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Defect initiation at subsurface grain boundary as a precursor of delamination in ultrahigh molecular weight polyethylene
Author(s) -
Shibata Nobuyuki,
Tomita Naohide,
Onmori Naoki,
Kato Koji,
Ikeuchi Ken
Publication year - 2003
Publication title -
journal of biomedical materials research part a
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.849
H-Index - 150
eISSN - 1552-4965
pISSN - 1549-3296
DOI - 10.1002/jbm.a.10133
Subject(s) - materials science , delamination (geology) , composite material , scanning electron microscope , irradiation , optical microscope , grain boundary , surface roughness , surface finish , ultra high molecular weight polyethylene , electron microscope , polyethylene , microstructure , optics , paleontology , tectonics , physics , nuclear physics , subduction , biology
In order to examine the initiation mechanism of delamination in ultrahigh molecular weight polyethylene (UHMWPE) knee components, a bi‐directional sliding fatigue test was performed for three types of UHMWPE specimens: nonirradiated, gamma‐irradiated (25 kGy) and gamma‐irradiated (25 kGy) with 0.1% vitamin E added. Sliding surfaces of post‐tested UHMWPE specimens were observed using an optical microscope and a scanning electron microscope. Also, surface roughness was measured at the sliding surfaces of UHMWPE specimens. Delamination was observed only in gamma‐irradiated specimens. A networked structure of surface asperity that resembled grain boundary was observed prior to delamination in gamma‐irradiated specimens. Surface roughness in the gamma‐irradiated specimens, higher than in any other specimen, showed a rapid increase prior to delamination. Detailed observation using an optical microscope and a scanning electron microscope showed microscopic crack initiation along subsurface grain boundaries in gamma‐irradiated specimens. These results suggest that subsurface crack initiation is a precursor of delamination and is accelerated by oxidative degradation due to gamma irradiation. Of the three types of specimens, UHMWPE with vitamin E added showed the lowest surface roughness values at all measuring points. The addition of vitamin E is effective in improving wear resistance and fatigue performance of UHMWPE. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 67A: 276–284, 2003