Polyethylene damage analysis

Figure 5 shows the effect of thermal damage on polyethylene when utilizing a 2 keV, 1 microamp electron beam for charge neutralization. "Carbonization" of the surface begins to take place within the first few seconds of analysis when the electron beam is used whereas with the mercury-lamp-photoelectron method, a stable spectrum is obtained for periods of several minutes. 

FAB SIMS in conjunction with charge neutralization utilizing mercury discharge lamp induced photoelectrons permits low-damage highly reproducible analysis of electrically insulating surfaces. Stable spectra can be obtained from polymeric materials such as polyethylene for periods of an hour or more. Minor spectrum differences between samples such as the various oxides of cobalt, which may have previously been due to thermal or surface potential effects, can now be more confidently assigned to compositional differences. 

Headspace-GC-MS analysis is useful for the determination of volatile compounds in samples that are difficult to analyze by conventional chromatographic means, e.g., when the matrix is too complex or contains substances that seriously interfere with the analysis or even damage the column. Peak area for equilibrium headspace gas chromatography depends on, e.g., sample volume and the partition coefficient of the compound of interest between the gas phase and matrix. The need to include the partition coefficient and thus the sample matrix into the calibration procedure causes serious problems with certain sample types, for which no calibration sample can be prepared. These problems can, however, be handled with multiple headspace extraction (MHE) [118]. Headspace-GC-MS has been used for studying the volatile organic compounds in polymers [119]. The degradation products of starch/polyethylene blends [120] and PHB [121] have also been identified. 

Several studies of a related nature have appeared on the photocrosslinking of polyethylene by benzophenone identifying benzopinacol as the main product by FT NMR analysis.Benzoin ethers have been used for the same reaction while in polypropylene little damage was found in terms of the morphological structure of the polymer. ... 

This present study attempted to establish the causes that led to the surface damage of polyethylene tibial insert from a knee prosthesis which was retrieved after 10 years in vivo. The patient was an elderly housewife who was a community ambulator, and was active and not overweight. Analysis on the worn surface polyethylene will provide information about the mechanism and process of the polyethylene degradation after 10 years implantation. 

Wright TM, Rimnac CM, Paris PM, Bansal M. Analysis of surface damage in retrieved carbon fiber-reinforced and plain polyethylene tibial components from posterior stabilized total knee replacements. J Bone Joint Surg [Am] 1988 70(9) 1312-19. 

Tipper JL, Ingham E, Hailey JL, Besong AA, Fisher J, Wroblewski BM, Stone MH. Quantitative analysis of polyethylene wear debris, wear rate and head damage in retrieved Chamley hip prostheses. J Mater Sci Mater Med 2000 February ll(2) l 17-24. 

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