TEMPO-Mediated Oxidation of Cotton Cellulose Fabrics with Sodium Dichloroisocyanurate

Abstract

Cotton fabrics were oxidized with sodium dichloroisocyanurate (SDIC) and catalytic amounts of 2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPO) and NaBr in water at pH 9 or 10 and temperatures of 15–40 ̊C for 5–15 min. The TEMPO-oxidized fabrics were post-treated with NaClO₂,H₂O₂ and NaBH₄. The oxidized cotton fabrics thus obtained had higher carboxylate contents and higher viscosity-average degrees of polymerization(DP_v), compared with the conventional TEMPO/NaBr/NaClO or TEMPO/NaClO/NaClO₂ system when the oxidation was carried out under similar conditions. Because SDIC gradually releases HOCl in water, forming NaOCl at pH 10, this NaClO is preferentially consumed for oxidation of C6-primary hydroxyl groups of cellulose, rather than cellulose depolymerization or formation of C2/C3 ketones. As a result, the decrease in whiteness of the oxidized cotton fabrics without post NaBH₄ treatment after heating was lower than those prepared with TEMPO/NaBr/NaClO system. Moreover, the TEMPO/NaBr/SDIC oxidation of cotton fabrics can be carried out in water at pH 9, which leads to the same carboxylate content as that prepared in water at pH 10 but higher DP_v. Thus, the TEMPO/NaBr/SDIC is an efficient and promising system for oxidation of cotton fabrics with high carboxylate contents and high DP_v values, suitable for functionalization of cotton fabrics for clothes and underwear.