V. A. Lysenko

Polyoxadiazole fibers modified by nano-additives

A method of increasing the oxygen index (OI) of polyoxadiazole fibers by introducing fire retardant nano(micro)-additives into the polymer before the fiber formation is presented. The following additives are studied: dicarboxydiphenyl oxide, brominated and chlorinated phthalocianines, and carbon black. The use of these additives in the amount of 2–5% of the polymer weight in spinning solutions makes it possible to produce fibers with OI of up to 34 % and thermal stability of up to 84%.

Thermochemical structural transformations of polyoxadiazoles

Changes in the physical and chemical structure of polyoxadiazole upon high-temperature heat treatment of Arselon fiber in inert and oxidizing atmosphere were studied. The role of the morphological rearrangement of the polymer in the turbostratic nucleation of carbon structures was determined. The mechanism of the thermochemical degradation and intramolecular cyclization of intermediate and final polyheterocyclic compounds formed in the process was elucidated.

Effect of carbon nanostructures on the carbonization of polyacrylonitrile

Composite materials based on polyacrylonitrile with carbon nanofillers (technical-grade carbon, thermally expanded graphite, carbon nanotubes) were synthesized. A carbonization of film and fiber composite samples in the temperature range 20–1000°C provided a noticeable increase in the thermal stability of fibers and a rise in the electrical conductivity of the composite material. Dependences of the degree of carbonization on the concentration of nanostructures, type of material, and nature of modifier were determined. Differential-thermal and X-ray diffraction analyses revealed the formation of oriented nucleus structures of turbostratic carbon in the temperature range 450–550°C.

Carbon—carbon composites based on precursors obtained by electrostatic spinning

Technical specifics of the preparation and properties of carbon—carbon electrically conductive porous composites were studied. Non-cloth material of ultrafine polyacrylonitrile fibers was used as the filler. It was shown that such composites could be used to fabricate gas-diffusion electrodes of fuel cells.

CARBON-FLUOROPOLYMER COMPOSITES: INCREASED ELECTRICAL CONDUCTIVITY

The ability to increase the electrical conductivity of carbon-fluoropolymer composites by depositing a graphite layer on their surface was demonstrated. This made it possible to use them, in particular, as gas-diffusion substrates of fuel cells with polymeric proton-exchange membranes.

Thermal Transformations of Polyoxadiazoles

Changes of the structural characteristics and electrical properties of fibers based on polyoxadiazole (Arselon) upon a low-temperature thermal treatment in an inert atmosphere were studied. Extremal dependences of the conductivity of the fibers on treatment temperature were observed and a mechanism of this process was suggested. The X-ray diffraction parameters of the Arselon fibers were determined for the extreme states and practical recommendations were made for using a preliminary heating of the fibers.

Systemic Transformations During Heating and Carbonization of Polyoxadiazole Fibers

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.

The Influence of Thermal Processing on the Properties of Carbon Fibers Based on Polyoxadiazole

The influence of heat treatment on the properties of carbon fibers based on polyparaphenylene-1,3,4-oxadiazole was studied. Dependences of mass loss, shrinkage, linear density and electrical resistance of carbon fibers on the final heat treatment temperature were obtained. It is shown that a decrease in the heating rate leads to an increase in the carbon residue and the linear density of fibers, and a decrease in shrinkage and electrical resistance. It was found that at a final heat treatment temperature of 900 °C for a heating rate of 5 °C/min, the volume resistivity of the elemental carbon fiber material is 2.8 ± 0.2 mΩ.cm. Increasing the final heat treatment temperature and reducing the heating rate leads to an increase in the uniformity of the distribution of electrical resistance along the fiber.

Information Modeling in Systems Design of Carbon—Carbon Electrically Conducting Porous Composites

An algorithm for designing fuel-cell gas-diffusion substrates (GDSs) based on systems design methods, was proposed. An information model of the process for fabricating carbon—carbon electrically, conducting porous composites (CCEPC) for GDSs was developed. The ability to apply polychromatic, set theory to information modeling of CCEPC GDS technology was demonstrated.

Electrically conducting carbon composites: systems design and information modeling

General systems theory is used to break down electrically conducting carbon composites (ECCs) and gas-diffusion substrates (GDTs) in fuel cells as objects for systems design. An information model is proposed for systems design and several general laws are discovered to describe the development ECCs and GDTs as part of their complete lifecycle. Methods are found to optimize systems design technology. Systems design and information modeling are shown to be effective tools for the development of ECCs, including nanocomposites with pre-assigned properties.