Water vapor permeability properties of edible whey protein-lipid emulsion films

The water vapor permeability (WVP) of whey protein emulsion films was investigated. The exponential effect of relative humidity on the WVP of whey protein films was reduced through lipid incorporation. Film orientation had a significant effect on WVP due to emulsion separation during film formation. Heat denaturation of whey proteins lowered emulsion film WVP. Increasing fatty acid and fatty alcohol chainlengths significantly reduced WVP, as did increasing lipid concentration. The WVPs of fatty acids, fatty alcohols and beeswax were compared in whey protein-lipid emulsion films. Scanning and transmission electron microscopy revealed the crystalline microstructure of lipid particles in emulsion films.     

Modeling oxygen permeability through topcoat and thermally grown oxide in dense Yb2Si2O7 environmental barrier coatings

The oxygen permeability of ytterbium disilicate (YbDS) topcoat (TC) and silicon dioxide (SiO₂) thermally grown oxide (TGO) is evaluated. The primary goal is to elucidate the oxidation mechanisms in environmental barrier coatings (EBCs). For this purpose, oxidant diffusion is investigated using physics-based and numerical modeling. The oxygen permeability constants are systematically evaluated and quantified in terms of thermodynamics using defect reactions and the parabolic rate constant (kp), respectively. Dry oxygen and wet oxygen conditions as well as different temperatures, partial pressures, and topcoat modifiers are investigated. The results offer evidence that the oxygen permeability constant for the YbDS topcoat is an order of magnitude higher than for the TGO. As such, the TGO hinders the oxidant diffusion stronger, proving to be the diffusion rate-controlling layer. Moreover, water vapor strongly increases the oxidant permeation with defect reactions playing a key role. It is suggested that the mass transfer through the topcoat is primarily by outward ytterbium ion diffusion and inward oxygen ion movement, with the latter being dominant, particularly in wet environments. The effect of topcoat modifiers on oxidant permeation is composition sensitive and seems to be related to their interaction with oxygen ions and their mobility.     

Amorphous hydrogenated carbon films as barrier for gas permeation through polymer films

The influence of amorphous hydrogenated carbon (a-C:H) coatings on the gas permeation through polymer films was investigated. a-C:H films were deposited from a 13.56-MHz RF glow discharge in methane or acetylene atmosphere. Thin poly(ethylene terephthalate) and polyimide foils were used as substrates. The permeation of the gases H₂, N₂, O₂ and CO₂ was measured and the reduction of the permeability coefficient was correlated to composition and density of the a-C:H films. The stoichiometry of the layers was analyzed using ion-beam techniques on films deposited onto silicon samples. The a-C:H/PET surfaces were analyzed using optical microscopy and atomic force microscopy (AFM). Multilayer structures comprising different types of a-C:H films were also investigated. A reduction of the permeability coefficient by 80% for hard, dense and 94% for soft, polymer-like layers was found. Surprisingly, the barrier efficacy of the coating decreases with increasing a-C:H film density. This unexpected result is attributed to the appearance of a network of deep cracks spread out over the whole coating.     

Thiol‐ene/clay nanocomposite thin film as novel transparent barrier

Thiol‐ene/clay (TE/clay) nanocomposite thin films were prepared by a simple photocuring process for use as transparent barrier films. In this work, tetrafunctional thiol and triene monomer were employed and organic clay surface modified with octadecylamine was mixed by sonication and a mechanical method as a reinforcing filler. The successful formation of the TE structure was confirmed by differential scanning calorimetry and X‐ray diffraction. The homogeneous dispersion (intercalation and exfoliation) of clay into the TE polymer matrix was observed with transmission electron microscopy. Atomic force microscopy images displayed the surface properties of the TE/clay nanocomposite thin films. The thermal expansion behavior of the resulting hybrid film was monitored by thermomechanical analysis. In addition, gas permeation properties as well as light transmittance of the TE/clay films were measured for potential applications in various fields as dimensionally stable films under heating and as a transparent barrier. Copyright © 2012 Society of Chemical Industry     

Thermal,mechanical, and gas barrier properties of ethylene–vinyl alcohol copolymer‐based nanocomposites for food packaging films: Effects of nanoclay loading

For the application of single‐layer food packaging films with improved barrier properties, an attempt was made to prepare ethylene‐vinyl alcohol (EVOH) copolymer‐based nanocomposite films by incorporation of organically modified montmorillonite nanoclays via a two‐step mixing process and solvent cast method. The highly intercalated tactoids coexisted with exfoliated clay nanosheets, and the extent of intercalation and exfoliation depended significantly on the level of clay loadings, which were confirmed from both XRD measurements and TEM observations. It was revealed that the inclusion of nanoclay up to an appropriate level of content resulted in a remarkable enhancement in the thermal, mechanical (tensile strength/modulus), optical, and barrier properties of the prepared EVOH/clay nanocomposite films. However, excess clay loadings gave rise to a reduction in the tensile properties (strength/modulus/elongation) and optical transparency due to the formation of clay tactoids with a larger domain size. With the addition of only 3 wt % clay, the oxygen and water vapor barrier performances of the nanocomposite films were substantially improved by 59 and 90%, respectively, compared to the performances of the neat EVOH film. In addition, the presence of clay nanosheets in the EVOH matrix was found to significantly suppress the moisture‐derived deterioration in the oxygen barrier performance, implying the feasibility of applying the nanocomposite films to single‐layer food packaging films. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40289.     

