Effect of processing conditions on the cellular morphology of polyethylene hollow fiber foams for membrane applications

2018 ◽  
Vol 37 (4-6) ◽  
pp. 169-188 ◽  
Author(s):  
Zahir Razzaz ◽  
Abolfazl Mohebbi ◽  
Denis Rodrigue
Keyword(s):  
Cell Density ◽  
Cellular Structure ◽  
High Cell Density ◽  
Gas Permeability ◽  
Low Cost ◽  
Linear Low Density Polyethylene ◽  
Cell Size Distribution ◽  
Separation Membranes ◽  
Gas Separation Membranes ◽  
Complete Set

A continuous method without any solvent is proposed to produce porous hollow fibers for membrane (HFM) applications. In this case, linear low-density polyethylene was combined with azodicarbonamide to produce samples via extrusion. In particular, the processing (chemical blowing agent content and temperature profile) and post-processing (stretching velocity) conditions were optimized to obtain a cellular structure having a high cell density and uniform cell size distribution. From the samples obtained, a complete set of characterization was performed (morphological, mechanical, physical, and gas transport). The results show that HFM having a higher cell density can increase gas permeability, especially for hydrogen. Overall, it is shown that low-cost polyolefins having a suitable cellular structure can be used for gas separation membranes.

Synthesis and properties of highly processable asymmetric polyimides with bulky phenoxy groups

2019 ◽  
Vol 32 (4) ◽  
pp. 455-468
Author(s):  
Mario Rojas-Rodríguez ◽  
Carla Aguilar-Lugo ◽  
Angel E Lozano ◽  
Antonio Hernández ◽  
Enoc Mancilla-Cetina ◽  
...  
Keyword(s):  
Volume Fraction ◽  
Gas Permeability ◽  
High Thermal Stability ◽  
Phenoxy Group ◽  
Separation Membranes ◽  
Permeability Enhancement ◽  
Gas Separation Membranes ◽  
Ideal Selectivity ◽  
Free Volume Fraction ◽  
One Step

A series of new aromatic polyimides (PIs) and co-PIs containing bulky tert-butyl phenoxy group was synthesized by one-step high-temperature polycondensation of 1,3-diamino-4-(4′- tert-butylphenoxy)benzene ( tBuPDAB) with different commercially available aromatic dianhydrides. The polymers were obtained in quantitative yields with inherent viscosities of 0.40–0.70 dL g−1. They exhibited high thermal stability with 10% weight loss above 480°C and were cast in films with good mechanical properties capable to be tested as gas separation membranes. These PIs were compared with analogs bearing phenoxy group (PDAB). The incorporation of tBu improved the solubility of the PIs, their free volume fraction, d-spacing, and gas permeability coefficients in comparison with their analogs obtained from PDAB. The permeability enhancement was from 2.5 to 8 times depended on the gas tested. The PI, based on tBuPDAB and 4,4’-(hexafluoroisopropylidene)diphtalic anhydride and, thus, containing two different bulky pendant groups, showed the highest gas permeability coefficient for CO2 (58.3 Barrer) and moderate ideal selectivity to the gas pair CO2/CH4 ( α = 18.0).

Impact of Magnetically Aligned CNT/PC Nanocomposites for Hydrogen Gas Separation Applications

MRS Advances ◽  
2016 ◽  
Vol 1 (42) ◽  
pp. 2873-2880
Author(s):  
Anshu Sharma ◽  
S. P. Nehra ◽  
Y. K. Vijay ◽  
I. P. Jain
Keyword(s):  
Magnetic Field ◽  
Dielectric Constant ◽  
Gas Separation ◽  
Gas Permeability ◽  
Gas Permeation ◽  
Hydrogen Gas ◽  
Nanocomposite Membranes ◽  
Separation Membranes ◽  
Gas Separation Membranes ◽  
Magnetically Aligned

ABSTRACTThe goal of this work is to study the properties of magnetically aligned CNT/PC nanocomposites towards the development of hydrogen gas separation membranes. A fraction (0.1 weight %) of synthesized carbon nanotubes (CNTs) have been dispersed homogeneously throughout polycarbonate (PC) matrix by ultrasonication. The alignment of CNT in PC matrix has been accomplished by applying an external magnetic field of 1200 Gauss. These nanocomposites have been studied by gas permeation using H2, N2and Co2electrical and dielectric constant measurements. Experimental results of gas permeability measurements exhibit here that H2is more selective than N2and Co2in magnetically aligned nanocomposite membranes which can be used as good hydrogen separating media. I-V characteristics show the electron hopping like behavior and dielectric constant shows the enhancement in permittivity of these nanocomposites.

