Study On Tribological Properties Of Polymer Materials Modified By Si₃N₄ Nano-Particles

Polymer matrix composites are widely used in machinery,automotive,aerospace,and marine fields because of their good vibration and noise reduction properties.However,polymer matrix composites tend to have significant deforming behaviors on the contact surface under long working process because of its defects such as poor mechanical properties and poor high temperature deforming resistance,in which weakens on the reliability and stability of the machineries operation.But the modification of polymer matrix composites by using additives is currently one of the important methods to improve its working performances and properties.Therefore,in this dissertation,the Si₃N₄ nano-particle was adopted to modify the HDPE matrix material in order to explore and analyze some important physical and mechanical properties.Besides,the tribological properties,frictional vibration and noise of this composite will also be explored in order to discern the influence of Si₃N₄ on the HDPE composite’s wear behaviors.The research contents are showed below:In this paper,high-density polyethylene materials（HDPE）,four-needle zinc oxide particles（T-Zn O_w）and silicon nitride nanoparticles（Si₃N₄）were first mixed and divided into 6 groups according to different Si₃N₄ nanoparticles composition ratios.The composite was manufactured into different testing samples by using a hot-press injection molding machine after being mixed uniformly through a twin-screw extruder.Besides,some inherent properties of the modified composite were characterized and results showed that the heat loss temperature of the modified composite increased with the climb of the content of Si₃N₄ nanoparticles,while the tensile and tear properties fell.The friction and wear tests of the modified HDPE composite under water friction were conducted by using tribo-tester to analyz its tribological properties.The results showed that the friction coefficient（COF）experienced the process of decending first and ascending than with the growth of the content of Si₃N₄ nanoparticles.Besides,the wear volume and the wear rate exhibited decreasing trend as the Si₃N₄ nanoparticles content rising,in which indicated that the anti-wear property was strengthened.However,the surface micromorphology became rougher evidently in the higher Si₃N₄content groups and ensued to fluactuation in the friction and wear process,in which caused to obvious vibration and noise behaviors.In addition,the Fourier transform infrared spectroscopy and X-ray diffractometer（XPS）were used to conduct tribo-chemical analysis and results showed that Si₃N₄ nanoparticles formed silicon-oxygen bonds and hydroxyl groups in the water environment and worked as a lubricant film on the contact surface to reduce the friction coefficient（COF）significantly.Si₃N₄ nanoparticles could obviously improve the thermal deformation temperature and deformation resistance and reduced the COF of the HDPE composites compared to the pure HDPE material.Therefore,this study could make necessary contribution to the design of high performance polymer engineering composites which has very important scientific significance and engineering practical value.