The Study On Mechanical Properties And Friction And Wear Properties Of Filled PTFE Composites

Polytetrafluoroethylene (PTFE) owns excellent resistance to heat,chemical corrosion, and dielectric properties, wear and friction properties,which is other resin can’t reach. It is wildly applied in electronics, chemicals,machinery, aeronautics and other fields. When in the high-load, low-glidespeed, the friction coefficient between PTFE and polymer can be as low as0.04.So it is an ideal self-lubricating material. But its hardness and abrasionresistance is not ideal, which greatly limits the application of single phasePTFE material. Thus, there is important significance to modified PTFE toimprove its hardness, reduce the wear loss, as well as to improve its creepproperties.This paper aimed to improve the mechanical properties and the friction andwear properties of PTFE matrix composites via filling PTFE. Main work andresults were summarized below:1. Optimized sintering process parameters via orthogonal, that was to say,heated to200℃at a rate of40℃/h from room temperature, subsequentlyheated to365℃at a rate of20℃/h and insulated4h, at the last cooling withfurnace, while tensile strength as the experimental index. At this time, thetensile strength of PTFE was15.06MPa, the elongation at break was327%;shore hardness (D-type) was54MPa; in the case that frictional load was20N, speed was3m/min, and test time was1h, coefficient friction was around0.11,wear loss was around4.6mg, wear mechanism was adhesive wear.2.663bronze powder (500mesh), graphite (powder), carbon fiber(powder), molybdenum disulfide (powder) as filler, and the addition massfraction was in accordance with the orthogonal. Examine the role of variousfillers on PTFE matrix while experimental index were tensile strength,hardness and wear loss respectively. The results show that carbon fiber wasmost effective to reinforce the strength of PTFE composite, while its’ massfraction was2wt%;663bronze powder is the most effective to increase thehardness of PTFE composites, while its’ mass fraction was9wt%; and forreducing wear loss, molybdenum disulfide is the most effective, while themass fraction was2wt%.3. Subjected to surface treatment of CNT and graphene by chemicalmethod. Surface of CNT and graphene were grafted to carboxyl group andamino group. PTFE matrix composites which were filled by modified CNTand graphene were prepared. Studied the mechanical properties, friction andwear properties of the PTFE matrix composites. The results are as follows:Function groups of CNT and graphene on the surface were interaction withthe fluorine atoms, so the dispersion of CNT and graphene in PTFE matrixwere improved, and the dispersion of amino-CNT and amino-graphene werebetter than carboxyl-CNT and carboxyl-graphene. Meanwhile, themechanical properties, friction and wear properties of amino-CNT/PTFEcomposites and amino-graphene/PTFE composites were better than those ofcarboxyl-CNT/PTFE composites and carboxyl-graphene/PTFE composites.About wear mechanism, with the increase of CNT content, wear mechanismof CNT/PTFE composites experienced a process from fatigue wear to adhesive wear and abrasive wear gradually; while graphene/PTFEcomposites experienced a process from adhesive wear to adhesive wear andabrasive wear gradually with the graphene content increasing.