Supramolecular structure of propionylated cotton cellulose

Heterogeneous propionylation of cotton cellulose, in the form of yarn, was carried out by reaction with propionyl chloride, in a medium of pyridine and dimethylformamide (DMF). The product was a mixed propionate–α-propionylpropionate ester of DS varying from 0.24 to 2.94. The supramolecular structure of these esters was studied by kinetic analysis as well as by the measurements of density, refractive index, and x-ray diffraction. The Sakurada plot of DS against time of reaction showed a discontinuity at a DS of about 2.0, where the x-ray diffraction pattern shows almost complete loss of crystalline structure. The interpretation, based on the assumption that the Sakurada curve actually represents the sum of two simultaneous rate processes acting in the amorphous phase and at the crystalline surfaces, seems to explain the data adequately. The density showed a continuous decrease, consistent with the idea of continuous destruction of crystalline structure with progressive substitution. Refractive indices showed a continuous decrease with substitution and birefringence was almost absent at complete substitution. The calculated value of molar refraction for the sample of DS 2.94 agreed closely with the experimentally observed value. The x-ray diffraction intensity traces gave convincing evidence of the progressive decrystallization of cellulose with the degree of substitution. Decrystallization seems to be more or less complete at about a DS of 2.0.     

On the conditions of fabrication of tubular cellulose acetate membranes

The conditions of fabrication of asymmetric tubular cellulose acetate membranes was investigated. In the fabrication process, the chief determining factor of membrane performance was the amount of evaporation of solvent in the casting solution. To measure the evaporation amount a test sample of a membrane was collected by using a device at each section of the tube.The evaporation amount of acetone and membrane performance were measured with the membranes fabricated by various methods of casting, and the relationship between them studied from their distribution curve. The vapor of acetone evaporated from a membrane caused a downward stream in the tube. Therefore a casting bob was modified to prevent the steam and maintain the atmosphere in the tube constant.In the fabrication process using a modified bob, the rate of evaporation and evaporation time were kept constant over the whole region of a tube to obtain a uniform tubular membrane.     

Connection between the supermolecular structure of viscose with characteristics of the cellulose and with the properties of fibres and films obtained

Conclusions -- The supermolecular structure of spinning solutions from viscose manufacturing operations in the Balakovskii Khimvolokno PO has been studied by the turbidity spectrum method.-- Multiple and paired correlation equations have been obtained for the parameters of viscose supermolecular structure and the characteristics of the cellulose and the physicomechanical characteristics of hydrocellulose fibres and films.Translated from Khimicheskie Volokna, No. 5, pp. 42–45, September–October, 1991.     

Effect of dampening on the supramolecular structure of cotton cellulose

X-ray structural analysis showed that both the crystallite content and the degree of perfection of their surface layer increase during dampening of cotton cellulose. The maximum structural ordering of cellulose is attained at a fibre moisture content 14.8%. The determining role of the absorption mechanism of dissolution of water in amorphous regions of cellulose is confirmed by a quantitative estimation of the X-ray diffuse scattering parameters for cotton with different moisture contents.Translated from Khimicheskie Volokna, No. 6, pp. 57–59, November–December, 2004.     

Properties of cotton fibers containing the cellulose IV crystal structure

Complete conversion of the crystal form in cotton fibers to cellulose IV (cell IV cotton) was obtained by heat treatment of ethylamine-treated cotton cellulose in either saturated steam or formamide. Degradation of the fibers was not extensive during the conversion process; oxidative damage appeared to have been confined primarily to the accessible regions of the fibers. Examination by scanning electron microscopy indicated that the surface of the cell IV cotton was smoother than that of the same cotton with other crystal forms, namely, the starting cotton (cell I cotton), mercerized cotton (cell II cotton), and ethylamine-treated cotton (cell III cotton). Fiber accessibility increased in the order cell I cotton < cell III cotton ≤ cell IV cotton < cell II cotton. Using leveling-off degree of polymerization as the measure, it appeared that the lengths of the crystallites in cell I cotton were much higher than those in cell II, III, and IV cotton. The strength of cell IV cotton was comparable to that of cell I cotton even though its degree of polymerization was significantly lower. It is suggested that heat treatments in formamide have an annealing effect on cotton that results in increases of strength.     

