Polarised ATR-FTIR Characterisation of Cellulosic Fibres in Relation to Historic Artefacts
| Hlavní autori: | , |
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| Médium: | Článok |
| Jazyk: | angličtina slovenčina |
| ISSN: | 0034-5806 |
| On-line prístup: | http://www.viks.sk/chk/res_4_04_249_259.doc |
| Abstrakt: | SUMMARY. The utility of polarised attenuated-total-reflectance (ATR) FTIR spectroscopy was investigated for the identification of cellulosic fibres and characterisation of their state of degradation. Turning the polariser so that the electric vector is parallel (Epll) or perpendicular (Eprp) provides a means of assessing the orientational crystallinity of cellulose from the polarised spectra of aligned plant fibres. Analysis of the spectra can reveal both the angle of microfibrillar wind and its directionality. Here, the best fits to the data suggest: flax 7°/S-spiral; sisal 25°/Z-spiral; coir 70°/S-spiral, where the predominant twist is given for the outer cell-wall regions sampled. Polarised-ATR-FTIR also allows degradation of the amorphous component of cellulose to be highlighted, by recording spectra with the optimum alignment of fibre and polariser. Changes observed on thermal ageing of flax in air at 190 °C are consistent with oxidation of amorphous cellulose and formation of carbonyl and carboxylate moieties; the non-dichroic nature of the carbonyl band confirms that the ordered crystalline regions were not primarily involved CONCLUSION. Our results suggest that polarised attenuated-total-reflectance (ATR) FTIR spec-troscopy has some utility in the study of cellulosic fibres. The orientational crystallinity of cellulose is highlighted in the polarised spectra of aligned plant fibres. Analysis of the spectra can reveal both the angle of microfibrillar wind and its directionality. Here, the best fits to the data suggest: flax 7°/S spiral; sisal 25°/Z spiral; coir 70°/S spiral, where the predominant direction of wind is indicated for the outer cell-wall layer of each. Ageing of the amorphous component of cellulose can be highlighted by recording spectra with the optimum alignment of fibre and polariser. Changes observed on thermal ageing are consistent with oxidation of amorphous cellulose and formation of carbonyl and carboxylate moieties; the non-dichroic nature of the carbonyl band confirms that the ordered crystalline regions were not primarily involved |
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| ISSN: | 0034-5806 |
