Abstract
Ultra-high molecular weight polyethylene (UHMWPE) is widely used in artificial joints in the replacement of knee, hip and shoulder that has been impaired as a result of arthritis or other degenerative joint diseases. The UHMWPE made plastic cup is placed in the joint socket in contact with a metal or ceramic ball affixed to a metal stem. Effective reinforcement of multi-walled carbon nanotubes (MWCNTs) in UHMWPE results in improved mechanical and tribological properties. The hydrophobic nature of the nanocomposites surface results in lesser contact with biological fluids during the physiological interaction. In this project, we investigate the UHMWPE/MWCNTs nanocomposites reinforced with MWCNTs at different concentrations. The samples were treated with cold argon plasma at different exposure times. The water contact angles for 60 min plasma-treated nanocomposites with 0.0, 0.5, 1.0, 1.5, and 2.0 wt % MWCNTs were found to be 55.65°, 52.51°, 48.01°, 43.72°, and 37.18° respectively. Increasing the treatment time of nanocomposites has shown transformation from a hydrophobic to a hydrophilic nature due to carboxyl groups being bonded on the surface for treated nanocomposites. Wear analysis was performed under dry, and also under biological lubrication, conditions of all treated samples. The wear factor of untreated pure UHMWPE sample was reduced by 68% and 80%, under dry and lubricated conditions, respectively, as compared to 2 wt % 60 min-treated sample. The kinetic friction co-efficient was also noted under both conditions. The hardness of nanocomposites increased with both MWCNTs loading and plasma treatment time. Similarly, the surface roughness of the nanocomposites was reduced.
Highlights
Ultra-high molecular weight polyethylene (UHMWPE) is a successful biomaterial used as an acetabular cup in hip joint replacement
It is observed that UHMPWE with increasing concentration of multi-walled carbon nanotubes (MWCNTs) shown there is a slight decrease in contact angle
This could be due to the fact that the MWCNTs were acid-treated for more than 24 h before used as reinforcement
Summary
Ultra-high molecular weight polyethylene (UHMWPE) is a successful biomaterial used as an acetabular cup in hip joint replacement. Research attempts were done to enhance the mechanical properties of UHMWPE by reinforcing with microor nano-sized particles, thereby improving wear resistance Different reinforcements, such as carbon nanotubes [9], carbon fibers [10], hydroxyapatite [11], zirconium [12], titanium particles [13], natural coral [14], alumina [15], zinc oxide [16], and kaolin [17] were used as fillers. All observations from these studies showed positive effects of reinforcement Reinforcements such as carbon fibers, carbon nanotubes, hydroxyapatite, zinc oxide (ZnO), etc., confirmed significant improvements in mechanical properties of UHMWPE which, in turn, increases the wear resistance. The structural changes in the polymer surface caused by plasma ions could induce improvements in hardness, wettability, surface chemical activity, cross-linking and other properties.
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