Epoxy systems were prepared with the same epoxide (diglycidyl ether of bisphenol A) with five different hardeners: 4,4'-diaminodiphenylmethane (H1), diethylenetriamine (H2), a cycloaliphatic amine based on isophorone diamine (H3), a polyaminoimidazoline-based hardener (H4), and a polyamidoamine-based adduct hardener (H5). Samples were subjected to four different postcure treatment temperatures (23, 55, 75, and 150 degrees C). Water absorption kinetics were obtained for each material and for each postcure treatment. The water absorption behaviors for the materials with H1, H2, and H3 were similar, whereas those for H4 and H5 were quite different. This is discussed in terms of the molecular structures of the hardeners. (c) 2005 Wiley Periodicals, Inc.