Rubber-based gas barrier materials: A review

Cellulose nanofibril (CNF) hybrid materials show great promise as sustainable alternatives to oil-based plastics owing to their abundance and renewability. Nonetheless, despite the enormous success achieved in preparing CNF hybrids at the laboratory scale, feasible implementation of these materials remains a major challenge due to the time-consuming and energy-intensive extraction and processing of CNFs. Here, we describe a scalable materials processing platform for rapid preparation (<10 min) of homogeneously distributed functional CNF–gibbsite and CNF–graphite hybrids through a pH-responsive self-assembly mechanism, followed by their application in gas barrier, flame retardancy, and energy storage materials. Incorporation of 5 wt % gibbsite results in strong, transparent, and oxygen barrier CNF–gibbsite hybrid films in 9 min. Increasing the gibbsite content to 20 wt % affords them self-extinguishing properties, while further lowering their dewatering time to 5 min. The strategy described herein also allows for the preparation of freestanding CNF–graphite hybrids (90 wt % graphite) that match the energy storage performance (330 mA h/g at low cycling rates) and processing speed (3 min dewatering) of commercial graphite anodes. Furthermore, these ecofriendly electrodes can be fully recycled, reformed, and reused while maintaining their initial performance. Overall, this versatile concept combines a green outlook with high processing speed and material performance, paving the way toward scalable processing of advanced ecofriendly hybrid materials.

Advanced nanocellulose-based gas barrier materials: Present status and prospects

Polymeric films for gas barrier applications such as food packaging and electronic devices have attracted great interest due to their cheap, light and easy processability among gas barrier materials. Especially in electronic devices, extremely low gas permeance is necessary for maintaining the device performance. However, current polymeric barrier films still suffer from relatively high gas permeance than other materials. Therefore, there have been strong needs to enhance the gas barrier performance of polymeric barrier films while keep their own advantages. Recently, graphene is highlighted as a 2D-layered material for gas barrier applications. However, owing to the poor workability and difficulty to produce in engineering scale, graphene oxide (GO) is on the rise. GO consists of oxygen-containing functional groups on surface with intrinsic 2D-layered structure and high aspect ratio, and it can be well-dispersed in aqueous polar solvents like water, resulting in scalable mass production. Here, we prepared GO incorporated polyimide (PI) nanocomposites. PI is widely used barrier polymer with high mechanical strength and thermal and chemical stability. We demonstrated that PI/GO nanocomposites could perform as a gas barrier. Furthermore, surfactants (Triton X-100 (TX) and Sodium deoxycholate (SDC)) are introduced to enhance the gas barrier performance by improving the degree of dispersion of GO in PI matrix. As a result, TX enhanced the gas barrier performance of PI/GO nanocomposites which is similar to predicted value. This finding will provide new insight to polymer nanocomposites for gas barrier applications.

[Introduction]Polymer electrolyte fuel cell (PEFC) is one of the promising technologies for decarbonization. Especially, PEFC is suitable to power heavy-duty vehicles (HDV) because of its high efficiency and high fuel capacity. However, there are some serious technical challenges for PEFC application for HDV such as the durability. When we focus on the chemical degradation of polymer electrolyte membranes (PEMs), it happens due to attack by radical species. One of the radical formation mechanisms is the reaction at the anode side by the penetrated oxygen from cathode. Therefore, a promising mitigation strategy against chemical degradation is the suppression of oxygen permeability through the PEM.To verify this concept, we developed high gas barrier PEM. As a model gas barrier PEM, we made a sandwich type PEM with high oxygen barrier property. The sandwich PEM was prepared by depositing a thin interlayer consisting blended poly(vinyl alcohol) (PVA) as a gas barrier material and poly(vinyl sulfonic acid) (PVS) as a proton conductor in between two layers of Nafion 211 membranes. We evaluate chemical durability using the sandwich gas barrier PEM and discuss about the mechanism.[Experimental]To fabricate thin sandwich PEMs (15-20 µm), ethanol diluted Nafion dispersion solution (20 mg/ml) and PVA/PVS solution (10 mg/ml) were sprayed on a polytetrafluoroethylene (PTFE) sheet by a spray gun (Tamiya HG wide airbrush). The thickness of each layer was controlled by controlling the deposited weight. Then, membrane characterization procedures such as surface roughness, proton conductivity, and dimensional stability were performed. To evaluate fuel cell performance, the PEMs were mounted to a JARI cell with 1 cm2 active area. Chemically accelerated stress test was performed by open circuit voltage (OCV) holding test following NEDO protocol.[Results and Discussion]Several areal densities of PVA/PVS interlayer were successfully incorporated into Nafion membrane to make sandwich PEM. The sandwich PEM shows considerable fuel cell performance, and thin sandwich PEMs show higher performance than the 50 µm sandwich PEM, although it is lower than the thin sprayed Nafion. For example, the peak power density of 15 µm sandwich PEM was 0.44 W cm-2 compared to 0.30 W cm-2 and 0.50 W cm-2 for 50 µm sandwich PEM and 15 µm Nafion, respectively. Furthermore, the incorporation of interlayer to thin PEM can suppress the hydrogen crossover current density from 7.8 mA cm-2 to 5.5 mA cm-2 indicating superior gas barrier property. From the higher gas barrier property, it is predicted thin sandwich PEMs will have higher chemical durability than Nafion with similar thickness.

