Factors affecting the interfacial adhesion of ultrahigh-modulus polyethylene fibre vinylester composites using gas plasma treatment

The interfacial adhesion of ultrahigh-modulus polyethylene (UHMPE) fibre-vi nylester composites was improved by the oxygen plasma treatment of the UHMP E fibre. The chemical functional group formations on the UHMPE fibre surfac e by oxygen plasma treatment were analysed using diffuse reflectance Fourie r transform infrared spectroscopy and the morphological changes of the UHMP E fibre surface by plasma etching were observed by scanning electron micros copy. The wettability enhancement by the chemical functional group formatio n and the mechanical intertocking due to the micropits were important facto rs in improving the interfacial adhesion of the UHMPE fibre-vinylester comp osites by oxygen plasma treatment. In order to investigate the relative imp ortance of the two factors, wettability enhancement and mechanical interloc king, in the improved interfacial adhesion of the UHMPE fibre-vinylester co mposites, nitrogen plasma treatment was also performed. Nitrogen plasma tre atment of the UHMPE fibre was proved to be effective in the formation of th e micropittings and ineffective in the chemical functional group formation in comparison with the oxygen plasma treatment. The interlaminar shear stre ngths of the nitrogen-plasma-treated UHMPE fibre-vinylester composites show ed almost the same value as those of the oxygen-plasma-treated UHMPE fibre- vinylester composites. The wettability enhancement and mechanical interlock ing are important in the improvement of interfacial adhesion of UHMPE fibre -vinylester composites by plasma treatment and mechanical interlocking seem s to be more important. (C) 1998 Kluwer Academic Publishers.