Preparation And Properties Of PTFE Reinforced With Ultra-fine Kaolin Particulates

Polymer composites have replaced many traditional metallic materials for sliding components. The increasing use of polymer composites in sliding components has made the studies of the tribological behavior of these materials. Polytertrafluoroethylene (PTFE) is one of the most commonly used self-lubricating materials, which exhibits very low coefficient of friction. However, neat PTFE shows very poor wear resistance. Numerous studies have confirmed that the higher angularity of filler particles increases the possibility of abrasion during sliding which is detrimental to wear resistance, and nanoscale particulates seemingly are better in this respect. Unfortunately, filling about 20wt.% nanoscale particulates will result in high product cost for PTFE composites. Recently, the kaolin particulates are potentially interesting in providing low production cost for commodity PTFE composites. In the present work, the ultra-fine kaolin particulates were selected as the reinforcing filler to increase the wear resistance of PTFE.Wide angle x-ray diffraction (WAXD) patterns were taken on a Bruker D8 ADVANCE diffract-meter (Germany) with Cu-filtered Cu ka radiation at room temperature. The crystalline area and the amorphous area were calculated with a software of this apparatus, then the mass faction crystallinity of the PTFE composites were obtained.PTFE composites filled with different proportions of the ultra-fine kaolin particulates were prepared by compression molding. The friction and wear tests were carried out in a reciprocating tribometer. These composites were tested against a 45 carbon steel track, at room temperature in ambient atmosphere (60±5) %RH. The conditions were a contact pressure of 5.5 MPa, and a reciprocating frequency of 1.0 Hz. Results show that a PTFE-10%kaolin composite exhibited a slightly high coefficient of friction and high wear resistance amongst the PTFE materials.For the PTFE-kaolin-graphite composites, the friction and wear tests were carried out in a reciprocating tribometer under two different humidity conditions. It is found that a PTFE-10%kaolin-5%graphite composite exhibited a relatively low coefficient of friction and high wear resistance amongst the POM materials.