In-situ constructing hybrid cross-linked networks in brominated butyl rubber via amphiphilic graphene oxide cross-linkers: Retaining excellent gas barrier and mechanical properties after fatigue

The demand for high-performance two-dimensional gas barrier materials is increasing owing to their potential for application in optoelectronic devices. These materials can help the devices maintain their properties over a long period. Therefore, in this study, we investigated the gas barrier performance of hexagonal boron nitride (h-BN) monolayers grown on copper foils via electrochemical polishing (ECP). The ECP treatment helped reduce the surface roughness of the copper foils. As a result, the nucleation density was reduced and highly crystalline h-BN monolayers were produced. The gas barrier performance of h-BN monolayers on copper foils with ECP was comparable to that of graphene. Our finding demonstrates the potential of monolayer h-BN as a high-performance and economical gas barrier material for organic-based optoelectronic devices.

In this paper, the performance of a gas barrier that consisted of polyacrylamide (PAM)-modified compacted clayey soil was experimentally explored. The moisture content and water loss characteristics of the tested soils were adopted as indicative indices of water retention capacity (WRC). The gas permeability (Kp) and gas diffusion coefficient (Dp) of the modified compacted clays were evaluated via gas permeability and gas diffusion tests. The test results showed that the moisture content of the modified compacted clay samples subjected to drying tests increased with increasing polyacrylamide content. Kp and Dp decreased with increasing PAM content. Compared with 0.2% PAM content, the Kp of the sample with 1.0% PAM was reduced by ten times, and the Dp was reduced to ~35%. Compared to the unmodified clay, the liquid limit of the PAM-modified clay increased by 45~55%. Comparison of the liquid limit tests between this study and previous studies revealed that the liquid limit ratio of the zwitterionic polyacrylamide (ZP)-modified soil was much higher than the other material-modified soils. The results of this study are useful to facilitate the application of modified compacted clays as gas barrier materials at industrial contaminated sites.

Herein, nano boron nitride (BN) laminated poly(ethyl methacrylate) (PEMA)/poly(vinyl alcohol) (PVA) nanocomposite films are fabricated by using a simple in situ polymerization technique with incorporation of silver nanoparticles (Ag NPs). Structural investigations of PEMA/PVA/Ag@BN nanocomposite thin films are carried out by Fourier‐transform infrared spectroscopy, dynamic light scattering, X‐ray diffraction analysis, 1H nuclear magnetic resonance, 13C nuclear magnetic resonance, and mass spectrometry. The change in morphology of PEMA/PVA matrix due to the reinforcement of BN platelets are identified by electron microscopic studies. The unique tortuous paths are achieved by the dispersion of BN platelets by which gas penetration is restricted with enhancing the barrier properties of the material by 6.5 folds at 5 wt% BN content as compared with neat PEMA/PVA. Acid and alkali resistant along with biodegradability behavior of as‐synthesized nanocomposites are studied. From limiting oxygen index (LOI) results, it is found that the prepared materials are fire retardant in nature owing to effective reinforcement of BN layers. Antibacterial activities of PEMA/PVA/Ag@BN nanocomposite are studied by Xanthomonas citri or axonopodis pv. Citri, Escherichia coli, and Xanthomonas oryzae pv. Oryzae because of Ag NPs reinforcement. The substantial improvements in gas barrier, fire retardant, and antibacterial properties enable the materials for packaging application.

Recently, high growth potential of barrier materials industry including high performance packing materials was expected with increasing the national income and well-being culture. As high barrier materials, polymer nanocomposites have considerable attractions due to their excellent physical properties compared to conventional composite materials. In general, polymer nanocomposites were consisted of polymer matrix and inorganic fillers, such as layered silicate, carbon nanotubes, and metal- or inorganic nanoparticles. Among these materials, layered silicate which was called as the clay was usually used as nano-fillers because of naturally abundant and most economical and structural properties. Clay-reinforced polymer nanocomposites have various advantages, such as high strength, flammability, gas barrier property, abrasion resistance, and low shrinkage and used for automotive and packing materials. Therefore, in this paper, we focused on the need of gas barrier materials and materials-related technologies.

