Lyocell yarns are treated with NaOH, liquid ammonia, high pressure steam, and polycarboxylic acids, then dyed with five reactive dyes. The degree of swelling and the micropore structure of the swollen samples in water are discussed in the context of the results obtained with size exclusion chromatography. The water content of the samples is also measured by centrifugal and chromatographic techniques. A good correlation is found between the values from the different techniques for all samples, except for the samples dyed with bi-functional reactive dyes. The total pore volume substantially increases with NaOH treatment and decreases with high pressure steaming. The pore size distributions for the dyed samples are essentially affected by the dyes used, i.e., depending on dye structure and reactive dye type.
Sulfonated hydroxyarylazo and aminoarylazo dyes were reacted with sodium percarbonte in water at pH 10.6 and at various temperatures. We have determined the initial rate and the apparent activation energy of the decoloration reaction. The results suggest a greater susceptibility to attack of the hydrazone form than the azo form. Aminoarylazo dyes are more resistant to degradation relative to similar hydroxyarylazo dyes, which contain a hydroxyl group that can be ionized in alkaline solutions. They are more resistant and have greater apparent activation energy than the others.
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