Porous PES Research Articles

One-pot synthesis of mechanically robust hierarchical graphene-polyethylene aerogels

Fabricating mechanically robust graphene aerogels (GAs) without compromising their notable features including superelasticity, large surface area, high porosity, and low density is challenging. This work presents a new one-pot strategy based on ambient drying to fabricate a three-dimensional (3D) graphene-polyethylene aerogel (G-PEA) with a unique hierarchical porous structure, in which the highly porous polyethylene is encapsulated by graphene frameworks. The hierarchical G-PEA exhibited substantially enhanced compressive strength while maintaining low density and superelasticity comparable to those of bare GAs. The G-PEAs with 5 wt% PE (G-PEA5) showed a significant improvement (up to 2083 %) in compressive stress compared to bare GAs, which can be attributed to the porous PE support within the GA framework. The G-PEA5 retained 94 % of its compressive stress after 100 compression cycles, which is still higher than that (∼80 %) of bare GAs, and maintained good elastic recovery. The designed hierarchical G-PEAs show great promise in the applications that require outstanding mechanical properties.

Highly solar reflectance and infrared transparent porous coating for non-contact heat dissipations

SummaryPassive daytime radiative cooling (PDRC) can dissipate heat to outer space with high solar reflectance and thermal emittance in the atmospheric transmission window. However, for the non-contact heat dissipation, besides the high , a high infrared transmittance is needed to directly emit thermal radiation through the IR-transparent coating to outer space. In this work, An IR-transparent porous PE (P-PE) coating with = 0.96 and = 0.88 was prepared for non-contact heat dissipations. Under the direct sunlight of 860 W m−2, the IR-transparent coating obtained a 4°C lower heater temperature than the normal PDRC coating under the same condition. In addition, the spectral reflectance of the P-PE coating after immersing in air or water changed little, which showed excellent durability for long-term outdoor applications. These results indicate the P-PE coating can be a potential IR-transparent coating for non-contact heat dissipations under direct sunlight.

Preparation of thin film nanocomposite hollow fiber membranes with polydopamine-encapsulated Engelhard titanosilicate-4 for gas separation applications

Among the various separation membranes, the thin-film nanocomposites (TFN) membranes have been widely applied for gas separation. In the present study, TFN hollow fiber membranes using polydopamine (PD)-encapsulated ETS-4 (Engelhard titanosilicate-4), PD-ETS-TFN, with a pore size of 3–4 Å were prepared for gas separation applications. The proposed TFN hollow fiber membranes were prepared by condensation-based interfacial polymerization (IP) between poly(ethylenimine) as an aqueous monomer and 1,3,5-benzenetricarbonyl trichloride as an organic monomer on a porous PES [poly(ether sulfone)] substrate. The dopamine-encapsulated ETS-4 was incorporated inside the polyamide layer to maximize the hydrophilicity of the membrane. Various methods were employed to analyze the structures and characteristics of the ETS-4 and TFN membranes, and tests were conducted to evaluate the permeance of H2, CO2, N2, and CH4 through PD-ETS-TFN. The results revealed a facilitated transport property toward CO2. Due to the molecular sieving effect of the ETS-4, the proposed membranes achieved a permeance as high as 60.4 GPU toward H2 and H2/CO2 selectivity of 14.3.

Additive Manufacturing of PE/fluorouracil/progesterone intrauterine device for endometrial and ovarian cancer treatments

Progesterone and fluorouracil loaded-intrauterine drug delivery systems were prepared using selective laser sintering (SLS). PE/FU/PG IUDs had small particles of fluorouracil spread over the IUD surface and progesterone was dispersed within the porous PE matrix. The existence of additional peaks related to the fluorouracil and progesterone confirm their presence at 10% concentration by both DSC and FTIR. The PE/FU/PG IUDs prepared using higher laser power (5 W) had the highest flexural modulus, probably due to better PE particle coalescence. The PE/FU/PG IUDs initially showed rapid drug release due to the hydrophilic characteristics of fluorouracil. This is a desirable profile as it provides a high initial concentration of the drug locally to the cancer cells following implantation. The slow and controlled release of the progesterone presented by PE/FU/PG IUDs is interesting for sustained levels of the hormone therapy agent in the region of the tumor with the potential to enhance the cancer treatment.

