Reduction In Gas Permeability Research Articles

Effects of calcium sulfate whiskers and basalt fiber on gas permeability and microstructure of concrete

This paper aims to investigate the influence of introducing calcium sulfate whiskers (CSW) and basalt fiber (BF) on the gas permeability coefficients of concrete. Employing the Cembureau method, the research quantifies gas permeability while utilizing Nuclear Magnetic Resonance (NMR) to precisely measure pore structure parameters. The results highlight that the incorporation of CSW leads to a substantial reduction in gas permeability, exhibiting a remarkable 57.6% decrease when utilized at a dosage of 3.0 kg/m³ compared to the standard concrete. In contrast, the introduction of BF at the same dosage does not yield a commensurate reduction in permeability. Notably, the combined application of CSW and BF at 3.0 kg/m³ each yields the most effective mitigation of gas permeability. Furthermore, the judicious addition of either CSW or BF demonstrates the capacity to diminish the overall porosity of concrete, alongside a reduction in the proportion of harmful pores (R100, featuring diameters larger than 100 nm). Optimal outcomes manifest when both CSW and BF are introduced at the 3.0 kg/m³ dosage, effectively minimizing R100 and the gas permeability coefficient. It is interesting to find that in comparison to the correlation observed between the total porosity and gas permeability of concrete, the relationship between the proportion of R100 and gas permeability emerges as more statistically significant (R2 approximately 0.800), especially for CSW concrete. This can reveal the interconnection between the concrete's pore structure and its gas permeability characteristics more appropriately.

Rapid assessment of water phase trapping on gas permeability reduction in typical tight gas reservoirs in China

Water phase trapping (WPT) is one of the primary formation damage issues which can cause a steep drop in tight gas production. This paper presented a rapid assessment of the damage potential of WPT in Daniudi, Nanpu 5th, and Keshen 9th tight gas reservoirs involving shallow to ultra-deep layers in China. Typical core samples of the three tight gas reservoirs were selected to perform water imbibition and drainage experiments to mimic the WPT occurrence. After that, the damage degree to core gas permeability induced by WPT was evaluated. Results showed that, for a 16-h vertical water imbibition experiment, the core samples of Daniudi gas reservoir experienced the fastest water imbibition process while the core samples of Keshen 9th gas reservoir established the highest water saturation. After water removal, the ranges of damage degree to core gas permeability induced by the incremental water saturation were 36.07%–78.13%, 36.06%–56.21%, and 61.00%–76.30% in Daniudi, Nanpu 5th, and Keshen 9th tight gas reservoirs, respectively. It found that with the increasing formation depth, tight gas reservoirs can suffer greater damage from WPT not only because of the decline in rock permeability but also the salting out of high salinity formation water. In general, it holds that strong water capillary imbibition phenomenon, low water removal capacity, and high gas permeability damage degree are found to be the striking features of WPT potential on these typical tight gas reservoirs in China.

Synergistic tuning mixed matrix membranes by Ag+-doping in UiO-66-NH2/polymers of intrinsic microporosity for remarkable CO2/N2 separation

Novel mixed matrix membranes (MMMs) with superior CO2/N2 separation properties are of great importance for post-combustion CO2 capture from flue gas. Metal-organic frameworks (MOFs) as one of the most attractive porous fillers for MMMs fabrication, are considered to provide a solid molecular sieving mechanism for enhancing CO2/N2 selectivity. However, it causes the reduction in gas permeability and limits its further industrialization. Herein, we proposed a new strategy for filler functionalization by doping silver ions (Ag+) into UiO-66-NH2 nanoparticles through the double-solvent method and used for the preparation of advanced MMMs. The double-solvent method is benefits for the enrichment of Ag+ in the hydrophilic pores of UiO-66-NH2. As a result, the prepared novel MMMs called Ag+@UiO@PIM-1 with the polymers of intrinsic microporosity (PIMs) as polymer matrix, show outstanding CO2 permeability. According to the mixed gases (CO2/N2 = 10:90) permeation experiments under 25 °C and 2 bar, the membrane with 30%Ag+@10%UiO loading achieves more than 65% increase in CO2/N2 selectivity (∼30) and 120% in CO2 permeability (>15,000 Barrer) compared to the pristine PIM-1 membrane. By optimizing the Ag+ doping amount and Ag+@UiO loading content, the separation performance exceeds the 2019 CO2/N2 upper bound. To figure out the separation mechanism, the pore texture properties and CO2 affinity of the functional filler (Ag+@UiO) together with the membrane structure were characterized by XPS, PXRD, SEM, gas sorption, etc. The synergistic mechanisms by combing CO2 facilitated transport and molecular sieving from pore regulation were identified to enable advanced CO2/N2 membrane separation.

