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In this work, electrospun PBI separators with a highly porous structure and nanofiber diameter of about 90-150 nm are prepared using a multi-nozzle under controlled conditions for lithium metal batteries. Cross-linking with α, α-dibromo-p-xylene and surface treatment using 4-(chloromethyl) benzoic acid successfully improve the electrochemical as well as mechanical properties of the separators. The resulting separator is endowed with high thermal stability and excellent wettability (1080 to 1150%) with commercial liquid electrolyte than PE and PP (Celgard 2400) separators. Besides, attractive cycling stability and rate capability in LiFePO

Considering the critical energy challenges and the generation of zero-emission anion exchange membrane (AEM) sources, chitosan-based anion exchange membranes have garnered considerable interest in fuel cell applications owing to their various advantages, including their eco-friendly nature, flexibility for structural modification, and improved mechanical, thermal, and chemical stability. The present mini-review highlights the advancements of chitosan-based biodegradable anion exchange membranes for fuel cell applications published between 2015 and 2022. Key points from the rigorous literature evaluation are: grafting with various counterions in addition to crosslinking contributed good conductivity and chemical as well as mechanical stability to the membranes; use of the interpenetrating network as well as layered structures, blending, and modified nanomaterials facilitated a significant reduction in membrane swelling and long-term alkaline stability. The study gives insightful guidance to the industry about replacing Nafion with a low-cost, environmentally friendly membrane source. It is suggested that more attention be given to exploring chitosan-based anion exchange membranes in consideration of effective strategies that focus on durability, as well as optimization of the operational conditions of fuel cells for large-scale applications.

To mitigate the dependence on fossil fuels and the associated global warming issues, numerous studies have focused on the development of eco-friendly energy conversion devices such as polymer electrolyte membrane fuel cells (PEMFCs) that directly convert chemical energy into electrical energy. As one of the key components in PEMFCs, polymer electrolyte membranes (PEMs) should have high proton conductivity and outstanding physicochemical stability during operation. Although the perfluorinated sulfonic acid (PFSA)-based PEMs and some of the hydrocarbon-based PEMs composed of rationally designed polymer structures are found to meet these criteria, there is an ongoing and pressing need to improve and fine-tune these further, to be useful in practical PEMFC operation. Incorporation of organic/inorganic fillers into the polymer matrix is one of the methods shown to be effective for controlling target PEM properties including thermal stability, mechanical properties, and physical stability, as well as proton conductivity. Functionalization of organic/inorganic fillers is critical to optimize the filler efficiency and dispersion, thus resulting in significant improvements to PEM properties. This review focused on the structural engineering of functionalized carbon and silica-based fillers and comparisons of the resulting PEM properties. Newly constructed composite membranes were compared to composite membrane containing non-functionalized fillers or pure polymer matrix membrane without fillers.

Anion exchange membranes (AEMs) with good alkaline stability and ion conductivity are fabricated by incorporating quaternary ammonium-modified silica into quaternary ammonium-functionalized poly(2,6-dimethyl-1,4-phenylene oxide) (QPPO). Quaternary ammonium with a long alkyl chain is chemically grafted to the silica in situ during synthesis. Glycidyltrimethylammoniumchloride functionalization on silica (QSiO2) is characterized by Fourier transform infrared and transmission electron microscopic techniques. The QPPO/QSiO2 membrane having an ion exchange capacity of 3.21 meq·g–1 exhibits the maximum hydration number (λ = 11.15) and highest hydroxide ion conductivity of 45.08 × 10–2 S cm–1 at 80 °C. In addition to the high ion conductivity, AEMs also exhibit good alkaline stability, and the conductivity retention of the QPPO/QSiO2-3 membrane after 1200 h of exposure in 1 M potassium hydroxide at room temperature is about 91% ascribed to the steric hindrance offered by the grafted long glycidyl trimethylammonium chain in QSiO2. The application of the QPPO/QSiO2-3 membrane to an alkaline fuel cell can yield a peak power density of 142 mW cm–2 at a current density of 323 mA cm–2 and 0.44 V, which is higher than those of commercially available FAA-3-50 Fumatech AEM (OCV: 0.91 V; maximum power density: 114 mW cm–2 at current density: 266 mA cm–2 and 0.43 V). These membranes provide valuable insights on future directions for advanced AEM development for fuel cells.

