Oxygen Gas Permeability Research Articles

Flat biofilms extrusion of poly(lactic acid)/poly(butylene adipate‐co‐terephthalate) grafted with glycidyl methacrylate blends: Toward ecological packaging for sustainability

AbstractBlends of poly(lactic acid) (PLA)/poly(butylene adipate‐co‐terephthalate) grafted with glycidyl methacrylate (PBAT‐g‐GMA) were developed to produce flat and flexible biofilms through extrusion. The PLA/PBAT‐g‐GMA (90%/10%, 80%/20%, 70%/30%, and 60%/40% by mass) blends were processed in the internal mixer, injection molded, and manufactured into flat films. The optimal composition to produce flexible biofilms was PLA/PBAT‐g‐GMA (60/40%), as it demonstrated a decrease in elastic modulus of 53.2% and a significant gain in elongation at a break of 4923% about pure PLA. The incorporation of 40% PBAT‐g‐GMA in PLA increased the torque (Z) by 208%, while the melt flow index (MFI) decreased by 51.57%, compared to PLA. Additionally, the degradation rate (Rz) and molar mass loss (Rm) during processing were minimized, indicating that 40% PBAT‐g‐GMA enhanced stability of the PLA matrix. Fourier transform infrared spectroscopy indicated interactions between the GMA of PBAT‐g‐GMA and PLA, justifying the increase in viscosity and elongation at break. The PLA/PBAT‐g‐GMA (60/40%) composition showed a transmittance in the range of 20%–48% (400–800 nm) and an oxygen gas permeability of 1.56 × 10−5 cm3 STP/cm−2 h bar, indicating its potential for applications in packaging with optical barrier properties. Scanning electron microscopy (SEM) revealed ligaments in the interfacial region between PLA and PBAT‐g‐GMA, confirming the good performance in elongation at break. The results presented are essential for the plastics processing sector, aiming to develop eco‐friendly packaging.

Mechanical and barrier properties of LLDPE/TPS/OMMT packaging film in the presence of POE-g-IA or POE-g-MA

This study investigates the influence of two functionalized polyethylene-1-octene elastomers (POEs), POE grafted itaconic acid (POE-g-IA) and POE grafted maleic anhydride (POE-g-MA), on mechanical and barrier properties of a novel nanocomposite. The composition was prepared from linear low-density polyethylene (LLDPE), thermoplastic starch (TPS), and organo-modified clay using the melt blending method. Characterization of the functionalized POEs and nanocomposites was performed using attenuated total reflection- Fourier transform infrared (ATR-FTIR) spectrophotometer, X-ray diffraction (XRD), transmission electron microscopy (TEM), field emission scanning electron microscopy (FE-SEM), mechanical, and barrier analysis. The ATR-FTIR spectrums confirmed the grafting of POE with itaconic acid and maleic anhydride. It was observed that the adding of compatibilizers have different effects on morphological, mechanical, and barrier properties of the nanocomposite. The d-spacing of the clay platelets was increased by 20 % and 15 % with POE-g-IA and POE-g-MA incorporation, respectively. The functionalized POEs improved the interfacial adhesion between starch and LLDPE. However, POE-g-IA showed better performance compared to POE-g-MA. Better dispersion of clay particles with POE-g-IA and profitable interaction of starch and LLDPE matrix improves mechanical properties. Besides, the oxygen gas permeability and diffusion coefficient from POE-g-IA contained nanocomposite decreased by 14 % and 22 %, respectively, compared with the other functionalized POE, due to the better dispersion of nanoclay.

