Structural changes in cellulose fibers treated with sodium hydroxide or liquid ammonia evaluated by relaxation behavior of solid-state 13C NMR spectroscopy

Structural Changes in cotton fabrics and Tencel fabrics treated with sodium hydroxide aqueous solution or liquid ammonia were evaluated by spin-lattice relaxation behavior (T-1C) in CP/MAS C-13 NMR spectroscopy. Distribution of T-1C for cotton was shifted to the shorter range of time by these treatments, which means the mobility of molecular chains increased. As the both treatments induced crystalline transition without remarkable change in the degree of crystallinity, coexistence of different crystalline phases may be related to this phenomenon. Similar tendency in T-1C distribution was observed for Tencel treated with liquid ammonia, in which crystalline transition also occurred. On the other hand, distribution of T-1C for Tencel treated with sodium hydroxide shifted to the longer range of time. As no crystalline transition was induced in this system, increase in the crystallite size may be one of the reasons to decrease the molecular mobility of the crystalline region.