Preparation and Characterization of Monovalent Cation Selective Membranes Prepared By a Double Pore-Filled Technique

In order to minimize membrane fouling in electrochemical systems using ion exchange membranes, we are having developed monovalent cation selective membranes prepared by a pore-filled technique. The transparent pore-filled membranes indicated that the porous PE substrate was successfully filled with polymer electrolyte by UV irradiation. The weight ratio of anion polymer electrolyte layer was 0.20 and 0.59. The dimensional stability and area resistance of the monovalent selective membranes increased with the weight content of anion polymer electrolyte. Lab-made monovalent selective membranes showed low ion permeability. However, they have similar permeability ratio between NaCl and MgCl2 (or CaCl2) than CMV, and the flux of the sample was slightly higher than commercial membrane. Further characterizations of the resulting membranes will be performed, and reported in the near future.

Preparation and Characterization of Monovalent Cation Selective Membranes Prepared by a Layer-By-Layer Pore-Filled Technique

Membrane fouling is one of fatal barriers in electrochemical water treating technologies using ion exchange membranes (IEM) such as electrodeionization (EDI), Electrodialysis (ED), capacitive deionization (CDI), and reverse electrodialysis (RED). Calcium and Magnesium ions are representative foulants which make cake-like scale on the IEMs, leading to high resistance and low durability. In order to minimize membrane fouling in systems using IEMs, we are having developed monovalent cation selective membranes prepared by a layer-by-layer pore-filled technique. Anion exchangeable electrolytes are pore-filled on both surfaces of a semi-pore-filled cation exchange membrane (layer-by-layer). A porous PE substrate (<20 um) is used to be filled with electrolytes and crosslinking agents and to be polymerized. Monovalent cation selectivity against divalent ions, calcium and magnesium ions, of the resulting membranes was evaluated using 1N MgCl2, CaCl2 and NaCl solutions.

A Moisture- and Oxygen-Impermeant Separator for Aprotic Lithium-Oxygen Batteries

Lithium-oxygen batteries (Li-O2) have lately received considerable attention because of their exceptional potential gravimetric energies, i.e., 3~5 times compared to those of conventional lithium ion batteries. In spite of the unparalleled theoretical gravimetric energy, lithium-oxygen batteries are still under research because of their insufficient cycle lives. This shortcoming is associated with several entangled fading mechanisms [1,2]: partly irreversible nature of the air-cathode, electrolyte evaporation, unstable lithium anode interface, etc. While the reversibility in air-cathodes has been recently improved significantly by the deepened understanding on the electrode-electrolyte reaction and the integration of diverse catalysts, the stability of the lithium anode interface has received relatively much less attention. The destabilization of the lithium anode interface by crossover of water and oxygen from the air-cathode side can indeed cause as fatal degradation for the cycle life as the irreversibility of the air-cathodes [3]. Here we report that cheap poreless polyurethane separator can effectively prevent this crossover while allowing the selective diffusion of lithium ions by high electrolyte uptake of the polyurethane separator through the interchain space. The polyurethane separator also protects lithium anodes from redox mediators, lithium iodide, used to enhance the reversibility of the air-cathode reaction. Based on the lithium anode protection, a consistent capacity of 600 mAh/g is preserved for more than 200 cycles. This study reveals that in most operation conditions, the destabilization of the lithium anode is more critical for the cycle life than the poor reversibility of air-cathode reaction. The present study can also be readily applicable to many other rechargeable batteries that suffer from similar interfacial degradation by side products from the other electrode.Fig. 1. Comparative schematic illustration of lithium-oxygen cells with (a) conventional polyolefin porous PE separator and (b) poreless PU separator. (c) The cycling performance of the PE, PU, PE+LiI, and PU+LiI cells at a current density of 200mA/g with a fixed capacity of 600 mAh/g. The inset shows XRD spectra and color changes of the Li metals of PE and PU cells after 70 and 100 cycles, respectively.

