Electron spin resonance spectra of some polymers irradiated at 77°K

Libby, D. R.; Ormerod, M.G.; Charlesby, A.

doi:10.1016/0032-3861(60)90030-6

Cited by 50 publications

(12 citation statements)

References 4 publications

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“…14,29 Similarly, the free radical signature of irradiated UHMWPE and irradiated UHMWPE annealed under pressure at room temperature displayed similar peaks, a combination of allyl, alkyl, and polyenyl free radicals. 39,40 These results showed that pressure treatment of 100-kGy irradiated UHMWPE alone did not induce enough mobility in the free radicals trapped in the crystalline regions to recombine and be extinguished. Therefore, irradiated UHMWPE annealed under pressure at room temperature would be expected to oxidize in the long-term.…”

Section: Discussionmentioning

confidence: 97%

The elimination of free radicals in irradiated UHMWPEs with and without vitamin E stabilization by annealing under pressure

2011

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Radiation crosslinking of ultrahigh molecular weight polyethylene (UHMWPE) has been used to decrease the wear of joint implant bearing surfaces. While radiation crosslinking has been successful in decreasing femoral head penetration into UHMWPE acetabular liners in vivo, postirradiation thermal treatment of the polymer is required to ensure the oxidative stability of joint implants in the long term. Two types of thermal treatment have been used: (i) annealing below the melting point preserves the mechanical properties but the residual free radicals trapped in the crystalline regions are not completely eliminated, leading to oxidation in the long-term and (ii) annealing above the melting point (melting) eliminates the free radicals but leads to a decrease in mechanical properties through loss of crystallinity during the melting process. In this study, we hypothesized that free radicals could be reduced by annealing below the melting point under pressure effectively without melting due to the elevation of the melting point. By avoiding the complete melting of UHMWPE, mechanical properties would be preserved. Our hypothesis tested positive in that we found the radiation-induced free radicals to be markedly reduced (below the detection limit of state-of-the-art electron spin resonance) by thermal annealing under pressure in radiation crosslinked virgin UHMWPE and UHMWPE/vitamin-E blends without loss of mechanical properties.

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Section: Discussionmentioning

confidence: 97%

The elimination of free radicals in irradiated UHMWPEs with and without vitamin E stabilization by annealing under pressure

2011

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“…In PE, three types of radicals have been detected upon irradiation in vacuo: those giving rise to a sextet ESR spectrum were found to be secondary alkyl radicals [58][59][60][61] -CH2 C HCH2--, the septet spectrum was ascribed to allyl radicals [61][62][63] -CH-CH=CH-and, finally, the broad singlet spectrum observed only at high irradiation doses, was attributed to polyenyl radicals [60][61][62][63][64] --CH--(CH=CH)~--.…”

Section: Types Of Radicalsmentioning

confidence: 99%

Radiation effects in polyethylene and n-alkanes

Ungar

1981

J Mater Sci

138

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The effect of high-energy radiation on n-alkanes and polyethylene (PE) are reviewed. The article includes a description of (a) primary radiation events, formation, spatial distribution and decay of free radicals and radical migration mechanisms, (b) formation of cross-lin ks and other sta ble products, (c) the effects of crystal linity, crystalline modifications and morphology on radiation cross-linking, and (d) radiation-induced changes in the crystal lattice and the destruction of crystallinity at high irradiation doses.An attempt is made to bring together conflicting views on various unsolved problems of the radiation physics and chemistry of these important and much studied substances. Long-chain paraffins are given considerable attention since their radiation behaviour often provides a link between that of PE and its short-chain analogues.

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“…5 1087,1117,1137,1275,1362,1569,1573,1574,1589,1602,1640,1642,1669,1812,1891,1982,[1985][1986][1987][1988]2116,2151,2154,2156,2242,2304,2402,2402) and electron beam radiation99, 102,103,439,730,1363,2026,2154,2248,2392,2459) has been the subject of a large number of ESR studies. 5 1087,1117,1137,1275,1362,1569,1573,1574,1589,…”

Section: Radiation and Photo-degradation Of Polymersmentioning

confidence: 99%

“…Chadesby et al 1363) have reported formation of a six-line spectrum of alkyl radicals (5.3) during 'Y-irradiation of polypropylene at 77 K. Ohnishi et al 1640 ) found that the spectrum of polypropylene irradiated and measured at 195 K consists of four different components, which could be characterized as eight-, seven-, six-and one-line spectra. Chadesby et al 1363) have reported formation of a six-line spectrum of alkyl radicals (5.3) during 'Y-irradiation of polypropylene at 77 K. Ohnishi et al 1640 ) found that the spectrum of polypropylene irradiated and measured at 195 K consists of four different components, which could be characterized as eight-, seven-, six-and one-line spectra.…”

Section: Radiation and Photo-degradation Of Polymersmentioning

confidence: 99%