Feasibility Studies on Ultra High Molecular Weight Polyethylene/Multi Walled Carbon Nanotubes Composites for Total Joint Replacements

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Ultra high molecular weight polyethylene (UHMWPE) has been the prime choice for total joint replacements (TJRs) owing to its unique attributes like good mechanical properties and wear resistance compared to most of the commonly used engineering polymers. However, some of the critical issues like osteolysis, wear debris generation, and property degradation after irradiation still remain prime concern. In order to seek a solution for some of the problems, it is proposed to develop multi walled carbon nanotubes (MWCNTs) based UHMWPE composites having improved mechanical properties and wear characteristics compared to that of UHMWPE. The MWCNTs were chemically functionalized and physically blended with UHMWPE in a ball milling machine for 45 minutes to form homogeneous mixture with different concentrations such as 0.5, 1.0, 1.5, 2.0, 2.5 and 5.0 wt. % of reinforcement. In order to compare the antioxidant activity of MWCNTs with currently employed antioxidant, UHMWPE was blended with 0.1, 0.3 and 0.5 wt. % of alpha-Tocopherol (DT). The physically blended powders of UHMWPE/MWCNTs and UHMWPE/DT were then compression moulded to obtain the test sample in the form of a sheet having the dimension of 20 mm D 20 mm and 0.5 mm thick. The mechanical properties of the composites and DT blends were studied according to ASTM D1708 standard. The optimum concentration of MWCNTs in UHMWPE was found to be 2 wt. %, where the work to failure, fracture stress, strain at fracture, and yield stress of the medical grade UHMWPE were enhanced by 176, 93, 70 and 44 %, respectively. However, the presence of DT was not found to influence the mechanical properties of UHMWPE. The mechanisms related to the enhancement of mechanical properties of UHMWPE upto an optimum concentration of MWCNTs were identified as inherent properties of reinforcement, homogenous dispersion of MWCNTs in UHMWPE, effective stress transfer from UHMWPE to MWCNTs,.
Supervisor: S. Kanakraj