Theory of Extremal Mechanical and Thermal Properties of Fibres and Needle Crystals. Comparison With Experimental Data

The current status of the problem of the extremal mechanical properties (modulus of elasticity, strength, thermal stability) of fibres and filamentary crystals that I elaborated over more than 50 years is presented. Two new integral energy indexes of the structure of polymers are proposed and evaluated — energy density of interatomic and intermolecular interactions, which determine many of the properties of oriented polymers and are important for predicting the mechanical properties. In addition to the theoretical modulus of elasticity and the theoretical strength of polymers (like the strength at absolute zero according to H. Mark and G. M. Bartenev), two new, practically important indexes are proposed — the maximum attainable moduli of elasticity and maximum attainable strength (in the given temperature-time conditions) are proposed. Models are developed and comparative calculations of the theoretical and maximum attainable moduli of elasticity, maximum attainable strength, and maximum thermal stability are performed with different methods for a number of linear (aliphatic and aromatic) and laminar (including carbon) structures. A comparison is made with the maximum values of the mechanical and thermal properties of the fundamental types of fibres and needle crystals based on aliphatic and aromatic polymers and materials with covalent bonds of laminar and three-dimensional structures. Oriented materials with the maximum possible properties among all of the elements of periods 2 and 3 in the Mendeleev Periodic System and their compounds — hexagonal boron nitride, graphite, and the linear carbon polymer, -carbyne, as a material with the highest modulus and strength possible in nature, are determined. New integral coefficients of completion of the structure of fibres as the ratios of the moduli of elasticity and strength attained to their maximum attainable values are proposed and evaluated. These coefficients characterize the level of the actually attained properties of oriented polymeric materials and consequently the perfection of the manufacturing technology. Ways of obtaining oriented polymeric materials with the maximum possible properties are discussed.     

Heat- and mass-exchange in spinning acetate fibres

Conclusions The process of heat- and mass-transfer have been examined in the spinning of acetate fibre. A calculation of the heat- and mass-transfer coefficients and of the diffusion coefficient has been carried out.It has been found that the fibre being spun passes through four zones in the spinning tower. Zones I and II are characterized by a high rate of mass-transfer; in these zones, 70–75% of the acetone is evaporated from the fibre. In zones III and IV, the heat-exchange process is intensified; here the heat-transfer coefficient is 1.7 to 2.0 times less than in zones I and II.Translated from Khimicheskie Volokna, No. 6, pp. 23–25, November–December, 1985.     

Change in properties of man-made fibres and fabrics made from them under the action of epoxy resins

Conclusions A prolonged action of a toluene solution epoxy resin on polyamide or polyester yarns and fabrics from them causes a change in their geometric characteristics and physico-mechanical properties.This changes are within acceptable limits; therefore textile materials based on the investigated yarns can be used for technological filtration of epoxy resins.Translated from Khimicheskie Volokna, No. 3, pp. 38–39, May–June, 1987.     

Inverse evaluation of the integral ordering of the structure and defectiveness of fibres and yarns for technical applications based on normalized values of the mechanical properties

Methods are proposed for an integral (generalized) evaluation of the degree of ordering of the structure and defectiveness of fibres based on the inverse use of indexes of their mechanical properties — modulus of elasticity and strength — normalized with respect to their maximum attainable values. These maximum attainable values are determined in defined temperature-time conditions for a defect-free polymer crystal by several methods, obtaining values in relatively good agreement. The coefficients characterizing the overall ordering and imperfection of the structure, and the defectiveness of different types of fibres based on linear (aliphatic and aromatic), laminar (carbon), and three-dimensional (silicate) polymers were estimated. Different types of fibres, including fibres of the same type, were compared with respect to the level of structural organization and defectiveness. This could serve as a measure of the perfection of the fabrication processes.St. Petersburg State University of Technology and Design. Translated from Khimicheskie Volokana, No. 5, pp. 34–41 September–October, 1996.     

Relationship between the structure and properties of sintered aluminum bronze base frictional materials

Conclusions The optimum combination of frictional characteristics and wear resistance under unlubricated friction conditions is exhibited by materials containing 11–14 wt.% Al in their bronze matrix. The structure of the matrix of these materials consists of a heterogeneous mixture of a ductile (an solid solution of aluminum in copper) and a brittle (the intermetallic compound Cu₂Al) component, the concentration of the latter being sufficiently low to produce no marked decrease in strength. The presence in the structure of a second phase reduces the plastic deformation of the surface layer of the material during its sliding on the mating part, results in lower temperatures being generated on the frictional surfaces, prevents the components of the frictional pair from seizing with each other and, hence, increases the wear resistance of these frictional materials.Translated from Poroshkovaya Metallurgiya, No. 9, (141), pp. 67–71, September, 1974.     

Sorption of water vapors by high-strength para-aramid fibres

The water vapor sorption isotherms were measured for different types of high-strength fibres based on carbocyclic and heterocyclic para-aramids: Rusar (copolymers of amidobenzimidazole and p-phenylene terephthalamide), Twaron and Kevlar (poly-p-phenylene terephthalamide), and for comparison, capron (polycaproamide). The parameters of the thermal sorption equation and the thermodynamic characteristics of sorption of water vapor were calculated with previously obtained sorption data with the previously developed theoretical-probability model of sorption. A correlation was found between the integral heat of sorption in amorphous regions of para-aramid fibres and the specific cohesive energy. __________ Translated from Khimicheskie Volokna, No. 5, pp. 50–53, September–October, 2007.     

Method and equipment for studying acoustic emission in failure of chemical fibres

St. Petersburg Institute of Textile and Light Industry. Translated from Khimicheskie Volokna, No. 6, pp. 60–61, November–December, 1992.