• citations in SCIndeks: 0
  • citations in CrossRef:0
  • citations in Google Scholar:[]
  • visits in previous 30 days:2
  • full-text downloads in 30 days:0


article: 8 from 11  
Back back to result list
2007, vol. 61, iss. 5, pp. 229-232
Supercritical CO2 impregnation of polyethylene components for medical purposes
aDepartment of Chemical Engineering and Environmental Technology, Graz, Austria
bDepartment of Chemistry of Polymeric Materials, Leoben, Austria
Keywords: supercritical CO2; impregnation; polymer; endo-prostheses
Modem hip and knee endoprosthesis are produced in titanium and to reduce the friction at the contact area polymer parts, mainly ultra-high molecular weight polyethylene (UHMW-PE), are installed. The polyethylene is impregnated with a-tocopherol (vitamin E) before processing for remarkable decrease of oxidative degradation. Cross linked UHMW-PE offers much higher stability, but a-tocopherol cannot be added before processing, because a-tocopherol hinders the cross linking process accompanied by a heavy degradation of the vitamin. The impregnation of UHMW-PE with a-tocopherol has to be performed after the cross linking process and an accurate concentration has to be achieved over the cross section of the whole material. In the first tests UHMW-PE-cubes were stored in pure a-tocopherol under inert atmosphere at temperatures from 100 to 150 °C resulting in a high mass fraction of a-tocopherol in the edge zones and no constant concentration over the cross section. For better distribution and for regulating the mass fraction of a-tocopherol in the cross linked UHMW-PE material supercritical CO2 impregnation tests were investigated. Again UHMW-PE-cubes were impregnated in an autoclave with a-tocopherol dissolved in supercritical CO2 at different pressures and temperatures with variable impregnation times and vitamin E concentrations. Based on the excellent results of supercritical CO2 impregnation standard hip and knee cups were stabilized nearly homogeneously with varying mass fraction of a-tocopherol.
Buchanan, F.J., Sim, B., Downes, S. (1998) Effect of sterilisation and aging on UHMW-PE used in medical implants. Plast., Rubber Compos. Process. Appl, 27, 148
Chen, C.C., Chang, C.J., Yang, P. (2000) Vapor-liquid equilibria of carbon dioxide with linoleic acid, a-tocopherol and triolein at elevated pressures. Fluid Phase Equilib, 175 107
Chrastil, W. (1982) Solubility of solids and liquids in supercritical gases. J Phys. Chem, 86 3016
Davidson, J.A., Schwartz, G. (1987) Wear, creep and frictional heating of femoral implant articulating surfaces and the effect on long-term performance: Part II. J Biomed Mater Res B Appl Biomater, 21 261
del Preyer, B.E., Crova, M., Costa, L., Dallera, A., Camino, G., Gallinaro, P. (1996) Unacceptable biodegradation of polyethylene in vivo. Biomater, 17 873
Deng, M., Shalaby, S.W. (1995) Effects of gamma irradiation, gas environment and postirradiation aging on UHMW-PE. J Appl. Polym. Sri, 58, 2111
Eyerer, P. (1987) Kunststoffe, 77, 617
Goldman, M., Gronsky, R., Pruitt, G.G., Long, L. (1998) The effect of hydrogen peroxide and sterilization on the structure of UHMW-PE. Polym. Degrad. Stab, 62, 97
Goldman, M., Gronsky, R., Ranganathan, R., Pruitt, L. (1996) Oxidation of UHMW-PE characterized by fourier transform infrared spectroscopy. Polymer, 37, 2909
Grood, E.S., Shastri, R., Hopson, C.N. (1982) Analysis of retrieved implants: Cristallinity changes in UHMW-PE. J Biomed. Mater. Res, 16, 399
Henry, J.L., Ascenion, L.R., Garton, A. (1992) The kinetics of polyolefin oxidation in aqueous media. J Polym. Sci.: Polym. Chem, 30, 1693
Škerget, M., Kotnik, P., Knez, Ž. (2003) Phase equilibria in systems containing α-tocopherol and dense gas. J Supercritical Fluids, 26 181


article language: English
document type: Scientific Paper
DOI: 10.2298/HEMIND0704229G
published in SCIndeks: 03/12/2007

Related records