硅灰石与石墨对聚四氟乙烯摩擦磨损性能的影响

以针状的硅灰石和鳞片石墨为填料，采用冷压—烧结工艺制备了不同填料含量的聚四氟乙烯（PTFE）复合材料，考察了复合材料的摩擦磨损性能，并利用扫描电子显微镜对磨痕和转移膜进行了分析。结果表明,单独填充硅灰石和石墨时，PTFE的磨损率都会随填料含量的增加而降低，硅灰石的作用要强于石墨；但硅灰石会使PTFE的摩擦因数明显增大，而石墨会使PTFE的摩擦因数降低;2种填料提升PTFE耐磨性的作用机理不同，硅灰石在摩擦过程中会在滑动界面区域上逐渐堆积，起到优先承担载荷的作用；而石墨在摩擦过程中会发生片层的滑移与剥离，有助于转移膜的形成;适量的硅灰石（含量为20 %，质量分数，下同）与石墨（含量为5 %或10 %）复合填充能产生协同效应，使PTFE的磨损率进一步降低，耐磨性比未填充的PTFE提高200倍。

Effect of Wollastonite and Graphite on Friction and Wear Properties of Polytetrafluoroethylene

Polytetrafluoroethylene(PTFE) composites with different contents of acicular wollastonite and flake graphite were prepared by a cold molding sintering method, and their friction and wear properties were investigated by the analysis of worn surface and transfer film with scanning electron microscope (SEM).The results indicated that, although the wear rates of the composites decreased with an increase of wollastonite and graphite contents, the wollastonite filled composites presented a lower wear rate at the same filler content.Compared to pure PTFE, the PTFE composites with graphite exhibited a smaller friction coefficient but the composites with wollastonite presented the higher value.Two different friction mechanisms could be deduced for the PTFE composites with different fillers according to the SEM observation on friction surfaces.The load dissipation was attributed to the accumulation of wollastonite at the sliding interface during the friction process, whereas the slipping and peeling effect of graphite in PTFE composites promoted the formation of transfer film.Moreover, the synergistic effect was achieved by a combination of 20 wt % wollastonite and 5 wt % graphite, which led to a further decrease in wear rate.The wear resistance of PTFE composites was improved by a factor of 200 compared to pure PTFE.