Enhanced Corrosion Protection of A-36 Steel Using Epoxy-Reinforced CSA-Doped Polyaniline-SnO2 Nanocomposite Smart Coatings

Reinforced epoxy polymer nanocomposites have been employed as anti-corrosion coatings on various metallic substrates due to their beneficial characteristics and high electrochemical performances. In this work, we explore the anti-corrosion behavior of reinforced epoxy (EP) polymer nanocomposite consists of polyaniline (PANI)-tin oxide (SnO2) doped with camphor sulfonic acid (CSA). PANI-SnO2 nanocomposites doped with CSA were prepared by in situ chemical oxidative polymerization of aniline in the presence of SnO2 nanoparticles. The morphological and structural features of the prepared nanocomposites were investigated through scanning electron microcopy (SEM), Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD). Further, the coatings of these PANI:SnO2 nanocomposites with epoxy were employed on A-36 steel (carbon steel) substrates to investigate their corrosion protection behavior. The effect of SnO2 presence in the composite towards enhancing the corrosion protection was discussed through the Tafel polarization, polarization resistance, and electrochemical impedance spectroscopy (EIS) as well as oxygen gas permeability studies. Successful formation of potential barriers and their corrosion inhibition abilities were discussed. The EP:PANI:SnO2 composite coatings demonstrate an excellent corrosion inhibition efficiency of 98% in comparison to neat epoxy (43%). The investigation on mechanical properties of these coatings indicates improved adhesion, Young’s modulus, and tensile strength due to the presence of SnO2 nanoparticles. Owing to their enhanced conductivity, superior electrochemical performance and excellent mechanical properties, these EP:PANI:SnO2 nanocomposite coatings could form smart anti-corrosion formulations in protecting A-36 steel against harsh environments.

Preparation, characterization and antimicrobial activity of betel-leaf-extract-doped polysaccharide blend films

Incorporation of betel leaf extract (BE) into chitosan and chitosan/vanillin (CH/Vn) blend films was carried out in order to improve the mechanical, thermal and antimicrobial properties of chitosan films. The influence of morphology, crystallinity and glass transition temperature (T g) on the mechanical properties of chitosan/betel leaf extract (CH/BE) and chitosan/vanillin/betel leaf extract (CH/Vn/BE) films was analyzed. The smooth homogeneous morphology, decreased crystallinity and shift of T g to a higher value resulted in improved mechanical properties. Scanning electron microscopy, atomic force microscopy, X-ray diffraction, differential scanning calorimetry, thermogravimetric analysis and Fourier transform infrared studies indicated that inclusion of BE into CH/Vn led to enhanced physicochemical properties. The results of antimicrobial activity, oxygen gas permeability and contact angle measurements confirmed the significantly improved activity and hydrophilic nature of the blend films compared with those of pure chitosan. The authors confirmed that the plant-extract-doped polymer material can be a novel antimicrobial agent for food-packaging application. Addition of BE at a higher weight percentage is a major limitation that has a major influence on the properties of the blend films.

Tuning the properties of regenerated cellulose: Effects of polarity and water solubility of the coagulation medium

In this study, the effect of different alcohols and esters as a coagulation medium in the regeneration of cellulose dissolved in an aqueous LiOH-urea-based solvent was thoroughly investigated using various methods such as solid state NMR, X-ray diffraction, water contact angle, oxygen gas permeability, mechanical testing, and scanning electron microscopy. It was observed that several material properties of the regenerated cellulose films follow trends that correlate to the degree of cellulose II crystallinity, which is determined to be set by the miscibility of the coagulant medium (nonsolvent) and the aqueous alkali cellulose solvent rather than the nonsolvents’ polarity. This article provides an insight, thus creating a possibility to carefully tune and control the cellulose material properties when tailor-made for different applications. [Display omitted] [Display omitted]

Property Investigation of Poly (Ethylene Co-vinyl Acetate)/Poly (l-Lactic Acid)/Organo Clay Nanocomposites

In this study, EVAc/PLA/organo clay nanocomposites were prepared via solution mixing method. The SEM images were used to investigate the morphology of nanocomposites revealing no phase separation or agglomeration of disperse phase in EVAc/PLA blends and nanocomposites. SAXS spectra confirmed the intercalated morphology of nanocomposites. Soil burial test were carried out and the rate of degradation of the samples were measured indirectly. Oxygen gas permeability of EVAc was slightly decreased by adding PLA to the matrix, when small loads of clay caused dramatic improvement in barrier properties. Melt rheological frequency sweep test illustrated the compatibility of EVAc with low contents of PLA. Tensile test cleared that increasing PLA’s content and clay’s load in EVAc results in increase in tensile strength and modulus of the composite.