Printed electronics will be essential in the implementation of next-generation electronic devices, because printing facilitates fabrication of devices on various rigid, thin, or flexible substrates. Inkjet printing enables precise placement of fine droplets of different functional materials; moreover, it is inexpensive and adaptable for mass production. Electrohydrodynamic (EHD) jet printing, a type of inkjet technology, can generate very fine ink droplets by applying an electric field between the substrate and the nozzle; therefore, it is a promising candidate for high-resolution direct printing, which is essential in the manufacturing of various devices. More significantly, the characteristics of EHD jet printing can be conveniently adjusted by modulating the electric field strength, and various functional inks can be used in this process. This paper is a comprehensive review of recent progress in EHD jet printing technology to fabricate various electronic devices and circuits. Applications of various functional inks (electrode, semiconductor, dielectric materials) for each electronic component are also described.

Due to increased environmental pressures, significant research has focused on finding suitable biodegradable plastics to replace ubiquitous petrochemical-derived polymers. Polyhydroxyalkanoates (PHAs) are a class of polymers that can be synthesized by microorganisms and are biodegradable, making them suitable candidates. The present study looks at the degradation properties of two PHA polymers: polyhydroxybutyrate (PHB) and polyhydroxybutyrate-co-polyhydroxyvalerate (PHBV; 8 wt.% valerate), in two different soil conditions: soil fully saturated with water (100% relative humidity, RH) and soil with 40% RH. The degradation was evaluated by observing the changes in appearance, chemical signatures, mechanical properties, and molecular weight of samples. Both PHB and PHBV were degraded completely after two weeks in 100% RH soil conditions and showed significant reductions in mechanical properties after just three days. The samples in 40% RH soil, however, showed minimal changes in mechanical properties, melting temperatures/crystallinity, and molecular weight over six weeks. By observing the degradation behavior for different soil conditions, these results can pave the way for identifying situations where the current use of plastics can be replaced with biodegradable alternatives.

Block copolymers generally have peculiar morphological characteristics, such as strong phase separation. They have been actively applied to polymer electrolyte membranes for proton exchange membrane fuel cells (PEMFCs) to obtain well-defined hydrophilic regions and water channels as a proton pathway. Although molecular simulation tools are advantageous to investigate the mechanism of water channel formation based on the chemical structure and property relationships, classical molecular dynamics simulation has limitations regarding the model size and time scale, and these issues need to be addressed. In this study, we investigated the morphology of sulfonated block copolymers synthesized for PEM applications using a mesoscale simulation based on the dynamic mean-field density functional method, widely applied to investigate macroscopic systems such as polymer blends, micelles, and multi-block/grafting copolymers. Despite the similar solubility parameters of the monomers in our block-copolymer models, very different morphologies in our 3D mesoscale models were obtained. The model with sulfonated monomers, in which the number of sulfonic acid groups is twice that of the other model, showed better phase separation and water channel formation, despite the short length of its hydrophilic block. In conclusion, this unexpected behavior indicates that the role of water molecules is important in making PEM mesoscale models well-equilibrated in the mesoscale simulation, which results in the strong phase separation between hydrophilic and hydrophobic regions and the ensuing well-defined water channel. PEM synthesis supports the conclusion that using the sulfonated monomers with a high sulfonation degree (32.5 mS/cm) will be more effective than using the long hydrophilic block with a low sulfonation degree (25.2 mS/cm).

This study illustrated the potential applications of thermoresponsive poly(N-isopropylacrylamide) (PNIPAm) grafted nylon membranes with different grafting yields and grafting architecture. The thermoresponsive gating performance at temperatures below and above the lower critical solution temperature (LCST) of PNIPAm (32 °C) were demonstrated. The linear PNIPAm-grafted nylon membrane exhibited a sharp response over the temperature range 20–40 °C. The grafting yield of 25.5% and 21.9%, for linear and crosslinked PNIPAm respectively, exhibited highest thermoresponsive gating function for water flux and had a stable and repeatable “open-closed” switching function over 5 cycle operations. An excellent oil/water separation was obtained at T < 32 °C, at which the hydrophilic behavior was observed. The linear PNIPAm-grafted nylon membrane with 35% grafting yield had the highest separation efficiency of 99.7%, while PNIPAm structures were found to be independent of the separation efficiency. In addition, the membranes with thermoresponsive gas permeability were successfully achieved. The O2 and CO2 transmission rates through the PNIPAm-grafted nylon membranes decreased when the grafting yield increased, showing the better gas barrier property. The permeability ratio of CO2 to O2 transmission rates of both PNIPAm architectures at 25 °C and 35 °C were around 0.85 for low grafting yields, and approximately 1 for high grafting yields. Ultimately, this study demonstrated the possibility of using these thermoresponsive smart membranes in various applications.

