Surface modification of an aramid fibre treated in a low-temperature microwave plasma

The surface modification of an aramid fibre treated in a low-temperature microwave (mw) plasma was investigated. Three different plasma gases, oxygen, argon and ammonia, were used to achieve different surface modifications during fibre treatment. The modification of the fibre surface was analysed with electron spectroscopy and electron microscopy. The influence of the surface modification on the fibre-matrix interaction was inspected by measuring the interlamellar shear strength of the composites and the pull-out strength of a fibre bundle in model composites. The process gas and thus the kind of plasma has no significant influence on the fibre modification resulting from plasma treatment. It was shown that a fibre cleaning with subsequent surface ablation is the dominate modification process during mw plasma treatment, independent of the process gas. The degree of surface cleaning and removal of a contamination layer strongly depended on the treatment range. No incorporation of oxygen or nitrogen containing functional groups was observed. This was explained with the composition of the process gas. The improvements of the composite properties demonstrate the advantage of the mw plasma treatment as a fast, environment-protected, cost-efficient process for fibre modification.