High oxygen permeable Zeolite‐4A poly(dimethylsiloxane) membrane for air separation

ABSTRACTHigh oxygen permeability with optimal selectivity of the membrane is required for advancement in air separation membrane technology. Zeolite 4A‐PDMS composite membranes were prepared by incorporation of Zeolite 4A nanoscale crystals during the polymerization process of PDMS membrane using toluene andn‐heptane solvents, and their oxygen gas permeability and selectivity were explored. Small angle neutron scattering (SANS) technique was further used to study the polymer chain conformation and structure of membranes influenced by Zeolite 4A loading. The intersegmental distance between polymer chains and polymer chain aggregation or clustering were found to be increased on increasing the Zeolite 4A content in the membranes. Increment in the O2permeability and O2/N2selectivity were observed for both type of membranes (toluene andn‐heptane) with 1 wt% Zeolite 4A loading. The best performance result with O2/N2selectivity of 2.6, and O2permeability of 1052 Barrer was exhibited by PDMS/toluene membrane loaded with 1 wt% Zeolite 4A. The PDMS/toluene membranes with 10 wt% Zeolite 4A loading exhibited increased O2permeability of 1245 Barrer with a fair O2/N2selectivity of ~1.7, while the PDMS/n‐heptane membrane with the same loading exhibited excellent O2permeability of 6773 Barrer but lesser O2/N2selectivity of ~1.2. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci.2019,136, 48047.

Studies on the mechanical, barrier, optical, and characterization of photo-/biodegradable LDPE-PLA blend with nanoclay for packaging film application

LDPE-poly-lactic acid (PLA) (60:40%) was melt blended with nanoclay (1, 2, and 3%) and benzophenone (3%) using maleic anhydride-grafted LLDPE (LLDPE- g-MAn; 3%) as compatibilizer in a twin screw compounding extruder. Tubular blown films extruded using Dr Collins blown film extruder were subjected to various mechanical tests like tensile strength, elongation at break, and so on, optical tests, and permeability tests for oxygen and water vapor. The tensile strength was increased as the nanoclay percentage was increased (upto 2 wt%) and the elongation at break was decreased. Tear strength was increased, burst strength was decreased, and the dart impact strength was constant. The coefficient of friction was little decreased. The haze was increased and luminous transmittance was decreased. Water vapor transmittance and oxygen gas permeability were decreased. Scanning electron microscope images were taken to determine the morphological changes on the samples. Characterization by X-ray diffraction was carried out to analyze the shift in peak when nanoclay was blended at various proportions. In conclusion, LDPE with benzophenone is photodegradable and PLA is biodegradable. Hence, in this study, LDPE-PLA (60:40%) with benzophenone (3%) is photo-/biodegradable. Inclusion of nanoclay increased the mechanical properties like tensile strength, tear strength, and barrier properties. Furthermore, nanoclay improves the compatibility apart from LLDPE- g-MAn.

Differently-charged graphene-based multilayer films by a layer-by-layer approach for oxygen gas barrier application

Polyelectrolyte-decorated graphene with positive and negative charges was prepared using graphene oxide as a precursor along with polyallylamine hydrochloride and poly (styrenesulfonate sodium) as surface modifiers, respectively. Driven by an electrostatic interaction, the as-obtained polyelectrolyte-decorated graphene sheets were self-assembled via a layer-by-layer method, producing graphene based composite multilayers. Field emission scanning electron microscopy (FE-SEM) images showed that the surface of composite film exhibited a mass of characteristic wrinkles of graphene. Interestingly, the cross-sectional FE-SEM of the film exhibited an unstratified structure, indicating a good dispersion of graphene sheets in the composite film. The results of oxygen gas permeability testing demonstrated that the resulting composite films exhibited excellent oxygen gas barrier properties. The oxygen gas transmission rate (OTR) of the composite film with 24 bilayers was as low as 1.2 cm3 m-2 d-1∙atm−1, exhibiting potential for use in packaging applications.

