Porous Polyethylene Substrate Research Articles

Imidazolium-Based Anion Exchange Membranes for Electrochemically Converted Liquid Organic Hydrogen Carrier

Liquid organic hydrogen carrier (LOHC) is a technology that uses renewable energy for hydrogen transportation, storage and utilization. LOHC have advantages that can store and utilize hydrogen rapidly in the lack of transportation infrastructure. A membrane-based LOHC system is a promising technology due to the dynamic operation using electrochemistry. Anion exchange membranes are widely used as electrolyte for electrochemical devices. The performance of LOHC could be determined by the properties of anion exchange membranes. Thus, high anion conducting ionomers must be developed for the superior conversion rates on the electrochemical reduction of liquid toluene to methylcyclohexane. In this study, anion exchangeable polymers containing imidazolium salt as anion-conducting group were synthesized to achieve good conduction of hydroxide ions and their chemical stability. Anion exchange membranes were prepared by a pore-filling method using porous polyethylene substrate. The pore-filling anion exchange membranes were characterized in terms of ion conductivity, areal resistance, ion exchange capacity, water uptake, swelling ratio and mechanical strength. Acknowledgment This research was supported in part by the Korea Institute of Science and Technology (No. 2E31871) and by 2021 Green Convergence Professional Manpower Training Program of the Korea Environmental Industry and Technology Institute funded by the Ministry of Environment.

Alkaline-Stable Anion Conducting Ionomers for Anion Exchange Membrane Water Electrolyzers

Water electrolysis is a process that uses renewable energy to decompose water into oxygen and hydrogen. It is one of the most promising alternatives to produce and store new energy from renewable energy resources. In this study, pore-filled anion exchange membranes (PFAEMs) were prepared by using quaternary ammonia groups along with various cross-linker groups with different chain lengths and using porous polyethylene substrates which were pretreated from hydrophobic into hydrophilic using surfactants. The conductivity of the anion exchange membranes was measured by the in-plane cell and through-plane at room temperature or 60 ℃. In addition, the characterizations of anion exchange membranes such as water uptake, swelling ratio, mechanical strength, contact angle and TGA were carried out. As a result, the PFAEM exhibited remarkably high ion conductivity at extremely low areal swelling ratio and excellent chemical stability in a NaOH solution for 500 h. As an essential component of anion exchange membrane water electrolyzers, catalyst layers prepared by the catalyst inks comprising of ionomer binder and electrocatalysts are sandwiched between the anion exchange membrane to form a membrane electrode assembly in order to evaluate its impedance and I-V polarization curves. Acknowledgment This research was supported in part by the New and Renewable Energy of the Korea Institute of Energy Technology Evaluation and Planning (KETEP) granted financial resource from the Ministry of Trade, Industry & Energy, Republic of Korea (No. 20213030040520) and by 2021 Green Convergence Professional Manpower Training Program of the Korea Environmental Industry and Technology Institute funded by the Ministry of Environment.

Reinforcement effect in tandemly sulfonated, partially fluorinated polyphenylene PEMs for fuel cells.

The mechanical and chemical durability is one of the most crucial properties for proton exchange membranes in practical fuel cell applications. In the present paper, we report the physical reinforcement of chemically stable, highly proton conductive tandemly sulfonated, partially fluorinated polyphenylenes using porous polyethylene (PE). With the PE pores completely and homogeneously filled by ionomers through a push coating approach, the resulting reinforced membranes were more proton conductive (183.1-389.2 mS cm-1) than the commercial perfluorinated ionomer (Nafion: 120.6-187.2 mS cm-1) membrane at high humidity (80-95% RH). Benefiting from the tough PE supporting layer, the reinforced membranes outperformed the parent ionomer membranes in stretchability with maximum strain up to 453%. The combination of intrinsic chemical stability of partially fluorinated polyphenylene ionomers and physical reinforcement with PE substrates contributed for the reinforced membranes to achieving superior durability to survive more than 20 000 cycles in severe accelerated durability test combining OCV hold and wet/dry frequent cycling.

