The effect of network structure on moisture absorption of epoxy resins

An investigation of the effect of modifying the network structure on moisture absorption of epoxies was performed. The network was modified by crosslinking the epoxides with various mono/diamine proportions, resulting in decreasing density and increasing free volume. It was discovered, however, that concomitant effects, i.e., the formation of a two‐phase structure, and changes in resin polarity and in resin–water affinity predominated. Thus, compositions with higher chain molecular weights between crosslink points yet exhibited lower diffusion coefficients. Also, when drastic swelling conditions (such as a water‐boil treatment) were employed, moisture absorption was facilitated by penetration via newly formed microcracks.