Interfacial and wetting properties between glass fiber and epoxy resins with different pot lifes

Abstract

Considerable research has been devoted to the study of interfacial adhesion, optimal wetting and interfacial properties of composites. In these studies, epoxy hardeners with different pot lifes were used for the manufacture of composites and their molding processes. Wettability and micromechanical testing revealed that these factors effected wetting, interfacial and mechanical properties. FT-IR studies revealed differences in the spectra with different 'C-N type' curing additives contained in the four different amine-type hardeners. For measurement of impregnation rate, a droplet of the different epoxy/hardener liquids was placed on glass fiber mat and the spreading behavior was measured as a function of time. The surface tension on PTFE was measured using the pendant drop method and the work of adhesion calculated for this surface tension was related to the spreading distance. The Drzal equation, based on the single fiber fragmentation test, was implemented to calculate the interfacial shear strength (IFSS) of the different composite materials. To relate the IFSS, the surface tension and the work of adhesion, static contact angle measurements were made using four solvents of known surface energy. A goal of the study was to identify an optimal epoxy hardener in terms of; pot life degree of curing, residual enthalpy, wettability and interfacial properties. From a practical standpoint the measured rate of resin transfer, and interlaminar shear strength (ILSS), mechanical and other properties were consistently affected by these manufacturing and processing differences.