Oxidized (Cyclized) Polyacrylonitrile Fibres — Oxypan. A Review

Fibres made of oxidized polyacrylonitrile of the Oxypan type are an independent group of thermostable fires with a possible temperature of use of up to 300°C and slightly higher for a short time. The principles and methods of fabrication, structure, assortment, and properties of Oxypan oxidized PAN fibres are examined. Oxypan fibres, widely manufactured in different countries, are now the least expensive of all thermostable fibres. It is expedient to organize manufacture of these fibres in Russia, and the necessary equipment is available and in place.     

Evaluation of the equilibrium sorption characteristics of textile fibres

The water vapor sorption — desorption isotherms of a series of natural and chemical fibres were determined and the hysteresis coefficients characterizing the nonequilibrium character of the structure and irreversibility of changes in it in sorption of water vapors were calculated. The moisture sorption — desorption isotherms are described by a single equation for a theoretical-probability model. The coefficients of the TPM equation were found for all types of fibres and can be used for predicting the magnitude of sorption and the change in the properties of textile materials in a wide range of external conditions. The points of the beginning of devitrification of the polymer under the effect of moisture were determined.St. Petersburg State University of Design and Technology. Translated from Khimicheskie Volokna, No. 4, pp. 20–23, July–August, 1995.     

Evaluation of the Nonuniformity of Filaments Based on Data from Pulsed-Acoustic Tests of Complex Chemical Fibres

The values of the elongation at break of filaments in a complex fibre are found by the method of combining the stress-strain diagrams and acoustic emission spectra of fracture of complex fibres. Experimental data are used to assess the correspondence of the empirical law of distribution of the elongation at break of filaments to the theoretical (normal) law. The behavior of filaments in extension of a complex fibre to breaking is described with the concepts of reliability theory and the statistical indexes characterizing the nonuniformity of the filaments and the working capacity of a complex fibre in elongation close to the elongation at break are calculated. Complex fibres fabricated by melt spinning (polyester, polypropylene) have higher reliability reserves than fibres wet-spun from solution (viscose). The results are of practical importance and can be used for optimizing industrial manufacture and processing of complex fibres.     

Effect of humidity on the creasability of fabrics based on chemical and flax fibres

A method for assessing the effect of the relative humidity on an important index of flax-containing cloth which characterizes the stability of their shape, their creasability, was improved. It was found that creasing of pure flax samples with maximum atmospheric humidity (=98%) increases their ability to recover the initial shape in comparison to tests in normal conditions (=65%). The kinetics of the recovery angle of the sample after bending with compression are described by an exponential equation which can be used to predict the behavior of cloth after creasing in time. The calculated coefficients of the equation can be used to predict the relaxation processes of recovery of the cloth after creasing.St. Petersburg State University of Design and Technology. Kostroma Technological Institute. Translated from Khimicheskie Volokna, No. 1, pp. 50–53, January–February, 1996.     

Parametric synthesis of multivariable systems based on the solution of the Lyapunov differential equation

A method of parametric synthesis of linear multivariable systems based on the solution of the Lyapunov differential equation is developed. The method makes it possible to take into account the constraints on the parameters of the plant and the regulator, to carry out the synthesis of static and dynamic feedback of the measurement vector, and to simultaneously perform parametric synthesis of the plant and regulator.     

An interactive problem-solving system with levelwise data access

Algorithmic and software support of an interactive problem-solving system based on levelwise image transmission through the Internet and hierarchical video data representation structures is described.     

Polylactide Fibres: Fabrication,Properties, Use,Prospects. A Review

The analysis of data on the fabrication, structure, and properties of polylactide and polylactide fibres will allow drawing a conclusion concerning the promise of using them for production of high-quality textiles and articles for domestic, medical, sanitary-hygienic, and industrial applications. The existence of a renewable raw material base (plant stock), the use of biotechnology for fabrication of the monomer (lactic acid and its dilactide), and the simple technology for fabrication and melt spinning of the polymer show that production of these fibres will be economically feasible. Manufacture of these fibres does not involve complicated environmental problems due to the nontoxicity of the initial, intermediate, and finished products, and the possibility of recycling and biodegradation in the environment. As oil, coal, and gas deposits are being exhausted, polylactide fibres could become a promising large-tonnage variety of fibre. In this respect, it is necessary to develop comprehensive research to create optimum processes for production of lactic acid, polylactide, and polylactide fibres in Russia and to create industrial plants. With a wide spectrum of applications, polylactide fibres can be considered to be at the same level as other chemical fibres. They will not directly compete with existing chemical fibres, although they can be successfully used in place of or combined with them in many cases. At the same time, they have their own niche because of their specific properties.     

Strain-rate dependence of the physicomechanical properties of oriented polymer materials (films,fibers)

Certain methods and instruments for testing oriented materials (films, fibers, yarns) at fast strain rates are described, and the effect of strain rate on the physicomechanical properties of oriented polymers and on the character of the stress/strain diagrams of these materials is analyzed.