Study On Wear-resistant Modification Of UHM WPE For Displaceable Joint Materials

Comparing with common polyethylene and other engineering plastics, ultra-high molecular weight polyethylene(UHMWPE), as a thermoplastic engineering plastic, has high abrasion resistance, self-lubrication, impact resistance, corrosion resistance and high biocompatibility,etc.It has very wide application prospect in machinery, chemical engineering, textile, medical industry and many other fields, especially acting as the artificial articular cartilage(displacement material of cotyla) to combine with metal or ceramic articular caput to constitute the artificial joint that is widely adopted in clinical applications. A large amount of abrasive dust caused by abrasion is easy to gather and can induce the body cells to create a series of bad biological responses during use, which will lead to osteolysis and aseptic loosening around prosthesis, so that they would have a strong impact on the quality and service life of artificial joint. Therefore, it is of great importance to improve the abrasion resistance of UHMWPE and reduce the generation of wear debris for increasing service life of artificial joint as well as easing patient’s pain. The main research contents and results are as follows:(1)The benzophenone(BP) was used as the initiator and perfluorinated alkyl methacrylate ethyl(PFAMAE) was grafted on the UHMWPE powder; effects of various factors on the grafting ratio and effects of grafting on the tribology performance of UHMWPE were discussed; based on grafting PFAMAE, nano polytetrafluoroethyleme(Nano-PTFE) was filled in UHMWPE-g-PFAMAE to investigate the mechanics and tribology performances of the composite material after filling and its abrasion mechanism; Based on infrared spectroscopic analysis on the product of grafting PFAMAE on UHMWPE by UV, the grafting of PFAMAE was proved to be successful, and the best grafting technology conditions were obtained through the single factor experiment. Tribology and mechanics tests were conducted on UHMWPE-g-PFAMAE material after grafting, the results of which indicated that: through the grafting of PFAMAE, the friction coefficient and wear rate reduced in varying degrees; and the tensile strength, elongation at break, and hardness were improved. The experiment of composites filled by Nano-PTFE to UHMWPE-g-PFAMAE proved that: when 1% of Nano-PTFE was added, the composite had the lowest wear rate and friction coefficient. What’s more, the abrasion mechanism before and after grafting was found by SEM to change from abrasive wear to adhesive wear.(2)Based on(1) and with the help of UV-light, BP was used as initiator and AA as grafting monomer for grafting modification of UHMWPE. Then blending modification was carried out on the grafted product UHMWPE-g-AA with PA powder. Investigations were made of the mechanical and tribological properties as well as the wear mechanism of UHMWPE-g-AA/PA blending materials. According to the results, where the PA contents came to 4%, UHMWPE-g-AA/PA blending materials performed best in tribological properties, with the friction coefficients reduced to 0.193 and the wear rate remaining at 5.89 ×10-7mm3/(N?m).At this time the materials featured the best performance in tensile strength and elongation at break. Judging by the wearing surface appearance of the blending materials under SEM, wear mechanism was mainly presented in abrasive wear, independent of the addition amount of PA.The addition of fillings just improved the width and depth of the furrow.(3) Silane coupling agent KH560 was used for surface treatment of Nano-Si O2. Then it was mixed with UHMWPE-g-AA, to probe into the effect of Nano-Si O2 on the mechanical and tribological properties of UHMWPE-g-AA/Nano-Si O2 composite materials. According to the results, the addition of Nano-Si O2 to UHMWPE-g-AA would significantly enhance the rigidity of composite materials. Where Nano-Si O2 contents came to 2%, the composite materials performed best in tensile strength and elongation at break. Where Nano-Si O2 contents rose to around 3%, UHMWPE-g-AA/Si O2 composite materials achieved the best tribological performance,with the friction coefficient remaining at 0.213 and the wear rate at 3.53×10-7mm3/(N?m). Judging from the SEM photos of the wear surface, the composite materials underwent mainly abrasive wear and slight plastic deformation when Nano-Si O2 contents fell below 3%; however, when Nano-Si O2 contents exceeded 3%, adhesive wear and fatigue wear constituted the wear mechanism. Only when Nano-Si O2 contents remained at 3% would the composite materials mainly featured adhesive wear.