Excellent Gas Barrier Properties Research Articles

Nanostructural morphology of plasticized wheat gluten and modified potato starch composites: relationship to mechanical and barrier properties.

In the present study, we were able to produce composites of wheat gluten (WG) protein and a novel genetically modified potato starch (MPS) with attractive mechanical and gas barrier properties using extrusion. Characterization of the MPS revealed an altered chain length distribution of the amylopectin fraction and slightly increased amylose content compared to wild type potato starch. WG and MPS of different ratios plasticized with either glycerol or glycerol and water were extruded at 110 and 130 °C. The nanomorphology of the composites showed the MPS having semicrystalline structure of a characteristic lamellar arrangement with an approximately 100 Å period observed by small-angle X-ray scattering and a B-type crystal structure observed by wide-angle X-ray scattering analysis. WG has a structure resembling the hexagonal macromolecular arrangement as reported previously in WG films. A larger amount of β-sheets was observed in the samples 70/30 and 30/70 WG-MPS processed at 130 °C with 45% glycerol. Highly polymerized WG protein was found in the samples processed at 130 °C versus 110 °C. Also, greater amounts of WG protein in the blend resulted in greater extensibility (110 °C) and a decrease in both E-modulus and maximum stress at 110 and 130 °C, respectively. Under ambient conditions the WG-MPS composite (70/30) with 45% glycerol showed excellent gas barrier properties to be further explored in multilayer film packaging applications.

Air-Stable flexible organic light-emitting diodes enabled by atomic layer deposition

Organic light-emitting diodes (OLED) are an energy-efficient light source with many desirable attributes, besides being an important display of technology, but its practical application has been limited by its low air-stability. This study demonstrates air-stable flexible OLEDs by utilizing two atomic-layer-deposited (ALD) films: (1) a ZnO film as both a stable electron-injection layer (EIL) and as a gas barrier in plastics-based OLED devices, and (2) an Al2O3/ZnO (AZO) nano-laminated film for encapsulating the devices. Through analyses of the morphology and electrical/gas-permeation properties of the films, we determined that a low ALD temperature of 70 °C resulted in optimal EIL performance from the ZnO film and excellent gas-barrier properties [water vapor transmission rate (WVTR) <5 × 10−4 g m−2 day−1] from both the ZnO EIL and the AZO encapsulating film. The low-temperature ALD processes eliminated thermal damage to the OLED devices, which were severe when a 90 °C encapsulation process was used, while enabling them to achieve an air-storage lifetime of >10 000 h.

Bionanocomposites based on gelatin matrix and nanocellulose

Cellulose nanofibres (CNF) and nanocrystals (CNC) have been used to develop bionanocomposite films based on a protein matrix. Nanocrystals were isolated using different hydrolysis times which affect in CNC aspect ratio. For obtaining bionanocomposites films, solvent casting method was used. Fourier transform infrared spectroscopy (FTIR), Thermogravimetric analysis (TGA), Differential Scanning Calorimetry (DSC) and oxygen and water vapour permeability tests were carried out to analyse the effect of nanocellulose addition to gelatin matrix. Gelatin matrix and nanocomposites tensile properties and fractured surface morphologies were also studied. After the addition of nanocellulose to gelatin matrix tensile strength decreased because there is a lack of adhesion between nanocellulose and gelatin matrix. Nanocellulose contributes to improve the excellent oxygen gas barrier properties of gelatin. Gelatin Tg value depends on the water content and shifted to higher temperatures as water content decreases. The addition of nanocellulose also slightly shifted dry gelatin Tg to higher temperatures.

Al2O3/TiO2 Nanolaminate Thin Film Encapsulation for Organic Thin Film Transistors via Plasma-Enhanced Atomic Layer Deposition

Organic electronic devices require a passivation layer that protects the active layers from moisture and oxygen because most organic materials are very sensitive to such gases. Passivation films for the encapsulation of organic electronic devices need excellent stability and mechanical properties. Although Al2O3 films obtained with plasma enhanced atomic layer deposition (PEALD) have been tested as passivation layers because of their excellent gas barrier properties, amorphous Al2O3 films are significantly corroded by water. In this study, we examined the deformation of PEALD Al2O3 films when immersed in water and attempted to fabricate a corrosion-resistant passivation film by using a PEALD-based Al2O3/TiO2 nanolamination (NL) technique. Our Al2O3/TiO2 NL films were found to exhibit excellent water anticorrosion and low gas permeation and require only low-temperature processing (<100 °C). Organic thin film transistors with excellent air-stability (52 days under high humidity (a relative humidity of 90% and a temperature of 38 °C)) were fabricated.

