Wettability and flotation of etched ultra high molecular weight polyethylene fibres

Abstract

The use of ultra high molecular weight polyethylene (UHMW-PE) fibres in composite materials is limited by their poor adhesion to the matrices. The wetting of the fibre is an integral step in the adhesion process but the extent of fibre wetting is often difficult to establish. Both surface roughness and surface polarity contribute to fibre wettability. A flotation method has been used to study the wettability of chemically etched UHMW-PE fibres. The flotation is defined by the percentage of fibres that float on a liquid flotation medium. The dependence of flotation on surface tension exhibits a float/sink transition that can be used to characterize the effects of surface roughness and surface oxidation. Chromic acid removes an oxygen-rich skin on the as-received fibre surface, increases surface roughness and oxidizes the UHMW PE yielding an increase in apparent surface tension.