Ruth R. Benerito

Modifications of Cotton Cellulose Surfaces by Use of Radiofrequency Cold Plasmas and Characterization of Surface Changes by ESCA

Radiofrequency (rf) cold plasmas of argon, nitrogen, and air were used to modify cotton fabrics and yarns. Changes in surface characteristics were detected by application of the techniques of electron emission spectroscopy for chemical analyses (ESCA), electron spin resonance, and chemiluminescence. Examples of polymeriza tion of selected monomers and depolymerization of chemically modified cottons within rf plasmas have been used to illustrate potentials of combinations of plasmas and ESCA in cellulose chemistry.

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.

Comparison of Properties of Anion-Exchange Cottons in Fabric Form

The effects of the substitution of various types of amino groups in cotton on the crease recovery properties have been investigated. The potentiometric titration curves of the various aminized cottons have been used to differentiate the presence of quaternary ammonium groups (strong-base anion exchangers) from the presence of primary, sec ondary, or tertiary amino groups (weak-base anion exchangers). Weak-base anion exchange cottons have been quaternized by treatment of cotton containing tertiary amine groups with methyl iodide and with epichlorohydrin. In addition, strong-base exchangers have been prepared directly by a one-step process in which cotton pretreated with a base is reacted with a mixture of epichlorohydrin and a tertiary amine at a 3: 1 molar ratio. Weak-base aminized cottons containing primary amino groups have been reacted with epichlorohydrin in the presence of an aqueous base to form cottons of improved dry- and high wet-crease resistance. Only those quaternized cottons prepared from the reaction of pure epichlorohydrin on cottons containing tertiary amine groups possessed both high dry- and improved wet-crease recovery properties. Equations are given to illustrate types of reactions investigated and mechanisms of reactions.

Kinetics of the Reactions of Ethyleneurea Derivatives with Cotton Cellulose Part II: The Cellulose—Bimethyloldihydroxyethyleneurea Reaction

The kineties of the reactions of cotton print cloth treated with 0.55 M solutions of 4.5-dihydroxy-1,3-bis(hydroxymethyl)-2-imidazolidinone (dimethyloldihydroxyethylene urea) in the presence of 0.03 M inorganic salt catalysts have been investigated. The present two-stage delayed-cure process for chemically modifying the performance of cellulosic fabrics depends on the significant differences in reactivities of cellu lose with methylol functional groups and with the hydroxyl groups of the urea derivatives. Specific reaction rate constants at 45, 55, 65, 75, and 85°C in the presence of ZnCl2, Zn(NO3)2, MgCl 2, and Mg(NO3)2 have been calculated by following the changes in nitrogen and formaldehyde contents and the changes in crease recovery properties of finished fabrics. These rates have been compared with those determined when cotton retets with an etherifying agent having ring hydroxyls only, as in the cellulose-dihydroxy ethyleneurea reactions, and with those determined when the etherifying agent has methylol hydroxyls only, as in the cellulose-dimethylolethyleneurea reactions. Enthalpies, entropies, and free energies of activation have been compared.

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.

Investigation of the Catalyst in the Cellulose-DMEU, Reaction Part I: Effect of Catalyst upon the Physical and Chemical Properties of the Finished Cottons'

Cotton print cloth (80 X 80) has been treated with 8% solutions of DMEU in the presence of inorganic salt catalysts at constant molar concentration of the metallic ion. The four catalysts employed—MgCl2, Zn(NO3)2, Mg(NO3)2, and ZnCl2—were studied at 0.006 M, 0.03 M, and 0.1 M concentrations. A comparative study has been made of the physical and chemical properties, swelling behavior as revealed by microscopical techniques, and infrared absorption spectra of all specimens. It has been found that absorption spectra differ with treatment, depending on the absence or presence of a catalyst; that the catalyst enters into the reaction; and that the final properties of the treated fabrics are influenced by catalyst concentration. Consideration is also given to the effect of catalyst upon chlorine damage.

Esterification of Cotton with Certain Monofunc tional Acid Chlorides and the Effect on Crease Recovery

It has been demonstrated that conditioned (dry) crease recovery of cotton fabric can be increased by partial esterification with monofunctional acid chlorides in dimethylform amide. In the range of C8 through C18 acid chlorides studied, the increase in dry-crease recovery varies linearly with the chain length of the added acyl group. Both odd- and even-numbered acyl groups and unsaturated and geometrical isomers have been con sidered. The unsaturated C18 acid chlorides, oleoyl and elaidoyl, were found to be more effective than saturated C18 acid at a similar D.S. The increase in conditioned crease recovery is suggested to be due to esterification in a nonaqueous medium at originally favored water adsorption sites in less ordered regions.

Durability of Oleophobicity of Cotton Fabrics Imparted by Fluorochemicals

Durability of oleophobicity imparted to cotton fabries by additive finishes (perfluorometallic complexes and perfluoro-acrylate) and hy the incorporation of fluorochemicals into the cellulose molecule by means of an ether linkage has been investigated. Studies on the relative effectiveness of additive finishes in maintaining oleophobicity on weathering have been made. Results of soil burial tests involving the use of aluminum triacetate and perfluorooctanoic acid on various fabric constructions are reported. Various techniques used in efforts to improve durability of the latter finish to aqueous laundenngs are described. Data are presented to explam losses in oleophobic properties when fabrics treated with perfluorooctanoic acid complex of chromium or aluminum are subjected to aqueous launderings. The preparation of 1,1-dihydroheptafluorobutoxyhydroxypropyl and 1,1-dihydropentadecafluorooctoxyhydroxypropyl ethers of cellulose which possessed hydrophobic and oleophobic properties durable to alkaline aqueous washings and commercial drycleaning solutions are described. The preparation of 1,1,7-trihydrododecafluoroheptoxyhydroxypropyl ether of cellulose which possessed only a small degree of oil repellency due to the presence of an omega-hydrogen atom is also

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.

Inconsistencies in Theories of Resiliency in Chemically Treated Cotton

Current theories explaining dry and wet wrinkle recovery in cotton, with well- documented experiments in support of each, are reviewed and observations not predicted by these theories are cited. Factors that should be considered in the develop ment of a new theory consistent with all experimental facts are presented in terms of the hydrogen-bonded structure of cotton cellulose, the modern hydrogen-bonded structure of water, and the interrelations between cotton or chemically modified cottons and water.