Tuning the Hydrophobic Component in Reinforced Poly(arylimidazolium)-Based Anion Exchange Membranes for Alkaline Fuel Cells

A series of imidazolium-based aromatic copolymers were synthesized using fluorinated and non-fluorinated hydrophobic monomers. The quaternized copolymers were reinforced with the plasma-treated porous polyethylene substrate to provide flexible, homogeneous membranes. Cross-sectional SEM images revealed a triple-layer structure. The reinforced membranes exhibited phase-separated morphology as confirmed through TEM images. Among the membranes, QQP-MEIm-PE-containing quinquephenylene hydrophobic groups exhibited the most balanced properties (ion conductivity, mechanical strength, and alkaline stability). In particular, QQP-MEIm-PE exhibited excellent elongation properties with 24 MPa maximum stress and 205% elongation at break. A single H2/O2 fuel cell using the QQP-MEIm-PE membrane (1.26 meq g–1) and non-PGM-(Fe–N–C) cathode achieved 222 mW cm–2, which accounted for 888 mW mg–1Pt at 560 mA cm–2. Reasonable durability was confirmed with the membrane in the operating fuel cell.

A reinforced composite membrane of two-layered asymmetric structure with Nafion ionomer and polyethylene substrate for improving proton exchange membrane fuel cell performance

The reinforced composite membrane with a two-layered asymmetric structure was fabricated by impregnating the Nafion on a porous polyethylene (PE) substrate to reduce the cost of the membrane used in proton exchange membrane fuel cells (PEMFCs) as well as to enhance the performance of the cell. The ion conductivity of the reinforced composite membrane annealed at 150 °C increases owing to the high crystallinity of the Nafion ionomer, and the mechanical strength is improved by the strong interaction between PE substrate and Nafion ionomer. The immiscibility between them was observed to intensify the interfacial resistance in the three-layered symmetric structure. On the other hand, the reduction of the interfacial resistance of the two-layered asymmetric structure membrane leads to similar results to the performance of traditional PEMFC using Nafion XL with a polytetrafluoroethylene (PTFE) substrate similar to a backbone of Nafion ionomer. Its high mechanical strength, low cost, and reliable ion conductivity make it a suitable substitute for PTFE-based membranes used in PEMFCs although the immiscibility with the ionomer in the membrane comprising a PE substrate is higher than that in the membrane with a PTFE substrate.

A coupled-layer ion-conducting membrane using composite ionomer and porous substrate for application to vanadium redox flow battery

A thin ionomer layer composed of perfluorosulfonic acid (PFSA) polymer in composite with functionalized alkoxysilane (FAS) is prepared and coated onto one side of a porous polyethylene (PE) substrate for vanadium redox flow battery (VRFB) to produce a coupled-layer membrane. The approaches are: (1) suppression of permeation through membrane using additive component, (2) the use of thin ionomer layer for lowering the amount of costly PFSA, and (3) strengthening the thin ionomer layer by coating onto an inexpensive PE substrate. The membrane is easily prepared using automatic control coater. The observation of morphology and infrared spectroscopy at both sides of the coupled-layer membrane confirm the thin ionomer layer on only one side of the PE substrate, plus the addition of FAS helps achieve lower diffusion coefficient. After the unit cell cycling, the coupled-layer membrane shows the good cycling performance closing to Nafion 212 membrane level. Additionally, the morphology after cycling of the coupled layers between PFSA ionomer and PE substrate can remain the same as in initial state, indicating a stable combination from both layers. Based on the easy production and the good performance, the developed membrane can be readily adapted by membrane manufacturer for the wide application in VRFB. • A thin ionomer layer is coated on one side of porous polyethylene substrate. • The thin layer reduces amount of costly perfluorinated sulfonic acid ionomer. • VRFB cell performance was good by closing to that of Nafion 212 membrane. • Unchanged morphology between two layer was found after VRFB unit cell operation.

