| Polyethylene is most widely used as artificial joints cartilage material for its non-toxic, little tissue reaction and excellent wear-resistant. After implanted for a long time, a lot of small wear debris of polyethylene will be worn out, which will stimulate the body's biological responses and generate osteolysis and bone inflammation. Then the prosthesis loose is caused and the life of artificial joints is shorten. Therefore, the wear-resistance and its surface lubrication state need to be improved, It is a good way to graft polar molecule to polyethylene surface to improve friction performance.In this paper , hydrophilic AA was grafted on polyethylene surface by UV in liquid phase to improve its friction performance, as the articular cartilage. The polyethylene surface change in functional groups, the molecular structure, surface morphology and topography were studied by infrared diffuse reflectance (ATR), X-ray spectroscopy (XPS), scanning electron microscopy (SEM), atomic force microscope (AFM). contact angles were measured by using JY-82 contact angle detector , and wetting of grafted surface were analyzed. The tribological properties were investigated under three different lubricating conditions including distilled water, saline and serum by sliding against Al2O3 ceramic ball. The effects of grafting and lubricating medium on the tribological properties of PE were studied.The results showed that acrylic acid(AA) was successfully grafted on polyethylene surface by UV. With the prolongation of photopolymerization time, the amount of grafted Poly(AA) on the PE surface increased. The wetting properties of PE can be effectively improved by grafted surface with PAA. Contanct angle decreased from 80～85°C to 21～24°C, and the contact angle markedly decreased with the increasing of grafting amounts. Friction and wear experiments show that the inital friction coefficient of grafted PE decreased from 0.25 to 0.08 and wear rate decreased from 3.45×10-6mm3/Nm to 1.52×10-6mm3/Nm after grafting. Then the wear resistance of polyethylene was obviously improved. In different lubrication medium, the inital friction coefficient of grafted PE decreases as following : distilled water> saline> serum.Keywords: polyethylene, photografting, acrylic acid, surface modification, wear, friction... |
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