Effects of styrene‐isoprene copolymer glass fiber coatings on woven glass cloth epoxy composite performance

Abstract Woven glass‐epoxy composites were prepared from mats that had been treated in a variety of ways. Fibers were coated with a commercial sizing, no sizing, and a surfactant coating. In addition, fibers were coated with styrene‐isoprene copolymers at varying molar ratios using a novel technique termed admicellar polymerization. Dynamic contact angle measurements were used to quantify the effect of the different coating techniques on the fiber, while dynamic mechanical analysis (DMA) and flexural testing were used to characterize the cured composites. Wetting studies conducted with EPON 828 resin revealed no difference in wetting for the polymer‐treated fiber compared to the commercially‐treated fiber. Aqueous wetting results were consistent with a surfactant layer adsorbed on the polymer treated and surfactant treated fiber surface. DMA established that both the polymer and surfactant treatment depressed the alpha transition temperature of the composite and suggested an interpenetrating network existed at the fiber‐matrix interface. Flexural strength testing showed the properties of the composites made from surfactant‐treated and polymer‐treated glass fibers were comparable to composites made from commercially‐sized fibers and exceeded the flexural strength of the composite made from glass fibers without sizing.