Large-scale self-assembled zirconium phosphate smectic layers via a simple spray-coating process

The large-scale assembly of asymmetric colloidal particles is used in creating high-performance fibres. A similar concept is extended to the manufacturing of thin films of self-assembled two-dimensional crystal-type materials with enhanced and tunable properties. Here we present a spray-coating method to manufacture thin, flexible and transparent epoxy films containing zirconium phosphate nanoplatelets self-assembled into a lamellar arrangement aligned parallel to the substrate. The self-assembled mesophase of zirconium phosphate nanoplatelets is stabilized by epoxy pre-polymer and exhibits rheology favourable towards large-scale manufacturing. The thermally cured film forms a mechanically robust coating and shows excellent gas barrier properties at both low- and high humidity levels as a result of the highly aligned and overlapping arrangement of nanoplatelets. This work shows that the large-scale ordering of high aspect ratio nanoplatelets is easier to achieve than previously thought and may have implications in the technological applications for similar materials.

Preparation and properties of gas barrier resin/rubber nanolaminated composites

An extremely high gas barrier resin was highly oriented and uniformly distributed in a rubber matrix layer by layer by the micro‐layer coextrusion technology and a special composite laminating device. The resulting composite had excellent gas barrier properties because of its alternating multilayer structure. Experimental tire samples were prepared and tested for high‐speed, endurance, and pressure performance. The results showed that because the barrier resin was evenly dispersed in the rubber matrix, the tire inner liner made of the composite showed excellent fatigue resistance and gas barrier performance. POLYM. ENG. SCI., 55:190–195, 2015. © 2014 Society of Plastics Engineers

Synthesis of biodegradable and flexible, polylactic acid based, thermoplastic polyurethane with high gas barrier properties

AbstractPolylactic acid (PLA) has the beneficial properties of good mechanical strength, biodegradability and biocompatibility, and these properties make it suitable for use as an environmentally friendly packaging material. However, its use has been limited by its brittleness and poor stability. In this work, we successfully developed an efficient synthesis scheme to improve the mechanical properties, flexibility and gas barrier properties of PLA‐based polymers. Four different PLA‐based thermoplastic polyurethane (PLAPU) polymers were synthesized through the reaction of PLA diol with hexamethylene diisocyanate, followed by chain extension with polycaprolactone (PCL) diol. The relative compositions of the hard PLA and the soft PCL diols in the PLAPU polymers were controlled systematically to optimize the physical properties of the polymers. For example, increasing the content of PCL resulted in higher molecular weight PLAPU polymers that had increased tensile strengths and elongations at break, but their moduli were decreased. At the optimized PLA:PCL ratio of 1:3, the PLAPU polymer had an excellent elongation at break of 1053% with a relatively high Young's modulus of 51.8 MPa. In addition, the gas barrier properties of the PLAPUs were significantly enhanced depending on the molecular weight and PCL content of the polymers. To demonstrate the feasibility of using PLAPU polymers for biodegradable packaging materials, hydrolytic degradation tests were performed in phosphate buffer solution, and the PLAPU polymers were degraded gradually at rates that depended on the content of PCL in the polymers. This optimized PLAPU polymer exhibited excellent flexibility and gas barrier property, as well as high elongation, demonstrating its potential utility as packaging materials. © 2013 Society of Chemical Industry

Titanium alloy foil-inserted carbon fiber/epoxy composites for cryogenic propellant tank application