Pebax and CMC@MXene-Based Mixed Matrix Membrane with High Mechanical Strength for the Highly Efficient Capture of CO2

Sustainable and energy-efficient molecular separation requires membranes with high permeability and selectivity. Among various membranes, the mixed matrix membranes (MMMs) prepared from two-dimensional MXene materials with well-defined nanochannels are expected to be used for the precise separation of molecules. However, the stacking of a large number of 2D MXene nanosheets creates gas mass transfer barriers, resulting in a significant reduction in gas permeability. To solve this issue, herein, a high-performance self-supporting Pebax/CMC@MXene MMM was prepared by a combination of 2D MXene nanosheets with branched carboxymethyl cellulose (CMC) for CO2 gas separation from natural gas and flue gas. Gas separation experimental results show that the as-prepared self-supporting Pebax/CMC@MXene MMMs can significantly improve gas permeance and selectivity. When the loading of MXene nanosheets in the CMC@MXene filler was fixed at 1.5 mg/mL, the CO2 permeance of Pebax/CMC@MXene MMMs was found to be 521 GPU, and the CO2/N2 selectivity was calculated to be 40.1. Meanwhile, the CO2 permeance was measured to be 444 GPU, and the CO2/CH4 selectivity was calculated to be 40.4. In addition, the resulted as-prepared self-supporting Pebax/CMC@MXene MMM possesses excellent thermal stability and long-term durability; after a 60 h test, its separation performance has no obvious change. The work provides a novel strategy to construct MMMs with less mass transfer barrier for highly efficient capture of CO2 from natural gas and flue gas.

Cross-Linked Polyimide/ZIF-8 Mixed-Matrix Membranes by In Situ Formation of ZIF-8: Effect of Cross-Linking on Their Propylene/Propane Separation.

Despite their potential for the scalable production of mixed-matrix membranes (MMMs), the MMMs prepared by the polymer-modification-enabled in situ metal–organic framework formation (PMMOF) process showed a considerable reduction in gas permeability as the filler loading increased. It was hypothesized that a correlation existed between the decrease in permeability and the change in the properties of the polymer, such as free volume and chain flexibility, upon in situ MOF formation. Herein, we aim to address the permeability reduction by using a cross-linked polyimide (6FDA-DAM:DABA (3:2)). It was found the degree of cross-linking affected not only the properties of the polymer, but also the in situ formation of the ZIF-8 filler particles in the cross-linked polymer. The proper degree of cross-linking resulted in suppressing C3H6 permeability reduction, suggesting a possible strategy to overcome the issue of PMMOF. The swelling of the polymer followed by chain rearrangement during the PMMOF, as well as the structural rigidity of the polymer, were found to be critical in mitigating permeability reduction.

Environmental treatment and remediation using h-BN based smart and hybrid membrane

Corrosion is a major problem resulting from acid gases found in natural gas being transported in pipelines. To solve this problem, high aspect ratio h-BN nanosheets have been incorporated and are properly assimilated in the CA matrix, this led to an increase in tortuous path of flow for the gas resulting in smooth, dense membrane samples causing exceptional permeability reduction. Hexagonal Boron Nitride (h-BN) nanosheets have been synthesized and incorporated into cellulose acetate (CA) matrix using solution casting method. Nanosheets of various sizes, separated by varying centrifugation speeds (i.e. 500 rpm, 700 rpm, 1500 rpm, 2000 rpm and 2500 rpm), have been prepared and used for our work. The resulting nanocomposites, having thickness ranging between 40 and 60 μm, were then tested for CO2 gas permeability reduction using both short-term (8 h) tests as well as long-term (72-h tests). As a result of these tests, a maximum CO2 permeability reduction of 99.84% is found with a minimum CO2 permeability of 3.25 barrer. For dimensional analysis of both nanosheets and nanocomposites, scanning electron microscopy (SEM) analysis is used. For verifying the presence of the required functional groups in our synthesized samples, FT-IR spectroscopy is used. Moreover, to confirm the presence of crystalline phases, X-ray Diffraction (XRD) analysis is used. Also, tensile testing is used to analyze the mechanical robustness and it was found that nanocomposite samples exhibited higher tensile strength as compared to pristine samples. Furthermore, tribological property analysis was also carried out for adhesion testing of polymeric material with steel.

