Water transportation in epoxy resin

In the present work, water sorption behaviors at different temperatures ranging from 20 to 80degreesC were monitored in a model Novolac cured epoxy resin (EP) and its esterfied ramifications (with CH3COO, CH3CH2CH2COO, and C6H5CH2COO side groups referred to as EPA, EPB, and EPP, respectively). In light of gravimetric measurements and positron annihilation lifetime spectroscopy, a sorption mechanism was established, which suggested that the equilibrium water content was thermodynamically controlled, while the diffusion process was kinetically controlled. The driving force of the diffusion resulted in energy released by the hydrogen bonds, whereas the transportation rate was essentially subject to the local-chain mobility as well as the dissociation of water molecules from the epoxy network. To verify this model, dynamic mechanical analysis and time-resolved attenuated total reflection Fourier transform infrared spectroscopy experiments were employed. With generalized two-dimensional correlation analysis, the results obtained from IR spectra were consistent with the mechanism proposed.