Kazuhiko Fukatsu

Degradation of poly(ethylene oxide) by electro-generated active species in aqueous halide medium

The degradation of poly(ethylene oxide) (PEO) by electrolysis was investigated in an aqueous chloride or bromide medium adjusted to pH 6.5 at 25°C. The degradation was monitored by the reduction in viscosity of the reaction system. The PEO was degraded more readily by electrolysis in the presence of halide ion than in their absence. The degradability of PEO increased with an increase in halide ion concentration under a constant current and the degradation in a chloride solution is easier than that in a bromide solution. The initiation mechanism of PEO degradation is discussed; a hypohalide ion is generated during electrolysis in the presence of a halide ion, and the hydroxyl radical may be generated from this ion. This radical abstracts a hydrogen atom from the polymer to form polymer alkyl radical, and further cause chain scission.

Thermal degradation behaviour of aromatic polyamide fiber blended with cotton fiber

The flammability behaviour of a blend fabric cannot be predicted from the flammability characteristics of its component fibers because of the physical or chemical interaction of the thermal degradation products of the blend during heating or combustion. In order to consider the design of flame retardant fabrics from blends of cotton as a flammable fiber and aromatic polyamide fiber as a nonflammable fiber, the thermal degradation of each and blends of fiber has been studied using a conventional dynamic thermogravimetric technique in a flowing air atmosphere at several heating rates. Quantitative data are presented which pinpoint how the thermal degradation behaviour of this blend differs from that of the components. Comparison of the thermogravimetric curves and calculated kinetic parameters indicates that interactions occur faintly between the cotton and aromatic polyamide components in the blends. The thermogravimetric analysis data show three degradation stages in an air atmosphere.

FORMATION OF HYDROXYL RADICALS FROM REACTION OF CU(II)/WOOL KERATIN COMPLEX WITH HYDROGEN PEROXIDE

In order to determine thatthe degradation of wool keratin molecules in the Cu(II)/ wool keratin complex / hydrogen peroxide system may be brought about by the hy droxyl radical formed in this system, hydroxyl radical formation was measured using the thiobarbituric acid method. The Cu(II)/wool keratin complex can yield hydroxyl radicals by reaction with hydrogen peroxide, but under anaerobic conditions the amount of hydroxyl radical formation is less than that under aerobic conditions. Epi nephrine oxidation, an indicator of superoxide radical generation, occurs in the reaction of this system. These results indicate that the Cu(II)/wool keratin complex appears to catalyze hydroxyl radical formation from the hydrogen peroxide superoxide radical being formed as an intermediate. The sequence of reactions leading to hydroxyl radical formation is essentially the metal catalyzed Haber-Weiss reaction.

Dyeing Behavior of Cu(II)-Wool Complex Fibers Pretreated with Hydrogen Peroxide

The dyeing rate and equilibrium dye uptake by Cu(II)-wool complex fibers pre treated with hydrogen peroxide were examined to elucidate the treatments structural effect on individual histological components of intact wool fibers. A comparison of the relationships between relative dye uptake (C t/C∞ ) and the square root of the dyeing time ( t 1/2) for different weight losses in the fibers revealed considerable differ ences in the initial dyeing behavior between the Cu(II)-wool complex fibers pretreated with hydrogen peroxide. There were differences in the slope of the line and the negative intercept of the extrapolated straight line at t = 0. Apparently, the surface barrier effect in dyeing was diminished by the hydrogen peroxide treatment. This treatment is be lieved to affect individual histological components of wool fibers and to promote acid dye penetration into them.

CONFORMATION OF FRAGMENTS FROM DEGRADATION OF WOOL-Cu (II) COMPLEX BY HYDROGEN PEROXIDE

The fragments from the degradation of wool-Cu (II) complex by hydrogen peroxide have a partly ordered structure (α-helix) in water. As the pH increases, the partly ordered structure transforms into a random coil. Further, the fragments undergo random coil-α-helix transition in ethanol-water mixtures with increasing ethanol component. These behaviors are similar to those of charged polyamino acids, in spite of that the fragments of wool undergo a less sharp transition in comparison with charged polyamino acids.