Certain fine structure and thermal properties of benzhydrylated cotton cellulose

The present paper describes the results of a preliminary study of certain physical and thermal properties of benzhydrylated cotton yarns. The 200-yd. lengths of 7/2 yarn consisting of purified mercerized cellulose were reacted in a special reactor to various degrees of substitution from DS 0.31 to DS 1.22 with benzhydryl bromide in a mixture of equal volumes of 2,6-lutidine and dimethylformamide. The products were examined for tensile strength at break, which decreased only slightly with substitution; ultimate elongation, which was relatively uniform at 60–70% of the control yarn; and tenacity, which decreased with substitution largely due to added weight. The energy of rupture remained relatively constant at about 50% above the control. Tensile stiffness decreased progressively with substitution to about 25% of the control. Density decreased 10–11% with substitution. Crystallinity of the cellulose largely disappeared with substitutions above DS 1, and the lattice of benzhydryl cellulose began to appear. Stiffness, elastic recovery and work recovery were measured on 5-in. specimens of the yarn in an oven while they were subjected to repeated extension to about 1–2% and relaxed as the temperature was raised twice to 200°C. and lowered. During the heating phase of the first cycle the yarn underwent considerable heat adaptation. However, during the cooling phase and during both heating and cooling phases of the second cycle, the yarns showed generally favorable behavior. Attempts are made to interpret the results in terms of molecular modifications.     

Effect of cotton cellulose manufacturing conditions on process quality indexes

The possibility of fabricating cotton cellulose from linters with a process scheme which provides for altering the order of the stages of alkaline and acid cooking was investigated. The molecular and process indexes of the cellulose obtained were determined. The possibility of fabricating cotton cellulose with a satisfactory content of α-cellulose, degree of polymerization, and reactivity was demonstrated.     

Use of statistical design of experiments to find the optimum conditions for the formation of viscose cord

Conclusions 1. We show that it is possible to use methods of statistical experimental design in finding the optimum technological conditions for the formation of viscose cord.2. The use of these methods in devising technological conditions for the formation of Cord 22V enables us to reduce the amount of experimental work to one-third of the previously planned, and to obtain information on the comparative influence of the various parameters in the ranges under consideration.3. We show that it is desirable to use additional experimental data to improve the correlation equation by the method of sequential design.All-Union Scientific Research Institute for Synthetic Fibres (VNIIV). Translated from Khimicheskie Volokna, No. 5, pp. 22–23, September–October, 1969.     

Properties of viscose prepared from modified cellulose

Conclusions Some basic characteristics of viscose prepared from radiation-modified cellulose as compared with standard viscose have been determined.It has been shown that viscose from RMC has an increased coagulation resistance and increased physicochemical uniformity as compared with standard viscose of analogous composition.Translated from Khimicheskie Volokna, No. 2, pp. 32–34, March–April, 1990.     

Sorption and desorption of carbon disulfide by cellulose for viscose manufacture

Conclusions -- The results of a study of the sorption and desorption of carbon disulfide may be used to characterize the structure of cellulose, particularly its accessibility to reagents during viscose manufacture.-- After high-temperature mercerization, the accessibility of cellulose with respect to carbon disulfide is increased.-- The reverse method of viscose preparation makes it possible to intensify the penetration of carbon disulfide into the cellulose fibres to a considerable extent, particularly into the most inaccessible portions of its structure.Higher Chemical Engineering Institute, Bulgaria. Translated from Khimicheskie Volokna, No. 3, pp. 17–19, May–June, 1992.