A strategy for constructing highly efficient Co3O4-C@SiO2 nanofibers catalytic membrane for NH3-SCR of NO and dust filtration

The strategy of constructing catalytic membrane has a significant influence on its structure and performance. In this work, Co3O4-Cx@SiO2 nanofiber membranes (NFMs) were fabricated by an in-situ growth–pyrolysis–oxidation strategy. The Co3O4-Cx catalyst derived from ZIF-67 was wrapped around nanofibers, which helps to maintain a stable membrane structure, then suppressing the reduction of gas permeability. Among the Co3O4-Cx catalyst, the carbon skeleton can prevent the agglomeration of Co3O4 nanoparticles, obtaining an ultra-fine Co3O4 nanoparticles with high dispersibility, redox property and surface area. The obtained Co3O4-C300@SiO2 NFM exhibits outstanding ammonia selective catalytic reduction (NH3-SCR) denitrification activity (T90 = 225 °C at a GHSV of 77,000 h−1). The effect of catalyst loading on PM2.5 filtration performance of SiO2 NFM was also tested. Co3O4-C300@SiO2 NFM has higher filtration efficiency (99.99%) than SiO2 NFM at a lower pressure drop of 58 Pa, which suggests that catalyst loading via our method can improve the filtration performance of SiO2 NFM. This work might provide a universal strategy for the design and preparation of highly efficient catalytic membrane.

An Experimental Investigation of the Gas Permeability of Tectonic Coal Mineral under Triaxial Loading Conditions

Underground coal mining of CH4 gas-rich tectonic coal seams often induces methane outburst disasters. Investigating gas permeability evolution in pores of the tectonic coal is vital to understanding the mechanism of gas outburst disasters. In this study, the triaxial loading–unloading stresses induced gas permeability evolutions in the briquette tectonic coal samples, which were studied by employing the triaxial-loading–gas-seepage test system. Specifically, effects of loading paths and initial gas pressures on the gas permeability of coal samples were analyzed. The results showed the following: (1) The gas permeability evolution of coal samples was correlated with the volumetric strain change during triaxial compression scenarios. In the initial compaction and elastic deformation stages, pores and cracks in the coal were compacted, resulting in a reduction in gas permeability in the coal body. However, after the yield stage, the gas permeability could be enhanced due to sample failure. (2) The gas permeability of the tectonic coal decreased as a negative exponential function with the increase in initial gas pressure, in which the permeability was decreased by 67.32% as the initial gas pressure increased from 0.3 MPa to 1.5 MPa. (3) Coal samples underwent a period of strain development before they began to fail during confining pressure releasing. After the stress releasing-induced yield stage, the coal sample was deformed and cracked, resulting in a quickly increase in gas permeability. With a further releasing process, failure of the sample occurred, and thus induced rapidly increasing gas permeability. These obtained results could provide foundations for gas outburst prevention in mining gas-rich tectonic coal seams.

Compatibilization of PLA grafted maleic anhydrate through blending of thermoplastic starch (TPS) and nanoclay nanocomposites for the reduction of gas permeability

ABSTRACT Here, the effects of compatibilization and clay nanoparticles on the gas permeability of nanocomposites of poly-lactic acid (PLA)/thermoplastic starch (TPS)/nanoclay were discussed. TPS and compatibilized PLA/TPS were tailored in the first step. The starch with D-sorbitol as a plasticizer was mingled through the internal mixer. Afterward, the maleination method was utilized on PLA to ameliorate the compatibilization of PLA and TPS. In this regard, maleic anhydrate (MA) has been grafted on PLA in the presence of L101 as a peroxide initiator via melt mixing to obtain PLA-g-MA. The optimum content of PLA-g-MA was about 4 phr, confirmed by DMTA and SEM. Noteworthy, the presence of PLA-g-MA has moderately improved the oxygen barrier. Then, the nanocomposites of PLA and TPS containing 1% of Cloisite-30B as well as the optimum compatibilizer (4phr), were produced by melt mixing in the masterbatch module leading to the formation of an extraordinary well-dispersed structure according to XRD patterns. The mixing order controlled the localization of nanosheets. It was concluded that the inclusion of 1% nanoclay in the PLA phase reduces the oxygen permeability by 55% compared to the pristine blend due to the tortuosity effect of nanosheets that are appropriately dispersed in the matrix.

