Article ID Journal Published Year Pages File Type
5202572 Polymer Degradation and Stability 2012 7 Pages PDF
Abstract

Today, UHMWPE implants are stabilized with α-tocopherol and cross-linked by irradiation in order to reduce wear. Little is known about the structural transformation of the antioxidant α-tocopherol upon irradiation. In the present investigation, the major irradiation reaction products of α-tocopherol dissolved at 0.1 wt.% in liquid model hydrocarbons were characterized spectroscopically and by independent synthesis. We observed only a single product group, namely phenolic alkyl ethers formed by radical recombination of a phenoxyl radical with a secondary alkyl radical. The irradiation dose is the parameter which controls the amount of consumption of α-tocopherol. At a dose of 27.5 kGy, 31-34% of α-tocopherol was transformed into the corresponding ether, while at 97.9 kGy, the degree of transformation was 68-76%. The observed ether formation in the liquid model hydrocarbons explains two significant observations for the α-tocopherol stabilized polymers, namely depletion of the α-tocopherol's phenol group upon irradiation and “grafting”, i.e. formation of a chemical bond between the polymer and its antioxidant.

Related Topics
Physical Sciences and Engineering Chemistry Organic Chemistry
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