Key Engineering Materials Vol. 899

Abstract: In this work an original installation (manipulator) has been created that allows one to obtain up to 30 samples of hollow fiber membranes in one molding cycle, while simultaneously varying the molding conditions in a wide range (polymer concentration, nature of solvent and precipitant, exposure time in air and in a precipitant environment, post-processing and washing modes samples, diameter of the carrier needle). This installation makes it possible to move to a fundamentally higher level of accumulation of experimental data on the relationship "the composition of the spinning solution - the structure of the hollow fiber membrane - the separating properties of the membrane." It will also make it possible to involve in these studies new laboratory samples of polymers whose synthesis volumes are insufficient for the existing methods of obtaining laboratory samples of hollow fiber membranes. The principle of operation of the manipulator was worked out when obtaining mini-samples of hollow fiber PSF membranes from 24 wt. % PSF solution in NMP with the addition of 19 wt. % PEG-400 blowing agent on a carrier needle with external deposition. Mini-samples were obtained for studies of morphology, mechanical, transport and separation properties in one molding cycle of the manipulator. The properties of mini-samples of hollow fiber PSF membrane were compared with the properties of a membrane made by the method of “dry-wet” molding with internal deposition from a solution of the same composition. It was found that the porous structures of the membranes differ significantly from each other. In a hollow fiber PSF membrane obtained on a manipulator, the porous structure was spongy with separate macrovoids of various shapes. However, in the membrane obtained by the “dry-wet” method, a dense selective layer was formed on the inner side of the backing layer of elongated finger-shaped pores. It is the formation of spongy pores along the entire perimeter of the fiber wall that led to a decrease in the permeability of the hollow fiber PSF membrane obtained on the manipulator. Thus, not only the composition of the solution, but also the molding method makes a significant contribution to the properties of the membrane.

Abstract: A new method with limited layer of polymeric solution was used to study the kinetics of precipitation of highly concentrated solutions of PAA in various precipitants; it allows to quickly estimate the rate of formation of the polymer membrane, adequately evaluate its morphology without membrane casting and reduce the experimental time for the preparation of a membrane with required porous structure. It was shown that the rate of precipitation of 18 wt. % PAA solution and the morphology of a layer resulting from the phase separation formed upon contact with water differ significantly in a “limited” layer and in a layer of infinite thickness. It was shown that morphology of a layer formed during phase separation of 18 wt. % PAA solution with water in the “unlimited” layer corresponds to morphology, which is formed in precipitation by 50% NMP-water solution of the same polymer solution in a “limited” layer. This supports the assumption about the strong dilution of the precipitant with a solvent when an “unlimited” layer method is used. In addition, during the investigation of the kinetics of the phase separation by water it was found that the rate of precipitation of highly concentrated polymer solution in a “limited” layer (ν = 8.3 μm/s) is significantly higher than in “unlimited” (ν = 1.7 μm/s). Using this method with “limited” layer, the kinetics of the phase separation of 18 wt. % PAA solution in aliphatic alcohols was also investigated; the rate of precipitation of the polymer solution is inversely proportional to their viscosity. Approximately twofold increase of dynamic viscosity with the chain length for each subsequent alcohol in the homologous series, the rate of precipitation of the PAA solution in them was also reduced by about 2 times

Abstract: Copolyarylates based on a mixture of 2,2-bis (4'-hydroxyphenyl) propane, 3,3-bis (4'-hydroxyphenyl) phthalide, terephthalic and isophthalic acid chlorides and 3,5-dibromo-p-hydroxybenzoic acid chloride were synthesized by low-temperature acceptor-catalytic polycondensation. To study the structure of the obtained polyesters and study the physical and mechanical properties, infrared spectroscopy, elemental, thermogravimetric, X-ray structural and thermomechanical analyzes were used. The obtained polymers have high values ​​of strength characteristics, thermal and heat resistance, good fire resistance.

Abstract: The regularities of acceptor-catalytic polycondensation in the synthesis of copolymers containing arylate, sulfone, and dichloroethylene groups in the main chain have been studied. The optimal conditions for their production have been found. Infrared spectroscopy, elemental analysis, turbidimetric titration and other methods confirmed the formation of copolymers of the proposed structure.

Abstract: New halogen-containing oligoethers based on 1,1-hydroxy-2,2-di (4-hydroxyphenyl) ethylene and 1,1-dichloro-2,2-di (4-hydroxyphenyl) ethylene of various degrees of condensation were synthesized by the method of high-temperature polycondensation. Features are investigated and optimal conditions of synthesis of new oligoethers are defined. On the basis of polysulfone compositions with various maintenance of oligoethers are prepared. With usage of the modern methods of researches, it is shown that new composites surpass industrial polysulfone in the main physical and chemical and production characteristics.

Abstract: New complex based on cobalt (II) acrylate and 4′-phenyl-2,2′:6′,2″-terpyridine (PhTpy) was synthesized and characterized using a number of analytical techniques including IR and UV- vis spectroscopy, elemental, X-Ray and TGA/DSC analysis. The complex has high thermal stability and crystallinity. It is found that decomposition of the complex is accompanied by thermal polymerization of acrylic fragments that is a potential way for the preparation nanoparticles of metals or their oxides stabilized by the polymer matrix.

Abstract: In this work, using polymer 3D printing, we obtained ceramic parts of complex shape with the topology of a triple periodic minimal surface (TPMS), of the “Schwarz primitive” type. The technology of manufacturing ceramic products from a diamond-silicon carbide composite ("Ideal") with the geometry of TPMS by pressing is described. The properties of 3D ceramics are similar to those of a monolithic material.

Abstract: A comparative assessment of the effect of two modifiers on the low-temperature properties of BND 90/130 bitumen was investigated using Asphalt Binder Cracking Device (ABCD test) and Dynamic Shear Rheometer (DSR 4-mm test). These modifiers are styrene-butadiene-styrene block copolymer (SBS) and active powder of discretely devulcanized rubber (APDDR) - powder elastomeric modifier obtained by high-temperature shear grinding of waste tire crumb rubber. ABCD results of RTFO-aged samples showed clear and gradual decrease of the ABCD cracking temperature (improvement) for all BC as the modifier concentration increases. It is noteworthy that the Bitumen Composites (modified bitumens) were cracking at higher strain and fracture stress values compared to neat bitumen. Results of DSR-4 mm test showed a decrease in the complex shear modulus (G*), storage modulus (G¢) and loss modulus (G²) BC compared to the neat bitumen. It is shown that bituminous composites have no maximum on the Cole-Cole diagram (dynamic vitrification) at T = -28°C which is observed in the neat bitumen.

Abstract: The properties of crumb rubber (CR) of unsorted end-of-life tires and of gas masks face part crushed at ambient temperature, as well as powder elastomeric materials (PEM) obtained by high-temperature shear grinding (HTSG) of CR and high-temperature shear co-grinding of CR with thermoplastic elastomer have been investigated. The methods of dry screening with vibrating sieve, wet laser diffraction, scanning electron microscopy, determination of the specific surface area by the BET method by sorption nitrogen and powder agglomeration were used. The effect of an anti-agglomerating additive on the results of determining the particle size distribution by the methods of dry vibrating sieving and wet laser diffraction has been investigated. Methodological recommendations for determining the particle size distribution of powder elastomeric materials (PEM) obtained by the HTSG have been developed.