Impact of prolonged water‐gas flow on the performance of polyacrylamide

AbstractExcessive water production from natural reservoirs is a major challenge in oil and gas industry. Relative permeability modifiers (RPM) are used to selectively reduce water production with minimum effect on the hydrocarbon production. This work examined the performance of polyacrylamide in terms of its water control efficiency at prolonged water‐gas flowing cycles. During each cycle, as the volume of injected water increased, the RPM demonstrated stronger performance in terms of reducing water permeability. This is attributed to the swelling of polymer layer adsorbed to the pore surfaces. Conversely, during each cycle, higher volume of gas injection led to less reduction in the gas effective permeability (PRg) which is due to polymer shrinkage. The reduction in water absolute permeability (PRw) of the treated micromodel in each injection cycle was significantly greater than the reduction in gas permeability. Interestingly, as water‐gas cycles progressed, a significant increase in water permeability reduction was observed. It is also found that polymer expansion and shrinkage are reversible. As such, the RPM performance depends on the injected fluid, injected fluid volumes and water‐gas injecting cycling. We thus conclude that that polymer swelling, and shrinkage and polymer‐gas interaction play a vital role in RPM performance.

Impact of de-ionized water on changes in porosity and permeability of shales mineralogy due to clay-swelling

Hydraulic fracturing is widely applied for economical gas production from shale reservoirs. Still, the swelling of the clay micro/nano pores due to retained fluid from hydraulic fracturing causes a gradual reduction of gas production. Four different gas-bearing shale samples with different mineralogical characteristics were investigated to study the expected shale swelling and reduction in gas permeability due to hydraulic fracturing. To simulate shale softening, these shale samples were immersed in deionized (DI) water heated to 100 °C temperature and subjected to 8 MPa pressure in a laboratory reactor for 72 hours to simulate shale softening. The low-temperature nitrogen adsorption and density measurements were performed on the original and treated shale to determine the changes in micro and nano pore structure. The micro and nano pore structures changed, and the porosity decreased after shale treatment. The porosity decreased by 4% for clayey shale, while for well-cemented shale the porosity only decreased by 0.52%. The findings showed that the initial mineralogical composition of shale plays a significant role in the change of micro and nano pores and the pore structure alteration due to retained fluid from hydraulic fracturing. A pore network model is used to simulate the permeability of shale used in this study. To define pore structure properties, specific factors such as porosity, pore size, pore throat distribution, and coordination number were used. Furthermore, the anisotropy characteristics of shale were integrated into the model via a coordination number ratio. Finally, the change in permeability due to shale softening was determined and compared with untreated with the progress of shale softening. The simulation showed that the permeability of Longmaxi shale could decrease from 3.82E–16 m2 to 4.71E–17 m2 after treatment.

Influence of ultraviolet aging on the structure, mechanical and gas permeability properties of hydrogenated nitrile butadiene rubber

AbstractThe effect of ultraviolet (UV) radiation on the structure and performance of hydrogenated nitrile butadiene rubber (HNBR) was studied in this paper. The HNBR was exposed to UV radiation for various durations (0, 7, 14, 21 and 28 days). The Fourier transform infrared spectroscopy (FTIR) results demonstrated that the surface molecular structures were oxidized to generate oxygenated species under UV radiation. The oxidative degree enhanced with the increase of aging time, resulting in thicker and denser cracks on the surface. The plausible aging mechanism of HNBR was suggested. The free volume of HNBR before and after UV aging was characterized by positron annihilation lifetime spectroscopy (PALS) and their cross‐linking density, compression set, mechanical and gas permeability properties were also analyzed. In the first 14 days of UV irradiation, the dominant chain‐scission reaction led to a decrease in cross‐linking density of HNBR, resulting in the enhancement of free volume and thereby the increase of gas permeability. When the aging time was longer than 14 days, cross‐linking reaction played a leading role and the free volume decreased, thus causing the reduction of gas permeability. As the aging time increased, the glass transition temperature (Tg), tensile strength and storage modulus of HNBR initially reduced and then increased, which was in agreement with the changing trend of cross‐linking density.

