WETTABILITY AND FLOTATION OF ETCHED ULTRA-HIGH-MOLECULAR-WEIGHT POLYETHYLENE FIBERS

The use of ultra high molecular weight polyethylene (UHMW-PE) fibres i n composite materials is limited by their poor adhesion to the matrice s. The wetting of the fibre is an integral step in the adhesion proces s but the extent of fibre wetting is often difficult to establish. Bot h surface roughness and surface polarity contribute to fibre wettabili ty. A flotation method has been used to study the wettability of chemi cally-etched UHMW-PE fibres. The flotation is defined by the percentag e of fibres that float on a liquid flotation medium. The dependence of flotation on surface tension exhibits a float/sink transition that ca n be used to characterize the effects of surface roughness and surface oxidation. Chromic acid removes an oxygen-rich skin on the as-receive d fibre surface, increases surface roughness and oxidizes the UHMW PE yielding an increase in apparent surface tension.