Organosilica-Modified Multiblock Copolymers for Membrane Gas Separation

Organosubstituted silica derivatives were synthesized and investigated as modifiers of block copolymers based on macroinitiator and 2,4-toluene diisocyanate. A peculiarity of the modified block copolymers is the existence in their structure of coplanar rigid polyisocyanate blocks of acetal nature (O-polyisocyanates). Organosubstituted silica derivatives have a non-additive effect on high-temperature relaxation and α-transitions of modified polymers and exhibit the ability to influence the supramolecular structure of block copolymers. The use of the developed modifiers leads to a change in the gas transport properties of block copolymers. The increase of the permeability coefficients is due to the increase of the diffusion coefficients. At the same time, the gas solubility coefficients do not change. An increase in the ideal selectivity for a number of gas pairs is observed. An increase in the selectivity for the CO2/N2 gas pair (from 25 to 39) by 1.5 times demonstrates the promising use of this material for flue gases separation.

Application of nanoclays in food packaging

Nanoclays have received special attention due to their wide range of industrial applications due to some inherent properties. Nowadays one of the most active areas of nanoclays research is their employ in food packaging. In this paper, at first, the reasons of nanoclay applications are introduced. Then critical issue in developing food packaging materials are reviewed to minimize gasses and other small molecules transfer between out-side packaging environment and food. The reason for improvement of permeability of films is discussed. The permeability of nanocomposite films may be determined using two factors: diffusion and solubility coefficients. Then antimicrobial activity of clay-based nanocomposites and its mechanism and factors influencing on it are mentioned. The way of evaluation of mechanical properties of the nanocomposite films and strategies for improvement are introduced. Finally, other applications of nanoclays e.g. controlled release of various bioactive molecules and development of reinforced food contact materials have been introduced.

Temperature and Pressure Dependence of Gas Permeation in a Microporous Tröger’s Base Polymer

Gas transport properties of PIM-EA(H2)-TB, a microporous Tröger’s base polymer, were systematically studied over a range of pressure and temperature. Permeability coefficients of pure CO2, N2, CH4 and H2 were determined for upstream pressures up to 20 bar and temperatures up to 200 °C. PIM-EA(H2)-TB exhibited high permeability coefficients in absence of plasticization phenomena. The permeability coefficient of N2, CH4 and H2 increased with increasing temperature while CO2 permeability decreased with increasing temperature as expected for a glassy polymer. The diffusion and solubility coefficients were also analysed individually and compared with other polymers of intrinsic microporosity. From these results, the activation energies of permeation, diffusion and sorption enthalpies were calculated using an Arrhenius equation.

Improved Hydrogen Separation Using Hybrid Membrane Composed of Nanodiamonds and P84 Copolyimide

Membrane gas separation is a prospective technology for hydrogen separation from various refinery and petrochemical process streams. To improve efficiency of gas separation, a novel hybrid membrane consisting of nanodiamonds and P84 copolyimide is developed. The particularities of the hybrid membrane structure, physicochemical, and gas transport properties were studied by comparison with that of pure P84 membrane. The gas permeability of H2, CO2, and CH4 through the hybrid membrane is lower than through the unmodified membrane, whereas ideal selectivity in separation of H2/CO2, H2/CH4, and CO2/CH4 gas pairs is higher for the hybrid membrane. Correlation analysis of diffusion and solubility coefficients confirms the reliability of the gas permeability results. The position of P84/ND membrane is among the most selective membranes on the Robeson diagram for H2/CH4 gas pair.

Gas transport properties of polyimide membranes based on triphenylamine unit

A series of polyimide (PI) membranes were prepared based on three triphenylamine-based diamines, namely 4,4′-diaminotriphenylamine, 4,4′-diamino-3′′,5′′-dimethyltriphenylamine, and 4,4′-diamino-3′′,5′′-ditrifluoromethyltriphenylamine, via thermal imidization procedure. The PI membranes displayed good thermal properties, with glass transition temperatures of 279–341°C and 5% weight loss temperatures above 515°C under a nitrogen atmosphere. The gas permeation properties of the membranes were investigated and interpreted from the viewpoint of the PI backbone structure. The gas permeation coefficients increased as the substituent pendant groups at the 3′′,5′′ positions of the triphenylamine varied from –H to –CH3 and –CF3, and the permselectivity of gas pairs (including hydrogen/nitrogen (N2), oxygen/N2, carbon dioxide (CO2)/N2, and CO2/methane) decreased in this order. The diffusion coefficients and solubility coefficients were calculated, and the results revealed the variation of the substituted triphenylamine units principally influenced the diffusion coefficients, indicating that the substituted triphenylamine affected the gas transport properties by “diffusivity-controlled” modification.

The Molecular Simulation Study of Optimum Blending Ratio for PVDF/PVC Membrane

The PVDF/PVC blending membrane has a certain application in the field of sewage treatment. In this paper, the simulation study for the blending ratio of the PVDF/PVC membrane has been carried on, which has an influence on the membrane’s ability of sewage treatment. Firstly, the membrane models were constructed via Amorphous Cell module of MS (material studios) 6.0. Secondly, the optimization processes were achieved via Minimizer and MD (Molecular Dynamics) method of the Discover module. Lastly, the diffusion coefficients D was calculated indirectly through the Mean square displacement (MSD) getting from Forcite module and the solubility coefficients S was calculated indirectly through the adsorption isotherm getting from Sorption module. It was found that the membrane had a best ability of sewage treatment when the content of PVC was 5% (mass fraction). And the calculated result was well consistent with experiment result.