Effect of coating steps on uniformity and gas permeability of mesoporous layers in ceramic membranes

Abstract Porous silica, silica-cobalt, silica-zirconia and zirconia membranes were synthesized by the sol-gel method. Multi-step coating (two, six, and ten steps) was used to reduce the defectiveness of the mesoporous layer. Scanning electron microscopy (SEM) images indicated that an increase in the number of coating steps improved the mesoporous layer quality. The results obtained from gas permeability tests with nitrogen and argon, however, indicated a reduction in the gas permeability with increasing coating steps. The reduction in gas permeability from two to six coating steps was more pronounced than from sixto ten- coating steps. It was found that six-step coating was economically justified in obtaining a uniform mesoporous layer. The results of pore radius calculations by Knudsen flow mechanism revealed that the pores in the silica, silica-cobalt, and zirconia membranes were in the mesoporous range. The sols with a mean particle size more than 100 nm are not recommended for synthesis of mesoporous layer free of defects. Furthermore, the type of acid used as a catalyst is also important in obtaining a layer without defectiveness.

Well injectivity loss during chemical gas stimulation process in gas-condensate tight reservoirs

After the injection of chemical treatment dispersed in gas (GaStim) in a Colombian mature gas-condensate tight reservoir, an injectivity loss was observed and led to a productivity reduction in the well. The main objective of this study is to evaluate the causes of the injectivity loss due to the GaStim process through static and dynamic tests. For this, adsorption isotherms of the treatment over the rock surface and contact angle (CA) measurements were performed. Furthermore, the interaction of reservoir fluids with chemical treatment was studied through interfacial tension measurements and emulsion formation. Reproduction of the field injection conditions at a laboratory scale was successfully accomplished and included the pressure drop of the gas stream from wellhead to the injection path and a core displacement test for different Liquid-to-Gas ratios (LGR). It was found that at LGR of 0.4 bbl·MMscf-1, 24% of the dispersed chemical treatment is condensated/retained, promoting both emulsion and capillary blockage that leads to a reduction of gas permeability (Kg) of 66%. Although at 0.025 bbl·MMscf-1 there is no evidence of capillary blocking, the reduction of Kg of 47.7% can be associated with emulsion blockage according to the emulsion drop and pore throat distribution. This research provides a landscape of the accurate design of GaStim operations based on a schematic experimental procedure to establish the injection flow conditions and the rock surface/reservoir fluids interaction with the dispersed treatment, showing that success of this technique depends on the chemical treatment employed and the liquid-to-gas ratio during the field intervention.

Quantification of gas permeability of epoxy resin composites with graphene nanoplatelets

This paper presents the development and validation of a numerical simulation method using the Lattice Boltzmann Method (LBM) to predict the permeability of epoxy resin (ER) composites with graphene nanoplatelets (GNPs).Gas permeability tests were carried out for a series of GNP/ER nanocomposites with different loadings and diameters of GNPs. The experimental results confirm that inclusion of GNPs in ER significantly decreased the effective gas permeability, with the highest reduction of 66% when the GNP loading was 3 wt%. The effects of using different diameters of GNPs show that using GNPs of 25 μm in diameter achieved less reduction in gas permeability than using GNPs of smaller diameters of 5 and 15 μm at the same loading of 1 wt%. This unexpected result has now been explained by the developed numerical model.The microstructures of GNPs filled ER composites were numerically reconstructed for the relative gas permeability prediction model using LBM. The 3D X-ray CT scan images clearly show agglomeration of GNPs, in particular when the diameter of GNPs is large (25 μm), due to strong van der Waals forces. An agglomeration sub-model was thus incorporated when numerically constructing the microstructure of GNPs filled ER composites. Agglomeration of GNPs results in the formation of a small number of super-thick GNPs, leaving large spaces as ER-rich area without any GNP. This led the GNPs filled ER with 25 μm of GNP diameter to obtain a lower reduction in gas permeability than smaller GNPs filled ER.The results of numerical sensitivity studies on surface area, rotation, curling and folding of GNP flakes suggest that it is acceptable to use flat disk shaped flakes to represent amorphous GNPs with small degrees of deformation (less than 20° and 1.5 for folding angle and curling rate respectively). The results also show that the projection area perpendicular to the overall gas flow direction dominates the overall gas barrier effect of GNPs. The feasibility of using 2D models is demonstrated and it is acceptable to assume that the GNPs in the prepared samples are uniformly sized with a diameter equal to the nominal diameter.This numerical simulation model significantly improves the accuracy for prediction of reduction in gas permeability, over that of existing analytical models, when compared against the authors’ experimental results and experimental data from literature.

