Modification of cotton fabrics via radiation graft copolymerization with acrylic acid, acrylonitrile and their mixtures

Radiation-induced grafting of acrylic acid (AAc), acrylonitrile (AN) and their mixtures onto cotton fabrics has been studied at 2.56 Gy/s gamma dose rate and 1:40 fabric-to-liquor ratio. The grafting process was performed in the presence of aqueous AAc containing 0.75% (owm) Mohr's salt, and 65:15 methanol-water mixture for AN. The effect of monomer concentration and irradiation time (dose) on the degree of grafting has also been investigated., The dependence of the initial grafting rate on monomer concentration follows a second order kinetics for AN and a negative first order one for AAc. Grafts from monomer mixtures show different kinetic behaviour, depending on AN/AAc ratios in solutions with constant monomers mixture concentration of 20%. The degree of grafting increases with the increase in AN/AAc ratio from 20/80 to 80/20 for all the doses applied. The reaction order changes from a positive order of 0.55 to a negative order of 0.41 as the ratio of AN/AAc decreases. The swelling properties of cotton fabrics improve with the increase in degree of grafting of AAc and deteriorate with the increase in graft yield of AN. Fabrics grafted with monomer mixtures show swelling behaviour between those of AAc and AN. The electrical conductivity of grafts prepared from the monomers or their mixtures shows a fast initial decrease followed by a tendency to level-off as the graft yield increases up to 35%, irrespective of the type of monomer or the mixture ratio. The dyeability of cotton fabrics towards Sandocryl Blue B-3G, a basic dye, improves considerably as the graft yield with AAc increases up to 20% with no further appreciable changes for higher degrees of grafting. Grafts with AN and AAc/AN mixtures show lower dyeing affinity than that for AAc grafts. The pH of the dye bath affects considerably the dyeability of the grafted fabrics, giving an optimum condition at pH 3.9. Proposed schemes for grafting and dyeing of cotton fabrics with Sandocryl Blue B-3G are given.