Structural interaction and gas barrier properties of ethylene‐vinyl alcohol/tin phosphate glass composites

ABSTRACTThe strength of interaction between tin phosphate glass (PGlass) filler droplets and an ethylene‐vinyl alcohol (EVOH) matrix were investigated by image, thermal, and rheological analysis. 10% PGlass droplets in EVOH were smaller than those previously observed in maleated polypropylene. Analysis using the Fox equation showed that EVOH/97 °C Tg PGlass composites are not miscible systems. Dynamic shear and extensional rheology data of those composites exhibited a weak physical network, with relaxation times longer than that of pure EVOH at all strain rates. The tensile properties of the EVOH/10 vol % PGlass composite showed it to be more ductile and flexible than a typical polymer/inorganic filler system, supporting interaction between PGlass and EVOH sufficient to interrupt polymer–polymer hydrogen bonding. While undrawn EVOH/PGlass composite films showed increased oxygen gas permeability when compared to undrawn neat EVOH film, the drawn composite films exhibited oxygen permeability 6–7 times lower than that of neat EVOH, attributed to the presence of high aspect ratio PGlass particles after orientation. The concept of hydrogen bonding between polymer and PGlass can likely be applied to other polymers such as polyamides which possess numerous hydrogen bonding sites. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018, 56, 989–998

Facile and cost-effective preparation of PVA/modified calcium carbonate nanocomposites via ultrasonic irradiation: Application in adsorption of heavy metal and oxygen permeation property

This work is focused on the fabrication and determination of physicochemical behaviors of new poly(vinyl alcohol) (PVA) nanocomposites (NCs) containing various contents of calcium carbonate (CC) nanoparticles modified with γ-aminopropyl triethoxy silane (ATS) (henceforth designated as CC-ATS) which could be a crucial treatment for their application as gas barrier to O2 gas and uptake of metal ions in waste waters. Samples were produced through the solution casting method under ultrasound irradiation. Thermal and mechanical performances were also evaluated for all ultrasonically synthesized nanocomposites and the results indicated that thermal and mechanical stability are dramatically enhanced by addition of a small amount of modified CC-ATS within PVA up to 5wt% and higher amounts has low effect on the composite properties. The result of oxygen gas permeability of PVA showed a 25.44% reduction by adding of 5wt% of CC-ATS into polymer matrix. Experimental adsorption isotherm data indicated that PVA NC has more efficiency for Cu(II) adsorption relative to pure PVA and well simulated by Langmuir model with maximum adsorption capacity of 45.45mgg−1. Moreover, study of sorption kinetic indicated that the solute adsorption on PVA/CC-ATS NC 5wt% was well modeled using the pseudo-second-order.

Effects of clay platelets and natural nanotubes on mechanical properties and gas permeability of Poly (lactic acid) nanocomposites

Environmental concerns have resulted in the increased use of biodegradable polymers and their nanocomposites. We have developed a facile method for measuring the work of adhesion (Wa) between nanoparticles and their matrix, which we showed can be used to determine their degree of intercalation within the matrix. This method was then applied to Poly (lactic acid) (PLA) nanocomposites with either sodium montmorillonite clays (C-Na+), organically modified clays (C-30B), resorcinol di (phenyl phosphate) (RDP) coated C-Na+ (C-RDP), Halloysite nanotubes (HNTs) and RDP coated HNTs (H-RDP). The C-30B showed the highest Wa within the PLA matrix, followed by the C-RDP and the C-Na+. X-ray diffraction and TEM indicated that the C-30B platelets were highly exfoliated, the C-RDP were intercalated, while the C-Na+ were aggregated in the PLA matrix. Oxygen gas permeability measurements showed the largest decrease in permeability for the C-30B nanocomposites, followed by the C-RDP, and the C-Na+ nanocomposites. The values of the particle aspect ratios obtained using Nielsen model were consistent with the TEM images. In contrast to clay platelets, HNTs and H-RDP were not effective in decreasing oxygen gas permeability of PLA matrix, which was in excellent agreement with the model we derived. Despite the higher degree of exfoliation, the C-30B nanocomposites had a significantly lower Izod impact than the C-RDP nanocomposites. SEM images showed numerous micro-voids on the Izod impact fracture surface of C-30B nanocomposites. On the other hand, the nanotubes were much more effective in reinforcing the mechanical properties, with RDP coated tubes having the better performance, consistent with their higher value of Wa with PLA matrix. These results showed that RDP coated silicate nanoparticles can provide environmentally safe alternatives for modifying the mechanical and gas barrier properties of PLA.