Here we suggest a simple and novel method for the preparation of a high-performance self-humidifying fuel cell membrane operating at high temperature (&gt, 100 °C) and low humidity conditions (&lt, 30% RH). A self-humidifying membrane was effectively prepared by laminating together proton and anion exchange membranes composed of acceptor-doped SnP2O7 composites, Sn0.9In0.1H0.1P2O7/Sn0.92Sb0.08(OH)0.08P2O7. At the operating temperature of 100 °C, the electrochemical performances of the membrane electrode assembly (MEA) with this heterojunction membrane at 3.5% RH were better than or comparable to those of each MEA with only the proton or anion exchange membranes at 50% RH or higher.

Here we suggest a simple and novel method for the preparation of a high-performance self-humidifying fuel cell membrane operating at high temperature (>100 °C) and low humidity conditions (

In this study, blended anion exchange membranes were prepared using polyphenylene oxide containing quaternary ammonium groups and polyvinylidene fluoride. A polyvinylidene fluoride with high hydrophobicity was blended in to lower the vanadium ion permeability, which increased when the hydrophilicity increased. At the same time, the dimensional stability also improved due to the excellent physical properties of polyvinylidene fluoride. Subsequently, permeation of the vanadium ions was prevented due to the positive charge of the anion exchange membrane, and thus the permeability was relatively lower than that of a commercial proton exchange membrane. Due to the above properties, the self-discharge of the blended anion exchange membrane (30.1 h for QA–PPO/PVDF(2/8)) was also lower than that of the commercial proton exchange membrane (27.9 h for Nafion), and it was confirmed that it was an applicable candidate for vanadium redox flow batteries.

Optimization and miniaturization of existing electronic devices require the development of advanced nanostructured materials with high phase and structural purity. Over the past decade, barium titanate (BaTiO3) has attracted considerable attention due to its outstanding ferroelectric and dielectric properties. The present study involved the investigation of the phase transition and structural stability of tetragonal BaTiO3 nanopowders with pseudo-cubic phase using an in-situ high resolution and high temperature X-ray diffraction method. Under ambient conditions, the coexistence the tetragonal and cubic phases with weight fractions of 75.7% and 24.3%, respectively, was determined in BaTiO3. In the temperature range of 25 °C-300 °C, phase boundaries of BaTiO3 (180 nm in size) exhibiting several phases were detected. The phase transformation behavior, relative crystal phase content, lattice parameters, crystallite size, and tetragonality of the BaTiO3 nanopowders were established by the Rietveld refinement method at the onset temperature from 25 °C to 300 °C. Up to 150 °C, the nanopowders exhibited a complete transition of the cubic phase. Additionally, a complete tetragonal to cubic transformation was accomplished by a decrease of tetragonality at 125 °C and an increase in the crystallite size at 300 °C.

Despite significant advancements in reinforcing material-embedded structural adhesives, the industry still hesitates to employ the new technologies in their production line. In this communication, we investigate what critically hampers the practical application of newly developed reinforcing material-embedded structural adhesives to the industry, and analyze the factors impeding their commercialization from an economic perspective. By dividing mechanical strengths of adhesives by input cost, e.g., material cost and processing cost, we propose an evaluation index that can assess cost effectiveness of adhesives in terms of materials and processing costs, respectively. We found that the cost mainly affecting the impediment of employing reinforcing materials in structural adhesives is the processing cost that mostly consists of labor cost and electricity fees while the materials cost increase has a negligible impact on their cost effectiveness. Based on our analysis considering current materials and processing costs, we finally suggest how much the processing cost needs to be reduced and what the target achievement in mechanical strength enhancement should be in order to cross the cost effectiveness of commercialized structural adhesives.

