Properties of cotton fibers containing the cellulose IV crystal structure

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Abstract
Complete conversion of the crystal form in cotton fibers to cellulose IV (cell IV cotton) was obtained by heat treatment of ethylamine‐treated cotton cellulose in either saturated steam or formamide. Degradation of the fibers was not extensive during the conversion process; oxidative damage appeared to have been confined primarily to the accessible regions of the fibers. Examination by scanning electron microscopy indicated that the surface of the cell IV cotton was smoother than that of the same cotton with other crystal forms, namely, the starting cotton (cell I cotton), mercerized cotton (cell II cotton), and ethylamine‐treated cotton (cell III cotton). Fiber accessibility increased in the order cell I cotton < cell III cotton ≤ cell IV cotton < cell II cotton. Using leveling‐off degree of polymerization as the measure, it appeared that the lengths of the crystallites in cell I cotton were much higher than those in cell II, III, and IV cotton. The strength of cell IV cotton was comparable to that of cell I cotton even though its degree of polymerization was significantly lower. It is suggested that heat treatments in formamide have an annealing effect on cotton that results in increases of strength.