Effect of intensive drying of viscose fibres on their properties

Conclusions Experimental data are given on the effect of moisture evaporation rate in drying viscose yarns on the strength and elongation, sorptive capacity for water vapor from the air, swelling, shrinkage, and wear resistance of yarns.It has been found that, by regulating the drying temperature, it is possible to affect the capillary-porous structure of a yarn to a considerable degree. Raising the temperature and the drying rate leads to an improvement in wear resistance and yarn elasticity. However, due to the decrease in internal surface area, one may expect a decrease in the sorptive capacity of the yarn in dyeing. A decrease in drying temperature helps increase the degree of swelling, and helps improve the absorption of dye by the yarn.Translated from Khimicheskie Volokna, No. 2, pp. 46–47, March–April, 1984.     

Effect of defects in high-modulus viscose fibres on their physicomechanical properties

Conclusions -- As a result of microscopic investigation of high-modulus viscose fibres, it has been found that the various types of defectiveness in them amounts to 90%.-- Four characteristic groups of fibre defects have been determined: breakdown in morphological structure - 25%; gas-bubble content - 20%; mechanical contaminants from the viscose - 25%; and mechanical contaminants from the precipitation bath - 20%.-- It has been shown that the presence of defects in the fibre reduces its strength characteristics from 7.7 to 33%, depending on the form of defect and increases nonuniformity in these figures.Translated from Khimicheskie Volokna, No. 4, pp. 49–51, July–August, 1991.     

Effect of the conditions of spinning viscose textile fibres on their properties

Rigorous respect of the standard character and purity of the spinning solution, spinning bath parameters, and orientation draw ratio ensures obtaining a complex fibre homogeneous over the length. By varying the flow rate of viscose from the spinneret and disk rotation, it is possible to vary the fibre tension, strength, elongation, and shrinkage within wide limits and ensure a high capacity for uniform dyeing. The limits of the overall draw ratio of viscose textile fibres of varying assortment without elementary fibre breakage and formation of nap were established. __________ Translated from Khimicheskie Volokna, No. 6, pp. 28–31, November–December, 2005.     

Dyeing of N-modified viscose rayon fibres with acid and metal-complex dyes

Viscose rayon N -modified by the incorporation of polydiallyldimethyl ammonium chloride gave good dye exhaustion and colour yield on dyeing with acid or metal complex dyes. The amount of additive present in the fibre was assessed from its nitrogen content, and percentage exhaustion was found to increase with increasing quantity of additive. Changes in hue, in addition to an increase in the light fastness of deeper shades, are attributed to aggregation of dye within the fibre. The light fastness of metal complex dyes on N -modified fibre was very good but acid dyes gave poor results. Wash fastness was improved after treating with a dye fixing agent.     

Surface properties of electrochemically oxidised viscose rayon based carbon fibres

A viscose rayon based activated carbon cloth (ACC) was subjected to electrochemical oxidation under a wide variety of current conditions to modify the surface properties. The changes in the surface properties were physically and chemically characterised. The cation exchange capacity of ACC increased with an increase in the extent of oxidation. The electrochemically oxidised ACC at 1.1 A for 6 h showed highest cation exchange capacity without any change in surface morphology. A loss of 49% BET surface area and a significant loss in microporosity were observed and attributed to blockage of pores through formation of carboxylic acidic groups and humic substances. However, the cation exchange capacity and oxygen content increased by about 365% and 121%, respectively. Increase in surface acidity shifted the point of zero charge from pH of 6.8 to 2.8 and the isoelectric point from pH of 3 to 1.15. The optimum constant current for electrochemical oxidation was found to be 1.1 A.     

Tube spinning of viscose fibres

Conclusions Tube spinning of viscose fibres makes it possible to reduce the hydrodynamic frictional resistance of the precipitation bath.The possibility is created of raising spinning speed, increasing the number of spinneret holes, and raising fibre quality.On use of tube spinning, questions of reducing gas contamination of the working zone and mechanizing spinneret replacement are solved more effectively.Translated from Khimicheskie Volokna, No. 2, pp. 8–13, March–April, 1986.     

Surface topography and mechanical properties of carbon fibres

Surface topography of polyacrylonitrile based carbon fibres preoxidized under a variety of conditions has been studied in detail. Only those carbon fibres processed under optimum conditions are found to possess defect free surface topography. Changes in surface topography and the tensile strength of carbon fibres with processing conditions have been discussed.     

Dyeing of N-modified viscose rayon fibres with reactive dyes

Modified viscose rayon fibres were produced by incorporation of different doses of a polydiallyldimethylammonium chloride based additive in the viscose dope prior to spinning. On dyeing the modified fibres with different reactive dyes, excellent dye exhaustion and total dye fixation above 90% were obtained without the use of electrolyte and with low salt concentration. Exhaustion and total dye fixation showed an exponential relationship. The wash fastness properties of the dyed fibres were excellent and the light fastness showed a slight drop in the modified fibres. The presence of the amino groups along with low density and crystallinity of the modified fibres may be responsible for the enhanced dyeability.