Effect of hygrothermal aging on the diffusion of seawater in epoxy/glass composites studied by positron lifetime spectroscopy

摘要

The effect of hygrothermal aging on the free volume controlled diffusion of seawater in the epoxy/glass (E/G) composite samples with E-glass fibers woven at 0 degrees and 45 degrees to the epoxy matrix has been studied using Positron lifetime technique. The equilibrium mass uptake of seawater is assessed by the gravimetric method. The positron results indicate that the free volume hole size increases with hygrothermal aging in the composite E/G (0 degrees) suggesting swelling while the hole size shows continuous decrease in the E/G (45 degrees) composite up to 45 degrees C. We also found that hygrothermal aging process in the present composites is an exothermic process. Although the equilibrium uptake of seawater decreases with the increasing temperature in both the cases, the magnitude of decrease is more in 0 degrees-oriented composite than in 45 degrees-oriented composite. The heat of absorption calculated from the temperature dependence of equilibrium mass uptake is found to be negative in both the cases.