A new approach is presented to the micromechanics or fiber assemblies, extending the current idea of the local fiber orientation distribution. The theory can predict all the differential elastic moduli of a mass in terms of its structural parameters, the density of fiber length, orientation density, fiber crimp parameters, and elastic modulus of the fiber, if the strain-force response of the elemental deformation unit of the fiber is explicitly given. The general scheme combined with the helical spring model is applied to the uniaxial compression of an isotropic mass and some effects of the fiber crimp on the compressional properties of the mass are examined and compared with experimental results.
Structural changes of cellulose molecules in non-crystalline region of cellulosic materials by thermal and hydrothermal treatments were studied by using new amorphous cellulose samples, which were prepared from cellulose/SO2-diethylamine-dimethylsulfoxide solutions. Dry-thermal treatments led to depolymerization of amorphous cellulose and a decrease in moisture contents by forming irreversible hydrogen bonds, and these changes depended on molecular weight of original amorphous samples, heating temperature, and heating time. However, no crystallization was detected by X-ray diffraction analyses. In the case of thermal treatments of amorphous cellulose samples at 80°C and 80% relative humidity for 1-14 days, no change in amorphous structure, molecular weight, or moisture contents was observed. Hydrothermal treatments of amorphous cellulose samples in water at temperature higher than 100°C brought about crystallization to cellulose IV, together with depolymerization and a decrease in moisture contents. These structural changes depended on molecular weight of original amorphous celluloses, heating temperature, and heating time. In comparison with the results of dry-thermal treatments, it was shown that the presence of water remarkably enhanced depolymerization and crystallization to cellulose IV.
X-ray and electron diffraction diagrams of three softwoods (Larix leptolepis, Pseudotsuga mensiesii and Pi_??_s densiflora) and three hardwoods (Shoren sp., Zelkova serrata and Fraxinus ear, japoniea) which were previously delignified and/or hydrolyzed to various extent were recorded and resolved into characteristic reflections of cellulose I. The monoclinic angle of the controls determined by X-ray reflection showed significant differences between the two groups. These differences, however, became smaller with extending hydrolysis time posterior to delignification. On the contrary, by the electron diffraction there were insignificant diffrences between two groups. These observations suggest that the structural variations of cellulose crystal between softwoods and hardwoods stem from non-crystalline substances such as amorphous cellulose, hemicellulose and lignin which may connect intimately with cellulose crystals in the cell walls.
Tri-O-decyl cellulose, a thermotropic liquid crystal polymer with a cholesteric structure, was blended with n-hexadecane (HD) at various concentrations and studied with its thermal and structural properties. The phase diagram of this blend system was characterized by four regions, i.e., an isotropic liquid phase (I), an anisotropic liquid phase (A), an A/I coexisting phase, and a phase including solid HD. The A/I coexisting phase was fairly long along both the temperature and concentration axes, thus an isotropic-anisotropic phase transition being induced by both concentration and temperature. With an increase of HD concentration, the helicodial pitch P increased at first and then decreased. This phenomena was interpreted as a monotonous change of the twist angle δ(_??_P-1) passing through the “nematic point” δ=0(or P=∞), that is, a concentration-induced inversion of the helical sense.
ABSTRACT: Products containing chlorine and chlorosulfate groups were prepared by the chlorination of cellulose powder with sulfuryl chloride in a mixture of lithium chloride and N, N-dimethylacetamide in the presence of pyridine. The sodium iodide treatment of this product yielded chlorodeoxycellulose with a maximum d. s. of 1.8 by chlorine, which was introduced at C-6 and C-3. Chlorosulfate groups were rather stable to acidic or neutral water, but unstable in alkaline water and were converted into hydroxyl groups or cyclic sulfates. They were replaced by azide and chloride ions or converted into cyclic sulfates by the sodium azide treatment in N, N-dimethylformamide at temperatures of 20 to 70°C. The same treatment of the chlorination product at 90°C resulted in the replacement of chlorine by azide and that at 110°C gave a product with a high d. s. of 1.1 by azide.
