Comparison of Mechanical and Frictional Properties of PTFE Matrix Composites Reinforced by Different Fibers and Graphite

The polytetrafluoroethylene (PTFE) matrix composites which filled with polyphenylene sulfide (PPS) fiber, poly-p-phenelenferephthalamide (PPTA) fibre or glass fiber (GF)) and graphite at various mass fractions were prepared by the processes of mechanical blending, compression molding and sintering. The mechanical properties of the composites, such as tensile strength, impact strength and hardness were investigated. The results show that tensile strength and elongation at break markedly decrease but elasticity increases by filling with fibers. Impact strength decreases by filling with PPS and GF, and the composite displays brittle characteristic. However, the impact strength rapidly increases by filling with PPTA fiber. Hardness increases with the fibers content increases, and decreases with graphite content increases. Filling graphite into PTFE has light effect on the impact and tensile strength of composites. The tribological properties of the composites were investigated on M-2000 wear tester at dry friction condition. The wear mechanism was also discussed and the wear surfaces were examined by SEM. The result indicates that fibers which diffused in PTFE matrix wind with PTFE molecule chain, and then form grid structure. The load-bearing capacity of composites can be obviously enhanced and the trend of block fragmentation's slide is inhibited, so that the tribological properties are improved markedly.