Tomiji Wakida

Studies on the surface free energy and surface structure of PTFE film treated with low temperature plasma

The surface free energy and surface structure of poly(tetrafluoroethylene) (PTFE) film treated with low temperature plasma in O2, Ar, He, H2, NH3, and CH4 gases are studied. The contact angles of the samples were measured, and the critical surface tension γc (Zisman) and γc (max) were determined on the basis of the Zismans plots. Furthermore, the values of nonpolar dispersion force γas, dipole force γbs, and hydrogen bonding force γcs to the surface tensions for the plasma-treated samples were evaluated by the extended Fowkes equation. Mainly because of the contribution of polar force, the surface free energy and surface wettability of PTFE film which was treated with H2, He, NH3, Ar, and CH4 for a short time increased greatly. Electron spectroscopy for chemical analysis (ESCA) shows that the reason was the decrease of fluorine and the increase of oxygen or nitrogen polar functional group on the surface of PTFE.

Effect of Corona Discharge on the Surface of Wool and Its Application to Printing

Corona discharge has been widely used to modify polymer surfaces because it can be operated at an atmospheric pressure in air. In this study, wool fiber and fabric were corona discharged, and afterwards wettability, laundry shrinkage, and frictional coef ficients were determined. An ESCA analysis was done to elucidate the changes of chemical composition on the fiber surface. The corona discharge incorporates oxygen atoms into the fiber and increases wettability and laundry shrink resistance of wool fabrics, but the effects are smaller than those from low temperature O2 plasma. After the pretreatment with corona discharge, the fabric was printed with color pastes of two acid dyes, and then treated with superheated or high pressure steam. The corona discharge pretreatment, in particular the single pretreatment, improved color depth considerably, which increased in the following order: untreated ≃O2 plasma treatment < three-fold corona discharge < single corona discharge. From these results it is likely that a small change in hydrophilic properties on the fiber surface plays an important role in improving the color depth of wool fabric in printing.

Surface Characteristics of Wool and Poly ( ethylene Terephthalate) Fabrics and Film Treated with Low-Temperature Plasma Under Atmospheric Pressure

Wool and poly ( ethylene terephthalate) fabrics and film were treated with low-tem perature plasmas of helium/argon or acetone/argon under atmospheric pressure for 10 to 180 seconds. Although argon itself cannot independently generate a plasma under atmospheric pressure by applying high frequency voltage, it is easily generated by adding a small quantity of helium or acetone to argon gas. Wettability of the fabrics and surface tension of the film increased considerably with the treatment within 30 seconds. ESCA analysis was used to elucidate the surface chemical composition of fibers treated with atmospheric low-temperature plasma. Relative O1 s intensity in creased considerably and oxygen was incorporated in the form of —CO— and —COO— on the fiber surface. From these results, it appears that low-temperature plasma by atmospheric pressure discharge is effective for modifying the polymer surface, as it acts in the same fashion as low-temperature plasma by glow discharge.

Effect of Low Temperature Plasma Treatment on Color of Wool and Nylon 6 Fabrics Dyed with Natural Dyes

In a previous article, we reported that oxygen low temperature plasma treatment of wool fibers increases both the dyeing rate and saturation dye exhaustion of acid dyes, despite increased electronegativity of the fiber surface with the treatment. In this article, wool and nylon 6 fabrics treated with oxygen, carbon tetrafluoride, and ammonia low temperature plasmas are dyed with several natural dyes, such as cochineal, Chinese cork tree, madder, and gromwell. The dyeing rate of the plasma-treated wool increases con siderably with cochineal, Chinese cork tree, and madder, but not with gromwell. How ever, the dyeing rate of nylon 6 with cochineal and Chinese cork tree is not changed by the plasma pretreatment. Furthermore, plasma-treated wool fabrics dyed with cochineal and Chinese cork tree have increased brightness compared with untreated wool.

CELLULASE TREATMENT OF COTTON FABRICS

We have investigated the rate of catalytic hydrolysis of cellulose fabrics by a cellulase enzyme in the presence of dyes on a cotton substrate. We found that both direct and reactive dyes on the substrate apparently inhibited the enzyme catalytic reaction, whereas a vat dye did not. The enzyme was more active for mercerized than for nonmercerized cotton. The enzyme treatment significantly reduced both tear strength and dye uptake of the fabrics. Enzyme-treated and successively dyed fabrics showed different color fading profiles compared to untreated fabrics after laundering.