With more deep construction in congested urban areas and an increase in the provision of residential basements, a more detailed assessment is required of the risks inherent in below-ground construction and how these might best be addressed, especially when considering factors other than water ingress such as ground gases and contamination. Strategies for dealing with all external sources of groundwater, surface/flood water, soil gases and contaminants should be determined from the very earliest stages of the planning and design processes for any project involving below-ground structures. Waterproofing systems are materials and methods used to protect a structure from water ingress, and which are often effective as ground gas barrier — ie a barrier between the structure and the ground intended to prevent or impede the ingress of radon, methane and other ground gases and contaminants. There has been much development and use of new materials for waterproofing and understanding how these waterproofing and gas barrier materials are applied to the structure is important when specifying, designing and constructing belowground structures. The relevant codes of practice for each subject offer guidance on how this can be achieved, but does the guidance contained within correspond between documents?

Graphene, which is a layer of carbon atoms in a hexagonal lattice, has been reported to have excellent mechanical, electrical, thermal, and gas barrier properties. One of the most widely used applications of graphene is graphene?polymer composites, which are one of the most promising solutions, since highly functional materials can be produced with a small amount graphene flakes incorporated in a lightweight polymer matrix. Graphene?polymer composites have been investigated for various types of applications such as thermal interface materials, electromagnetic interference shielding materials, gas sensor materials, and gas barrier materials.

ABSTRACTPolymer nanocomposites offer a great interest as gas barrier materials because of their much‐enhanced properties arising from the nanoparticles shape, size, and spatial arrangement within the matrix. However, optimization and further development of such materials requires fundamental understanding of the influence of the nanocomposite structure on permeating gas diffusion. This step can be greatly facilitated through modeling/simulation strategies able to establish relationships between the material microstructure and the achieved enhancement of barrier properties. This review first presents the analytical models developed to estimate the effective diffusivity in polymer nanocomposites. The predictions of the models are analyzed with respect to experimental data reported in the literature and their ability to describe accurately the nanocomposite transport properties when the microstructure complexity increases is discussed. Then, modeling approaches based on numerical simulation techniques (e.g., the finite element method) that allow simulating the diffusion processes and assessing the effect of filler shape, orientation, dispersion, and spatial arrangement are reviewed and discussed. Finally, the importance of 3D simulation strategies for the understanding and prediction of transport properties in the most complex nanocomposite microstructures is addressed. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018, 56, 621–638

Poly(hydroxyurethane) was synthesized by polyaddition of difunctional alicyclic carbonate (DCHC) and m-xylylenediamine (mXDA), and its oxygen transmittance rate was examined. DCHC was prepared from industrially available difunctional alicyclic epoxide, 3′,4′-epoxycyclohexylmethyl 3,4-epoxycyclohexane carboxylate (CEL2021P), by insertion of carbon dioxide using N-methyltetrahydroprimidine as a promoter and tetrabutylammonium bromide as a catalyst. Poly(hydroxyurethane), poly(DCHC-mXDA) (M n = 2600, M w = 5700 GPC relative to polystyrene standards), was obtained by heating DCHC and mXDA in N,N-dimethylacetamide at 100 °C. The obtained polymer was thermally stable up to 220 °C, and exhibited good processability in film preparation. The oxygen transmission rate of the polymer was found to be 127 cm3/m2 day atm at 5 μm film thickness laminated with polypropylene films, indicating its relatively high gas barrier property. Polyhydroxyurethane was synthesized by polyaddition of difunctional alicyclic carbonate (DCHC) and m-xylylenediamine (mXDA) and its oxygen transmission rate was examined. We found that the polymer possess high gas barrier property.

The flammability and gas barrier properties are essential for package material. Herein, a highly-oriented self-assembly nanocoating composed of polyvinyl alcohol (PVA) and montmorillonite (MMT) was prepared for endowing polyethylene terephthalate (PET) films with excellent flame retardancy and gas barrier properties. The specific regular nanosheet structure of the PVA/MMT composite nanocoating was confirmed by Fourier transform infrared (FTIR) and X-ray diffraction (XRD). Thermogravimetric analysis (TGA) and the vertical burning test (VBT) suggested that the thermal stability and flame-retardancy of the coated PET films were considerably improved with more pick-up of the resulting nanocoating. When reaching 650 °C, there was still 22.6% char residual left for coated PET film, while only 6% char residual left for pristine PET film. During the vertical burning test, the flame did not spread through the whole PET film with the protection of PVA/MMT nanocoating, and no afterflame was observed. Scanning electron microscopy (SEM) is consistent with vertical burning test, proving that the thermal stability and flame retardancy of coated PET films were considerably enhanced with the increment of PVA/MMT. Thanks to the multi-layer structure, PVA/MMT nanocoating could effectively improve the gas barrier properties of PET films, and the oxygen vapor transmittance rate and water vapor transmittance rate of PET films were more than four hundred times lower and 30% lower than those of neat PET film. Our work demonstrates that bi-functional flame retardant and gas barrier materials could be gained via constructing inorganic/organic highly-oriented self-assembly nanocoating, which is promising in the area of packaging.

Feasibility of compacted attapulgite/diatomite amended clayey soils as gas barrier materials