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Abstract: Ultra-high molecular weight polyethylene (UHMWPE) powder was modified with a zwitterion monomer with good biocompatibility of MPDSAH (3-dimethy (3-(N-methacryamido) propyl) ammonium propane sulfonate) by UV irradiation and then hot pressed. The microstructure and mechanical properties of modified UHMWPE are investigated. The results show that the structure of powder and bulk materials has been changed. The modified powders have more filaments than that of untreated. The surface of modified bulk materials is more rough and displays the granular protuberances which have the random loose arrangement compared with untreated UHMWPE. The crystallinity, uniaxial tensile and compressive properties decreased after grafting. Ultimate elongations decrease with the increase of the monomer concentration and are higher than 300% which is recommended by ASTM and ISO except the sample with 0.45mol/L MPDSAH. The friction coefficient of modified UHMWPE is lower than that of the untreated UHMWPE and it decreases gradually with the increase of monomer concentration. The wear rates have been decreased and the wear resistance has been improved under saline and distilled water lubrication. [Copyright &y& Elsevier]

Highlights: [•] Wettability and blood compatibility of PMPC-grafted UHMWPE were improved. [•] The friction properties including the short and long term under high contact stress were investigated. [•] The PMPC brushes were sheared off from the surface with the increase of sliding cycles. [Copyright &y& Elsevier]

Abstract: In order to prolong the service life of artificial joints, a zwitterion monomer of MPDSAH ((3-(methacryloylamino)propyl)dimethyl (3-sulfopropyl)ammonium hydroxide) was grafted onto ultra-high molecular weight polyethylene (UHMWPE) powders to construct a brush-like structure by UV irradiation, and then the grafted UHMWPE powders were hot pressed as the bulk materials. The wettability of bulk materials surface with different monomer concentrations was analyzed. The tribological properties of modified UHMWPE bulk materials were investigated under distilled water and saline by sliding against stainless steel ball. The measurement of Fourier-transform infrared (FT-IR) spectroscopy indicates that MPDSAH is successfully grafted onto the surface of UHMWPE powders by UV irradiation. The contact angles of modified UHMWPE are decreased and the surface wettability is effectively improved. The friction coefficient of the modified sample is lower than that of untreated UHMWPE in aqueous lubricants during a long-term friction. With the increase of monomer concentration, the wear rate of grafted UHMWPE decreases gradually in distilled water. The grafting hydrophilic macromolecule polymer is helpful to form a lubricating film of water, which leads to the improvement of the lubricity of UHMWPE. [Copyright &y& Elsevier]

Abstract: In order to improve the tribological properties of UHMWPE sliding against Ti6Al4V alloy, three different methods were applied to modified the alloys surface, namely two-step plasma immersion ion implantation, thermal oxidation (TO) and laser surface texturing (LST). Structure and wettability of surface modified titanium alloy were investigated. Friction and wear properties of UHMWPE sliding against modified alloys were tested by a pin-on-disc tribometer under distilled water and bovine serum respectively. The results showed that a graded titanium oxide–titanium nitride film and a titanium oxide film formed separately after being treated by ion implantation and TO, thus contributing to the improvement of wettability of alloy surfaces. The friction coefficients of modified Ti6Al4V alloys decreased obviously, especially for the TO-treated one, which reached as low as 0.015. The wear rate of UHMWPE was reduced and the lowest wear rate was obtained when sliding against the ion implanted one. Almost no notable wear features presented on the titanium alloy treated by ion implantation. [Copyright &y& Elsevier]