Factors affecting H2O absorption of the epoxy tetraglycidyl‐4,4′‐diaminodiphenyl methane cured with diaminodiphenyl sulfone

It was found that the amount of water absorbed at room temperature in cured tetraglycidyl‐4,4′‐diaminodiphenyl methane/diaminodiphenyl sulfone epoxy resins increases as the curing time or temperature increases while the amount of tetrahydrofuran‐soluble extractables and the room temperature density decreases. These data suggest that the free volume increases with the extent of cure and the resins become more accessible to water. While the driving force for water absorption is the electrostatic attraction between water and the functional groups in the epoxy, the results suggest that equilibrium H2O absorption is determined primarily by unoccupied volume of the epoxy resin.