Limiting PV Value Test And Comparative Study Of Mechanical And Tribological Properties Based On Modified PET

In order to accurately test the PV value of modified polyethylene terephthalate(PET)material and explore its tribological properties,and expand its application in bearing industry,the modified PET plastic ring and plastic disc were prepared by extrusion granulation and injection molding of modified PET material.The elemental content,crystallinity,melting temperature and density of the modified PET plastic samples were tested.The mechanical properties of the modified PET material and pure PET material were compared and analyzed.Then in MPV-3 horizontal microcomputer control samples(ring)and MWW-1a vertical pin-plate samples(disc),two kinds of wear testing machine respectively discusses their extreme pressure speed value(PV)and tribological properties of differences,and discusses the two kinds of testing machine under the same PV value,the volatility of friction coefficient and wear them the change of the quantity,The wear morphology was analyzed by scanning electron microscope and electron microscope.The main conclusions are as follows:(1)The elemental composition and crystallization rule of the modified PET material were tested and analyzed.It is found that the modified PET material contains trace elements of fluorine,Na20,oxide ZnO2,SiO2 and other trace elements.The crystallization temperature of modified PET material is higher than that of pure PET,and the crystallization rate is faster than that of pure PET,but the melting temperature is lower than that of pure PET.(2)The mechanical properties and thermal conductivity of the modified PET material were investigated and analyzed.It was found that the mechanical properties and thermal conductivity of the modified PET material were better than the corresponding parameters of the pure PET material.But the hardness and density are very similar.(3)It is found that when the two kinds of friction and wear test methods reach the ultimate load,the ultimate pressure measured by the horizontal test method is less than that of the vertical test method,and their minimum values are 0.37MPa and 2.10MPa respectively.With the increase of rotating speed,the ultimate pressure of the latter decreases relatively greatly.The limiting PV value of the former is less than that of the latter,and the fluctuation of the limiting PV value of the former is relatively small.The wear mechanism of the former is adhesive wear,while the latter is a large amount of wear debris spilling out.(4)It is proved that with the increase of load,the wear quantity measured by the vertical friction and wear test method is greater than that by the horizontal friction and wear test method,but the friction coefficient of the former is smaller than that of the latter,and the friction coefficient of both decreases with the increase of test force.The wear of the plastic ring is relatively stable at the begining.When the test force is loaded to 300N,the wear increases significantly.(5)It is proved that the variation trend of friction coefficient measured by vertical pin-disk and horizontal shaft ring friction and wear test method is quite different with the increase of rotating speed.The friction coefficient of the former increases first and then decreases,while the friction coefficient of the latter decreases slowly and then increases sharply.Compared with the influence of load on the wear of modified PET material,the influence of rotation speed on the wear is small.The wear of plastic ring increases sharply after 300r/min while that of plastic disc increases sharply after 350r/min.(6)It is proved that the variation trend of the friction coefficient measured by the vertical pin-disk and horizontal shaft ring friction and wear test method is little different with the wear time.The friction coefficients of them all increase at first,and then decrease slowly after 60min.In both cases,the wear increases sharply after 80min.(7)It is proved that under the same pressure velocity(PV)and wear time of 60min,with the increase of test force,the friction coefficients measured by the two friction and wear methods experience gentle,maximum and small changes.When the test force is between 150N and 200N,the higher rotational speed and the lower test force make the friction coefficient in a relatively stable state and the minimum wear.(8)AnsysWorkbench is used to simulate and analyze the wear quantity of the two friction and wear test methods with time.It is proved that the wear quantity of the vertical pin and disk test method after the 50S is greater than that of the horizontal shaft ring test method.