scholarly journals Preparation of Hollow Fiber Membranes Based On Poly(4-methyl-1-pentene) for Gas Separation

Fibers ◽  
2021 ◽  
Vol 10 (1) ◽  
pp. 1
Author(s):  
Anton Dukhov ◽  
Martin Pelzer ◽  
Svetlana Markova ◽  
Daria Syrtsova ◽  
Maxim Shalygin ◽  
...  
Keyword(s):  
Gas Separation ◽  
Hollow Fiber ◽  
Melt Spinning ◽  
Gas Permeability ◽  
Separation Membranes ◽  
Preparation Conditions ◽  
Gas Separation Membranes ◽  
Temperature Dependences ◽  
Spinning Process ◽  
Apparent Activation Energies

New hollow fiber gas separation membranes with a non-porous selective layer based on poly(4-methyl-1-pentene) (PMP) granules have been obtained using the solution-free melt spinning process. The influence of the preparation conditions on the geometry of the obtained samples was studied. It was found that a spin head temperature of 280 °C and a specific mass throughput of 103 g mm−2 h−1 are optimal to obtain defect-free, thin-walled hollow fibers in a stable melt spinning process, using the given spinneret geometry and a winding speed of 25 m/min. The gas permeability and separation properties of new fibers were studied using CO2/N2 and CO2/CH4 mixtures, and it was found that the level of gas selectivity characteristic of homogeneous polymer films can be achieved. The features of the gas mixture components permeability below and above the PMP glass transition temperature have been experimentally studied in the range of CO2 concentrations from 10 to 90% vol. The temperature dependences of the permeability of the CO2/CH4/N2 mixture through the obtained HF based on PMP have been investigated, and the values of the apparent activation energies of the permeability have been calculated, which make it possible to predict the properties of membrane modules based on the obtained membranes in a wide temperature range.

scholarly journals Synthesis and Characterization of Novel Nanoporous Gl-POSS-Branched Polymeric Gas Separation Membranes

Membranes ◽  
2020 ◽  
Vol 10 (5) ◽  
pp. 110 ◽  
Author(s):  
Ilnaz I. Zaripov ◽  
Ilsiya M. Davletbaeva ◽  
Zulfiya Z. Faizulina ◽  
Ruslan S. Davletbaev ◽  
Aidar T. Gubaidullin ◽  
...  
Keyword(s):  
Gas Separation ◽  
Gas Permeability ◽  
Chemical Properties ◽  
Toluene Diisocyanate ◽  
Main Reaction ◽  
Separation Membranes ◽  
Gas Separation Membranes ◽  
Oligomeric Silsesquioxane ◽  
Physical And Chemical

Novel nanoporous Gl-POSS-branched polymers based on the macroinitiator of anionic nature, 2,4-toluene diisocyanate, and octaglycidyl polyhedral oligomeric silsesquioxane (Gl-POSS) were obtained as gas separation membranes. The synthesis of polymers was carried out using various loads of Gl-POSS. It was found that the main reaction proceeding with 2,4-toluene diisocyanate is the polyaddition, accompanied by the isocyanate groups opening of the carbonyl part. This unusual opening of isocyanate groups leads to the formation of coplanar acetal nature polyisocyanates (O-polyisocyanate). The terminal O-polyisocyanate links initiate the subsequent opening of the epoxide rings in Gl-POSS. As a result, Gl-POSS serves as a hard and bulky branching agent and creates the specific framing supramolecular structure, which leads to the formation of nanopores in the polymer, where the flexible polyether components are located inside the cavities. Thermal, mechanical, physical, and chemical properties of the obtained polymers were studied at various Gl-POSS contents in the polymer matrix. It was found that these polymers show high selectivity of gas transport properties for pure ammonia relative to nitrogen and hydrogen at ambient temperature. Measurements showed that the gas permeability coefficients and the values of ideal selectivity were in a non-additive dependence to the Gl-POSS content.

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