Reinforced poly(fluorenyl-co-terphenyl piperidinium) anion exchange membranes for fuel cells

Mechanically tough and durable anion exchange membranes (AEMs) are vital materials for AEM fuel cells (AEMFCs). Here, we report a series of high-performance high density polyethylene (PE)-reinforced in-house AEMs based on poly(fluorenyl-co-terphenyl piperidinium) (PFTP@PE) using EtOH as an assistant co-solvent. We found that EtOH showed low contact angle and interface tension on the PE substrate, which improved the penetration efficiency of polymer solutions in the PE substrate. Specifically, 15% EtOH-assisted PFTP@PE membranes displayed ∼100% visible light transmittance and outstanding tensile strength greater than 120 MPa (along with ∼50% elongation at break) compared to PFTP@PE without EtOH assistance (51% light transmittance and 80 MPa tensile strength). Moreover, the peak power densities of PFTP@PE-based AEMFCs reach 1.7 W cm −2 in H 2 –O 2 and 1.08 W cm −2 in H 2 -air(CO 2 free) at 80 °C. The present work provides a facile and scalable method to fabricate high-performance reinforced AEMs. • Reinforced PFTP membranes (RCM) were prepared with a porous polyethylene substrate. • Ethanol aids the preparation of RCM due to the low contact angle and surface tension. • PFTP RCMs displayed excellent mechanical stability and transparency. • The power densities of RCM AEMFCs reached 1.7 W cm −2 in H 2 –O 2 and 1.08 W cm −2 in H 2 -air at 80 °C.

Thin Reinforced Ion-Exchange Membranes Containing Fluorine Moiety for All-Vanadium Redox Flow Battery.

In this work, we developed pore-filled ion-exchange membranes (PFIEMs) fabricated for the application to an all-vanadium redox flow battery (VRFB) by filling a hydrocarbon-based ionomer containing a fluorine moiety into the pores of a porous polyethylene (PE) substrate having excellent physical and chemical stabilities. The prepared PFIEMs were shown to possess superior tensile strength (i.e., 136.6 MPa for anion-exchange membrane; 129.9 MPa for cation-exchange membrane) and lower electrical resistance compared with commercial membranes by employing a thin porous PE substrate as a reinforcing material. In addition, by introducing a fluorine moiety into the filling ionomer along with the use of the porous PE substrate, the oxidation stability of the PFIEMs could be greatly improved, and the permeability of vanadium ions could also be significantly reduced. As a result of the evaluation of the charge–discharge performance in the VRFB, it was revealed that the higher the fluorine content in the PFIEMs was, the higher the current efficiency was. Moreover, the voltage efficiency of the PFIEMs was shown to be higher than those of the commercial membranes due to the lower electrical resistance. Consequently, both of the pore-filled anion- and cation-exchange membranes showed superior charge–discharge performances in the VRFB compared with those of hydrocarbon-based commercial membranes.

Reinforced Polyphenylene Ionomer Membranes Exhibiting High Fuel Cell Performance and Mechanical Durability.

We report on the preparation of reinforced membranes (SPP-QP-PE, where SPP stands for sulfonated polyphenylene), composed of an in-house proton-conductive polyphenylene ionomer (SPP-QP) and a flexible porous polyethylene (PE) mechanical support layer. By applying the push coating method, dense, uniform, transparent, and thin SPP-QP-PE membranes were obtainable. The use of SPP-QP with higher ion exchange capacity induced very high proton conductivity of SPP-QP-PE, leading to high fuel cell performance even at low humidified conditions (e.g., at 80 °C and 30% relative humidity), which had not been attainable with the existing reinforced aromatic ionomer membranes. The flexible porous PE substrate improved the mechanical toughness of the membranes; the elongation at break increased by a factor of 7.1 for SPP-QP-PE compared to that with the bare SPP-QP membrane, leading to mechanical durability at least 3850 wet-dry cycles under practical fuel cell operating conditions (the United States Department of Energy protocol). Overall, the reinforced aromatic ionomer membranes, SPP-QP-PE with balanced proton conductivity, mechanical toughness, and gas impermeability, functioned well in fuel cells with high performance and durability.

Metallization of Porous Polyethylene Using a Wire-Arc Spray Process for Heat Transfer Applications.

