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Title: Dyeing of cellulosic fibres : how the structure of cellulose and the dye molecules affect the dyeing process
Author: Adams, Katherine Victoria
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2001
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The understanding of the dyeing of cellulosic fibres has been limited by the lack of fundamental knowledge about the structures and processes that occur on the molecular scale. The work reported in this dissertation has begun to address some of the areas where greater insight into these structures and processes is required. This information can then be used as input into existing empirical models of the dyeing process used in industry. The solid state structure of various cellulosic fibres were investigated using carbon-13 cross polarisation/magic angle spinning nuclear magnetic resonance (¹³C CP/MAS NMR) spectroscopy. The percentage crystallinities and the proportions of the different crystalline forms of cellulose, Iα, Iβ and II, in each sample were calculated from lineshape analyses of the spectra. The presence of cellulose II in mercerised cotton was confirmed and it is proposed that the degree of mercerisation is indicated by the percentage crystallinity and the proportion of cellulose II present in the sample. The pulsed-gradient spin-echo (PGSE) NMR technique has been used to characterise the self-diffusion of water within various cellulose samples. A new model, defined by a three-component diffusivity, has been proposed to describe this diffusion and it is consistent with the known structures of various cellulosic fibres, such as native cotton and Tencel. It is also proposed that some of the variations in dyeability of cellulose fibres might be partially explained by the observed differences in the self-diffusion of water within the samples. The characterisation of the self-diffusion and aggregation of acid dyes in aqueous solution has been investigated for the first time using the PGSE NMR method. The results found agree well with the literature, and the main trends, such as an increase in the average aggregation number caused by a corresponding increase in dye molecular weight, dye concentration or addition of NaCl, were observable by this method. Finally, the self-diffusion of dye molecules within cotton fibres was investigated using the PGSE NMR technique. Not all dyes could be studied using this method as it was found that an increase in the affinity of the dye for the cotton fibre surface caused the dye molecules to be associated with fast relaxation times and therefore become 'invisible' to the NMR experiment. Major variations were apparent when comparing the diffusion of dye within the unmercerised and mercerised cotton. It is proposed that this difference is found because of the increased affinity of dyes towards the surface of mercerised cotton.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available