Study of the oxygen treatment of high‐modulus polyethylene fibres

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Abstract
It has been found that three possible mechanisms can contribute to the improvement in fibre/resin adhesion when high‐modulus polyethylene fibres are subjected to oxygen gas plasma treatment. These mechanisms are surface oxidation, cross‐linking and surface etching. In this paper it is attempted to estimate the relative importance of these three mechanisms in the improvement of the interlaminar shear strength (ILSS) of polyethylene fibre/epoxy resin composites.From a comparison of plasma treatment in oxygen gas and nitrogen gas it is concluded that surface oxidation makes a major contribution to the initial increase in ILSS for short treatment times. Examination of fibres cross‐linked by γ‐irradiation has demonstrated the effect of cross‐linking on ILLS independently of the surface oxidation and etching that accompany oxygen gas plasma treatment. Finally, scanning electron microscopy has shown the presence of micro‐surface cracks after relatively short plasma treatment times, and confirmed the unique cellular structures produced at long treatment times.A comparison of the results from both batch and continuous plasma treatment processes for a range of melt‐ and gel‐spul fibres shows that the effect of oxygen plasma treatment for all these fibres are broadly similar in terms of ILSS, fibre strength and surface appearance.