Authors Fuchs, B. ; Lappan, U. ; Lunkwitz, K. ; Scheler, U.
Title Radiochemical Yields for Cross-Links and Branches in Radiation-Modified Poly(tetrafluoroethylene)
Date 19.11.2002
Number 10104
Abstract For the enhancement of the compatibility of fluoropolymers with other materials radiationmodification is applied, for which irradiation with high-energy electrons provides an efficient and flexiblepossibility. Poly(tetrafluoroethylene) (PTFE) is known to predominantly undergo chain scission underirradiation. To counteract this chain scission and the resulting deterioration of the mechanical properties,PTFE has been irradiated at temperatures above the melting temperature under inert atmospheres.Under these conditions, in addition to chain scission long chain branches and cross-links are formed.The resulting structures have been studied by high-resolution fluorine-19 solid-state NMR applying high-speed magic-angle sample spinning. The structural changes as a function of energy dose and irradiationcondition have been investigated upon irradiation under nitrogen atmosphere at 385 <IMG SRC="/images/entities/deg.gif">C and under vacuumat 365 and 385 <IMG SRC="/images/entities/deg.gif">C. Structures of interest are terminal groups, CF<SUB>3</SUB> side groups, branches, and cross-links. From quantitative information derived from the <SUP>19</SUP>F NMR spectra, the radiochemical yields, <I>G</I>(<I>x</I>)values, for the formation of CF<SUB>3</SUB> side groups, branches, and cross-links have been calculated. <I>G</I>(<I>x</I>) valuesof side groups and branches decrease with radiation dose, while the radiochemical yield of cross-links isnearly constant. These results are interpreted that in the first step in addition to main-chain scissionthe CF<SUB>3</SUB> side groups and branches were formed and in the second step after forming a sufficient quantityof side groups and branches the cross-links are formed.
Publisher Macromolecules
Citation Macromolecules 35 (2002) 9079-9082

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