합성 윤활유 및 고압 작동유 누출감지 필름형 센서의 구현

Chemical sensors are used in various industrial facilities such high-risk and prevent the leakage of substances, important in life and environmental protection and the safe use of industry, used for management. In particular, high-temperature environments such as power generation equipment of the rotating part due to leakage generated by the various oil, power plants Shut Down, fire, work environment (exposure to various chemical solution and gas leak) and various water, air and soil pollution causes. Thus, over the long term through various channels such as crops and groundwater contamination caused by the slow, serious adverse effect on the ecosystem. In this paper, synthetic lube oil and high pressure hydraulic fluid leakage and immediately detect a new Printed Electronic implementation of technology-based film-type sensors, and its performance test. Thus, industrial accidents and environmental pollution and for early detection of problems, large accidents can be prevented. Experimental results of the synthetic lube oil and high pressure hydraulic fluid solution after the contact time depending on the experiment and the oil solution of the sensor material of the conductive porous PE resistance value by a chemical reaction could be confirmed that rapid increase. Also implemented in the film-type oil sensor electrical resistance change over time of the reaction rate and the synthetic lube oil is about 2 minutes or less, the high pressure hydraulic fluid is less than about 1 minute was. Therefore, more high-pressure hydraulic fluid such as a low volatility synthetic lube oils are the resistance change and the reaction rate was confirmed to be the slowest.

Stability and Performance Study of Polyethersulfone Membranes Modified Using Polyelectrolytes

In this research work, porous PES membranes were initially pre-heated for certain duration of time and then surface-modified to reject the MgSO4 salt solutions through self-adsorption of polyelectrolytes. From the experimental work, higher membrane salt rejection capability can be obtained when the number of polyelectrolyte bilayers is increased. The images of the cross-sectional morphology of modified and non-modified membranes were obtained using field emission scanning electron microscopy (FESEM). All modified membranes showed relatively lower contact angle values.

Hydrophilization of porous polyethylene films by cold plasma of different types

Porous PE films have been modified using high-frequency discharge plasma (in air) and dielectric surface barrier discharge plasma in static (in oxygen and nitrogen) and dynamic (in argon) regime. A noticeable increase in the hydrophilicity of samples and their adhesion to coatings has been established. Changes in chemical composition and morphology of the surface resulting from plasma treatment and subsequent aging have been studied. The treatment regime have been established under which sufficient hydrophilicity is reached and mechanical strength is preserved.

Gaseous infiltration method for preparation of three-dimensionally ordered macroporous polyethylene

Three-dimensionally ordered macroporous polyethylenes (3DOM PE) with pore size ranging from 135nm to 410nm were prepared using supported catalysts on the surface of silica microsphere as template, followed infiltration of gaseous ethylene and polymerization. The morphology of 3DOM PE was characterized by SEM and the reflectance spectrum was recorded by UV–vis. It is shown that the pores are uniform, flexible and arranged in a highly ordered fashion. Reflectance spectrum of 3DOM PE also provided verification of the uniform nature of the sample. Moreover, the effect of confined space on polymerization was investigated by GPC and DSC. The results indicate that the porous PE possesses higher Mw compared with bulk PE, and exhibits lower melting temperature and crystallinity than those of bulk PE.

Proton conducting membrane using multi-layer acid–base complex formation on porous PE film

A new type of proton conducting membrane was fabricated by multi-layer acid–base complex formation on a porous PE-g-PSS film. Polystyrene was initially grafted on a porous PE substrate using a supercritical carbon dioxide (sc-CO 2) medium, and the grafted polystyrene was subsequently sulfonated to yield the PE-g-PSS membrane. The multi-layer acid base complex structure was obtained by the repetitive alternating deposition of poly(vinylimidazole) (PVIm) and poly(2-acrylamido-2-methyl-1-propanesulfonic acid) (PAMPSA) on the PE-g-PSS film. The multi-layer acid–base complex structure was designed to suppress methanol crossover due to the more compact pore-filling structure as well as to control the hydrophilicity. As expected, the methanol permeability of the optimized multi-layer membrane was much lower, however, the proton conductivity of the membrane was higher than that of Nafion 115.

