Effect of processing and reactive dyeing on the swelling and pore structure of lyocell fibers

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.