Vol 58, No 4 (2024)

The stress diagram of polymer composite material based on PDI-3A rubber filled with thermally expanded graphite or potassium chloride before and after microwave treatment for 300, 600, 900 and 1200 s has been studied. A twofold increase in tensile strength and deformability was found after microwave treatment for 300 c and testing at 223 K. With increasing the test temperature or microwave treatment time, a marked decrease in the deformation and tensile strength characteristics of the obtained composites was observed.

Laser material Y₃Al₅O₁₂ (YAG), originally known in the form of a single-crystal, has been distributed and widely commercialized in the form of optical ceramics. The desire to expand the functionality of materials made of nanocrystals due to the size effect actualizes the study of the influence of their structure on the optical (vibrational and electronic) and other properties of new promising materials with the YAG base including glass ceramics. In this work, models of crystalline alumina-iodine garnet fragments have been calculated by DFT/uPBEPBE/SDD, DFT/uPBEPBE/lanl2DZ, and DFT/uB3PW91/SDD methods. The IR spectra were calculated by DFT/uPBEPBE/lanl2DZ method and the absorption bands of the calculated wave numbers were correlated with the measured ones. The electronic absorption spectrum and energy levels were calculated by the DFT/RB3PW91/SDD method.

Polymeric luminescent compositions based on polycarbonate and polystyrene doped with β-ketoiminates of boron difluoride were obtained. The luminescent properties of 12 dyes with different substituents were investigated. The influence of the concentration of boron difluoride βketoiminates on the spectral properties of the samples was studied. It was found that the investigated dyes are characterized by monomeric luminescence even at tenfold increase of luminophore concentration (0.05–0.5%). It was found that compositions containing the dyes 3-amino-1-phenyl-2-buten-1-oneate of boron difluoride (1a) and 3-amino-1-phenyl-2-buten-1-oneate of boron difluoride (2a) exhibit exciplex luminescence in polystyrene.

The photolysis of phenanthroline-containing imidazole in DMSO solution and the initiating ability of the compound in photopolymerization of multifunctional (meth)acrylates under LED irradiation (λ = 395 nm) under aerobic conditions were investigated for the first time. The relationship of kinetic parameters of photopolymerization with light intensity, chemical structure, and viscosity of multifunctional monomers was established.

The results of FT-IR spectral study of polypropylene (PP) subjected to gamma irradiation and postradiation high-temperature shear milling are presented. Absorption peaks of hydroxyl and oxygen-containing groups appear in the IR spectra of air-irradiated PP pellets, the intensity of which decreases markedly in the powder obtained after grinding of irradiated polymer pellets. Toxic properties of PP obtained by grinding by high-temperature shear milling of irradiated polymer pellets were investigated. It was shown that gamma-irradiation of polymer pellets in air has no effect on toxic properties of its powder obtained by grinding of irradiated pellets with 700–4500 kGy dose. It was found that when administered intragastrically to BDF mice₁ PP powder from non-irradiated and irradiated granules is moderately toxic.

The results of modeling of radiation-chemical transformations in the coolant of the VVER primary circuit are presented. It is shown that under conditions of intensive irradiation molecular nitrogen dissolved in the coolant exhibits chemical activity. The reaction of N₂ molecule with excited hydroxyl initiates the formation of ammonia and nitrous acid. Further decomposition of ammonia yields only oxidized forms of nitrogen, with N₂ acting as an intermediate product. Maintenance of hydrogen and oxygen concentrations within the norms at ammonia water-chemical regime (WCR) appears to be possible only at constant dosing of NH₃ and degassing of the coolant. On the contrary, in the case of WCR with dosing (at the initial moment) of H₂ in the absence of perturbations the steady-state regime is quickly established, satisfying the requirements of the WCR norms for VVER. The difference between the two WCRs is due to the presence of nitrogen in the NH₃ molecule and its transformations as an element, regardless of the initial chemical form.

Kinetics of the decrease in the strength of polyamide PA-6 (poly-ε-caprolactam) fibers by X-ray irradiation in air at absorbed dose rates ranging within 0.16–10 Gy/s has been studied. It has been shown that strength of irradiated polyamide PA-6 fibers decreases to a certain limiting value depending on the dose rate and can be described by the kinetics of a reversible pseudo-first-order reaction. The proposed structural-kinetic model of radiation–oxidative aging of fibers takes into account the opposite effects of destruction and crosslinking of tie macromolecules on the strength of the oriented polymer (fiber),and structural features of the oriented polymer. The model agrees well with experiment and allows us to describe the change in the strength of an oriented polymer (fibers PA-6) and a unidirectional composite (impregnated strands) based on them during the simultaneous occurrence of processes of radiation–oxidative degradation and crosslinking of macromolecular chains.

Electron beams with energies up to 3 MeV, widely used in technological and research practice, have a relatively low penetration depth into matter, and the nonuniformity of energy absorption can reach 30% per 1 mm of path. High nonuniformity, as well as the high cost of radiation, requires the researcher to have skills in optimizing the uniformity of irradiation and reducing energy losses. This work presents the dependence of the average absorbed dose and dose nonuniformity when irradiating a liquid with a horizontal beam in test tubes or pipes with different glass wall thicknesses (0.2–2 mm Pyrex). The dependencies are applicable to clarify, predict and analyze the distribution of absorbed dose in materials.

Changes in the composition of the surface layer of polyethylene film after treatment in the positive column of glow discharge of direct current in the flow of oxygen and argon have been studied. The possibility of copolymerization of diallyldimethylammonium chloride monomer and polyethylene surface modified in plasma is shown.