H. Z. Jung

The Effect of Argon Cold Plasma on Water Absorption of Cotton

Cotton printcloth was treated with low-temperature, low-pressure argon plasma created by passing argon gas through a radiofrequency electric field of 13.56 MHz. Fabrics were exposed to plasma for 0–90 min. Pressure was maintained at 100 millitorrs and RF power at 40 watts. Plasma-treated cottons wetted readily and uniformly with water and aqueous dye solutions. Loss of weight on relatively long plasma treatment was greater than that due to usual removal of moisture under reduced pressure. Spectral changes observed by x-ray photoelectron-emission spectroscopy and infrared spectroscopy indicated surface oxidation of the cotton, and electron-spin-resonance spectra showed presence of free radicals. Although surface oxidation occurred, gross topographical changes of the cotton surface were not evident, even when viewed under the scanning electron microscope. The rate of wetting of argon-activated cotton was significantly greater than it was prior to plasma treatment. At comparable immersion times the amount of water wicked into an argon-activated cotton fabric was about twice that taken up by untreated material. The rate of drying was also faster after plasma treatment.

Effect of rf cold plasmas on polysaccharides

Abstract Low temperature-low pressure argon, nitrogen, and air plasmas generated with rf radiation have been used to treat cotton cellulose and other saccharides. The physical and chemical nature of each substrate was altered by the cold plasma. Although no gross topographical changes of the cotton surface were visible even under the electron microscope, plasma-treated cotton wetted more rapidly and more uniformly than its control, and other saccharides were more soluble in water and other chemical reagents (such as ammonium hydroxide) after plasma treatment. Free radicals were created within the cellulose matrix and structures of all other saccharides. ESR signals, which indicate presence of carbon radicals, degenerated asymmetrically, implying that other types of radicals also existed. ESCA spectra of cotton cellulose showed that some carbon atoms had been oxidized and some oxygen atoms reduced during plasma activation. Activated cottons displayed chemiluminescence and had redox powers that varied with their environments. When cotton and organic monomers were simultaneously present in cold plasma, reactive centers initiated polymerization ofthin films upon the cotton surface. Plasmaactivated cottons exhibited the same chemical reactions as a-hydroxyperoxides or their precursors from living organisms.

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.

Urea-Phosphoric Acid Hydrolysis of Cotton Modified with N-Methylolated Ethylene Ureas

Native and mercerized cotton cellulose, modified with N-methylolated derivatives of ethylene urea, were examined before and after urea-phosphoric acid hydrolyses. Fine structural changes accompanying chemical reactions were evaluated by infrared absorption spectroscopy, x-ray diffraction, and electron microscopy. Final fabric properties and extent of restoration of original tensile properties after urea-phosphoric acid hydrolysis varied with the reagent applied and the lattice structure of the cotton control.

Urea-Phosphoric Acid Hydrolysis of Mercerized Cotton Modified with Methylated Methylolmelamine

Mercerized cotton finished with a methylated methylolmelamine (MeMM) responded differently to hydiolysis with urea-phosphoric acid (UPac) than did similarly finished native cotton. UPac hydrolysis did not affect dry and wet wrinkle recoveries of mercerized cotton, but caused reduction in dry recovery angles of the unmodified native cotton control. Treatment with MeMM produced specimens with equally high dry and wet wrinkle-recovery angles regardless of nature of the control fabric; behavior of MeMM-treated fabrics, when subjected to UPac hydrolysis, was influenced by nature of the control fabric. With MeMM-treated mercerized fabrics, each subsequent hydrolysis removed about one-half of the bound nitrogen and virtually all formaldehyde; it destroyed dry recoveries, but had little effect upon wet wrinkle-recovery angles. Each MeMM retreatment completely restored these properties in products from mercerized cotton, but resulted in only partial restoration of recoveries in products from native cotton. X-ray diffractions after MeMM-UPac treatments of mercerized cottons indicated retention of the mixed cellulose I and II lattice of the unmodified control while products from native cotton retained the cellulose I lattice. Infrared spectra indicated that reaction, with MeMM in both cases, proceeded with loss of adsorbed water and occurred preferentially at the primary hydroxyl of cellulose. Unlike products from native cotton, modified mercerized fabrics did not show a buildup of polymer on the periphery of fiber cross sections after an increasing number of MeMM-UPac treatments. Hence, homopolymerization was not indicated in the MeMM treatment of mercerized fabrics.

Urea Phosphoric Acid as a Quality-Control Reagent for the Poly-Set Process

Native cotton was modified with methylated methylolmelamine in combination with dimethyloldihydroxyethyleneurea by a two-step treatment similar to that of the Poly-Set process. Physical properties were determined before and after urea phosphoric acid (UPac) hydrolysis to determine if the stripping action of UPac could be used in quality control in the Poly-Set process. UPac does provide a means of correcting treatment errors occurring at any stage of the Poly-Set treatment.