Vol 57, No 11 (2017)

Polypentafluorostyrene (PPFS) (M_w = 1.7 × 10⁵ Da, M_w/M_n = 1.6, and Т_g = 110°С) has been synthesized by radical polymerization of pentafluorostyrene. The chemical structure of the polymer has been confirmed by ¹H and ¹⁹F NMR data. The permeability and diffusion coefficients of gases (He, H₂, O₂, N₂, CO₂, and CH₄) have been measured on a barometric setup. The permeability, diffusion, and solubility coefficients of gases have been shown to increase with the increases in the fluorine content in the repeat unit of the polymer in the polystyrene–poly(p-fluorostyrene)–PPFS series. Such behavior of transport parameters in the polymer series is associated with the growth in the fractional free volume and decrease in the cohesive energy density. The investigated polymers on the basis of styrene and its derivatives including PPFS are located in the middle of clouds of Robeson diagrams for N₂/CH₄, CO₂/CH₄, and O₂/N₂ and are not of interest for their separation.

The influence of the thickness of a Pd–Ru alloy membrane on the H₂ flux from binary mixtures containing about 5 and 20% CO, CO₂, CH₄, and steam has been studied. It has been shown that with a decrease in the membrane thickness from 30 to 10 μm, the negative influence of these impurities on the H₂ flux increases. In experiments with pure H₂, it has been established that a decrease in the membrane thickness does not affect the nature of the rate-limiting step in the H₂ flow mechanism. The values for the effective activation energy of the H₂ permeability of the 30- and 10-μm membranes are 13.6 and 23.4 kJ/mol, respectively. A mathematical model describing the flow of hydrogen from binary mixtures through membranes of various thicknesses with varying temperature and pressure is proposed.

The synthesis of composite materials based on silver nanotubes and PET track-etched membranes (TMs) has been studied. A systematic study of the catalytic properties of the resulting composites has been conducted using the example of the hydrogen peroxide decomposition reaction. Changes in the catalytic properties of the composites as a function of the pore density of the initial PET template and the duration of the chemical template synthesis of silver nanotubes have been analyzed. The Ag/PET TM structure has been studied by SEM; the phase composition and the crystallite sizes have been analyzed by X-ray diffraction. To study the kinetic parameters of the reaction in a temperature range of 25–45°C, the activation energies of both the composite samples and the PET film with silver nanoparticles deposited on the surface have been calculated; it has been found that the lowest activation energy is exhibited by Ag/PET TM composites with a pore density of 1 × 10⁹ ion/cm². Optimum synthesis conditions providing the formation of Ag/PET TM composite catalysts that preserve their integrity and mechanical strength during testing and mediate the studied reaction at the highest rate have been determined. The stability of the catalyst properties has been studied; it has been shown that, at 25°C, the catalyst activity decreases by 35% after the third test run.

The structure and properties of a water–oil emulsion have been studied. The ultrafiltration of the water–oil emulsion has been performed with the use of spiral wound and hollow fiber membranes to separate the emulsion into a filtrate and a concentrate. The effect of pH on the following performance characteristics of the ultrafiltration process has been studied: the efficiency and the degree of separation of oil products and nonionic surfactants. It was found that an increase in the pH value of the emulsion decreased the efficiency of membranes and the degree of separation of nonionic surfactants. It has been found that a Raifil UF membrane effectively rejects oil products from acidic emulsion and, on the contrary, an EMU 45-300 membrane is effective in an alkaline medium. This behavior has been associated with to a positive surface charge of the EMU 45-300 membrane. The maximum efficiencies and degrees of separation of oil products and nonionic surfactants from emulsions with the use of the Raifil UF ultrafiltration membrane and the EMU 45-300 membrane have been attained in the pH ranges from 2.1 to 2.9 and from 2.2 to 2.5, respectively. After ultrafiltration, the size of particles in the filtrate increased by a factor of about 18 due to the coalescence of oil particles in the near-membrane layer because of polarization effects. The increase in the particle size of the dispersed phase in the filtrate can also be explained by a positive surface charge of polysulfonamide membranes.