Dyeing Properties of Wool Treated with Low-Temperature Plasma Under Atmospheric Pressure

Merino wool top was treated with low-temperature plasmas of helium/ argon and acetone/argon under atmospheric pressure for 30 seconds and then dyed with two leveling-type acid dyes, CI acid orange 7 and CI acid red 18, and two milling-type acid dyes, CI acid blue 113 and CI acid blue 83. Dyeing rate and saturation dye exhaustion increased with the atmospheric low-temperature plasma treatments as with the dyeing of wools pretreated with low-temperature plasma by glow discharge of O2 and CF4. In particular, helium/ argon plasma was much more effective than acetone / argon plasma at improving dyeing properties, except for CI acid blue 113.

Free Radicals in Cellulose Fibers Treated with Low Temperature Plasma

Cellulose fibers such as cotton, linen, viscose rayon, and polynosic fibers were treated with low temperature plasmas of O2, N2, H2, Ar, CO, CH4, and CF4. For comparison wool, silk, nylon 6, and poly ( ethylene terephthalate ) (PET) were also subjected to the plasma treatments. The relative free-radical intensity of the plasma-treated fibers was measured by means of ESR spectroscopy. The free radicals in the fibers treated in the plasmas increased in the following order: cotton > wool > silk > nylon 6 ≃ PET. cotton > linen > mercerized cotton > polynosic fibers ≃ viscose rayon, and CF4 > CO > H2 > Ar > CH4 > N2 ≃ O2. The natural fibers, in particular cotton and linen, showed larger free-radical intensity than the regenerated cellulose and the synthetic fibers. The free-radical intensity of the plasma-treated fibers depended considerably on the plasma characteristics and the fine structure of the fibers as well as their chemical constitution.

Effect of Crosslinking Agents on Water Repellency of Cotton Fabrics Treated with Fluorocarbon Resin

Cotton fabrics and cellulose films treated with fluorocarbon resin (Asahi Guard AG-480 ) with and without crosslinking agents (isocyanate blocked copolymer and aziridine) were washed and subsequently heat treated. Water repellency of the fabrics decreased with washing and recovered with heat treatment. The decreased water re pellency with washing was controlled by using the resin with a crosslinking agent. To investigate surface tension and surface chemical composition of the fabrics after washing and subsequent heat treatment, the contact angle to water and critical surface tension of the films were measured along with an ESCA analysis of the fabrics. Adding cross linking agents to the fluorocarbon resin treatment controlled the decrease in F1s intensity and the increase in O1s intensity with subsequent washing.

Cellulase Treatment of Cotton Fabrics, Part II:Inhibitory Effect of Surfactants on Cellulase Catalytic Reaction

We have studied the rate of catalytic hydrolysis of cotton fabrics by a cellulase enzyme in the presence of surfactants in treatment solution. We found that both anionic and cationic surfactants apparently inhibit the cellulase catalytic reaction, whereas nonionic surfactant do not. The inhibitory actions of the surfactants are similar to that of dyes that were studied in a previous paper. The actions have been attributed to the electrostatic interactions between charged inhibitory compounds and the cellulase enzyme in a treatment solution and on the cotton substrate.

Dyeing and Mechanical Properties of Cotton Fabrics Treated with Sodium Hydroxide/Liquid Ammonia and Liquid Ammonia/Sodium Hydroxide

Desized and scoured cotton fabric is treated in a two-step process with sodium hydroxide/ liquid ammonia and liquid ammonia/sodium hydroxide to investigate the effect of the treat ment sequence. Crystallinity, moisture regain, water absorbency, dyeability, and KES mechan ical properties are measured. Despite a considerable decrease in crystallinity with both treatments, water absorbency decreases with NaOH/NH3 and increases with NH3/NaOH compared with the untreated fabric. Furthermore, the NaOH/NH3 treatment decreases the early dyeing rate with CI Direct Blue 1, whereas the NH 3/NaOH treatment increases the rate remarkably compared to the untreated fabric. Nevertheless, saturation dye uptake with the same dye increases with both treatments compared with the untreated. As a measure of fabric hand, shearing and bending hysteresis curves are obtained with a KES instrument. The shearing modulus and shearing hysteresis width of the NaOH/NH3 treated fabric are much smaller than those of the NH3 treated fabric, while those of the NH3/NaOH treated fabric are smaller compared with the NaOH treated fabric. From these results, it is clear that two-step processes such as NaOH/NH3 and NH3/NaOH are much more effective for softening hand than the NH3 and NaOH treatments independently.