The Effect of PTFE Powder Adhesive Activation on the Wear Resistance of Block PTFE

Abstract

The effect of adhesive activation of polytetrafluoroethylene (PTFE) powder by sodium ammonia solution on the structure and tribological behavior of sintered polymer is studied. The friction coefficient of the adhesion-activated PTFE (PTFE-A) increases, while the rate of wear decreases compared to the original PTFE by about 50-fold on friction against 40X13 stainless steel and by up to 800-fold on friction against 40X chromium steel. The difference is attributed to the dependence of the rate of wear on activation of the tribochemical mechanism, which is responsible for chemisorption of the transfer film on the metal counterface and increases its life, wear resistance and, eventually, the wear resistance of PTFE-A. When the friction conditions preclude its activation (friction against 40X13 stainless steel), the modest improvement in wear resistance is achieved through increased intermolecular interaction in PTFE-A. On friction against corrosion-active 40X steel, an iron oxide layer facilitates chemisorption of the transfer film providing for additional reduction in the wear rate by more than an order of magnitude. Functionalization of PTFE-A also inhibits the dependence of the wear rate on the relative humidity of the surrounding atmosphere observed during friction of some PTFE-based composites, which may be useful for practical applications.