Friction and wear of rare-earth modified glass-fiber filled PTFE composites in dry reciprocating sliding motion with impact loads

Polytetrafluoroethylene (PTFE) composites were developed by filling with 60 wt.% Pb and 5 wt.% glass fiber (GF). The GF was modified with an alcoholic solution (SGS) of N-beta-aminoethyl-gamma-aminopropyltrimethoxysilane coupling agent (SG-Si900), an alcoholic solution (SGS/RES) of SG-Si900 and rare earths, and an alcoholic solution (RES) of rare earths, respectively. The friction and wear properties of these PTFE composites, reciprocating sliding against chromium-plated steel in dry friction, under both static loads and impact loads, were investigated. The worn surfaces of the PTFE composites and the transfer films formed on the counterface were examined with a scanning electron microscope (SEM). Experimental results reveal that the wear resistance of PTFE composites filled with modified GF can be largely improved. The friction property of PTFE + 60 wt.% Pb + 5 wt.% RES modified GF composite is the best of the PTFE composites filled with modified GF. However, the wear resistance of PTFE composites is largely decreased under impact loads, compared to that under static load conditions. The PTFE + 60 wt.% Pb + 5 wt.% RES modified GF composite registers excellent impact wear resistance in dry reciprocating sliding under impact load conditions. SEM investigation reveals that the modified GF can enhance the adhesion of the transfer films to the counterface, so they largely decrease the wear of the PTFE composites. Under impact load conditions, the PTFE debris on the worn surfaces of the PTFE composites is characterized by fine powder, owing to the repetitive impact in dry reciprocating sliding, which can decrease the ability of PTFE to form its transfer films, and then leads to the decrease of the friction and wear properties of the PTFE composites. (C) 2002 Elsevier Science B.V. All rights reserved.