Study On Mechanical And Tribological Properties Of Glass Fiber-reinforced Polyamide6Composites Filled With Solid Lubricants

Polyamide6(PA6) has been wildly used in engineering applications as a friction material due to its excellent mechanical properties, good resistance and self-lubricating performance. The properties of PA6could be improved further by reinforcements and fillers, resulting in higher strength, higher wear resistance and lower coefficient of friction. PA6composites have, therefore, been a promising material to replace many traditional metallic materials for sliding components.In this thesis, PA6composites friction materials were prepared using a modular intermeshing co-rotating twin-screw extruder. Glass fiber (GF) was firstly employed to reinforce PA6material. The effects of GF content on mechanical and tribological behaviors of PA6have been studied. Then, various solid lubricants, such as PTFE, graphite and UHMWPE, were used to further improve tribological properties of PA6/GF composites material. We also investigated the mechanical and tribological performance of PA6/GF composites material filled by different content and proportion of solid lubricants. The worn surfaces were examined using scanning electron microscope (SEM) to discuss wear mechanism. The main results are as following:(1) Glass fiber reinforcement was found effective not only in improving tensile strength and impact strength, but also lowering coefficient of friction of PA6. When filling15wt%GF, COF of composites material was lowered to only0.1177, by65%decrease compared to pure PA6. The wear mechanism for pure PA6was adhesive wear, which changed to abrasive wear after GF reinforcement. However, the wear performance was worse for PA6/GF composites.(2) When filled with single solid lubricant, PTFE was found much more effective to lower COF of PA6/GF composite than graphite and UHMWPE, which can be attributed to formation of the stable transfer film. The maximum reduction in COF was obtained by filling PA6/GF with single15wt%PTFE and the COF was0.09412, decreased by 20%.The wear surface indicated that main mechanism was abrasive wear.(3) The complex solid lubricants were of benefit for improving wear properties.PTFE-UHMWPE performed better than PTFE-Graphite and Graphite-UHMWPE. When filling with10wt%/5wt%PTFE-UHMWPE complex lubricants, PA6/GF composite material showed best wear behavior with the low wear rate of3.65×10-8cm3/Nm, which was56.5%and44%lower than PA6/GF and pure PA6, respectively. The main mechanism was also abrasive wear. However, COF of composite increased, which demonstrated that the friction properties were not effectively improved.(4) By comparing different types and contents of solid lubricant,15wt%PTFE filling PA6/GF composites material showed lowest COF and10wt%/5wt%PTFE-UHMWPE filling PA6/GF composites material had lowest mass wear rate. As for mechanical properties, PA6/GF filled with12wt%/3wt%Graphite-PTFE and3wt%/12wt%Graphite-UHMWPE performed best tensile strength and impact strength, respectively.