20 research outputs found

    The Physics of the B Factories

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    On morphology of consolidated UHMWPE resin in hip cups

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    The microstructure of replacement hip cups made from ultra-high molecular weight polyethylene (UHMWPE) has been revealed by permanganic etching to bring out the fine details. Specimens are examined by optical microscopy according to the Nomarski technique, and by scanning and transmission electron microscopy. In all cups the original reactor particles are visible. Optical microscopy is most productive in revealing variations not only in the texture of different individual particles, but also in the degree of consolidation of a particle with its neighbours. Both these factors differ according to the material and process. Electron microscopy reveals the existence of pockets of lower molecular weight material which has been expelled from the particles by the original sintering process

    Novel Production Methods

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    Mechanical changes linked to embrittlement at the wear surface ofpolyethylene implants in hip joints

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    5 pags, 4 figs, 1 tabA study of microhardness at the wear surface of polyethylene implants before and after use is reported. The microhardness values supportprevious electron microscopic observations of an embrittled region extending into used implants by showing that, after use, the hardness ofpolyethylene implants increases above the initial value the nearer the wear surface is approached. It is shown that these changes accompany ahardening of the surface layer and are related to an increase in the crystallinity of the polymer. The increasing hardness towards the edge ofthe concave surface of the implant is discussed in terms both of the local variation of crystallinity and changes in the interlamellar regions.Peer reviewe
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