Evaluation of the Thickness and Oxygen Transmission Rate before and after Thermoforming Mono- and Multi-layer Sheets into Trays with Variable Depth

During thermoforming, plastic sheets are heated and subsequently deformed through the application of mechanical stretching and/or pressure. This process directly impacts sheet properties such as material thickness in walls, corners, and bottom, crystallinity in the constituent layers, and particularly the oxygen gas permeability. The aim of this study was to quantify the impact of thermoforming on thickness and oxygen transmission rate (OTR) of selected packaging materials (polypropylene (PP); PP/ethylene-vinyl alcohol co-polymer/PP (PP/EVOH/PP); polystyrene/EVOH/polyethylene (PS/EVOH/PE); amorphous polyethylene terephtalate/PE (APET/PE); APET/PE/EVOH/PE; polyamide/PE (PA/PE); and (PE/)PA/EVOH/PA/PE). These materials were extruded in two different thicknesses and thermoformed into trays with the same top dimensions and variable depths of 25, 50, and/or 75 mm and a 50 mm tray with a variable radius of the corners. The distribution of the material thickness in the trays was visualized, showing the locations that were most affected by the deep drawn process. The OTR results indicate that the calculated OTR, based on a homogeneous material distribution, can be used as a rough approximation of the measured OTR. However, detailed analysis of crystallization and unequal thinning, which is also related to the tray design, remains necessary to explain the deviation of the measured OTR as compared to the predicted one.

The structure-property relationships of LLDPE–EVOH blend films fabricated by multiplication extrusion

The blend of linear low density polyethylene (LLDPE) and ethylene vinyl alcohol (EVOH) with weight fraction of 50–50 is extruded through a series of multipliers to fabricate thin films. Different numbers of multipliers are utilized to tailor the morphology of the extruded blend films. We discover that as the number of multipliers increases, the blend film morphology evolves dramatically. The elongated and layer-like structure is gradually replaced by well-dispersed nano-blend morphology when the number of multipliers reaches eight. The domain size of each component decreases due to the effect of multiplication process. This is because during the multiplication process, multipliers behave similar to static mixers that physically break the elongated and layer-like structure of LLDPE and EVOH into tiny domains. Along with the morphological evolution, the physical properties of the extruded blend films change greatly. Atomic force microscopy (AFM) and wide angle X-ray scattering (WAXS) are utilized to investigate the morphology and crystalline structure of the blend films. Oxygen gas permeability and water vapor transport rate (WVTR) are measured by MOCON units. The transmission rate and mechanical properties are studied by the UV–vis and a mechanical tensile stretcher (MTS) respectively. We report that both oxygen permeability and WVTR increase as the number of multipliers increases. The transparency is improved as more multipliers are used. The last but not the least, tensile mechanical behaviors gradually become isotropic at different deformation directions as the morphology changes.

