Volume 49, Nº 5 (2018)

The properties of solutions of copolymers of 1,1,5-trihydroperfluoroamylacrylate and styrene in various ratios, i.e., the polymer—solvent solubility parameter, rheological characteristics, and surface tension, were studied to produce nanofibrous materials with improved anti-adhesive properties. The copolymer composition and electrospinning conditions that produced nanofibrous materials with ultrahydrophobic and improved acid-repellent properties were determined.

The effect of thermal degradation, including at low temperatures (50-350°C), of poly-p-phenylene-1,3,4-oxadiazole fibers on their electrical conductivity during carbonization (900°C) was studied. The electrical conductivity of carbonized fibers showed several local extrema depending on the thermal-degradation regime that were due to features of transforming the structure and phase states of the polymer fiber system into the electrically conducting states of the carbon fiber system. It was found that the carbon fibers had semiconductor properties that depended on the direction of oriented drawing and the thermal-degradation regimes of the starting polymer fibers.

A combined physicochemical study was carried out on Zetesoft FF100, Synthesin SE 128 Fill, and Shtanteks S 6125 finishing compositions used in the manufacture of polyester fibres with enhanced slippage (filled fibres). The resilience of the fixation of a composition film on a polyester surface relative to chemical composition was discussed.

A modernized scheme of the structure of native cotton cellulose microfibrils is proposed, providing for the presence of slit-shaped pores in its structure and satisfying most of the results of modern studies of its supramolecular structure and sorption properties. It is shown that within the framework of this scheme it is possible to determine the content of elementary fibrils in microfibrils and the degree of crystallinity of cellulose using 1H-NMR and sorption measurements. The mechanism and character of dispersion of microfibrils, accompanied by supramolecular rearrangements of moistened cellulose, was investigated.

By mixing a melt of polyethylene terephthalate and 1,1,9-trihydroperfluorononanol-1 immobilized on a montmorillonite carrier, composite monofilaments were obtained. Small- and wide-angle X-ray scattering and electron microscopy have shown that the structural perfection of the macromolecular system is improved under the influence of a modifier, which contributes to a decrease in the defectiveness of the surface of the fluorine-containing polyethylene monofilament and to an increase in its tensile strength.

The mechanism of stretching and breaking of structurally diverse needle-punched materials obtained under varying punching conditions was studied. It was found that stretching occurs in two stages because of uneven density of fibre packing in bundles and between bundles. The first stretching stage does not depend on the structure of the materials and punching conditions. The second stretching and breaking stage depends on the ratio of the strength of bonding between the fibres in the bundles and the fibre strength.

A mathematical model of heat transfer in a solar air collector with planar porous absorber is described. The temperature fields in the absorber as well as the heating capacity and efficiency of the collector as a function of the rate of air flow and the intensity of the flow of solar radiation are calculated.

An analysis of the flow characteristics of the control valves of a digital control system that possesses significant backlash that appears and increases in the course of use is conducted. A scheme for compensation of the backlash of the control valve is developed, by means of which the flow characteristic of the valve may be corrected, rendering its properties close to the linear.

The following should be added to the acknowledgement on page 73:

The work was financed within the framework of the base part of the state task of the Ministry of Education and Science of the Russian Federation, Project No. 11.4696.2017/8.9.