This paper presents the mechanical and gas barrier properties of titanium alloy foil-inserted carbon fiber/epoxy composites (CFRPs) undertaken to improve gas barrier properties for cryogenic propellant tank applications. A newly developed β-titanium alloy (GumMetal, GM) was applied. A sheet of titanium foil (α-Ti or GM, 0.05 or 0.1 mm) was inserted between cross-plied composite laminates ([0°2/90°2]S) without adhesive. Epoxy resin in the prepreg contributes to bonding between the Ti-foil and CFRP. The Ti-alloy foil insert did not strongly affect the tensile or compressive strength. Transverse cracks in the 90° layer never penetrated into the Ti-alloy foil layer before the final failure under tensile loading. Nonlinear stress–strain behaviors attributable to the pseudo-elastic behaviors of both unidirectional CFRP and β-Ti alloy (GM) were estimated using high-order stiffness and classical lamina theory. The numerical results agreed with the experimentally obtained results. Helium gas leakage under tensile stress was not observed before the final failure of the composites (1.4% of tensile strain). The excellent mechanical and gas barrier properties were successfully demonstrated.

폴리(비닐 알코올)/사포나이트 나노 복합체 필름 및 연신된 필름의 열적 성질, 모폴로지, 광학 투명성, 및 기체 투과성

용액 삽입법을 이용하여 다양한 함량의 사포나이트(SPT) 점토를 포함한 폴리(비닐 알코올)(poly(vinyl alcohol), PVA) 나노 복합체 필름을 제조하였다. SPT를 0에서 10 wt%까지 첨가한 PVA 나노 복합체 필름들의 열적 특성, 모폴로지, 광학 투명성 및 기체 투과성에 대해 조사하였다. 특히 5 wt% SPT 포함한 PVA 복합체 필름이 매우 우수한 열적 특성과 기체 차단성을 나타내었다. 5 wt% SPT 포함된 복합체 필름을 연신율에 따라 150에서 250%까지 이축 연신하였고, 이축 연신율에 따른 점토 분산성, 광학적 특성 및 기체 투과성에 대한 조사를 하였다. 다양한 비로 이축 연신한 PVA 나노 복합체 필름은 우수한 광학 투명성과 산소 차단성을 보였다. Poly(vinyl alcohol)(PVA) nanocomposite films containing various saponite (SPT) clay contents were synthesized using a solution intercalation method. The thermal property, morphology, optical transparency, and gas permeability of the PVA nanocomposite films with various SPT contents in the range of 0 to 10 wt% were examined. PVA nanocomposite film containing 5 wt% SPT showed excellent thermal and gas barrier property. The hybrid films containing 5 wt% SPT were equibiaxially stretched with stretching ratios ranging from 150 to 250%. The clay dispersion, optical transparency, and gas permeability were also examined as a function of equibiaxial stretching ratio. The PVA nanocomposite films with various equibiaxial stretching ratios showed excellent optical transparency and barrier to oxygen permeability.

Manufacture of optical substrates with high gas resistance as well as antistatic capability and their applications for flexible organic light emitting diodes (flexible OLEDs)

With modification of layered double hydroxide (LDH) and prescription of additives, optical substrates with good transparency, high antistatic capability, and excellent gas barrier properties have been manufactured by a single-screw extruder and a T-Die. Moreover, we have also applied them for flexible OLEDs. The experimental results reveal that lab-made optical substrates can effectively hinder the invasion of moisture and oxygen in the air into the devices, therefore drastically prolonging the lifetimes.

The Gas Barrier Property and Structure of Rubber Nano-Laminated Composites

This article mainly introduced the structure and the principle of gas barrier of the rubber nano-laminated composite materials with alternating layer structure and excellent gas barrier property. Due to the fact that the barrier resin material was dispersed in matrix rubber evenly and parallelly in nanometer, the phase structure lead to the existence of multipath movement and deep penetration in the composite materials, thus the permeability coefficient of composite materials were reduced significantly. So the rubber nano-laminated composite materials owned excellent gas barrier performance.