Oxygen Diffusion and Dissolution Rates in Sulfonated Polyetheretherketone Copolymer Thin Film Electrolyte Formed on Pt Microelectrode

Introduction Proton exchange membrane fuel cells (PEMFCs) are promising alternative devices for electrochemical energy transformers. In the PEMFCs, electrolyte materials are one of the key components. So far, perfluorinated sulfonic acid (PFSA) membranes, such as Nafion®(DuPont), have been used as the electrolyte membrane in the PEMFCs. Recently, sulfonated polyetheretherketone copolymers (SPEEK, Fig. 1) have been synthesized as low-cost and high-temperature-resistant alternative polymer electrolyte membranes [1], and the SPEEK copolymers exhibited high proton conductivity and excellent thermal stability.Oxygen gas permeability is an important property for the electrolyte. For example, it is widely recognized that oxygen gas crossover from the cathode to the anode through the electrolyte membrane leads to membrane degradation [2, 3]. In contrast, high oxygen gas permeability is required for ionomer which is added in the catalyst layer and cover Pt NP catalysts, influencing the PEMFCs performance. In this study, oxygen transport across the SPEEK thin film electrolyte was investigated. We used a Pt microelectrode (ME) covered with recast SPEEK thin film electrolyte. Oxygen diffusion and oxygen dissolution rates were determined from the limiting currents across the films of different thicknesses. The rate dependence on temperature was investigated to understand the mechanism for the gas transport across the SPEEK thin film electrolyte. Experimental Pt ME (100 μmφ) working electrode (W.E.) and Pt ME (250 μmφ) counter electrode (C.E.) were sealed in a glass rod (8 mmφ). A dynamic hydrogen electrode (DHE) consisting of two Pt MEs (250 μmφ) was used as a reference electrode (Fig. 2). SPEEK was dissolved in N,N-dimethyl-formamide (DMF) and casted onto the glass rod surface, followed by heat treatment at 120°C for 3 h in air. The resultant rod was soaked in 0.5 M H2SO4at room temperature for 24 h and repeatedly washed by DI water. The thickness of the SPEEK thin film electrolyte formed on the Pt ME W.E. was measured by contacting surface profile meter.The rod was set up in a solid-state electrochemical cell placed in temperature-humidity-controllable chamber. Cyclic voltammograms (CVs) were measured in the chamber under atmospheric pressure. Oxygen transport parameters, DCeq/d and kCeq , were determined from the limiting current (I lim) for oxygen reduction reaction (ORR) on the Pt ME W.E. using eq. (1) [3], where F is the Faraday constant (96485 C/mol), kCeq is the oxygen dissolution rate (mol/cm2/s), d is the thickness (cm) and DCeq is the oxygen permeability (mol/cm/s), respectively. Results and discussion Figure 3 shows CVs of Pt ME W.E. covered with SPEEK thin film electrolyte of 1.13 μm in thickness at different temperatures (R.H. 80 %). Characteristic Pt redox waves were clearly observed, indicating a sufficient interface contact between the W.E. and the SPEEK thin film electrolyte. The I limfor the ORR increased with an increase in temperature.The oxygen diffusion rate (DCeq/d) and the oxygen dissolution rate (kCeq ) were determined from I lim at various SPEEK thicknesses using eq. (1). Figure 4 summarizes DCeq/d and kC eq at different temperatures (80 %R.H). Here, the ionomer thickness d of 1.13 μm, which was the thinnest film in this work, was used for adjusting unit of DCeq in mol/cm2/s (y axis in Fig. 4). Both the oxygen diffusion and the oxygen dissolution rates increased with increase in temperature, however, the oxygen dissolution rates (kCeq ) were lower than the oxygen diffusion rates (DCeq/d) in the temperature range tested (40-80°C). Similar results on recast Nafion®thin film electrolyte have been reported by us [4]. Therefore, it could be concluded that the oxygen dissolution rate at the air/ionomer interface is the rate-determining step for the oxygen transport across the ionomer thin film formed the Pt catalyst. It is considered that increase in the oxygen dissolution rate is crucial for the enhancement of the cathode performance at high current densities in PEMFCs.