Graphene reinforced aluminum matrix composites (GRAMCs) with improved thermal conductivity were prepared via a pH-controlled self-assembly process that involved adjusting the concentration of dispersed graphene oxide (GO) solutions. Uniform dispersion was achieved using GO coating on the aluminum (Al) surfaces. Graphene encapsulated Al powders (Al/GO) were sintered through spark plasma sintering (SPS) to prepare bulk composites, these were then analyzed to determine the thermal and mechanical properties. The density of the Al/GO composites was determined to be 99% or more compared to the theoretical density of pure Al. The Vicker&rsquo, s hardness and thermal conductivity increased by about 47% and 15% more than the pristine Al bulks. These processes can improve properties of the thermal interface between GO and Al, enabling uniform coating without a crosslinking agent. An Al/GO composite, fabricated through the pH-controlled self-assembly process, should be useful for various applications requiring to high thermal conductivity.

The new hydrophilic–hydrophobic comb-type anion exchange membrane (AEM) was prepared from SEBS grafted with hexyl quaternary ammonium (HQA) and fluorobenzoyl. As confirmed by XRD and TEM, a better phase separation was obtained by adding a highly hydrophobic fluorine-substituted pendant as an enhanced hydrophobic spacer to the conducting head group (which contained a hexyl spacer as a hydrophilic unit). The HQA-F1-SEBS and HQA-F5-SEBS membranes, with fluorobenzoyl and pentafluorobenzoyl pendants, respectively, showed enhanced hydrophobicity compared to their non-fluorinated counterpart (HQA-SEBS). The highest hydroxide ion conductivity (87.0 in water and 14.37 mS cm-1 at 95% RH) was obtained at 80 °C with HQA-F5-SEBS, which exhibited the most thermodynamic incompatibility between hydrophilic and hydrophobic units. The mechanical properties (tensile strength and Young's Modulus) of the HQA-F5-SEBS membrane were also improved; they were almost 2.5 times higher than those of the HQA-SEBS. The HQA-F5-SEBS showed a current density of 500 mA cm-2 at a potential of 0.6 V and a peak power density of 354 mW cm-2. It also showed stable-cell durability for up to 100 hours. Compared with the typical hydrophilic comb-type SEBS membrane and the previously reported SEBS-based AEM, its cell performance was significantly higher.

The dynamics of hydronium ions and methanol molecules in hydrated SPAES and blend membranes are investigated via molecular dynamics simulations using the COMPASS force field. In addition to calculating the diffusion coefficients as a function of the hydration level, an amorphous cell with a specific composition of H2O molecules and H3O+ determined from the experimental data is constructed and tested. The water and methanol diffusion coefficients are considerably smaller at lower hydration levels and room temperature. The diffusion coefficient of the water and methanol molecules increases with increases in the hydration level, and this is in good agreement with experiment data. Analysis of the pair correlation functions supports the experimental observations of the membrane performance with hydration related to the water and methanol diffusion behavior in hydrated SPAES and blend membranes.

s Polymer composites are recently being deployed to buildings and vehicles that are required to meet both load-bearing properties and aesthetic needs. Since color is one of the most essential elements of a design, coloring of structural composites is drawing great attention. Despite various attempts of coloration of polymer composites, there is a lack of study on the impact of coloration on mechanical properties of polymer composites. Here, we investigate the influence of colorants (one pigment and three dyes) on mechanical properties of epoxy-based fiber composites. In this study, we found that incorporation of 0.1wt% pigment (Cinquasia® Magenta D4570) enhances mechanical strengths of epoxy-based fiber composites by 10 %, which might be attributed to enhanced Tg of epoxy resin matrix where pigment acts as a particle reinforcement. Among three dyes (disperse, acid, and reactive dyes), only disperse dye was dissolved in epoxy resin monomer, but mechanical strengths of resulting composites decreased as the disperse dye reduces Tg of epoxy resin matrix, acting like a plasticizer in the matrix. With epoxy-based fiber composites colored with the pigment, we finally suggest implication of coloration that can be applied to early diagnosis of flexure of colored composites.

