Diffusion mechanism and properties of chemical liquids and their mixtures in 977-2 epoxy resin

Epoxy resin is a versatile high-performance thermosetting material with attractive properties for many engineering applications. However, epoxy resins may come into contact with various chemical liquid environments while in service which can degrade their mechanical properties and deteriorate their performance. Water diffusion into epoxy resins is well-studied; however, little research has been reported on the diffusion mechanisms of other liquids/solvents and their mixtures. Therefore, this study addresses this gap through the use of gravimetric analysis to investigate the absorption of water and various chemical liquids, and their mixtures into epoxy resin. The liquid diffusion characterizations, which include weight gain, diffusion coefficients, and edge effects have been investigated. A two-stage absorption process was observed for water, ethanol, methanol, and their mixtures. A unique three-stage diffusion process of butyl formate, decalin, and their mixtures in 977-2 epoxy resin was observed. A correction factor was used to account for the edge effects. The experimental results showed a dependency of saturation levels and diffusion coefficients on the polarity of the liquids and on the interaction level between the penetrants and the polymer. Furthermore, the absorption rate of the binary mixtures is intermediate between the rates of either penetrant.