Positron lifetime measurements are made in the semicrystalline polymer polytetrafluorethylene (PTFE) of different initial crystallinity in the y-dose range up to 20 Mrad. The lifetime spectra are clearly resolved into four components, and corresponding annihilation mechanisms are discussed. The results for a high-crystalline and for a low-crystalline (quenched) PTFE sample are compared. It may be shown for the first time to what extent in this material free radicals on the one hand and radiation-induced structure alterations on the other hand change the positron lifetime parameters.
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Peter Kindl (1984) studied this question.
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