Surface Energetics Evolution during Processing of Epoxy Resins.

The surface energetics evolution throughout the entire curing process of two epoxy resins is predicted using a previously developed semiempirical relationship between surface tension and the solubility parameter. Evolution of the temperature and time of both the solubility parameter and density is investigated and used for this prediction, as is the concept of molar volume or mass of the interacting element. The theoretical prediction is compared with measured surface tensions. Experimental data are determined at different times during an isothermal curing process by the Wilhelmy wetting force method for surface tension with viscous drag corrections. Once corrections for viscous effects on measured surface tensions are made, very good agreement is found for the surface energetics evolution. Moreover, the total surface energies of solid cured epoxy resins, which cannot be directly measured, can be estimated with this prediction. Finally, this study provides a tool for further understanding the final adhesive properties of polymeric material considering the time evolution of surface energetics during processing. Copyright 2000 Academic Press.