Permeability Of Different Gases Research Articles

Effect of Biobased SiO2 on the Morphological, Thermal, Mechanical, Rheological, and Permeability Properties of PLLA/PEG/SiO2 Biocomposites

Nowadays, companies and researchers are concerned about the negative consequences of using synthetic polymers and direct their efforts to create new alternatives such as biocomposites. This study investigated the effect of biobased SiO2 on the properties of poly(L-lactic acid)/SiO2 (PLLA/SiO2) and poly(L-lactic acid)/SiO2/poly(ethylene glycol) (PLLA/SiO2/PEG) composites. The SiO2 was obtained from rice husk incineration and mixed with PLLA at various concentrations (5, 10, and 15 wt.%) via melt extrusion before compression molding. Furthermore, PLLA/SiO2/PEG composites with various PEG concentrations (0, 3, 5, and 10 wt.%) with 10 wt.% SiO2 were produced. The sample morphology was studied by scanning electron microscopy (SEM) to analyze the dispersion/adhesion of SiO2 in the polymer matrix and differential scanning calorimetry (DSC) was used under isothermal and non-isothermal conditions to study the thermal properties of the samples, which was complemented by thermal stability study using thermogravimetric analysis (TGA). Rheological analysis was performed to investigate the viscoelastic behavior of the composites in the melt state. At the same time, tensile mechanical properties were obtained at room temperature to determine their properties in the solid state. DSC and X-ray diffraction analysis (XRD) were combined to determine the crystalline state of the samples. Finally, gas permeation measurements were performed using a variable pressure (constant volume) method to analyze the permeability of different gases (CO2, CH4, O2, and H2). The results showed that SiO2 decreased the PLLA chain mobility, slowing the crystallization process and lowering the gas permeability while increasing Young’s modulus, thermal stability, and viscosity. However, PEG addition increased the crystallization rate compared to the neat PLLA (+40%), and its elongation at break (+26%), leading to more flexible/ductile samples. Due to improved silica dispersion and PLLA chain mobility, the material’s viscosity and gas permeability (+50%) were also improved with PEG addition. This research uses material considered as waste to improve the properties of PLA, obtaining a material with the potential to be used for packaging.

Controlled Covalent Functionalization of ZIF-90 for Selective CO2 Capture & Separation.

Mixed Matrix Membranes (MMM) with enhanced selectivity and permeability are preferred for gas separations. The porous metal-organic frameworks (MOFs) materials incorporated in them play a crucial part in improving the performance of MMM. In this study, Zeolitic imidazolate frameworks (ZIF-90) are selected to fabricate Polyetherimide (PEI) MMMs owing to their lucrative structural and chemical properties. This work reports new controlled post-synthetic modifications of ZIF-90 (50-PSM-ZIF-90) with ethanolamine to control the diffusion and uptake of CO2. Physical and chemical properties of ZIF-90, such as stability and presence of aldehyde functionality in the imidazolate linker, allow for easy modulation of the ZIF-90 pores and window size to tune the gas transport properties across ZIF-90-based membranes. Effects of these materials were investigated on the performance of MMMs and compared with pure PEI membranes. Performance of the MMMs was evaluated in terms of permeability of different gases and selective separation of CO2 and H2 gas. Results presented that the permeability of all membranes was in the following order, i.e., P(H2) > P(CO2) > P(O2) > P(CH4) > P(C2H6) > P(C3H8) > P(N2), demonstrating that kinetic gas diffusion is the predominant gas transport mode in these membranes. Among all the membranes, permeability of pure PEI membrane was highest for all gases due to the uniform porous morphology. The pure PEI membrane showed highest permeability of H2, which is 486.5 Barrer, followed by 49 Barrer for O2, 29 Barrer for N2, 142 Barrer for CO2, 41 Barrer for CH4, 40 Barrer for C2H6 and 39.6 Barrer for C3H8. Results also confirm the superiority of controlled PSM-ZIF-90-PEI membrane over the pure PEI and ZIF-90-PEI membranes in CO2 and H2 separation performance. The 50-PSM-ZIF-90 PEI membrane exhibited a 20% increase in CO2 separation from methane and a 26% increase over nitrogen compared to the ZIF-90-PEI membrane. The 50-PSM-ZIF-90 PEI membrane showed 15% more H2/O2 separation and 9% more H2/CH4 separation than ZIF-90 PEI membrane. Overall, this study represents the role of controlled PSM in enhancing the property of new materials like ZIF and its application in MMMs fabrication to develop a promising approach for the CO2 capture and separation.

A convenient and practical triaxial coupled seepage testing apparatus for deep buried coal.

