The Effects of Gamma Radiation on Cotton: Part V: Post-Irradiation Reactions

Abstract

Purified cotton cellulose dried to less than 0.5% moisture was irradiated in a nitrogen atmosphere with high-energy gamma radiation from cobalt-60 at selected dosages up to 6 × 106 roentgens. Post-irradiation chain cleavages of the cellulose molecule on exposure to air were indicated by decreases in the viscosity of the irradiated cellulose with increasing time after irradiation. Post-irradiation reactions of the irradiated cellulose with acrylonitrile were investigated. Low yields of graft polymer were obtained on treatment of the irradiated cottons with pure acrylonitrile, 5% acrylonitrile in water, and 32% acrylonitrile in N,N-dimethylformamide. The effect of temperature in the 23°-100° C range on these treatments was investigated. High yields of graft polymer were obtained when the irradiated cottons were treated with acrylonitrile solutions in concentrated aqueous zinc chloride. The mechanical properties of selected fibrous graft polymers of cellulose–polyacrylonitrile were determined. Some irradiations were carried out in the presence of oxygen and moisture for comparison of these post-irradiation reactions. Results were discussed with relation to the production of long-lived free radicals in the cotton cellulose by high-energy gamma radiation.