Effects of variation of oil and zinc oxide type on the gas barrier and mechanical properties of chlorobutyl rubber/epoxidised natural rubber blends

In many polymer applications such as inner tire liners and fuel hoses, imparting excellent gas barrier property is of prime importance. Researches in this direction had been done based on a judicious choice of polymer type or a blend thereof and the compounding ingredients. Though butyl rubber has been the polymer of choice because of its excellent gas barrier property, yet researches were targeted to improve the same with further modification in the polymer type and variation in compounding ingredients. In this study, a (90:10) blend of chlorobutyl rubber (CIIR) and Epoxdised Natural Rubber (ENR) by weight was used as the base. Four different types of process oil and three different types of zinc oxide (ZnO) at fixed predetermined concentrations were used to optimize the gas barrier and mechanical properties. In this blend, recycled aromatic oil (RAE) and sheet zinc oxide were effective in imparting the best overall combination of properties. Scanning Electron Microscopic (SEM) studies of ZnO were done to understand the structure property relationship.

Glycolic acid production in the engineered yeasts Saccharomyces cerevisiae and Kluyveromyces lactis

BackgroundGlycolic acid is a C2 hydroxy acid that is a widely used chemical compound. It can be polymerised to produce biodegradable polymers with excellent gas barrier properties. Currently, glycolic acid is produced in a chemical process using fossil resources and toxic chemicals. Biotechnological production of glycolic acid using renewable resources is a desirable alternative.ResultsThe yeasts Saccharomyces cerevisiae and Kluyveromyces lactis are suitable organisms for glycolic acid production since they are acid tolerant and can grow in the presence of up to 50 g l-1 glycolic acid. We engineered S. cerevisiae and K. lactis for glycolic acid production using the reactions of the glyoxylate cycle to produce glyoxylic acid and then reducing it to glycolic acid. The expression of a high affinity glyoxylate reductase alone already led to glycolic acid production. The production was further improved by deleting genes encoding malate synthase and the cytosolic form of isocitrate dehydrogenase. The engineered S. cerevisiae strain produced up to about 1 g l-1 of glycolic acid in a medium containing d-xylose and ethanol. Similar modifications in K. lactis resulted in a much higher glycolic acid titer. In a bioreactor cultivation with d-xylose and ethanol up to 15 g l-1 of glycolic acid was obtained.ConclusionsThis is the first demonstration of engineering yeast to produce glycolic acid. Prior to this work glycolic acid production through the glyoxylate cycle has only been reported in bacteria. The benefit of a yeast host is the possibility for glycolic acid production also at low pH, which was demonstrated in flask cultivations. Production of glycolic acid was first shown in S. cerevisiae. To test whether a Crabtree negative yeast would be better suited for glycolic acid production we engineered K. lactis in the same way and demonstrated it to be a better host for glycolic acid production.

Effects of modified Clay on the morphology and thermal stability of PMMA/clay nanocomposites

The potential to improve the mechanical, thermal, and optical properties of poly(methyl methacrylate) (PMMA)/clay nanocomposites prepared with clay containing an organic modifier was investigated. Pristine sodium montmorillonite clay was modified using cocoamphodipropionate, which absorbs UVB in the 280–320 nm range, via ion exchange to enhance the compatibility between the clay platelets and the methyl methacrylate polymer matrix. PMMA/clay nanocomposites were synthesized via in situ free-radical polymerization. Three types of clay with various cation-exchange capacities (CEC) were used as inorganic layered materials in these organic–inorganic hybrid nanocomposites: CL42, CL120, and CL88 with CEC values of 116, 168, and 200 meq/100 g of clay, respectively. We characterized the effects of the organoclay dispersion on UV resistance, effectiveness as an O2 gas barrier, thermal stability, and mechanical properties of PMMA/clay nanocomposites. Gas permeability analysis demonstrated the excellent gas barrier properties of the nanocomposites, consistent with the intercalated or exfoliated morphologies observed. The optical properties were assessed using UV–Visible spectroscopy, which revealed that these materials have good optical clarity, UV resistance, and scratch resistance. The effect of the dispersion capability of organoclay on the thermal properties of PMMA/clay nanocomposites was investigated by thermogravimetric analysis and differential scanning calorimetry; these analyses revealed excellent thermal stability of some of the modified clay nanocomposites.

