Tribological Properties Of PA6/UHMWPE/SiO₂ Composites

Polyamide 6 (PA6) is one of the commonly used thermoplastic engineering plastics. Because of high mechanical strength and self-lubrication, PA6 is widely used in tribological field. However, pure PA6 has higher friction coefficient under dry sliding, which can bring severe adhesive wear and cause material wear away, restricted its more extensive applications in tribological field. The research on PA6/UHMWPE blend was mainly focused on the relationship between structure, compatibility and mechanical properties, but little on friction and wear behavior at present time. The tribological and mechanical properties of PA6/UHMWPE blends compatibilized with EAA, EAA/PBO and MAH-g-HDPE was first researched in this paper. On this basis, the inorganic particles and UHMWPE were used to prepare PA6/UHMWPE/SiO₂ composites. Main contents and results are as follows:It was found that the addition of UHMWPE could significantly improve the tribological properties of PA6/UHMWPE blends. The friction coefficient was reduced from 0.481 for pure PA6 to 0.419 for blends. When the ratio of PA6/UHMWPE was 80/20, the tribological properties of the blends compatibilized with EAA were further improved. The friction coefficient and wear rate of blend compatibilized with EAA and PBO decreased from 0.419 and 6×10^-6mm³(/N.m) for incompatibilized blend to 0.286 and 4.3×10^-6mm³(/N.m).Besides, the friction coefficient of blend which was compatibilized with MAH-g-HDPE was 0.324, and the wear rate was reduced by 70% compared with the blend with no compatibilizer and 88.5% compared with pure PA6.Mainwhile,the blend maintained higher mechanical properties.The worn surfaces of the blends were observed with SEM,and the results showed that the wear mechanism of PA6/UHMWPE blend compatibilized with MAH-g-HDPE was abrasive wear and a small amount of adhesive wear.Nano-SiO₂ and Micro-SiO₂ had a certain impact on mechanical properties and tribological properties of PA6.DSC results showed that Nano-SiO₂ and Micro-SiO₂ increased the crystallinity of PA6. Nano-SiO₂ paticles could effectively improve the tribological properties of PA6.However, Micro-SiO₂ damaged the friction coefficient of composites, while have a positive impact on the wear rate. The addition of Nano-SiO₂ on the basis of the PA6/UHMWPE could further reduce the friction coefficient and wear rate. The friction coefficient was only 0.312,and the wear rate was 0.4×10^-6mm³/(N.m).That was to say Nano-SiO₂ and UHMWPE had a synergistic effect to improve the tribological properties of PA6.The paper also studied the tribological properties of PA6 and its composites under different loads and lubrication. The results showed that the material had lower friction coefficient and higher wear rate under high load, while it had higher friction coefficient and lower wear rate under low load. The wear mechanism of PA6/UHMWPE/SiO₂ composites were abrasive wear and adhesive wear under 300N, and abrasive wear and slight fatigue wear under 200N.PA6 and its composites exhibited different tribological behavior under water lubrication from dry sliding due to the different wear mechanism under two conditions, Because of the boundary film formed in the friction process under water lubrication ,the friction coefficient decreased significantly, while the wear rate increased.