Liquid Ammonia vs. NaOH Mercerization as Pretreatment for the Cotton- Butadienediepoxide Reaction. Spectral and Microscopical Studies

Native, mercerized, and ammonia-treated cottons were reacted with butadienediepoxide (BDO), and their fine struc tural changes were followed by x-ray diffractograms, infrared absorption spectra, refractive indices, and in micro scopical cross sections. Conventional mercerization and liquid NH₃ pretreatment of native cotton generally produced a more isotropic fiber. But the nature and mode of decomposition of cellulose swelling complexes formed with either NaOH or liquid NH₃ differed, as evidenced by differences in crystalline lattices and the optical properties of reaction products. Optical density increased only in the direction of the fiber axis with NH₃ but also perpendicularly to the fiber axis with NaOH. Subsequent treatment of NH₃-cellulose controls with mercerizing strength NaOH converted their crystalline lattices to Cellulose II. BDO reaction and postmercerization affected the refractive index only in the direction of the fiber axis (η||). Generally, BDO reaction reduced η|| of all but the NH₃-cellulose I control; and postmercerization further reduced η|| of only BDO-reaction products that retained the cellulose I lattice. Birefringence of postmercerized BDO-reaction products derived from NH₃-cellulose I was lower than that of comparable BDO-reaction products from conventionally mercerized cotton. Before and after BDO reaction, cross sections of most fibers in reaction products from native and NH₃-treated cottons with the cellulose I lattice were elliptical, while comparable cross sec tions from conventionally mercerized cotton were round. Changing the catalyst from 2% to 15% NaOH generally increased the number of circular fibers in BDO-treated cottons having the cellulose I structure. All control cottons dissolved in cupriethylenediamine, but BDO-reaction products were insoluble and cross sections appeared solid. Gen erally, reaction products from cottons pretreated with liquid NH₃ had a softer hand and dyed more uniformly than did comparable products from conventionally mercerized cotton.