Carboxymethylation of viscose and cotton fibers: comparisons of water retention and moisture sorption

The aim of the work was to compare the water retention and moisture sorption of viscose (CV) and cotton (Co) fibers carboxymethylated from aqueous media, in presence of NaOH, with sodium monochloroacetate. It was shown previously that under the same treatment conditions, the degree of carboxymethylation was higher in CV and so was the depth within fiber structures to which the carboxymethylation reactions occurred. It was also shown previously, that in terms of their capacity for sorption of a cationic dye (methylene blue), the Co performed better than CV. In this work, the same fibers were tested for their water retention and moisture sorption propensities. The two were sensitive both to the degree of carboxymethylation and the inherent properties of fibers (accessibility, degree of swelling, hornification). But the moisture sorption levels were less sensitive to the degree of carboxymethylation and more to inherent fiber properties whereas the reverse was observed for water retention. In contrast to the prior observations with dye sorption, CV performed better than Co in both moisture sorption and water retention. The poor performance of CV in dye sorption was attributed to the greater depth of carboxymethylation within the fibers that hindered dye permeation, but the same feature was observed to result in better performance (water retention) or not to hinder performance (moisture sorption). These observations highlight the contrasting effects that may arise, of a given set of treatment parameters (fiber type, alkali level in treatment), on efficacy of the product performance.