Measurement of Oxygen Gas Transport Resistance in Cathode Catalyst Layers of PEFC

Introduction Polymer electrolyte fuel cells (PEFCs) are a promising power sources for automotive use. For the commercialization, cost reduction is one of the most important issues. In order to reduce cost, the Pt-loading of a membrane electrode assembly (MAE) should be reduced. Many studies for this purpose have been done. As a part of such studies, in-situ analytical methods for evaluating oxygen transport properties have been developed using limiting current measurements1)2). It is said that oxygen gas transport resistance in catalyst layers CLs (RCL) is mainly consisted of two parts, diffusion resistance in micro pore (Rpore) and diffusion resistance around Pt particles (RPt). And it has been found that the diffusion resistance RCL was significantly increased when Pt loading in CLs was reduced2). In this study, the oxygen diffusion resistances in CLs of two types of Pt/carbon catalysts with different kind of carbon support are measured by changing the ionomer carbon ratio (I/C) and the relation between I/C and RPt, Rporewas investigated. Experimental Table 1 shows the specifications of the MEAs used in this study. The MEA samples with an active area of 1cm2 were fabricated by coating CLs consisting of catalysis powders (Pt/C) and NafionR ionomer onto the perfluorosulfonated polymer membrane (NafionR NR212). Pt-loadings of the samples for the working electrode were 0.05 -0.6 mg cm-2 respectively. In order to evaluate the oxygen gas transport resistance in the CLs, limiting currents were measured in nitrogen balance gases. RCL was measured by the method of Mashio et al1). Rpore and RPt were determined by the method we described before3). Results and discussions In order to estimate Rpore and RPt, an Equation (1) was introduced with the analogy of porous electrode model and value was determined from RCL with different I/C. A imaginary limiting current inversely proportional to RCL was also introduced (eq.(2)). In Fig.1, each dot shows measured RCL, full line shows the calculation curves of RCL with eq.(1) and dotted line shows imaginary limiting current calculated by the eq.(2) with using the obtained values of Rpt and Rpore. Table2 shows Rpt and Rporevalues obtained. Rpore increased very much at I/C was 1.3 for both catalysts.Thisseems to because oftheclosure or isoration of pore by ionomer.RPtshows minimum values at some I/C whichdepend on catalyst types.From this result,RPt seems to be affected with the state of three-phase interface4)and oxygen gas permeability through ionomer. Acknowledgement This research was performed under a grant from the Cell Evaluation Project of the New Energy and Industrial Technology Development Organization (NEDO). References T.Mashio, A.Ohma, S.Yamamoto and K.Shinohara, ECS Transactions, 11(1) 529 (2007).K.Sakai, K.Sato, T.Mashio, A.Ohma, K.Yamaguchi and K.Shinohara, ECS Transactions, 25(1) 1193 (2009).H.Yasuda, K.Kobayashi, A.Daimaru and M.Hori., ECS Transactions, 50(2) 261 (2012)M. Lee, M. Uchida, H. Yano, D.A. Tryk, H. Uchida and M.Watanabe, Elecrochim. Acta 55 8504 (2010) Table 1 MEA specificationCounter ElectrodeWorking ElectrodeCatalystPt/C (CB) (TEC10E50E, TKK)Pt/C (GCB) (TEC10EA50E, TKK)IonomerNafionR (D2020, Dupont)Pt loading /mgcm-2 0.05 – 0.6Ionomer Carbon Ratio (I/C)0.4 – 1.3 Active Area /cm2 1.0MembraneNafionR (NR212, Dupont)GDLTGP H060, Toray (without MPL) Table 2 RPt and Rpore with different I/CI/CTEC10E50ETEC10EA50ERPt Rpore RPt Rpore 0.44.3194.3100.5--2.8290.73.5134.0121.02.8464.87.81.33.5885.269

