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Friction and wear behavior of ultra-high molecular weight polyethylene as a function of polymer crystallinity
K S Kanaga Karuppiah1, Angela L Bruck, Sriram Sundararajan
1Department of Mechanical Engineering, Iowa State University, Ames, IA 50011, USA.
Abstract:
In this study the friction, wear and surface mechanical behavior of medical-grade ultra-high molecular weight polyethylene (UHMWPE) (GUR 1050 resin) were evaluated as a function of polymer crystallinity. Crystallinity was controlled by heating UHMWPE to a temperature above its melting point and varying the hold time and cooling rates. The degree of crystallinity of the samples was evaluated using differential scanning calorimetry (DSC). A higher degree of crystallinity in the UHMWPE resulted in lower friction force and an increase in scratch resistance at the micro- and nanoscales. On the nanoscale, the lamellar structure appeared to affect the observed wear resistance. Reciprocating-wear tests performed using a microtribometer showed that an increase in crystallinity also resulted in lower wear depth and width. Nanoindentation experiments also showed an increase in hardness values with an increase in sample crystallinity.
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