Polyurethane/functionalized-graphene nanocomposite films with enhanced weather resistance and gas barrier properties

This study explores the potential of graphene for improvement of weather resistance and helium gas barrier properties of thermoplastic polyurethane (PU) film. PU/functionalized-graphene nanocomposite (PGN) films were produced by solution master-batching and subsequent melt mixing, followed by compression molding, with varying concentrations (0–3 wt%) of graphene, which resulted in uniform dispersion and partial exfoliation of graphene-sheets in PU matrix. The helium gas barrier of nanocomposite films improved gradually with increasing graphene concentration, showing about 30% reduction in gas-permeability at 3 wt% graphene-loading. The tensile strength and stiffness of the nanocomposite films also increased significantly with increasing concentration of graphene. The prepared PGN films were exposed to accelerated artificial weathering conditions up to 300 h. Due to excellent UV absorption capability of graphene, the weather resistance of nanocomposite films improved significantly, resulting in lower photooxidative and carbonyl index. Best weather resistance in terms of retention in tensile and gas barrier properties was obtained with 2–3 wt% of graphene.

Influence of Microcracks on Flow and Storage Capacities of Gas Shales at Core Scale

This work investigates the interplay of gas transport in the microcracks and matrix of shale using He and $$\hbox {CO}_2$$ via transient upstream pressure-pulse-decay experiments. The microcracks are natural in the sense no laboratory pretreatment created them. A novel setup of the pressure-pulse-decay experiment was used to determine the storage and flow capacities simultaneously. Experimentally, the pressure signals are used to define time-dependent pore volume partitioning between the microcracks and the matrix. A dual continuum simulator is constructed to decouple the flow and storage capacities at early time where the gas flows simultaneously in both media. A history-matching process quantifies the pore volume partitioning of the microcracks and matrix, the permeability in the microcracks, and the diffusivity of gas in the matrix. A series of experiments were conducted on four shale samples from Eagle Ford and Haynesville shale plays at constant net effective stress of 500 psi and at increasing net effective stresses of 500, 1000, and 2000 psi. Results show that the pore volume of the microcracks in sample 180Ha (Eagle Ford) was from 8.0 to 24.1% of the total pore volume in all experiments at constant and variable net effective stresses. The Haynesville samples (TWG 1-3 & 3-3) had between 68.9 and 87.0% of the total porosity in the microcracks while the remaining percentage represents the pore volume in the matrix. These proportions are related to the magnitude of permeability and void volumes in the system. The values of Klinkenberg-corrected permeability estimated using He vary between 396 and 1.6 $$\upmu \mathrm{D}$$ . The role of adsorption was also investigated using $$\hbox {CO}_2$$ in the same experimental apparatus and conditions. It was found that the influence of pore volume partitioning is suppressed by the large adsorption capacity in the shale samples. It was found that adsorption occurs in the microcracks in permeabilities less than 50 $$\upmu \mathrm{D}$$ along with adsorption in the matrix. For permeabilities greater than that value, adsorption had no importance on microcracks. Adsorption in both media required different adsorption–pressure functions. The $$\hbox {CO}_2$$ permeability was found to be smaller than the He permeability by 2–3 factors. $$\hbox {CO}_2$$ injection into the core caused a reduction in permeability that was observed with He injection after $$\hbox {CO}_2$$ flooding. The He permeability dropped by a factor of 2–3. This permeability hysteresis is attributed to the reduction in pore size accessed by the gas. This observation provides another reason why $$\hbox {CO}_2$$ storage in depleted shale gas reservoirs is practical. Reduction in gas permeability may be essential to keep $$\hbox {CO}_2$$ underground for as long as possible.

