Antifriction properties of filled Teflon

Abstract

The antifriction properties of Teflon(polytetra fluoroethylene) are superior to those of many natural and manmade materials [1]. At the same time, this plastic is seldom used as a structural material because of its insufficient strength, low-temperature creep, low thermal conductivity, and large thermal expansion coefficient. These deficiencies, common to many plastic materials, can be eliminated by the use of fillers and reinforcing materials [1, 2]. However, no satisfactory method of reinforcing Teflonor introducing fillers has yet been developed. This is because polytetrafluoroe thylene is very viscous in the liquid state, not readily soluble in any known solvents, and not friable. As a result the standard methods of filling polymers (in the form of powders, solutions, or melts) are not applicable in this case. Additional grinding of the polymer, highly homogeneous mixing, and firing under pressure ensure a high packing density of the component and, as a result, facilitate the realization of forces of molecular interaction in the material. The compositions prepared in this way contained 15, 30, and 40% of grade S-1 colloidal graphite. The friction and wear characteristics of these materials were tested on an MDP-1 machine by the standard method [5]. We determined also the deformation characteristics of filled Teflon at room temperature. St. 40 steel machined to a Class 7 surface finish was used as the counterbody. The test results, reproduced in Figs. 1 and 2, show that the wear resistance of teflon can be increased more than 1000-fold by filling it with graphite. The friction coefficient of filled Teflonat Psp = = 10-50 kg/cm 2 and Vsl = 1-5 m/sec ranges from 0.005 to 0.28.