Superhydrophobic UHMWPE/nanosilica composite films on glass and silicon and their tribological behavior

Abstract

A kind of nanosilica was used to modify ultrahigh molecular weight polyethylene (UHMWPE) to prepare superhydrophobic films on glass and silicon using a dip-coating method. The wetting ability of the films with water was investigated by a contacting angle method. The tribological behavior of the films was measured using a ball-on-disk configuration in reciprocating mode at the sliding speed of 40 mm s−1. The counterface was a GCr15 steel ball with diameter of 3 mm and the normal loads were 10 g ∼ 300 g. The surface topographies of the films, the worn surfaces on the films, wear scars on the steel ball, and the wear debris were observed and analyzed using SEM. The water contact angles and the sliding angles of water on the films of UHMWPE/nanosilica (6 wt%) were about 163° ∼ 165° and 3° ∼ 4°, respectively, which indicates the nanosilica can make the UHMWPE/nanosilica film superhydrophobic. It is believed that, due to the difference in thermal conductivity of the substrates, which has direct influence on the solidification behavior of the films, the films on glass and silicon have different morphologies. The friction coefficient of about 0.1 ∼ 0.2 indicates these composite films are self-lubricant. The wear life of the UHMWPE/nanosilica films is dramatically reduced by the increase of the friction load. Extrusion is believed to be the main wear mechanism of the UHMWPE/nanosilica films. Main part of the ‘wear debris’ kept connecting with the film at both sides of the friction track.