Preparation of Multi-layer Proton Conducting Membrane Using Porous PE Substrate Film

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Preparation of Multi-Layer Proton Conducting Membrane on Porous PE Substrate Film

not Available.

Radiation‐induced GMA/DMAA graft copolymerization onto porous PE hollow‐fiber membrane

AbstractRadiation‐induced graft copolymerization is a powerful technique to prepare a grafted chain with the desired properties pending onto the trunk material. In this work, a polyethylene hollow‐fiber membrane was modified by this technique. The monomers glycidyl methacrylate (GMA) and N,N‐dimethylacrylamide (DMAA) were cografted onto macroporous polyethylene hollow fiber with a grafting degree in the order of 200%. DMAA/GMA cografted membranes were compared to GMA grafted ones for the introduction of an amino acid as a specific ligand. Grafted membranes with a copolymer composition between 0 and 2 DMAA/GMA were prepared by soaking them in solutions of different mixtures of monomers. Copolymers were characterized by FTIR and their composition was estimated by the analysis of the ratio of carbonyl signals. Copolymers with a higher proportion of DMAA showed improved hydrophilic properties and higher conversion rates of epoxy groups on phenyalanine ligands than those of the GMA grafted ones. However, copolymers with a DMAA/GMA ratio higher than 1 showed a detrimental effect on the pure water flux. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1646–1653, 2003

PNIPAAm and PMAA co-grafted porous PE membranes: living radical co-grafting mechanism and multi-stimuli responsive permeability

PNIPAAm and PMAA co-grafted porous PE membranes were prepared by a living radical, sequential photografting method, and shown to have a di-block covalent structure. In addition, DSC results suggest that complexes between the two blocks are formed under certain conditions. The effect of total co-graft yield and co-graft composition on the temperature- and pH responsive membrane permeability was examined. The results were explained using a two layer model, and by considering the effect of a graft conformation on the permeability of the individual layers. Finally, by imposing various combinations of temperature and pH, it was shown that the co-grafted membranes could be reversibly manipulated to exhibit more sophisticated permeability response than the singly grafted porous membranes.

PH-responsive permeability of PE-g-PMAA membranes

Poly(methacrylic acid) (PMAA) grafted porous PE membranes (PE-g-PMAA) were studied. It was found that (1) a wide range of graft yields can be achieved by varying irradiation time (20–240 min) and monomer concentration (0.22M–0.66M), (2) the grafted membrane exhibits reversible permeability response, (3) the membrane shows a maximum permeability response at an intermediate permeant molecular weight due to size exclusion effect, and (4) depending on the graft yield, two types of permeability response can be obtained. These observations are consistent with our earlier study on poly(N-isopropylacrylamide) (PNIPAAm)–grafted porous polyethylene membranes. In addition, it was observed that the solvent used during grafting may influence the graft location—presumably due to variations in pore wetting. Specifically, compared to water solvent, methanol can increase grafting inside membrane pores, an observation inferred from membrane swelling, thickness measurement, and SEM characterization. Moreover, preferential grafting inside the membrane pores, as affected by increasing methanol content in the grafting solvent, results in lower membrane permeability and a greater pore graft-controlled type of permeability response. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 778–786, 2000

Calorimetric study of the porosity of nascent polyethylene obtained by polymerization of ethylene on the surface of filler particles

Isothermal calorimetry has been used to study the kinetics of hear release on interaction of fillers, synthetic PE composites based on them and isolated nascent PE with non-polymerizable substrates-water and methane. Nascent PE coatings on the surface of filler particles are porous and permeable for the substyrates, which is determined by the method of polymerization, the density of the arrangement of the active centres on the surface of the filler particles and by the content of polymer in the composite. The interaction of fillers with the substrates in synthetic composites may be limited by mass transfer of the substrate through the porous synthetic nascent PE coating.