Preparation And Tribological Properties Researches Of Biomimetic Polymer Artificial Cartilage Materials

Injury of bone and joints are the most familiar diseases in people's lives. Artificial joint replacement is an effective and widely used method to cure various bone and joint ailments. But, as a non-physiological operation, it was suffered many desiderated problems in implant materials, artificial joints matches, long-time invalidation, and surgery accepting ages, et al. Researches are searching for better artificial articular replacement materials to enhance the life quality of patients.First of all, this paper studies the structure and properties of natural cartilage materials, using the methods and theories of Bionic, we confirmed that the researches of bio-mimetic cartilage material were focused on porous permeability structure, porous viscoelastic behavior, high intensity and toughness composites, and can firmly connect with artificial joint, or can bioactive ankylose with underline bone. The contents and the results of this work are as follows:1. Using template-leaching (T-L) technical, a series of UHMWPE samples with different porousity were prepared. Then we studied the mechanical properties, tribological properties, and hydrophilicity of each samples. UHMWPE sample with the porousity of 27.7% had the best mechanical properties and porous structure in our test. Although porous UHMWPE had higher wear loss than ordinary UHMWPE under dry wear condition, its wear loss was decreased sharply under BSA lubricant condition. There were slight adhesion particles on the surface of porous UHMWPE.The tribological properties of porous UHMWPE were enhanced byγradialized treatment. The research of hydrophilicity properties of porous UHMWPE proved that porous structure decreased the contact angle and enhanced the hydrophilicity of UHMWPE.γradialized treatment also enhanced the hydrophilicity of UHMWPE. The contact angle of porous UHMWPE/water is higher than porous UHMWPE/BSA, because the high molecule protein contained in BSA prevented themselves penetrated into porous UHMWPE matrix.2. A series of PVA-H samples were prepared by different crosslink method with various PVA contentes; a series of PVA-H/HA composites were prepared by different compound methods with different HA content. The effects of preparing parameters on samples'properties were studied. Although PVA hydrogel prepared by physical crosslink method have higher water content than that prepared by chemical crosslink method, the mechanical and tribological properties of samples prepared by chemical crosslink method were higher than that prepared by physical crosslink method, due to chemical crosslink treatment increase the crosslink point of PVA molecule chain. Both PVA contain and physical crosslink times enhanced the properties of samples. Organic/inorganic composite materials can be formed by PVA hydrogel and bioactive HA. Although nano-HA had better reinforced effect than that of micro-HA particles, the introduction of HA particles by ultrasonic mixed method decreased mechanical and tribological properties when the content of HA were higher than 2% weight percent. PVA-H/HA composite prepared by Sol-gel in situ method had better tribological and mechanical properties under the same HA contents.3. The tribological properties of PVA-H/HA composites under different wear conditions were studied: Coefficient and wear loss of samples was sharply increased alone with the increase of loads. The wear mechanism of sample under loads mainly was abrasion. On the other hand, wear loss of PVA-H/HA samples were slowly decreased alone with the increased of sliding speed when the loads were constant. For three wear partners of PVA-H/HA, UHMWPE and stainless steel, the wear loss of PVA-H/HA/stainless steel pair was lower than others. We also found that decrease the roughness of stainless steel partner can obviously decreased the wear loss and coefficient of this pairs. The addition of BSA enhanced the lubricated capability and viscosity of lubricant, and sequentially decreased the wear loss of PVA-H/HA composites. The changes of PVA-H and PVA-H/HA composite before and after soaking in SBF (Stimulated Body Fluid) were studied. The mechanical properties of both PVA-H and PVA-H/HA were slightly increased after soaking in SBF. We also noticed that some white substances were deposited on PVA-H/HA composite, while nothing happened on the surface of pure PVA-H. Ion concentrate analyse showed that the Ca and P were decreased in the SBF solution soaking by PVA-H/HA. FTIR research proved that these white substances were HCA. Characteristic Peaks of HCA were also found in XRD researches. We also found that HCA covered on PVA-H/HA surface were increased alone with soaking periods during the first several days. Additional soaking periods had scarcely effect on HCA depositing. These results indicated that PVA-H/HA would form bioactive joint with natural bone after implant.4. Comparing the tribological properties of PVA-H/HA and porous UHMWPE under same wear condition, we found that porous UHMWPE has lower wear loss than that of PVA-H/HA under dry wear condition, but the result were converse under lubricant condition. Porous UHMWPE under BSA lubricant has a litter higher wear loss than that of samples under water lubricant, due to the bad compatibility between porous UHMWPE and BSA. Stribeck curve was used to analyse the lubricated condition under water and BSA. The results indicated that UHMWPE was always in the boundary lubricant region, the special structure of porous UHMWPE formed mix lubrication regions and decrease friction coefficient, while PVA-H/HA composite has better hydrophilic property and formed mix lubrication region and hydrodynamic lubrication during wear process.Lastly, we expect that next works will focus on reducing wear loss of samples, enhance the combine intensity between PVA-H/HA and HCA layer, animal test and so on.