An NMR Imaging Study of the Interface of Epoxy Resin-Glass Fiber Reinforced Composites

NMR imaging was used to analyze E-glass fiber/epoxy composites. The NMR images revealed specific interactions between the glass fiber and epoxy, as indicated by the different degree of curing in the proximity of the fiber. When as-received glass fibers were used, an accelerated degree of curing in the proximity of the fibers as compared with the bulk was observed, whereas when heat-treated glass fibers were used the above trend was substantially inhibited. Finally, when E-glass fibers treated with an aminosilane coupling agent (γ-APS) were used, no variation in the degree of curing in the proximity of the glass fiber was observed. The above results suggest that physisorbed or chemisorbed molecular water present in the surface of the glass fiber assists in the opening of the epoxy ring by hydrogen bonding effects.