As the world's shallow coal resources are being depleted, resource development continues to progress faster. To explore the coupled hydromechanical behavior of coal reserves that are buried deep underground under high stress, complex seepage, high temperature, adsorption, and desorption, we have developed a triaxial seepage testing apparatus under multifactor coupling effect. The system consists of a high-pressure and high-precision servo control loading system, a triaxial core holder (TEMCO), a seepage dynamic control system, a low-field Nuclear Magnetic Resonance (NMR) test system, a constant temperature control system, and a data acquisition and monitoring system. This system is capable of applying high pressure and long-term loading for specimens under adsorption or desorption. In addition, both steady-state method and pressure transient methods can be applied, thus covering the entire range for coal reserves buried deep from ultralow permeability to high permeability and significantly shortening the testing time. The characteristics of pores and fractures in the specimens and their impacts on permeability can be quantitatively evaluated by the low-field NMR experimental technique. We conducted experiments to understand the evolution of permeability of different gases under different stress conditions and to study the impact of adsorption on pore size distribution. Our experimental results show that the performance of this system is stable and reliable, which allow it to reflect the coupled hydromechanical response of coal buried deep underground. We envision this apparatus has a wide range of application value and can provide a scientific experimental basis for improving the recovery of coalbed methane and geological sequestration of CO2 in the future.

Synthesis and gas permeation analysis of TiO2 nanotube-embedded cellulose acetate mixed matrix membranes

Pristine cellulose acetate (CA) membranes and CA mixed matrix membranes (MMM) embedded with titania (TiO2) nanotubes (Tnts) were synthesized by loading different weight percentages of Tnts (2%, 5%, 7%, 10%) in them by employing solution casting technique. The Tnts were prepared by hydrothermal treatment of TiO2 nanoparticles in aqueous NaOH solution. Permeability of different gases; CO2, N2, O2 and CH4, was studied across these membranes and the results were compared for pure and mixed matrix membranes. Effect of pressure on permeability of different gases was also studied. The membranes were then analyzed by Scanning Electron Microscopy (SEM), Tensile Testing (TT) and Fourier transformation infrared spectroscopy (FTIR) techniques. Results showed that homogeneous dispersion of tubes was achieved up till 5 wt%-CA loading. The average permeation of CO2 obtained was 25 barrer at 5 bar pressure. It was further identified that the ultimate tensile strength of mixed matrix membranes was roughly 7 times greater than the pristine membranes.

Development and Characterization of Defect-Free Matrimid® Mixed-Matrix Membranes Containing Activated Carbon Particles for Gas Separation.

In this work, mixed-matrix membranes (MMMs) for gas separation in the form of thick films were prepared via the combination of the polymer Matrimid® 5218 and activated carbons (AC). The AC particles had a mean particle size of 1.5 μm and a mean pore diameter of 1.9 nm. The films were prepared by slow solvent evaporation from casting solutions in chloroform, which had a varying polymer–AC ratio. It was possible to produce stable films with up to a content of 50 vol % of AC. Thorough characterization experiments were accomplished via differential scanning calorimetry and thermogravimetric analysis, while the morphology of the MMMs was also investigated via scanning electron microscopy. The gas transport properties were revealed by employing time-lag measurements for different pure gases as well as sorption balance experiments for the filler particles. It was found that defect free Matrimid® MMMs with AC were prepared and the increase of the filler content led to a higher effective permeability for different gases. The single gas selectivity αij of different gas pairs maintained stable values with the increase of AC content, regardless of the steep increase in the effective permeability of the pure gases. Estimation of the solubilities and the diffusivities of the Matrimid®, AC, and MMMs allowed for the explanation of the increasing permeabilities of the MMMs, with the increase of AC content by modelling.

Synthesis and gas separation properties of metathesis poly(5-ethylidene-2-norbornene)

High molecular weight metathesis poly(5-ethylidene-2-norbornene) (PENB) has been synthesized in the presence of the 1st generation Grubbs catalyst at a high monomer/catalyst ratio (3000/1 and higher). The yields of the corresponding polymer have been more than 90% at all monomer/catalyst ratios and molecular weights (Mw) of PENB have been higher than 3 × 105. The gas permeability of different gases (He, H2, O2, N2, CO2, and CH4) through PENB films has been studied, and diffusivity and selectivity coefficients have been determined. It has been found that PENB is more permeable than unsubstituted metathesis polynorbornene and cycloalkyl-substituted polynorbornene dicarboximides, but it is less permeable than some Si-containing polynorbornenes. Despite the fact that PENB is more permeable than metathesis polynorbornene and cycloalkyl-substituted polynorbornene dicarboximides, it is close to these polymers in ideal selectivities for some gas pairs.