Continuous fiber reinforcements are widely used to enhance mechanical properties of composite materials, but the impregnation of continuous fiber reinforcements with thermoplastics is a challenge due to high melt viscosity of the thermoplastic matrix. One of promising routes to improve the impregnation is to prepare commingled yarns with continuous matrix filaments and reinforcement fibers. In this study, we investigate mechanical properties of commingled yarns comprising different ratios of continuous glass fibers and polypropylene filaments, and of the composite plates made up of fabrics woven by the commingled yarns with a different polypropylene content. We found that undistributed or bunched glass fibers occur at high PP contents (>50 wt%), inducing an inhomogeneous mixing of the continuous reinforcement fibers and polypropylene filaments, which resultantly leads to abrupt changes in mechanical properties of both commingled yarns and resulting composites. Notably, the inhomogeneous distribution of continuous glass fibers in the commingled yarn at high PP contents gives rise to unexpected viscoelastic characteristics of resulting composites although impregnation of continuous glass fibers with polypropylene matrix is enhanced as the absolute amount of the polymer matrix increases.

Thermoplastic composites are rapidly emerging as alternative materials for auto parts owing to recyclability as well as excellent stiffness- and strength-to weight ratios. In this study, an optimal stacking sequence using twill-weave carbon fiber-reinforced polypropylene (CF/PP) prepregs and random fiber-reinforced polypropylene (RFP) sheets were investigated for the fabrication of an automobile fender. The lamination consisting of CF/PP only incurred imperfect resin impregnation. RFP insertion between CF/PP layers improved the resin impregnation. The hybrid stacking sequence not only reduced internal void contents but also increased the flexural and impact strength of the composite laminate. Using the optimal stacking sequence, a real-scale composite fender was fabricated and impact tests were performed. The test results were compared with the ones from an existing steel fender. In case of the steel fender, permanent deformation was observed even in one attempt, while no visible damage was found from the composite fender even after five consecutive impact tests.

Poly(dibenzylated benzimidazolium) bromides (Bz-PBI-Br) were converted successfully to OH− ion conducting poly(dibenzylated benzimidazolium) hydroxides (Bz-PBI-hydroxides) by the treatment of KOH. The Bz-PBI-hydroxides obtained in this study showed an excellent alkali tolerance compared to previously synthesized poly(dimethylated benzimidazolium) hydroxides (Me-PBI-hydroxides). According to 1H-NMR analysis, Me-PBI-hydroxides were decomposed during KOH treatment. In order to find out the reason, density functional theory (DFT) calculations of two benzimidazolium structures, e.g., dimethylated benzimidazolium (Me-BI+) and dibenzylated benzimidazolium (Bz-BI+), were performed. Bz-BI+ showed lower electron affinity and OH−-binding energies at the C2 position of the benzimidazolium ring than Me-BI+. These DFT results strongly confirm that Bz-BI+ is less vulnerable to an OH− attack than Me-BI+; this contributes to the enhanced stability and OH− ion conductivity of the Bz-PBI-hydroxides.

The weight reduction and improved mechanical property are one of the prime factors to develop new materials for the aerospace industry. Composite materials have thus become the most attractive candidate for aircraft and other means of transportations due to their excellent property and light weight. In particular, fiber reinforced polymer (FRP) composite materials have been used as an alternative to metals in the aircraft. The composite materials have shown improved properties compared to those of metal and polymeric materials, which made the composites being used as the skin structure of the airplane. This review introduces different types of materials which have been developed from the FRP composite material and also one of the most advantageous ways to employ the composites in aircraft.

In this study, novel crosslinked pore-filling membranes were fabricated by using a centrifugal force from the cylindrical centrifugal machine. For preparing these crosslinked pore-filling membranes, the poly(phenylene oxide) containing long side chains to improve the water management (hydrophilic), porous polyethylene support (hydrophobic) and crosslinker based on the diamine were used. The resulting membranes showed a uniform thickness, flexible and transparent because it is well filled. Among them, PF-XAc-PPO70_25 showed good mechanical properties (56.1 MPa of tensile strength and 781.0 MPa of Young&rsquo, s modulus) and dimensional stability due to the support. In addition, it has a high hydroxide conductivity (87.1 mS/cm at 80 &deg, C) and low area specific resistance (0.040 &Omega, &middot, cm2), at the same time showing stable alkaline stability. These data outperformed the commercial FAA-3-50 membrane sold by Fumatech in Germany. Based on the optimized properties, membrane electrode assembly using XAc-PPO70_25 revealed excellent cell performance (maximum power density: 239 mW/cm2 at 0.49 V) than those of commercial FAA-3-50 Fumatech anion exchange membrane (maximum power density: 212 mW/cm2 at 0.54 V) under the operating condition of 60 &deg, C and 100% RH as well. It was expected that PF-XAc-PPO70_25 could be an excellent candidate based on the results superior to those of commercial membranes in these essential characteristics of fuel cells.

