Truman L. Ward

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.

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.

Correlation of Visual Luster with Measured Reflectance of Cotton Fabrics

A group of 20 white fabrics and 12 blue fabrics, that were carefully constructed from specially prepared cotton yarns to produce fabrics of varying degrees of luster were used in this study. Some of each group were chemically modified with dimethylolethyleneurea and some of these resin-treated fabrics were calendered to produce fabrics of high luster. These fabrics were rated by a panel and the consensus of visual luster rankings was compared with ranking of luster obtained by measurements of specular and disuse re flectances. Reflectances were measured with both the Photovolt Reflection and Glossmeter and the Farrand Spectrofluorometer modified as a reflectometer. The latter instrument was used to hieasure reflectance of both polarized and unpolarized light. Consideration has been given to angle of incidence and reflectance, peak intensities, areas under re flectance curves, depolarization techniques, size of sample irradiated, and treatment of combinations of specular and diffuse reflectance data in the correlation of measured luster and visual luster indices. Use of polarized light was slightly advantageous when used with blue fabrics. While various treatments of reflectance data obtained with both instruments yielded agreement of approximately 75% between instrument and panel con sensus, the best correlation (82%) was obtained by ranking fabrics according to the ratio of specular to diffuse reflectances as measured with the Photovolt instrument.

Testing Based on Wettability to Differentiate Washed and Unwashed Cotton Fibers

Cotton fibers from four varieties were washed with water using two procedures that included several combinations of temperatures and water volumes. Wettability of unwashed and washed fibers was determined by contact angle measurement and by a sink-float technique. The sink-float technique could be used to sort washed and unwashed cotton fibers.

Chemiluminescence Produced in Saccharides by Cold Plasmas

Abstract Cotton cellulose and other saccharides varying in molecular size and in type of glucosidic linkage were treated with cold plasmas generated by radiofrequency (rf) radiation (13.56 MHz). Plasma treatment produced reactive centers on all compounds, and activated samples were capable of producing chemiluminescence (CL). CL was greatest for long-chain structures. Subsequent immersion of plasma-activated compounds in either CHCl3/CH3OH, or the 2:1 v/v mixed-solvent system (CHCl3/CH3OH) increased CL significantly, with the latter solvent and the large molecules exhibiting the greatest effect. Reagents that caused an increase in CL reduced intensity of the ESR (electron spin resonance) signal, indicating a possible dependence of CL on the decay of free radicals formed during plasma treatment. CL quenched by nitrogen gas was partially regenerated when nitrogen was exchanged with oxygen. CL decay curves showed an initial fast rate followed by a slower one and especially in case of large molecules indicate...

The Effects of Plasma Irradiation on Saccharides

Abstract Monosaccharides and polysaccharides are chemically modified when they are subjected to rf plasmas derived from oxygen, nitrogen, or argon. The plasma treatment converts hydroxyl groups within the bulk to carbonyl groups on the order of one per anhydroglucose unit. On the surface, the concentration of carbonyl groups is greater than in the bulk. The activated surfaces formed by the plasma treatments are stable for at least 1.5 h. The observed spectral (IR, ESCA, and ESR) changes of the irradiated samples are the direct result of the plasma and not the secondary result of plasma-activated surfaces reacting with the atmosphere.

Rating Fabric Luster: A Statistical Evaluation of Panelists and Reflectance Data

, other set consisting of twenty ’white cotton fabrics processed under known laboratory conditions to provide a wide range of luster, were used in a statistical evaluation of fabric luster. The method of paired comparisons was used for presentation of ten fabrics to a panel for ranking according to luster. The coefficient of consistence of each panelist and coefficients of agreement among panelists were calculated. The coefficient of consistence for the same set of paired fabrics was calculated from measured reflectance data. The second set of fabrics was ranked according to decreasing luster by a second group of six consistent panelists and by the instrument. The total numerical rankings of the six panelists for each fabric were used as the consensus ranking Y. Relationships between Y and the instrument values were calculated by use of the correlation coefficients between Y. and the gloss (primarily specular) reflectance X1 and between Y and the diffuse reflectance X2. Possible curvilinearity and joint effects of X1 and X2 were also considered. The gloss component of reflected light was apparently the primary gauge of panelists in ranking luster of fabrics, as the diffuse component of reflected light did not contribute significantly to correlation between panelist rankings and instrument rankings based on gloss as the independent varialbe.

Relationship of chemiluminescence and electron spin resonance of plasma irradiated saccharides

Abstract Electron spin resonance (ESR) and chemiluminescence (CL) were measured on six saccharide samples irradiated in argon plasma and on celluloses from six sources irradiated in plasma of a nitrogen-hydrogen mixture. ESR readings were taken immediately after irradiation on samples kept under argon. The statistical relationship between the maximum levels of CL for irradiated samples exposed to air and their ESR signal intensities was determined by regression analysis. A relationship of CL to ESR was shown to exist within each of the two sets of samples and the linear regression equation was developed for each set so that the CL intensity could be predicted if the ESR intensity was known. The correlation between CL and ESR was 0·85 (significant at p

Addition of Lead from Sodium Plumbite Solution to Modified and Unmodified Cottons

Lead monoxide was treated with a strong aqueous sodium hydroxide solution to yield an alkaline solution containing sodium plumbite. The lead from this solution added to unmodified cotton and to cotton containing either acidic or basic groups. The amount of lead added was compared to amounts added from other lead compounds, amounts added from nonaqueous solvents, and to amounts of copper or tin added under similar conditions. Some treated cotton samples contained almost 40% lead. Wrinkle recoveries were improved but flame retardance and rot resistance remained poor. Chemical procedures, electron microscopy, X-ray diffraction, and wrinkle recoveries indicated that a chemical bond was formed between the lead and cotton and that some bonds were intermolecular.