Synthesis and gas transport properties of crosslinked poly(dimethylsiloxane) nanocomposite membranes using octatrimethylsiloxy POSS nanoparticles

For separation of hydrocarbon compounds from light gases, nanocomposite membranes were prepared by incorporation of polyhedral oligomeric silsesquioxane (POSS) nanoparticles into poly(dimethylsiloxane) (PDMS). First, scanning electron microscopy (SEM) revealed a homogenous dispersion of POSS nanoparticles in PDMS since octatrimethylsiloxy constituents have favorable interactions with the polymer chains. Then, the effect of octatrimethylsiloxy POSS nanoparticles on the thermal stability of the nanocomposite membranes was investigated using thermo-gravimetric analysis (TGA) to propose a decomposition mechanism and discuss the mechanism leading to their increased thermal stability. Thermodynamically, dipole-dipole interaction between POSS and PDMS was found effective to increase thermal stability. Finally, permeability for different gases (H2, C3H8, CO2, and CH4) was measured. The results show that incorporation of only 2% wt. octatrimethylsiloxy POSS in PDMS substantially improved the heat resistance of silicon based membranes with limited reduction in permeabilities for all the gases tested, but C3H8/H2, C3H8/CO2, and C3H8/CH4 selectivities were found to increase.

Synthesis, Characterization and Gas Transport Properties of Polyamide-Tethered Polyhedral Oligomeric Silsesquioxane (POSS) Nanocomposites

Polyamide-tethered polyhedral oligosilsesquioxane (POSS) nanocomposites (PAMIP) with well-defined architectures have been synthesized through Michael addition reaction between the maleimide-containing fluorinated new copolyamides (PAMI) with amino-functionalized POSS (POSS-NH2) nanofiller. The chemical structures of the polyamide–POSS nanocomposites were characterized by 1H NMR and Fourier transform infrared spectroscopy. The effects of POSS-NH2 on the morphology and properties of the PAMIP membranes were examined by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), X-ray diffraction and transmission electron microscopy (TEM) analysis. POSS molecules tethered to polyamide form sphere shaped POSS aggregate cages (phase separated morphology) were confirmed by TEM analysis. All the PAMIP membranes showed very high permeability for different gases compared to PAMI membranes. The increase in permeability is accompanied by increase in diffusivity coefficient of the PAMIP membranes for d...

Investigation of gas permeation properties of systematically modified polybenzimidazoles by N-substitution

Gas permeation behavior of a series of thermally stable N-substituted polybenzimidazoles by systematically varying bulk and flexibility of the substituent was investigated. Two different PBIs having variation in their acid moiety, viz., PBI-I (based on isophthalic acid) and PBI-BuI (based on 5- tert-butyl isophthalic acid) were selected for N-substitution by alkyl groups possessing different bulk and flexibility. These substituent groups were methyl, n-butyl, methylene trimethylsilane and 4- tert-butylbenzyl. Pure gas sorption and permeability using H 2, N 2, O 2, CH 4 and CO 2 were investigated and correlated with physical properties of formed polymers. Estimation of dual-mode sorption parameters, coefficients of sorption, permeability and diffusion for different gases provided an insight towards effects of nature of a substituent group and parent PBI on governing gas sorption and permeation properties. By changing the substituent group, diffusivity coefficients was found to vary to a larger extent than the solubility coefficient. This significantly enhanced gas permeability for different gases by 1.2–129 times than that of parent PBIs. The permselectivity P O 2 / P N 2 was increased (up to 237%), while for other gas pairs, it was decreased to a different extent.

The blood pigment of Arenicola

The object which we had in view when we undertook the present research was to ascertain whether the pigment commonly alluded to as hæmoglobin in the worms was identical with that known by the same name in the vertebrates. Even in the mammalia there is some evidence that all hæmoglobin is not the same, many of the older observers held this to be the case; but since the discovery that the dissociation curve of hæmoglobin depends largely upon the conditions under which it is studied very little work has been done on the subject. It is known, for instance, that the blood of different persons differs slightly in its affinity of oxygen, under identical conditions, but such differences may be ascribed, rightly or wrongly, to variations in the intra-corpuscular atmosphere. More convincing evidence was put forward by C. G. Douglas, J. S. Haldane and J. B. S. Haldane (1) who showed that the blood of the mouse differed markedly from that of the human being. Their observations showed, among other things, that the curve which represents the reaction COHb+ O 2 ⇌ CO+HbO 2 in the mouse differed from that in man. This curve is little affected by the intra-corpuscular conditions of reaction and saline constitution, etc. Nevertheless one possibility was not excluded, namely, that the corpuscles of different animals should have a selective permeability for different gases.