Facile fabrication of transparent cellulose films with high water repellency and gas barrier properties

Transparent and water repellent gas barrier cellulose films were fabricated by surface modification of alkali/urea regenerated cellulose (AUC) films by soaking in cationic alkylketene dimer (AKD) dispersion, drying, and heating. Highly water repellent and excellent gas barrier properties were obtained for AKD-treated and heated AUC films due to covering of the film surfaces by hydrophobic AKD components. The maximum AKD content of the films was 0.2 %. Oxygen transmission rates for AKD-treated AUC films at 0 % relative humidity (RH) were less than 0.0005 mL m−2 day−1 kPa−1, the lowest detection limit of the instrument. Water contact angles on the AUC film increased from 50 to 110° after AKD treatment, and water uptake (immersion in water for 6 days) decreased from 92 to 20 %. Moreover, oxygen permeability decreased from 0.56 and 5.8 to 0.13 and 2.1 mL μm m−2 day−1 kPa−1 at 50 and 75 % RH, respectively, when the AKD content of the film was increased from 0 to 0.2 %. The present AKD-treated AUC film also had high light transparency (88 % at 600 nm), tensile strength (168 MPa), elongation at break (29 %), and work of fracture (37 MJ m−3). FT–IR analysis showed that AKD components were still present as major species on the AKD-treated film surfaces without hydrolysis at 2 months after conditioning the films at 23 °C and 50 % RH, indicating that such AKD molecules contributed to the hydrophobic nature of the AKD-treated AUC films.

Exploring the potential of exfoliated graphene nanoplatelets as the conductive filler in polymeric nanocomposites for bipolar plates

This research explored the potential of using exfoliated graphene nanoplatelets, GNP, as the conductive filler to construct highly conductive polymeric nanocomposites to substitute for conventional metallic and graphite bipolar plates in the polymer electrolyte membrane (PEM) fuel cells. Polyphenylene sulfide (PPS) was selected as the polymer matrix because of its high thermal and chemical tolerance. Solid state ball milling (SSBM) followed by compression molding was then applied to fabricate PPS/GNP nanocomposites. Results showed that PPS/GNP nanocomposites made by this method exhibit excellent mechanical and gas barrier properties but unsatisfied electrical conductivity. However, it was found that the electrical conductivity of these nanocomposites could be substantially enhanced if we combine GNP with second minor conductive filler for a positive synergistic effect and also optimize the processing time of SSBM. Meanwhile, PPS impregnated GNP papers were embedded into these PPS/GNP nanocomposites in order to further improve various properties of the resulting bipolar plates. It is believed that the bipolar plates made from PPS/GNP nanocomposites will allow lighter weight of PEM fuel cells with enhanced performance which is particularly suited for automotive applications.

Compact Tilt And Vibration Sensor And Method For Manufacturing The Same

Provided are a tilted vibration sensor incorporating a plurality of electrodes and a conductive spherical body which is turned on and off by the moving displacement of the spherical body, and which may be remarkably reduced in size and may have high performance and high operating sensitivity, high durability, and high reliability; and a method of manufacturing the sensor. The case ( 1 ) of the sensor comprises a case body ( 5 ) formed of a non-conductive material having such excellent gas-barrier property and heat resistance that can stop the transmission of gases which affects on the on/off operation of the sensor due to the moving displacement of the conductive spherical body ( 4 ) and a cover body ( 7 ) sealing airtight the opening part ( 6 ) of the case body. In the method of manufacturing the vibration sensor, moisture and particulate impurities affecting the on/off operation are removed from the hollow part ( 2 ) of the case ( 1 ), and the hollow part is evacuated.

High Proton Conductive and Low Gas Permeable Sulfonated Graft Copolyimide Membrane

We describe the syntheses of novel sulfonated graft copolyimides and investigate their proton conductivity and gas permeability properties. The graft copolyimide membrane showed significantly higher proton conductivity exceeding that of Nafion, and the proton conductivity at 90 °C and 98% RH was 1.2 S/cm, more than 7 times that of Nafion. Furthermore, the oxygen permeability of the membrane was approximately one-eighth the value of Nafion and had a very excellent gas barrier property. The selectivity ratio calculated from the proton and oxygen transports of the graft copolyimide membrane was 66 times that determined in Nafion. We first demonstrated that the graft copolymer membrane could realize a high proton conductivity and low gas permeability of the fuel. Consequently, this material proved to be promising as a proton exchange membrane and may have potential applications for use in fuel cells.

