Research On Mechanical Properties And Tribological Properties Of CF/UHMWPE Biocomposites

Carbon fiber(CF)is one of the popular new materials due to its excellent performance and has been widely applied to various fields.In this paper,UHMWPE was modified by carbon fiber filling.UHMWPE and CF/UHMWPE composites were prepared by hot compression molding method.According to the principle of bionics,CF/UHMWPE bionic artificial joint material was prepared by simulating the structure of natural joints.The surface morphology and chemical composition of carbon fiber,the microstructure and composition of CF/UHMWPE composites were characterized by means of metallographic microscope,SEM,XPS and contact angle.The mechanical properties and biotribological properties of CF/UHMWPE composites were systematically studied.Draw the following conclusions:1.After the carbon fiber treated by concentrated nitric acid,the results of SEM and XPS analysis showed that the surface roughness of the carbon fiber and the type and concentration of reactive functional groups were increased.The analysis of contact angle test showed that the hydrophilic of the oxidized carbon fiber was improved obviously,which provided favorable conditions for the formation of a good interface between the two phases.The SEM image of CF/UHMWPE composites showed that the probability of agglomeration and debonding of carbon fibers in composites increased with the increase of carbon fiber content,and the dispersion of carbon fibers decreased accordingly.The dispersibility of the modified carbon fiber in the composite was better than that of the unmodified one,and the probability of agglomeration and non-infiltration of the carbon fiber were reduced significantly.2.The research on the mechanical properties of CF/UHMWPE composites showed that the tensile strength and elastic modulus of the composites increased with carbon fiber content increased.While the CF content rised from10 wt% to 40 wt%,the tensile strength and elastic modulus of the CF/UHMWPE biocomposites increased from 29.20 MPa,1.30 GPa to 125.34 MPa,4.792 GPa respectively.The flexural strength and modulus of CF/UHMWPE composites showed a trend of increasing first and then decreasing with the increase of carbon fiber.When the carbon fiber content reached 30 wt%,the flexural strength and modulus of the composite reached the maximum values of 157.61 MPa and 9.815 GPa,respectively.In addition,with the increase of carbon fiber content,the fracture mode of composites gradually changed from plastic fracture to brittle fracture.3.The bio-tribological performance test results of UHMWPE indicated that the friction coefficient value increased with the increase of the load under the dry friction when the 316 L stainless steel ball and UHMWPE grinding.When the rotation speed was 100r/min,the friction coefficient of UHMWPE reached the minimum value;when the diameter of the stainless steel ball was 16 mm,the friction coefficient value of the friction pair reaches the minimum.In water,simulated body fluids,bovine calf serum and sodium hyaluronate four kinds of lubricating fluids,the friction coefficient value of UHMWPE was minimum under water lubrication,which was about 0.033;followed by sodium hyaluronate solution and calf serum,the friction coefficient was highest in simulated body fluid.The lubricant effectively promoted the dissipation of frictional heat and reduced the frictional resistance between the friction pairs.At this time,the friction mechanism of UHMWPE was dominated by fatigue wear,and there was a significant wear of abrasive particles in the simulated body fluid.4.According to the research on the friction properties of CF/UHMWPE composites,the friction coefficient value of CF/UHMWPE composites was obviously larger than that of UHMWPE under dry friction conditions,and the friction coefficient of CF/UHMWPE increased with the increase of carbon fiber content.When the carbon fiber content in the composite increased from 0 to 40 wt%,the friction coefficient gradually increased from 0.086 to 0.142.Under the conditions of water lubrication,the friction coefficient of CF/UHMWPE composites decreased first and then increases with the increase of carbon fiber content.When the carbon fiber loading reached 20wt%,the friction coefficient is the lowest,and its value is 0.021.Under different lubricant conditions,the friction coefficient value of CF/UHMWPE composites in sodium hyaluronate solution was the minimum,the average friction coefficient of the material was basically stable at 0.026,followed by deionized water.And the friction coefficient of CF/UHMWPE composites reached maximum value in simulated body fluid lubrication medium.In addition,the carbon fiber surface modification could effectively reduce the friction coefficient of CF/UHMWPE composites.5.PVA gel-CF/UHMWPE biomimetic artificial joint material was prepared by combining chemical modification with freezing-thawing.The results of ATR analysis indicated that the concentration of oxygen containing functional groups on the UHMWPE surface was increased after dichromate oxidation,and the hydrophilicity of the surface of the material was improved.After the graft reaction with PVA,PVA provided a large number of hydroxyl groups on the UHMWPE surface,and increased further the hydrophilicity of UHMWPE.The result of shearing tests indicated that a good interface was formed between the PVA hydrogel and materials,and interfacial shear strength was strong.From the results of the friction test,we can saw that the friction coefficient of the bionic artificial joint material was slightly different under the dry friction condition and the water lubrication condition.But with the sliding distance prolonging,the coefficient of friction increased sharply under the condition of dry rubbing.The friction coefficient of the composites in sodium hyaluronate solution reached minimum value,as low as about 0.01.