Fischer-tropsch waxes. III. Indications of molecular order in molten wax
| Autor: | J. H. le Roux |
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| Rok vydání: | 2007 |
| Předmět: | |
| Zdroj: | Journal of Applied Chemistry. 19:209-212 |
| ISSN: | 1934-998X 0021-8871 |
| DOI: | 10.1002/jctb.5010190708 |
| Popis: | Although paraffins cannot form liquid crystals, evidence of the existence of some kind of molecular order at temperatures above their melting points can be found in the literature. When the infra-red spectra of certain Fischer–Tropsch waxes were recorded at different temperatures, it was noticed that the intensity of the 1303 cm−1 band (A1303), which is due to methylene groups in amorphous regions, was abnormally low just above the melting points of the waxes. At higher temperatures the intensity rose to a maximum followed by the normal decline. This effect was shown most strikingly by super-hard wax, which has a high crystallinity and high average molecular weight. A dilatometric experiment with super-hard wax showed that the specific volume rises linearly from the melting point (111°) to ∼ 125°. At higher temperatures, although the volume continues to rise linearly, the slope is reduced by 11%. The explanation presented for both phenomena is that bundles of molecules are present above the melting point. They are remnants from crystallites and disappear at ∼ 125°. in the case of super-hard wax. Upon cooling, however, the ordering of molecules only starts taking place near the congealing point. This is borne out by the linear changes in A1303 and specific volume that have been observed. |
| Databáze: | OpenAIRE |
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