Metallization of polyethylene (PE) using thermal spray techniques has proved difficult due to its low melting point and softness. In this study, metallic coatings were applied on porous polyethylene substrates using a twin wire-arc spray process. Commercially available polyethylene sheets, 3 mm in thickness, were used as substrates. Copper (Cu), aluminum (Al), and zinc (Zn) were successfully deposited on the porous polymer, without prior surface preparation, to form coatings with thickness of about 400 µm. Coating surface morphology and cross-sections were examined using a scanning electron microscope. Individual metal splats on the porous and non-porous substrates were observed to study the differences in the bonding mechanisms. The adhesion strength and electrical resistivity of the coatings on porous PE were evaluated. It was found that the bond strength of all three metallic coatings was found to be higher than the ultimate fracture strength of the porous. These results suggest that porosity in the polymer helps to overcome the challenges of metallizing polyethylene and provides a significant reduction in the weight of the polymer. Therefore, all these properties aided in fabricating an extremely lightweight, composite material with potential use in thermal management applications.

Communication—Polyethylene/PBI Pore-Filling Composite Membrane for High Performance Vanadium Redox Flow Battery

A pore-filling proton exchange membrane is fabricated by combining a porous polyethylene (PE) substrate and polybenzimidazole (PBI) resin for vanadium redox flow batteries (VRFB). The PE substrate not only optimized the structure of the composite membrane, but also significantly reduces its cost (< 30$·m−2). Compared with Nafion212 and pure PBI membrane, PE/PBI composite membrane exhibits higher VRFB energy efficiency (88.62%–80.11%) in a current density range of 100–200 mA cm−2. And within 150 cycles at 180 mA cm−2, the composite membrane maintains stable charge-discharge performance with slower capacity decay rate, indicating a promising membrane candidate for VRFBs.

Fabrication of photocured anion-exchange membranes using water-soluble siloxane resins as cross-linking agents and their application in reverse electrodialysis

The utilization of large amounts of volatile organic solvents and the complicated process required for industrial manufacturing of ion-exchange membranes necessitate the development of simple, rapid, and environmentally friendly fabrication methods such as those based on photopolymerization. We employed hydrolytic sol–gel reactions between ammonium- and acrylamide-functionalized silane coupling agents to synthesize water-soluble siloxane resins that exhibit high condensation levels (>80%) and comprise oligomers with molecular weights below 2000 Da. These resins were then mixed with a hydrophilic monomer bearing ammonium and acrylamide groups, and porous polyethylene substrates were impregnated with the resulting mixtures and then irradiated with ultraviolet light. The hydrophilicity, mechanical strength, and other properties of the resulting membranes depended on the resin composition, indicating that the substrate pores were efficiently filled with the prepared resins and further suggesting that the membrane performance could be effectively altered by varying the resin composition. Moreover, the obtained membranes exhibited chemical stability in the pH range between 0 and 11 and in hot water at 60 °C. The reverse electrodialysis stack consisting of these membranes showed higher power density than a stack of commercial membranes. Therefore, it can be concluded that without employing volatile organic solvents for reverse electrodialysis, the developed technique is well-suited for the fabrication of ion-exchange membranes.

Photoinduced Surface Zwitterionization for Antifouling of Porous Polymer Substrates

Surface functionalization of polymeric porous substrates is one of the most important requirements to enhance their applications in the biomedical field. In this study, we achieved photoinduced surface modification using a highly efficient reaction of hydrophilic polymers bearing phosphorylcholine groups. Polymers composed of 2-methacryloyloxyethyl phosphorylcholine (MPC) units and 2-( N-ethylanilino)ethyl methacrylate units were synthesized with attention to the polymer architectures. The surface modification of the porous polyethylene (PE) substrates was carried out by the coating of the MPC polymers with a photochemical radical generator, followed by photoirradiation for a few minutes. Surface analysis by attenuated total reflectance Fourier transform IR spectroscopy and X-ray photoelectron spectroscopy indicated that the MPC polymer layer was generated on the PE surface. Cross-sectional confocal microscopy images showed that the MPC polymers were coated on the polymer surface, even inside the porous structure of the PE substrate. After modification, the porous PE substrates showed a significant increase in hydrophilicity and the water-penetration rate through the pores. Furthermore, the amount of protein adsorbed on the PE substrate was reduced significantly by the surface modification. These functionalities were dependent on the MPC polymer architectures. Thus, we concluded that the photoreactive polymer system developed furnished the porous substrates with antifouling properties.