Plasma-Activated Substrate with a Tropoelastin Anchor for the Maintenance and Delivery of Multipotent Adult Progenitor Cells.

Conventional wound therapy utilizes wound coverage to prevent infection, trauma, and fluid and thermal loss. However, this approach is often inadequate for large and/or chronic wounds, which require active intervention via therapeutic cells to promote healing. To address this need, a patch which delivers multipotent adult progenitor cells (MAPCs) is developed. Medical-grade polyurethane (PU) films are modified using plasma immersion ion implantation (PIII), which creates a radical-rich layer capable of rapidly and covalently attaching biomolecules. It is demonstrated that a short treatment duration of 400 s maximizes surface activation and wettability, minimizes reduction in gas permeability, and preserves the hydrolytic resistance of the PU film. The reactivity of PIII-treated PU is utilized to immobilize the extracellular matrix protein tropoelastin in a functional conformation that stably withstands medical-grade ethylene oxide sterilization. The PIII-treated tropoelastin-functionalized patch significantly promotes MAPC adhesion and proliferation over standard PU, while fully maintaining cell phenotype. Topical application of the MAPC-seeded patch transfers cells to a human skin model, while undelivered MAPCs repopulate the patch surface for subsequent cell transfer. The potential of this new wound patch as a reservoir for the sustained delivery of therapeutic MAPCs and cell-secreted factors for large and/or non-healing wounds is indicated in the findings.

Graphene oxide nanosheet‐embedded crosslinked poly(ethylene oxide) hydrogel

ABSTRACTNanofiller‐reinforced polymer nanocomposites can be used to improve the mechanical, thermal, electrical, and barrier properties of neat polymers. In this study, two‐dimensional graphene oxide (GO) nanosheets were successfully incorporated into hydrophilic crosslinked poly(ethylene oxide) (XPEG) hydrogels. Change in the gas permeability and mechanical strength were monitored as functions of the GO content and average GO flake size. The experimental results are discussed with two theoretical models (i.e., the modified Nielsen and Halpin‐Tsai models) to predict the effect of two‐dimensional GO nanofillers (e.g., loading content and alignment) on the gas permeability and mechanical properties of the GO‐embedded XPEG hydrogels (GO–XPEGs). When the GO sheets were fully exfoliated and homogeneously dispersed in the XPEG matrix, their significant reduction in gas permeability and improvement in mechanical strength were in good agreement with those theoretical models. In particular, the incorporation of 4 wt % GO into the XPEG hydrogel matrix resulted in an 80–90% reduction in the gas permeability for various gases, including He, H2, O2, N2, CH4, and CO2. Also, with increasing GO content, both the Young's modulus and tensile strength of the GO–XPEG nanocomposite hydrogels increased significantly compared to those of the neat XPEG hydrogel. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 45417.

Analysis of methane recovery through CO2–N2 mixed gas injection considering gas diffusion phenomenon in coal seam

When enhancing coalbed methane recovery using CO2 or N2 injection, injected gas flows into coal matrix by diffusion. Gas diffusion velocity varies, depending on gas molecular size and pore geometry which causes different sorption rates of the gas in coal seam. In this aspect, this study provides the fundamental reason for the reduction in gas permeability through cleats and methane recovery during enhanced coalbed methane (ECBM) processes. This reduction occurs not only because of the sorption affinity as reported in previous works, but also because of the characteristics of gas diffusional flow which this study attempted to examine experimentally. From the results obtained by diffusional flow experiment, diffusion coefficient is no longer increased at high pressure. Although CO2 injection rate is very high, a large amount of CO2 moves through cleat instead of adsorbed in matrix, which causes early CO2 breakthrough. In ECBM, N2 mostly acts as a displacing agent of methane, because co-diffusion of N2 with methane is more dominant than counter-diffusion owing to its extremely low adsorption affinity. On the other hand, CO2 is rapidly adsorbed due to its fast increasing rate of diffusion coefficient with pressure increase. Consequently, CO2 permeability is greatly reduced at the beginning of injection and ultimately becomes the lowest value at the maximum adsorption pressure. Also, delayed methane recovery by fast diffusion and high adsorption affinity of CO2 occurs accordingly. This study confirms that the CO2–N2 mixed gas injection is advisable comparing to only injecting CO2 to pursue the prevention of CO2 injectivity reduction and enhanced methane recovery, simultaneously.