IUVSTA 15th International Vacuum Congress (IVC-15), AVS 48th International Symposium (AVS-48), 11th International Conference on Solid Surfaces (ICSS-11)
    Tribology Tuesday Sessions
       Session TR+MM-TuP

Paper TR+MM-TuP6
Nanomechanical Response of Ultra High Molecular Weight Polyethylene Nanostructure

Tuesday, October 30, 2001, 5:30 pm, Room 134/135

Session: Poster Session
Presenter: L. Riester, Oak Ridge National Laboratory
Authors: L. Riester, Oak Ridge National Laboratory
S.P. Ho, Clemson University
T. Boland, Clemson University
M. LaBerge, Clemson University
Correspondent: Click to Email
Over the past three decades studies on patients with total joint replacement (TJR) prosthesis have shown that ultra high molecular weight polyethylene (UHMWPE) nanoscale wear debris causes osteolysis leading to subsequent aseptic loosening of the implant and total failure of the implant. At the nanoscale, UHMWPE is a semicrystalline material defined by a crystalline domain within an amorphous matrix. Previous work focused on determining the average mechanical properties assuming isotropy within the material proved insufficient for the consideration of failure analysis due to its composite-like anisotropic nanostructure. While several factors can influence the mechanical failure of a material, this study is limited to investigating the mechanical response of the nanostructure of UHMWPE insert in TJR prosthesis. In this study, the effects of sample preparation technique on the nanostructure and the nanomechanical response of compression molded UHMWPE nanostructure were investigated The nanostructure of UHMWPE samples prepared by ultramicrotoming, cryo-ultramicrotoming and etching techniques was studied using an atomic force microscope. The nanomechanical response of the nanostructure as a function of the sample preparation technique was studied using a Nanoindenter II with a diamond Berkovich indenter tip. The samples were indented using continuos stiffness method at a constant displacement rate for penetration depth range of 50-1000 nanometers respectively. This study shows that sample preparation techniques possibly introduced artifacts as illustrated by the changes in the morphology of UHMWPE, which was especially evident in polymers that were ultrasectioned above their glass transition temperature. It was also shown that the technique of etching a sample surface with a permanganate etchant to reveal the crystalline regions changed the neighboring boundary conditions, which in turn redefined the crystalline nanomechanical response to mechanical loading.