Anisotropic radio-chemically pore-filled anion exchange membranes for solid alkaline fuel cell (SAFC)

Anion exchange pore-filled membranes based on meso-porous polyethylene support are fabricated through a radio-chemical grafting process. Vinylbenzylchloride (VBC) monomers are grafted onto porous polyethylene substrate by a simultaneous irradiation grafting method. The porous polyethylene substrate provides high chemical and mechanical stability. The pore-filled membranes are subsequently functionalized by trimethylamine (TMA) and ion exchange with sodium hydroxide, yielding alkaline anion exchange membranes that are capable of conducting hydroxide ions. The meso-porous support structure contributes to a reduction in dimensional swelling while maintaining high water uptake, high ion exchange capacity, and enhanced mechanical strength of over 50MPa. In particular, these radio-chemically pore-filled membranes exhibits anisotropic through-plane oriented ion conductive behavior due to the low resistance of the hydrated cross-sectional structure derived from the nonwoven porous substrate. As a result of reinforced mechanical strength and anisotropic electrochemical property, the membrane exhibits good membrane-electrode assembly (MEA) performance (at 0.6V, max. current density=174mAcm−2 and max. power density=127mWcm−2) in solid alkaline fuel cell.

Development of thin anion-exchange pore-filled membranes for high diffusion dialysis performance

Pore-filled anion-exchange membranes (PFAEMs) with a thickness of about 25μm have been prepared using porous polyethylene substrates and tested for diffusion dialysis (DD) application. The membranes possess strong mechanical properties (tensile strength and elongation at break of 125.8MPa and 76.2%, respectively) as well as excellent electrochemical characteristics such as low electrical resistance (<0.4Ωcm2), high anion transport number (>0.97), and high fraction of conductive region on the membrane surface etc. Moreover, in order to further improve the diffusion dialysis performance of the PFAEMs, the surface of PFAEMs was modified by introducing a thin polypyrrole layer with good affinity to anions. As a result, the PFAEMs exhibited excellent DD performances (high acid permeability and selectivity) superior to that of commercial membrane (i.e. Neosepta-AFX, Astom Corp., Japan) by the surface-modification.

Plasma Modification of Solid and Porous Polyethylene

AbstractThe use of electron beam generated plasmas to modify the surface of solid and porous polyethylene substrates is discussed. In both cases, the hydrophobicity of the material was increased by exposing the substrates to electron beam generated plasmas produced in Ar/SF6 mixtures. The solid material studies served as a basis for understanding the plasma‐induced changes at the substrate surface, while the porous material was treated using a system designed for two‐sided processing applications and proved to be the best way to maximize treatment. Plasma diagnostics were used to characterize the ion and neutral fluxes at the substrates and thereby obtain a better understanding of the plasma–polymer interaction.magnified image

The effect of a porous polyethylene matrix on the structure and mechanical and deformational properties of electroactive composites

Two types of new electroactive composite systems based on elastic substrates (porous polyethylene films) have been elaborated. The systems of the first type are composed of electroconductive polymers (polypyrrole and polyaniline) obtained by in situ oxidative polymerization of their monomers on porous polyethylene substrates. The composites of the second type contain a cross-linked polyelectrolyte, and they were prepared by polymerization of acrylic acid with a macromolecular cross-linker on the porous substrates. The mechanical properties and the deformational behavior of the porous films and composites have been investigated and analyzed.

Development of a Molecular Recognition Separation Membrane Using Cyclodextrin Complexation Controlled by Thermosensitive Polymer Chains

A molecular recognition polymer membrane that uses a thermosensitive polymer with a host receptor has been developed. The membrane exhibits a high selectivity, in which β-cyclodextrin (CD) moieties recognize a specific guest molecule, and poly(N-isopropylacrylamide) [P(NIPAM)] controls the molecular recognition ability. A pendant CD monomer was introduced into the linear P(NIPAM) chain, and this resulted in a faster volume change from the increased diffusivity of water over the normal cross-linked gel. The copolymer was fixed onto the pore surface of a porous polyethylene substrate using plasma-graft polymerization. The temperature dependence of the binding constant of 8-anilino-1-naphthalenesulfonic acid ammonium salt showed a drastic decrease at temperatures above the lower critical solution temperature of the copolymer chains. The defining mechanism of the inclusion properties is the steric hindrance of the host−guest interaction, which depends on the thermosensitive volume change of the grafted chains...