Gas barrier properties of natural rubber/kaolin composites prepared by melt blending

A series of highly filled natural rubber (NR) composites based on silane modified kaolin (SMK), precipitated silica (PS) and their mixed-compound additions (SMK + PS) were prepared by melt blending. The transmission electron microscopy (TEM) was employed to characterize the NR composites. The kaolinite particles were finely dispersed into the natural rubber matrix and arranged in parallel orientation. Compared to the pure NR, these highly filled NR/SMK composites exhibited outstanding mechanical properties, excellent gas barrier properties and much higher thermal stability. The gas barrier properties of NR composites with SMK and PS were much higher than those of NR/PS composites and better than those of NR/SMK. The nitrogen permeability of NR/SMK composites was decreased by 20–40% after filling with kaolin. The significant improvements in the mechanical properties, thermal stability and gas barrier properties may be attributed to the parallel kaolinite particles which restricted the free movement of rubber chains and retarded the diffusion of the gas molecules. Thus, the highly filled NR/SMK composites may be used to improve the air-tightness of rubber products.

Highly Electrophilic Organometallics for Carbocationic Polymerizations: From Anion Engineering to New Polymer Materials

Ion-ion interactions are a crucial but often overlooked aspect of many polymerization reactions. The precise nature of cation-anion binding is as yet poorly understood, and little is known of the extent of ionic interactions in the typically nonaqueous, low-polarity reaction media of most polymerizations. Nevertheless, adequate control of cation-anion interactions can greatly enhance the productivity and efficiency of chemical processes and can provide low-energy alternatives to current methods. This is illustrated here with the carbocationic polymerization of isoalkenes. Carbocationic polymerizations involve, as the name implies, carbocations as propagating species. Of the various types of substrates that can be polymerized cationically, the copolymerization of isobutene to isobutene-isoprene rubber stands out as the only large-scale, industrially important implementation of this reaction type. The products, elastomers with controlled degrees of unsaturation for subsequent cross-linking, have excellent gas barrier and mechanical dampening properties that make them indispensable components in polymer composites. For such applications, the polymer molecular weight has to be high, ∼5 × 10(5) g/mol, with 1-2 mol % isoprene. Cationic polymerizations are however notoriously difficult to control. As a means of suppressing chain transfer, the process is carried out at temperatures as low as -100 °C, with aluminum chloride initiators in chloromethane. Current industrial production of isobutene-isoprene butyl rubber is thus highly energy intensive and produces aluminum and chloride effluent. This Account summarizes how highly electrophilic organometallics coupled with new types of very weakly coordinating counteranions can provide the basis for a more environmentally friendly, lower energy alternative. Because any copolymerization of two monomers, here primarily isobutene and isoprene, leads to two different propagating species, each of which is characterized by different chain growth and chain termination kinetics, variation of the associated counteranions can give rather unexpected results. With judicious choice of the initiator and the counteranion, new chemistry can be injected into such processes and can open avenues to new families of polymer materials. Mechanistic investigations of the initiation process with zirconocene hydrides illustrate the complexity of this first step. Replacing aluminum with zinc initiators not only provides a nontoxic alternative but also generates a system in which the polymer molecular weight is much less affected by temperature and comonomer concentration, which can lead to a range of products, from oligomeric lubricant precursors to C═C-rich high-molecular-weight elastomers. The key in all these cases is the construction of either preformed or in situ-generated complex anions that are resistant to electrophilic or redox degradation and are capable of stabilizing tightly associated carbocations. Such initiator systems allow much more benign operating temperatures, reduce the need for chlorocarbon solvents, and can operate at concentrations as low as 5 × 10(-5) M. Along the way are provided the first examples of structurally characterized sec-alkyl carbocations and carbocation salts of organometallic zincates.