Wear Properties Of Ultra-low Wear Polyethylene As Artificial Joint Materials

At present,the most commonly used artificial joint bearing materials are the ultra-high molecular weight polyethylene(UHMWPE).However,the UHMWPE wear debris is one of the key factors that shortens the life of joint implants in clinical.To mitigate such wear-related failure,seeking to a new type of artificial joint bearing material is a most effective solution.Ultra-low wear polyethylene(ULWPE)is a new high-density polyethylene material independently developed by Petrochemical Research Institute.Previous studies have demonstrated that this material is a candidate material of prosthesis which has excellent biocompatibility and wear resistance.However,the research on wear resistance mechanism of material is still insufficient.Therefore,the wear resistance mechanism of ULWPE material is studied in this paper.This thesis studied the wear mechanism,structure,physical properties,mechanical properties of ULWPE and revealed the wear resistance mechanism of ULWPE.The structure(molecular structure,characteristic functional group,crystallinity,lamella thickness,crystal morphology),physical properties(microhardness,contact angle,tensile properties)and wear mechanism of ULWPE were characterized by using Fourier transform infrared spectroscopy(FTIR),differential scanning calorimetry(DSC),polarized light microscopy,contact angle measurement,microhardness measurement,tensile performance test and multi-directional motion artificial implant material wear tester.The main results and conclusions of the full text are as follows:(1)FTIR results show that ULWPE material has a long linear molecular chain structure,and the degree of branching of ULWPE is much lower than that of HDPE,UHMWPE and HXLPE.All materials were oxidized and introduced oxygen-containing functional groups.ULWPE was oxidized to a lower extent than UHMWPE and HXLPE materials.The long linear structure of ULWPE gives the material high crystallization performance,crystallization behavior analysis demonstrates that the crystallinity and lamella thickness of ULWPE materials are higher than other three materials(p<0.05).The analysis of crystal morphology shows that ULWPE material has more complete and compact crystal structure formed.(2)The high crystallization properties of ULWPE affect the hardness,strength and toughness of ULWPE.Microhardness analysis shows that ULWPE material has a highest microhardness.Tensile performance analysis results demonstrates that ULWPE material has the highest elongation at break,and the tensile strength of ULWPE material is better than HDPE material.The results of contact angle test indicate that the surface of ULWPE has the lowest contact angle and the highest surface energy.(3)The results of wear resistance tests show that whether with metal or with ceramic ULWPE has the lowest wear rate and the best wear resistance,and the wear rate is much lower than that of UHMWPE and HDPE materials(p<0.05),13% and 17% lower than HXLPE,respectively(p>0.05).From the wear morphology analysis,the ULWPE surface is the most slight,ULWPE,UHMWPE,HDPE and HXLPE materials all have abrasive wear mechanism,and HDPE material has obvious adhesion wear mechanism.Due to the high microhardness and surface energy,ULWPE materials demonstrates the lowest surface wear.The high linearity and low-branched structure of ULWPE material generates high crystallization performance,and the high crystallization property of ULWPE affects the hardness and strength of the material,in addition,ULWPE has good wettability which reduces the friction of the material.The high hardness,high strength,high ductility and good wetting of ULWPE materials reduce the damage of the material to adhesion and abrasive wear,resulting in excellent wear resistance.