ABSTRACT: The hydrolytic reactions of three vinylsulfonyl (VS) reactive dyes, C. I. Reactive Yellow 17, Orange 16 and Blue 19, were kinetically investigated. The second-order rate constants of the hydrolysis for the sulfatoethylsulfonyl and VS types as well as of the forward and backward reactions of dimerization between the VS and β-hydroxyethylsulfonyl types were estimated. The kinetic parameters were determined so that the theoretical concentrations calculated numerically from the simultaneous reaction equations coincided with the corresponding experimental ones each other. The rate constants of dimerization varied considerably with dyes: Blue 19 > Yellow 17 > Orange 16. Those of decomposition for the dimer were in the following order: Yellow 17 > Blue 19 > Orange 16. Blue 19 has a high stability of dimer and Yellow 17 a low one. Orange 16 forms it only at higher concentrations. The ratios of the second-order rate constant of the hydrolysis to that of the reaction with cellulose were confirmed to be nearly constant for VS dyes examined.
ABSTRACT: Various nickel salts have been synthesized, and their protecting effects on photofading of Orange I (C. I. Acid Orange 20), Rose Bengal (C. I. Acid Red 94), Crystal Violet (C. I. Basic Violet 3) and Eosine (C. I. Acid Red 87) were examined in cellulose acetate film with carbon arc Fade Ometer. The rates of photofading of the dyes were remarkably suppressed in the presence of nickel salts, while the addition of UV absorber afforded little retardation of the rate of fading. The effects of combined use of nickel salt and UV absorber on the photostability of dyes were also examined.
Wool and silk fabrics dyed with Kayakalan Black 2RL (C. I. Acid Black 155) were plasmatreated with O2, N2, Ar, NH3, and CF4 gases. Part of the dyed fabric was plasma-treated after silicone resin treatment. While O2 plasma treatment considerably increased the color depth, other gases had so significant effect on the depth. Although, silicone resin treatment itself increased the color depth because of the low refractive index, aftertreatment with O2 plasma was not effective. The O2 plasma treatment formed many microcraters on the fiber surface, but N2, Ar, NH3, and CF4 gases did not, Judging from the results of scanning electron microscope (SEM) and electron spectroscopy for chemical analysis (ESCA), it is considered that the microcrater formation by the O2 plasma treatment plays an important role in increasing the color depth.
Copolyimide fibers were prepared by thermal imidization method, starting from 4, 4'-diaminodiphenyl ether, pyromellitic dianhydride (PMDA), and 3, 3', 4, 4'-benzophenonetetracarboxylic dianhydride (BTDA), and their tensile and thermal properties were evaluated. In general, long term thermal stability (290°C) of the copolyimide fibers increased with increasing content of BTDA, because the copolymers containing more BTDA unit had lower crystallinity and lacked the physical deterioration by heat aging. In the case of the same polymer composition, thermal durability of the fiber drawn at lower temperature was better than that drawn at higher temperature because of the same reason. Dimensional stability at a high temperature (450°C) was good for the fibers containing PMDA ≥ 60mole%. A typical example was as follows: the fiber of PMDA/BTDA (mole ratio 60/40) hot-drawn 1.5 times at 350°C had tenacity (T) of 4.0g/d, elongation (E) of 16% and initial modulus of 62g/d, and percents retained of T and E after 112h at 290°C in air were 91 and 92%, respectively, and its shrinkage at 450°C was only 6%.
In order to obtain a highly dyeable aramid fiber having good dimensional stability at high temperature, poly [m-phenyleneterephthalamide/isophthalamide (mole ratio 90/10)] was wet-spun, drawn 2.4 times in N-methylpyrroridone/water (volume ratio 60/40) at 98°C and washed with hot water. The dried fiber had moderate tensile property and could be dyed to heavy shade with disperse dyes at 135°C without carrier. Its shrinkage at 450°C was 18%.
In order to obtain high-strength, high-modulus and thermo-stable fibers, copolyimide fibers were prepared from p-phenylenediamine/pyromellitic dianhydride (PMDA)/3, 3', 4, 4'-biphenyltetra carboxylic dianhydride (BPDA) copolymers by chemical imidization and subsequent hot-drawing. Drawability and tenacity increased with increasing content of BPDA in the copolymers, and PMDA/BPDA (mole ratio 30/70) copolyimide fiber showed tenacity 21.6g/d and initial modulus 1130g/d. Heat durabilities of these copolyimide fibers were much superior to those of para-aramid fibers such as Kevlar® and Technora®.