Volume 51, Nº 2 (2019)

The process of dynamic deformation of polymer systems with a polymer concentration below the critical value is investigated. The complex viscosity and its components – viscosity and elasticity, were determined over the entire range of changes in the circular frequency, including the section of destruction of the initial structure of the polymer system. It was established that almost until the destruction of the initial structure, the constancy of the complex viscosity is maintained, within which its viscous and elastic components change. It is shown that the cause of the destruction of the initial structure of the polymer system (entanglement network) is its transition from a viscoelastic state to a forced elastic one, when the complex viscosity is almost completely determined by its elastic component. When the ultimate strength of the polymer network is reached, the initial structure is destroyed, accompanied by a decrease in the complex viscosity and its elastic component with their subsequent increase.

The conditions for depositing a ceramic-forming compound interphase coating on carbon fibers were investigated. Use of polycarbosilane and Rolivsan ceramic-forming compounds in hexane (<3 mass%) and polymer derived ceramic infiltration in an inert medium produced according to the optimal regime based on thermal kinetic calculations an even interphase coating that increased the thermal-oxidation resistance of the starting carbon fibers. The combustion products of carbon fibers with the deposited interphase were hollow SiO₂ structures.

A preliminary feasibility assessment for recycling composites reinforced with carbon fibers and cloths was performed. The recommended pyrolysis temperature ranges for extracting secondary carbon fiber from the samples were determined using synchronous thermal analysis as 450-500°C for disperse-reinforced composite EPAN-2B and 500-550°C for composite UTZF-2UMN. The sorption properties of the secondary carbon fibers after activation in CO₂ were 222.4 m²/g specific sorption area by BET with 80 and 20% micro- and mesopores, respectively. The limiting adsorption volume for UTZF-2UMN composite fiber was 0.1169 cm³/g with a sorption capacity for benzene vapor of 0.134 cm³/g. The sorbents had high characteristic adsorption energies (by the Dubinin—Radushkevich method) that averaged 14.6 kJ/mol, which was only 30% less than primary fiber sorbents. The sample of UTZF-2UMN consisting of carbon cloth and phenol-formaldehyde resin had higher sorption properties with BET specific sorption areas for sorbents made of it that were three times higher than fibers made of EPAN-2B epoxide carbon-fiber plastic. The specific capacity for benzene vapor was 2.2 times higher, which was explained by the EPAN-2B fibers being highly contaminated by mineral impurities.

The conditions of use of personal protective aids presume impact not only of injuring agents, but also of various environmental factors that affect in no mean degree the level of performance properties that ensure personal safety. This article examines the influence of the rate of penetration of an indenter, the number of layers, and the moisture content on the load of cutting and force of punching of fabrics for body armor and establishes the correlation of these properties.

A mathematical model of heat and mass exchange in a bundle of textile material where moisture permeability is present is developed. The problem of heat transport in a bundle of textile material is considered.

Relationships among the chemical compositions of Rusar-NT and Rusar-S aramid fibers and their degrees of crystallization are found. Results from stability studies of their supramolecular structure over time are presented.

Non-woven agrofibers of polylactide and poly-3-hydroxybutyrate were produced. Both agrofibers absorbed ~12% water vapor. Tests in phosphate buffers showed the non-woven agrofibers were highly susceptible to hydrolytic destruction. Differential scanning calorimetry showed that the melting points and degrees of crystallinity of the polymers decreased as the destruction proceeded.

The technology for manufacture of aviation products from polymer composites based on threedimensional reinforced woven preforms is analyzed on the foundation of previously conducted studies and published reports and research papers. Examples of polymer composite products made by using three-dimensional reinforced woven preforms by western companies are given.

Model concepts are developed of polymer and carbon fibers as systems and microcomposites, and of system transitions during heat treatment and carbonization. The patterns of influence of heat treatment regimes on the properties of polyparaphenylene-1,3,4-oxadiazole fibers and carbon fibers based on them are revealed. It is shown that a decrease in the rate of heat treatment of the fibers, including at temperatures below the temperature of the onset of thermal decomposition, as well as their annealing lead to a 1.36-fold increase in the electrical conductivity of carbonized fibers at the points of local extremes of electrothermal dependencies and a 5.8-fold decrease of the semiconductor effect.

A technique for calculating explosive loads on production equipment, buildings, and structures subjected to external and internal accident factors is considered. A device for operation of equipment prone to fire and explosion in the production chains of modern industry is developed. The computational formulas obtained may be used in the design of explosive valves and diaphragms for explosion protection of production equipment as well as in the design of easily jettisoned roofing and propulsive bays for explosion protection of buildings.