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Authors
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Pompe, G. ; Lappan, U. ; Häußler, L.
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Title
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Analysis of the influence of the polymerisation degree on the thermal properties of irradiation-modified poly(tetrafluoroethylene)
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Date
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17.09.2002
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Number
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10105
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Abstract
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The influence of the polymerisation degree on the thermal properties of poly(tetrafluoroethylene) (PTFE) irradiated with 1.5 MeV electrons under various conditions was investigated. The polymerisation degree of radiation-degraded and radiation-crosslinked PTFE was determined by the analysis of chemical structure such as end groups and branching points using <sup>19</sup>F NMR and IR methods. The melting heat and temperature observed in the as-polymerised and melt-crystallised states deviate from each other for high molecular weight PTFE. The differences vanish at polymerisation degree <i>X</i><sub><i>n</i></sub><1600 produced by irradiation with dose of 100–200 kGy. The representation of melting temperature of the melt-crystallised state as function of <i>X</i><sub><i>n</i></sub> permits the estimation of the equilibrium melting temperature <i>T</i>°<sub>m</sub> as 605 K, which agrees with values given in the literature for the extended-chain crystals. We conclude that mainly extended-chain crystals were formed for PTFE of <i>X</i><sub><i>n</i></sub>≤1600 at the melt-crystallisation, whereas PTFE of <i>X</i><sub><i>n</i></sub>>1600 crystallises as folded-chain crystals. The lamellar thickness <i>l</i><sub>c</sub> of the folded-chain crystals can be estimated as about 100 nm. The irradiation of PTFE in the melt results in crosslinking and branching with a strong influence on the thermal properties.
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Publisher
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Thermochimica Acta
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Wikidata
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Citation
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Thermochimica Acta 391 (2002) 257-269
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DOI
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https://doi.org/10.1016/S0040-6031(02)00188-0
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