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Title: Effect of Cross-Linking Ultrahigh Molecular Weight Polyethylene: Surface Molecular Orientation and Wear Characteristics

Authors:
; ;
Publication Date:
Research Org.:
Brookhaven National Laboratory (BNL) National Synchrotron Light Source
Sponsoring Org.:
Doe - Office Of Science
OSTI Identifier:
930535
Report Number(s):
BNL-80583-2008-JA
DOE Contract Number:
DE-AC02-98CH10886
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Vacuum Sci. and Tech. A: Vacuum, Surfaces, and Films; Journal Volume: 25; Journal Issue: 4
Country of Publication:
United States
Language:
English
Subject:
national synchrotron light source

Citation Formats

Sambasivan,S., Fischer, D., and Hsu, S. Effect of Cross-Linking Ultrahigh Molecular Weight Polyethylene: Surface Molecular Orientation and Wear Characteristics. United States: N. p., 2007. Web. doi:10.1116/1.2723767.
Sambasivan,S., Fischer, D., & Hsu, S. Effect of Cross-Linking Ultrahigh Molecular Weight Polyethylene: Surface Molecular Orientation and Wear Characteristics. United States. doi:10.1116/1.2723767.
Sambasivan,S., Fischer, D., and Hsu, S. Mon . "Effect of Cross-Linking Ultrahigh Molecular Weight Polyethylene: Surface Molecular Orientation and Wear Characteristics". United States. doi:10.1116/1.2723767.
@article{osti_930535,
title = {Effect of Cross-Linking Ultrahigh Molecular Weight Polyethylene: Surface Molecular Orientation and Wear Characteristics},
author = {Sambasivan,S. and Fischer, D. and Hsu, S.},
abstractNote = {},
doi = {10.1116/1.2723767},
journal = {Journal of Vacuum Sci. and Tech. A: Vacuum, Surfaces, and Films},
number = 4,
volume = 25,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}
  • Molecular orientation at the surface layer of cross-linked ultrahigh molecular weight polyethylene (UHMWPE) has been examined. Molecular orientation has been shown to affect the wear resistance and surface mechanical properties of UHMWPE under biomechanical loading conditions. This study utilizes a nondestructive synchrotron based soft x-ray technique; near edge x-ray absorption fine structure at the carbon K-edge to examine the degree of surface molecular orientation of UHMWPE subjected to various cross-linking/sterilization techniques as a function of stress and wear. UHMWPE samples prepared under gamma irradiation, ethylene-oxide (EtO) treatment, and electron beam irradiation were worn in a wear tester systematically. Results suggestmore » that the cross-linking resists surface orientation when the samples were under tensile and biomechanical stresses. The molecular orientation in the C-C chains in the polymer showed a monotonic decrease with an increase in gamma irradiation dosage levels. EtO sterilized samples showed more C-C chain orientation than the electron beam irradiated samples, but lower than the 30 kGy gamma irradiated samples. Ordered C-C chains in UHMWPE samples have been associated with more crystallinity or large strain plastic deformation of the polymer. Higher levels of gamma irradiation appear to induce cross-linking of C-C chains and render a polymer with more amorphous phase which resists orientation after wear and imparts wear resistance to the polymer.« less
  • No abstract prepared.
  • Ultrahigh molecular weight polyethylene (UHMWPE) has been irradiated (0--40 Mrad) with a Co[sup 60] source at room temperature under vacuum. The crystallinity has been investigated by differential scanning calorimetry (DSC) and small-angle X-ray scattering (SAXS). The mechanical properties have been determined at room temperature. A significant increase of heat of fusion can be seen at low irradiation doses, which is attributed to crystallization, caused by chain scission during the process of irradiation. It is also observed that the thickness of the lamellae changes with irradiation dose. The Young's modulus has been improved significantly after irradiation at low doses.
  • The mechanical properties of polyethylene components used in prosthesis are altered after fabrication by the sterilization procedure and by the environmental and mechanical aging which occurs after implantation. To assess the importance and extent of these alterations, ultrahigh molecular weight polyethylenes from two sources, Hercules 1900 and RCH 1000C, were subjected to gamma-ray irradiation and aging in serum and argon environments. Changes induced by these treatments in the structural and mechanical parameters have been determined by a variety of experimental techniques. The effect of irradiation is to introduce crosslinks and to increase the degree of crystallinity resulting in changes inmore » the tensile properties in the direction of higher stiffness and reduced ductility. Aging for six months produced similar changes with subtle differences. The results suggest that the initially low degree of crystallinity which results from the sluggish mobility of the very long chain molecules offers the opportunity for significant changes in the properties during use in the long run.« less