Water uptake of epoxy–clay nanocomposites: Experiments and model validation

Models for the diffusion of water into pure epoxy and for epoxy nanocomposites were presented in a previous paper [Liu W, Hoa SV, Pugh M. Water uptake of epoxy/clay nanocomposites. Part I: Model development. J Compos Sci Technol 2007;67:3308--15]. In this paper, two different types of epoxies were examined for water absorption behavior. Specimens of epoxies and of epoxy/nanocomposites were immersed in distilled water at constant temperatures of 23 °C, 50 °C and 80 °C for 5000 h. The equilibrium moisture content of the nanocomposites was measured, and diffusivities were determined by fitting Fick’s Law, Langmuir model of diffusion (LMD) and diffusion with time varying diffusivity (DTVD) to the experimental data, employing a least-square approach. Diffusion models for nanocomposites are discussed, and confirmed by experimental data for different types of nanocomposites. The effects of materials, dispersion processes and morphology on water uptake behavior of nanocomposites are investigated.