The efficient CO2 separation process depends on the trade-off among permeability and selectivity requirements. In this work, copolymers of polyhedral oligomeric silsesquioxanes (POSS) with cage-like rigid structure and polyethylene glycol (PEG) with good CO2 affinity were synthesized by introducing allyl-POSS and allyl-EO into the side chain of polymethylhydrosiloxane (PMHS) in different proportions. The POSS80PEG20 copolymer fashioned into membrane showed good CO2 separation performance (permeability of 679 barrer and CO2/N2 selectivity of 38.1). The effect of POSS content on morphology, thermal stability and mechanical properties was also investigated. Multilayered composite membranes using POSS80PEG20 copolymer of different concentration as a selective layer, polyacrylonitrile (PAN) support layer and polydimethylsiloxane (PDMS) middle layer were also fabricated to achieve improved mechanical stability. The composite membrane with selective layer concentration of 0.25 wt% (POSS-PEG-0.25) offered optimum CO2/N2 and CO2/O2 selectivity performances. Moreover, the effect of feed pressure on mixed gas permeance was also reported.

Poly(styrene-b-ethylene-co-butylene-b-styrene) (SEBS) triblock copolymers are prepared with 50% hexyl quaternary ammonium (HQA) and 20% alkyl chains of different chain lengths: C4 (50HQA-20C4-SEBS) and C12 (50HQA-20C12-SEBS). Their physicochemical and electrical properties are investigated for use as novel alkaline anion exchange membranes. In most other comb-type polymers, the alkyl chain is introduced as a hydrophilic spacer unit between the polymer backbone and conducting head group. In the current study, additional alkyl chains are grafted onto the SEBS polymer as hydrophobic side chains as well as typical hydrophilic side chains. Introduction of this extra hydrophobic alkyl spacer group is done to obtain well-connected morphology, increased free volume, enhanced water uptake and related conductivity, together with improved physicochemical properties of the membranes obtained. The results are compared with HQA-functionalized SEBS without the hydrophobic alkyl spacer group (50HQA-20C0-SEBS), and the effects of the alkyl chain lengths on the structure of polymers and physicochemical properties of the corresponding membranes are investigated.

A series of poly(ethylene glycol)–imidazolium-functionalized 6FDA–durene polyimides (PEG–Im-PIs) with a range of PEG chain lengths was developed. The structures and properties of this series, as well as the gas separation properties of the corresponding polymer membranes, were studied. A PEG group and an imidazolium-based ionic group, both of which acted as CO2-solubilizing groups, were incorporated onto a rigid polyimide backbone to yield a very high CO2 solubility and, hence, excellent CO2/CH4 (49.2) and CO2/N2 (40.1) permselectivities while maintaining a good permeability of polyimide.

Crosslinked poly(arylene ether sulfone)s (PES) with pendant alkyl bisimidazolium units, which act as both crosslinkage sites and hydroxide conductors, were developed as anion exchange membranes (AEMs). These bisimidazolium-mediated crosslinked membranes (BI-cPESs) display a high hydroxide conductivity exceeding 0.012 S cm−1 at 20 °C and 0.061 S cm−1 at 80 °C, together with good chemical, thermal, mechanical, oxidative and dimensional stabilities. The BI-cPES membrane, which includes a long alkyl chain (C10, BI-cPES-10), form self-aggregated structures due to the long pendant hydrophobic side chain that forms a comb shape. The benefit of this crosslinked comb-shaped system is its high conductivity of 0.027 S cm−1 at 20 °C, even at an IEC as low as 1.13 meq. g−1 and a low water uptake of 8.70%.