Influence Of Slack Caustic Treatment On Structure And Properties Of Natural Bamboo Fibers

It is well known that caustic treatment can change the structure and properties of natural cellulosic fibers. But the influence of caustic treatment on the structure and properties of natural bamboo fibers for textile purposes has not been reported. The research on the changes in the structure and properties of natural bamboo fibers subjected to caustic treatment is of importance for chemical processing of natural bamboo fibers.In the present research, the influence of slack caustic treatment on the morphological and crystalline structure and thermal behavior of natural bamboo fibers was investigated by SEM, FT-IR, WAXD, TGA and DSC analyses. The tensile strength and elongation, moisture regain and dyeability of the alkalized and not alkalized bamboo fibers were determined.The concentration of caustic soda during slack caustic treatment has great influence on the structure and properties of natural bamboo fibers. The concentration of 130 g/L is a turning point at which the obvious changes in the structure and properties of bamboo fibers occur.After the slack caustic treatment, the bamboo fibers are swollen, the central hole or lumen becomes small, and the crystallinity is reduced. When the concentration of caustic soda arrives at 130 g/L, bamboo fibers start to retort, and the structure of cellulose I begins to transform to the structure of cellulose II. When the concentration of caustic soda exceeds 160 g/L, the cellulose I completely transforms into cellulose II. The reduction in the hydrogen bond interactions between the molecular chains of bamboo fibers gives rise to the remarkable decrease in their thermal decomposition enthalpy.The shrinkage of bamboo fibers during caustic treatment is increased with the increase in caustic soda concentration. After caustic treatment, the tensile strength of bamboo fibers is reduced, the elongation percent and moisture regain are increased,and the adsorbability to direct dyes is greatly enhanced. The maximum increase in the uptake of direct dyes occurs for the bamboo fibers alkalized with the caustic soda solutions of the concentrations ranging between 115 g/L and 130 g/L.The equilibrium exhaustion, dyeing rate and building up properties of bamboo fibers can be greatly increased to the comparable extents with those of cotton fibers if they are alkalized with the caustic soda solution of the concentration exceeding 190 g/L.