A new chemical method of surface-treatment of kevlar fiber for composites with epoxy resin

Abstract

It was previously found that sodium hydride and dimethyl sulfoxide (DMSO) form sodium methylsulfinylcarbanion, which ionizes the proton of amide group of aramid molecules to dissolve them homogeneously in DMSO. Metalated poly(p-phenylene terephthalamide) reacted with alkyl halides and epoxy compounds. By utilizing this reaction, the surface layer of Kevlar fibers was partly decorated by functional groups. The interfacial adhesion between fiber surface and epoxy-amine resin was evaluated by a pull-out test of monofilament. Kevlar filament surface-modified by polyfunctional epoxy resin was proven to give the highest adhesive strength. ESCA spectra supported an enrichment of epoxy on fiber surface. SEM micrographs of pulled out filament surface also suggested increased adhesion by epoxy decoration. The bending modulus of the composite of Kevlar cloth/epoxy-amine resin was increased by epoxy decoration and especially the T-peel strength of laminates with epoxy was remarkably increased. SEM micrographs revealed that the surface layer of Kevlar fibers was drastically damaged. This fact tells us that the ultimate adhesion has been achieved by our chemical method to the limit. © 1987 The Society of Polymer Science, Japan. All rights reserved.