hygrothermal conditions on an epoxy resin were investigated experimentally. The repeated hygrothermal conditions were obtained by immersing the samples in hot water then keeping them in dry condition followed by immersing in hot water for the second time reaching steady state condition at each section. The water absorption and desorption of the samples were obtained using gravimetric measurements and the resulting residual mechanical strengths were obtained by conducting tensile tests. The gravimetric results indicated that the maximum moisture uptake and absorption rate in the second absorption were higher compared to the first absorption. The mechanical test results indicated that the residual strength reduced in the course of the first absorption section then it partially recovered as a result of water desorption and then further degraded due to the second absorption stage. The same trend was observed for the resin stiffness.