Epoxy systems with improved water resistance,and the non-fickian behaviour of epoxy systems during water ageing

N,N-Bis (2, 3-epoxypropyl) aniline and 4,4′-methylenebis-N,N-bis (2,3-epoxypropyl) aniline] containing bromo, chloro, trifluoromethyl or polyfluoroalkoxy substituents were synthesised and cured with aromatic diamines in order to investigate the effect of substituted halogen on water absorption. Significant improvements were achieved: thus use of 4,4′-methylenebis-N, N-bis (2, 3-epoxypropyl)-3, 5-dichloroaniline] and 4,4′-methylenebis-N,N-bis (2,3-epoxypropyl)-3-(trifluoromethyl) aniline] instead of 4,4′-methylenebis-N,N-bis (2,3-epoxypropyl) aniline] reduced the water absorption by about a half. Departures from Fickian behaviour were observed during water immersion ageing at room temperature and were a general feature of the epoxy systems examined. Plots of water absorption against the Fickian parameter (√t/d) usually showed at least mild sigmoid character and were not independent of specimen thickness. Further, slow continued uptake of water occurred during long-term ageing, and evidence is provided that the associated network distortions are reversible.