The Macroporosity of Polyacrylonitrile Fibre

The closed porosity of polyacrylonitrile fibres wet-spun from dimethyl acetamide solutions was investigated in raising the spinning bath temperature from 2 to 20°C. The dependence of the porosity of the fibre on the conditions of plasticization treatment is established. The fibre treated in saturated vapor medium has higher porosity values (narrow transmission factors in chlorobenzene) than the fibre treated with a hot aqueous solution of dimethyl acetamide. The dependence of the fibre porosity on the drying and repeated washing and subsequent drying temperatures is demonstrated. The mobility of the structural elements increases and the porosity of the fibre decreases with an increase in the drying temperature.     

Stable flow regions for highly concentrated solutions of polyacrylonitrile in dimethyl sulfoxide

Conclusions Conclusions about the decrease in critical values of shear stress and shear rate with increase in the ratio of capillary length to capillary diameter at constant flow rates, and about the increase in critical values of shear stress and shear rate on the use of spinnerets with a conical inlet have been confirmed on polyacrylonitrile solutions having a high concentration.A second region of stable flow of polyacrylonitrile solutions having concentrations of 17.7% by wt. has been found in short capillaries (with a length of 3 or 10 mm).Translated from Khimicheskie Volokna, No. 2, pp. 23–24, March–April, 1990.     

Morphological and structural features of polyacrylonitrile fibres spun by the dry-wet method

Conclusions -- A technological regime for the preparation of polyacrylonitrile fibres from binary and ternary copolymers has been chosen; these differ from known specimens in having a more uniform cross-sectional structure and a smoother elementary filament surface.-- A considerable difference in crystalline structure of fibres from binary and ternary copolymers which have been spun into a dimethyl sulfoxide—water bath has been shown.-- Fibres from the binary or ternary copolymer which have been spun into a precipitation bath having a large dimethyl sulfoxide content in water are characterized by a lower degree of swelling.-- Shrinkage of fibres from the binary copolymer in the temperature range 200–220°C is twice as small as the shrinkage of fibres from the ternary copolymer.Deceased.VNIIPV. Translated from Khimicheskie Volokna, No. 3, pp. 19–22, May–June, 1991.     

Synthesis and Anti-Proliferative Activity of Novel Quinolin-8-ol Derivatives

Through the coupling of substituted benzaldehydes with 8-hydroxy 5-amino methyl quinoline scaffold, a series of new derivatives has been synthesized. In vitro growth inhibitory effects on cancer cell line model have been evaluated. Discussion on the chemical reactivity of these new polycyclic aromatic analogs to generate alkylating species led to the hypothesis that the presence of an imine moiety impedes the formation of quinone methide intermediate and consequently abolishes in part their antiproliferative activity.     

Enhanced transport properties of Sn-substituted proton-conducting BaZr0.8Sc0.2O3–δ ceramic materials

High-temperature proton conductors based on acceptor-doped barium zirconate exhibit excellent chemical stability in atmospheres containing CO₂ or H₂O. However, due to their refractory nature, these conductors have a low grain growth rate, which negatively affects the overall electrical conductivity. A possible strategy for increasing the ionic conductivity of zirconates lies in the partial substitution of Zr-ions with other isovalent dopants. In this work, we carried out systematic studies of the crystal structure, microstructure, hydration capacity, transport, and thermal properties of BaZr_0.8–xSn_xSc_0.2O_3–δ (x = 0, 0.1, and 0.2). According to X-ray powder diffraction and scanning electron microscopy data, all studied ceramic samples have a cubic perovskite structure, whose average grain size decreases with tin doping. It is found that the composition with x = 0.1 exhibits the highest values in terms of total, ionic, grain, and grain-boundary conductivities. The complex analysis of the obtained data shows that a low-level substitution of Zr⁴⁺- with Sn⁴⁺-ions is a competent approach for designing new proton-conducting electrolytes attractive for high-temperature applications.     

Hydrogen Permeability of Microspheres Based on Ash and Slag

The compositions of aluminosilicate microspheres made of TPP ash and slag are investigated. A correlation-regression analysis of the criteria characterizing the glass structure is implemented. The role of the components and the effect of the structure cohesion, internal porosity, molar volumes of oxides, and aluminosilicate and silicate moduli on hydrogen permeability of microspheres is established. A composition promising for designing microspheres for use as gas containers is identified.     

Hydrogen Permeability of Borosilicate Glasses

Borosilicate glass-forming compositions R₂O – B₂O₃ – SiO₂ – R_aO_b (R — Li, Na, K; R_a — Zn, PbO) are investigated. A correlation-regression analysis of the criteria (the silicate modulus, the oxygen number, the structure cohesion factor, the relative molar volumes of the components) affecting the hydrogen permeability of glasses is carried out. The tendency for permeability variations depending on the component composition and the above specified criteria is identified.     

Selection of Structural Parameters in Developing Chemical Compositions for Glass Microspheres

The author analyzes certain parameters determining the structure of glasses, which ought to be taken into account in developing chemical compositions for microspheres, namely, the molar volume, the silicate modulus (for silicate glasses), the gas permeability coefficient, and the structure coherence factor. Furthermore, the parameter of internal porosity is proposed.     

Molecular dynamics simulations and experimental studies of the thermomechanical response of an epoxy thermoset polymer

We report a detailed comparison between molecular dynamics predictions and experimental results for a wide range of thermo-mechanical properties of an epoxy resin system: diglycidyl ether of bisphenol A (DGEBA) cured with 3,3′ diamino-diphenyl sulfone (33DDS). A set of carefully designed and characterized experiments provides validation data for the simulations that predict the molecular structure and properties of the thermoset. Our results show that current state-of-the-art molecular dynamics simulations provide quantitative predictions for this epoxy system in its glassy state, including elastic moduli, coefficient of thermal expansion and specific heat. The glass transition temperature is also accurately predicted once a correction is included to account for the difference in cooling rates between the simulations and experiments. Our results also indicate that viscoelastic and thermal properties of the thermoset polymer in its rubbery state are more challenging to predict since the effect of timescales is not well understood.