Key Engineering Materials Vol. 869

Abstract: Has been analysed the aging, biodegradation and toxic effects of biomedical implants in dentistry. Physico-chemical aspects of aging as well as biodegradation and toxicity of polymer dental implants were viewed. The prospects of development and application of polymer smart implants in dentistry are described.

Abstract: A polyamide acid (PAA) based on diamine 4,4'-bis (4-aminophenoxy) diphenyl and 1,3-bis (3',4-dicarboxyphenoxy) benzene dianhydride was synthesized. PAA fibers were obtained by wet spinning. Then, these fibers were converted into polyimide by thermal imidization. Dependence of the structure and properties of fibers on the die drawing and the composition of the coagulation bath was studied. It is shown that the composition of the coagulation bath has a significant effect on the morphology and mechanical properties of polyimide (PI) fibers. To obtain defect-free fibers, a coagulation bath consisting of ethylene glycol/ethanol at 50/50 vol. % was found to be optimal. An increase in the die drawing of fibers from 1 to 2 times leads to an increase in tensile strength and strain at break of the polyimide fibers.

Abstract: A synthesis of new di-and triblock polyurethane thermoplastic copolymers containing different mass ratio of two crystallizing blocks - poly (1,4-butylene glycol) adipate and poly-ε-caprolactone diols was developed. Using combination of danamometric analysis, IR-spectroscopy, differential scanning calorimetry and X-ray diffraction, the effect of the soft block composition and crystallization conditions on crystal structure and thermal behavior of the obtained polymers have been studied. For the triblock copolymers we have shown a possibility of control the kinetics of material hardening and final mechanical characteristics due to the mutual influence of polydiols during crystallization. In the result, the second crystallizing component allows to control amount, structure and quality of crystalline domains in polyurethanes by variation of crystallization conditions.

Abstract: The series of compositions containing thermodynamically incompatible flexible blocks of aliphatic polyesters and rigid blocks of aromatic bis (urethane) imides in the volume of polymers was obtained on the basis of multiblock (segmented) poly (urethane-imides) and related aromatic polyimides. The series includes segmented poly (urethane-imides) with different relative content of flexible and rigid blocks, non-segregating mixtures of poly (urethane-imides) and thermoplastic partially crystalline polyimide, statistical copolymers of poly (urethane-imide) with imide, and non-segregating mixtures of statistical copolymers with thermoplastic polyimide. The derived polymer systems were studied using thermogravimetric analysis, differential scanning calorimetry, and dynamic mechanical analysis. The deformation and strength properties of film samples are determined. It is shown that the properties of the studied polymers change as their content of imides blocks increases, and the transition from thermoplastic poly (urethane-imide) elastomers to thermoplastic polyimides is observed.

Abstract: Roughing operation is used to improve the adhesive properties of footwear upper to footwear bottom polyurethane compositions in the manufacture of special purpose footwear with an upper made of genuine leather by the injection molding method of attachment. Roughing operation is an operation of coating removal and partial removal of the front layer from the protracted edge of footwear upper workpiece. This operation has a disadvantage, it often causes technological defects. A method for increasing the adhesive properties of genuine leather special purpose footwear upper workpiece with a front layer by means of non-equilibrium low temperature plasma modification and technological scheme that allows this operation to be integrated into the production process are considered in the article.

Abstract: The paper presents the results of the copolymerization of α-halogens of acrylic acid and N-vinylpyrrolidone in the presence of a radical initiator. The copolymerization equations are presented and activity factors are calculated. IR spectra of the obtained copolymers confirm the amination reaction. The synthesized aminated polymers form intramuscular compounds with divalent metal halides at room temperature. The kinetics of the copolymerization reaction of these systems shows that the presence of a reactive halogen atom in the structure of the copolymer has a great influence on the formation and properties of the copolymers.

Abstract: Using differential scanning calorimetry, phase transitions in polycarbonate-polytetramethylene oxide block copolymers were studied. It is shown that, depending on the ratio of rigid polycarbonate and flexible polytetramethylene oxide units, block copolymers can be two-phase or four-phase. It is shown that phase transitions in copolymers of a polyester-polyether depend on the ability to crystallize the components.

Abstract: This papper is about the use of biopolymer of polyvinyl alcohol (PVA) as a coat of different fertilizer granules (Azafoska 16:16:16 and Yara Kristalon 19:19:19) as a core material in presence of nitric acid. The biodegradable polymer layer provides uniform diffusion of minerals into the soil as the PVA shell decays. Scanning Electron Microscope (SEM) and Energy – Dispersive X-ray spectroscopy (EDX - 3600) were carried out for the characterization of bio-modified materials. The agrochemical changes of the soil in terms of macro-and microelements were also determined.

Abstract: The operating efficiency of asymmetric porous and composite membranes with a thin non-porous selective layer was compared in the processes of CO₂ absorption and desorption in gas-liquid membrane contactors using aqueous solutions of monoethanolamine (MEA) with low concentration (<14 %). Composite membranes were prepared by direct deposition of poly (1-trimethylsilyl-1-propyne) (PTMSP) in a hollow fiber membrane module. The effects of gas flow rate and MEA solvent linear velocity on the CO₂ mass transfer were evaluated. Porous membranes were shown to be more effective in the process of CO₂ absorption, because they allow to remove more than 90 % of CO₂ from the gas mixture during one pass of the solvent through the contactor. Composite membranes were more promising for CO₂ desorption, since they provide half as much of the solvent vapor losses with comparable desorbed CO₂ fluxes (0.12-(STP)/(m²·h)). The contributions of membrane and liquid phase to the overall mass transfer resistance during the CO₂ absorption process were estimated. It was demonstrated that deposition of a thin selective layer from a highly permeable PTMSP with a thickness of only 3 μm increases the membrane contribution to the total mass transfer resistance from 10-20 % to 60-80 %.

Abstract: The study of liquid corrosion of cement concrete was carried out, the results of which allow to determine the mass transfer parameters in the studied system and calculate the service life of the concrete product in environments of varying degrees of aggressiveness. Dates of the beginning of electrochemical corrosion of steel reinforcement in reinforced concrete and the achievement of the limit state of steel reinforcement in the conditions of liquid corrosion of reinforced concrete in a chloride-containing medium were mathematically calculated and experimentally established. Investigations of the corrosion resistance of fiberglass reinforcement in various environments have been carried out. The possibility of replacing steel reinforcement with fiberglass when reinforcing concrete products is considered.