Measurements of free radical in vitamin E-doped ultra-high molecular weight polyethylene: Dependence on materials processing and irradiation environments

摘要: Abstract Ultra-high molecular weight polyethylene (UHMWPE), doped with vitamin E (α-tocopherol (α-T)), was irradiated gamma rays in nitrogen (N2) or air, and the resulting free radicals were detected air using an electron spin resonance (ESR) technique. Two groups of samples investigated. In one group, prepared from blends α-T (20 wt%) UHMWPE powder (PPE-α-T) and, other, compression molded blocks (CMPE-α-T). The CMPE-α-T contained 0% (control), 0.5%, 1.0%, 10.0%, 15.0%, 20.0% 25.0% by weight. When irradiation performed ESR spectrum showed presence only radical (tocopheroxyl, α-T-O ), there no detectable signal due to PE (alkyl/allyl). Most likely, all quenched during air. However, when N2, composite spectra both radicals. Compared control (PPE, α-T) PPE-20% found be significantly reduced α-T. samples, however, did not affect long-term (71 days this study) oxidation behavior Compression without α-T, produced identical irrespective their environment N2 concentration, measured immediately after irradiation, order magnitude less than (CMPE-0% α-T). They also evidenced structural changes respective subsequent for 24 open These observations suggest that can effectively quench a significant fraction but has measurable effect on reactions. No difference containing different concentration.