Long-Term Physical Stability of Plasticized Hemicellulose Films

Oat spelt arabinoxylan (OsAX) and spruce galactoglucomannan (GGM) are hemicelluloses that can be extracted in large quantities from side-streams of the agriculture and forest industries. They both form self-standing films, making them potential future packaging materials. This systematic study focuses on the effect of long-term storage on the physical stability of hemicellulose-based films. OsAX and GGM films were plasticized with 40% (w/w of the polysaccharide) of glycerol, sorbitol, or their blends, and their stability was followed for four months. Ageing especially affected the glycerol-containing films, in which the tensile strength and Young’s modulus increased and elongation at break decreased. Although the mechanical properties were altered, storage did not affect crystallinity of the films. Oxygen gas permeability (OP) and water vapor permeability (WVP) properties were monitored in OsAX films. Interestingly WVP decreased during storage; more than a 40% decrease was seen when plasticizer blends contained 50% or more glycerol. In contrast, there were no drastic changes in the OP during storage; all the OPs obtained were between 3.7 and 8.9 [cm3 µm/ (m2 d kPa)].

Perfluorocyclobutane and poly(vinylidene fluoride) blend membranes for fuel cells

Polymer electrolytes based on block copolymers are considered promising proton exchange membrane (PEM) materials for fuel cell applications. A new class of block copolymers of perfluorocyclobutane (PFCB) units with pendant side chains containing sulfonic acid groups have recently been developed and studied for fuel cell applications. In order to enhance the membrane mechanical and hydrothermal stability, sulfonated PFCB copolymers are blended with fluoropolymers such as poly(vinylidene fluoride) (PVDF). Membrane fundamental properties (e.g., proton conductivity, gas permeability, water uptake) and fuel cell performance and durability were evaluated as a function of PVDF content. The proton conductivity and fuel cell performance only decrease slightly with PVDF content at PVDF blend levels of up to 30wt.%. However, at the PVDF levels higher than 40wt.%, the proton conductivity and fuel cell performance decrease rapidly with increasing PVDF content. The PFCB/PVDF composite membranes have lower hydrogen, oxygen and nitrogen gas permeability as well as a higher ratio of conductivity to permeability than perfluorosulfonic acid PFSA membranes (e.g., Nafion®). Membrane hydrothermal swelling is significantly reduced by blending sulfonated PFCB with PVDF. This reduced swelling leads to improved membrane mechanical durability as measured by increased lifetimes in RH cycling tests with increasing PVDF content.

Organosilicon Coatings Deposited in Atmospheric Pressure Townsend Discharge for Gas Barrier Purpose: Effect of Substrate Temperature on Structure and Properties

Organosilicon plasma polymer and silicalike layers are deposited at different temperatures in a dielectric barrier discharge at atmospheric pressure operating in the Townsend regime. Final properties of these two kinds of layers can be finely tuned by the plasma process conditions. In particular, influence of deposition temperature is investigated when hexamethyldisiloxane based monolayers are deposited on poly(ethylene naphtalate) substrate. Coating chemical structure is tested by means of Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. Their thickness, topography, and mechanical properties are evaluated by ellipsometry, scanning electron microscopy observation of coatings cross sections, atomic force microscopy, and nanoscratch testing. Permeability of coated polymer is measured for transparent silicalike layers, and the effect of coating structure on the oxygen gas permeability is discussed. The deposition temperature of coatings at 90 °C provides a strong improvement in barrier property compared to room temperature deposition, thanks to a densification of the SiO₂ matrix and to a decrease in the silanol group content.

Improving the oxygen barrier properties of polyethylene terephthalate by graphite nanoplatelets

AbstractEnhancement of the oxygen gas barrier properties of polyethylene terephthalate (PET), used in the packaging industry, is the main objective here. For this purpose, nanocomposites of PET containing graphite nanoplatelets (GNPs) were prepared by melt compounding. The effects of the nanocomposites' structural morphology on oxygen gas permeability were analyzed using a range of thermal, microscopic, and mechanical characterization techniques. The investigated nanocomposite films exhibited GNP exfoliated morphology and good mixing with PET, as well as uniform dispersion within the polymer. All nanocomposite films were shown to possess superior oxygen barrier properties and improved thermal and dimensional stability compared with the plain PET films. In the best case, for 1.5 wt % GNP, the oxygen permeation was reduced by more than 99%. The improved barrier properties are attributed to the direct effect of the GNPs and to their induced increase of degree of crystallinity. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013