PHOTODEGRADATION OF OXIDIZED COTTON CELLULOSE

Different functional groups were systematically introduced into cotton cellulose and their effect on the stability of cotton toward photochemical degradation was examined. First, the cotton was progressively oxidized with sodium metaperiodate up to an oxygen consumption of 2.45 atom per 100 anhydroglucose units (agu) to form 2,3-dialdehyde cellulose. These products were reduced with potassium borohydride to obtain 2,3-dialcohol cellulose or were oxidized with sodium chlorite to obtain 2,3-dicarboxyl cellulose. The chemical modifications of the cellulose structure caused a drop in tensile strength of 34% for the dialdehyde of 2.45 oxygen consumption per 100 agu compared to 27% and 37% in the case of the dialcohol and the dicarboxyl celluloses, respectively. Upon irradiation with UV light, the breaking strengths of the dialcohol and the dicarboxyl celluloses were generally higher up to an oxygen consumption of 0.63 per 100 agu when compared to the dialdehyde and then fell more drastically. The tensile data of the exposed oxycelluloses correlated well with the reciprocal of their intrinsic viscosities (R2 = 0.89). The primary alcohol groups appeared to accelerate the progress of the photochemical degradation. The photochemical effects of the carboxyl groups could not be differentiated from the autohydrolysis to which dicarboxyl cellulose is susceptible. No indication of a change in morphology was detected for any of the treatment types.