Research On The Tribological Behaviors Of Polyamide6

Owing to its advantages of excellent abrasive resistance, favorable self-lubricating property and high strength, Polyamide6(PA6) shows its wide application prospects in the fields of friction materials. In earlier papers, most studies investigating the modification of PA6have been made in terms of mechanical properties. And some limited research for tribological properties mainly focus on the nano-modified.Polytetrafluorothylene (PTFE), graphite and ultra-high molecular weight polyethylene (UHMWPE) were selected to improve the properties of PA6as solid lubricants. PA6composites were prepared by molten blending method. The effects of the content and proportion of solid lubricants and the operating conditions on the tribological properties of PA6composites were discussed. To understand the wear mechanisms, the worn surfaces of materials were observed by SEM. In addition, the mechanical and crystallization properties of PA6composites were investigated. Analysis results are shown as below.(1) Friction and wear experiments were run at a rotating speed of200r/min and under a load of100N. The tribological properties were studied in terms of the COF, the friction stability and the wear rate. The results indicated that PTFE was most effective to improve the friction and wear properties in the three kinds of solid lubricants. With the optimal fill amount of15%,64.7%decreasing of friction coefficient occurred. And the friction stability was also improved obviously.(2) When combination solid lubricants were applied, PA6composites filled with PTFE/UHMWPE exhibited more excellent tribological properties than the others did. In detail, there was a67.5%reduction when PA6was filled with7%PTFE-8%UHMWPE. The modification of friction stability and wear resistance was acquired at the same time. Compared with the addition of PTFE, the combination solid lubricants of7%PTFE/8%UHMWPE could have7.9%more decreasing of COF,69.9%more decreasing of wear rate respectively. Compared with the addition of UHMWPE, the combination solid lubricants of7%PTFE/8%UHMWPE could have52.3%more decreasing of COF,77.6%more decreasing of wear rate respectively. It suggested that more superior modification effect can be gained for the tribology capabilities of PA6composites.(3) The worn surfaces were examined using a scanning electron microscope (SEM). It was found that various characteristics can be observed. In the case of neat PA6, the surface showed spalling flaps and irregular pits. Thus, it can be concluded that adhesive wear was the main wear mechanism, with slight fatigue wear happened also. With the inclusion of PTFE, there was parallel and regular ploughing ditch on the worn surface. That means that significant abrasive wear occurred. Contrary to the above, there existed clear plastic deformation and adhesion among the appearance of other PA6composites, which was mainly resulted from adhesive wear.(4) Compared with pure PA6, the addition of solid lubricants had an increase of the impact strength, while a reduction of the tensile strength and hardness. In addition, differential scanning calorimetry (DSC) was applied to study the crystalline properties of PA6composites. The experimental results indicated that the inclusion of solid lubricants decreased the crystallinities of PA6composites.(5) The tribological behaviors of PA6composites were observed under different operating conditions. With the applied load and revolving speed increasing, the COF showed a descending tendency. By comparison, an increasing of applied load gave rise to more mass loss. With the higher revolving speed, the mass loss did not vary with certain rules. At the same time, the wear mechanism would be different from the operating conditions.In short, this research will have a certain guiding significance for developing the advanced PA6composites with superior tribological properties.