Sliding wear behavior of PTFE composites

The tribological behavior of polytetrafluroethylene (PTFE) and PTFE composites with filler materials such as carbon, graphite, E glass fibers, MoS2 and poly-p-phenyleneterephthalamide (PPDT) fibers, was studied. The present filler additions found to increase hardness and wear resistance in all composites studied. The highest wear resistance was found for composites containing (i) 18% carbon+7% graphite, (ii) 20% glass fibers+5% MoS2 and (iii) 10% PPDT fibers. Scanning electron microscopy (SEM) was utilized to examine composite microstructures and study modes of failure. Wear testing and SEM analysis showed that three-body abrasion was probably the dominant mode of failure for PTFE+18% carbon+7% graphite composite, while fiber pull out and fragmentation caused failure of PTFE+20% glass fiber+5% MoS2 composite. The composite with 10% PPDT fibers caused wear reduction due to the ability of the fibers to remain embedded in the matrix and preferentially support the load. Differential scanning calorimetry (DSC) analysis was also performed to study the relative heat absorbing capacity and thermal stability of the various composites in an effort to correlate these properties to the tribological performance. The results indicated that composites with higher heat absorption capacity exhibited improved wear resistance. The dominant interactive wear mechanisms during sliding of PTFE and its composites are discussed in view of the present findings.