Permeation of oxygen and water vapor through EVOH films as influenced by relative humidity

The transport properties of oxygen and water vapor through EVOH films as functions of relative humidity (RH) and temperature were studied. The results of oxygen and water vapor permeation demonstrated that temperature and RH markedly affected barrier properties of these films. In general, the EVOH films had minimal oxygen and water vapor permeabilities at a low RH, attributed to the reduced mobility of the polymer resulting from strong interactions between small water molecules and the polymeric matrix at low RH. Beyond 75% RH, the permeabilities increased considerably. In addition, the barrier performance of the EVOH films was found to be dependent on their ethylene content and orientation. From the experimental data, semiempirical equations describing oxygen transmission rates (O₂TR) as functions of RH and temperature were developed. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 1866–1872, 2001     

Influence of counter-ions on the permeability of polypyrrole films to hydrogen

The influence of the size and nature of counter-ions on the permeability of polypyrrole films to hydrogen was tested. The permeabilities were determined using the method of limiting currents on a Pt rotating disc electrode with subsequent Koutecky-Levich analysis. The work has focused mainly on the influence of the anion size, but the effect of polymeric anion hydrophilicity was also considered. Attention was especially paid to Nafion^® as a counter-ion. It was found that Nafion^® markedly increases polypyrrole permeability. The film growth was followed by means of EQCN, which allowed determination of the polypyrrole film densities. ^†ISE member     

Nanocomposites‐based polyolefins as alternative to improve barrier properties

This work investigates the influence of some ammonium quaternary compounds as coupling agent in polyethylene/clay nanocomposites to improve the performance of polyethylene used as packaging barrier material. The 3 wt % of vermiculite used as a nanofiller was added to linear low‐density polyethylene (LLDPE) and to linear low‐density polyethylene grafted with maleic anhydride (LLDPE‐g‐MA). The analysis results revealed that the influence of both the clay exfoliation in a polymer matrix and the coupling agents on the barrier properties were significant. Among the coupling agents used, cetylpropyldimethylammonium chloride yielded the best result for vermiculite exfoliation. A reduction of up to 18% in the oxygen‐permeability coefficient was observed in the nanocompounds with exfoliated vermiculite. The nanocomposite produced with vermiculite did not prove to be efficient as a moisture barrier against according to the analysis performed. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Responses of 6FDA-based polyimide thin membranes to CO2 exposure and physical aging as monitored by gas permeability

Membranes made from glassy polymers have been of great interest in the past decade for CO₂ removal from natural gas streams; however, strongly soluble gases, such as CO₂, can cause “plasticization” of polymer membranes, which greatly reduces the separation efficiency. This work examines the response of several 6FDA-based polyimides thin film membranes with thicknesses around 200 nm to CO₂ exposure and physical aging. DABA units are incorporated to create crosslinkable sites for such materials. Introducing DABA units to the 6FDA-DAM and 6FDA-mPDA polymers seems to result in materials even more prone to CO₂ plasticization. A unique thermal annealing approach is used to crosslink the polyimides via decarboxylation of the DABA units; the resulting crosslinked polymers appear to be much more plasticization resistant at high CO₂ pressures compared to their DABA containing counterparts prior to crosslinking. Prior thermal history plays a significant role in both the physical aging of the thin film membranes and their CO₂ plasticization resistance particularly for chemical structures that tend to lead to high free volume and permeability.     

Nano boron nitride laminated poly(ethyl methacrylate)/poly(vinyl alcohol) composite films imprinted with silver nanoparticles as gas barrier and bacteria resistant packaging materials

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.     

Adhesion of diamond-like carbon films on polymers: an assessment of the validity of the scratch test technique applied to flexible substrates

The validity of the scratch test as a method of assessing the adhesion of diamond-like carbon (DLC) on polymers has been studied. Sheets of 12 μm thick polyethylene terephthalate (PET) and 100 μm thick polypropylene (PP) were adhesively bonded to glass slides in order to perform the scratch tests. The critical load is defined as the load at which tensile cracks occur in the coating homogeneously throughout the scratch. It is shown that the type and the thickness of the adhesive used have an influence on the critical load value. However, the calculated values of the interfacial shear strength do not depend on the adhesive thickness, and qualitative results in agreement with the literature have thus been obtained. The influence of a nitrogen plasma pretreatment on the adhesion of DLC films on PET and PP has been determined by both scratch test and tensile test techniques. The results follow the same trend and show that the scratch test technique is a good tool for semi-quantitative comparisons.     

Sol–gel derived CeO2/α‐Al2O3 bilayer thin film as an anti‐coking barrier and its catalytic coke oxidation performance

A CeO₂/α‐Al₂O₃ bilayer was coated on a high temperature alloy (Incoloy 800H) by sol–gel dip‐coating and was evaluated for its potential as an anticoking barrier and coke oxidation catalyst. The bilayer effectively functioned as a barrier to metal surface catalyzed coking. The film prevented filamentous catalytic coking via blocking surface active metallic sites on the Incoloy substrate. Furthermore, the bilayer reduced the oxidation temperature of pyrolytic coke deposited on the film surface as compared to a bare oxidized Incoloy substrate, mostly owing to the oxidation catalytic activity of the CeO₂ layer. Finally, it is demonstrated that the presence of the α‐Al₂O₃ buffer layer is critically important to the overall performance. Without the α‐Al₂O₃ layer, a CeO₂ layer nearly completely lost both its barrier and oxidation catalytic functions. It is presumed that metallic species migrating from the substrate during high temperature treatments are responsible for the CeO₂ deactivation, likely by blocking catalytic sites on the CeO₂ surface. © 2018 American Institute of Chemical Engineers AIChE J, 64: 4019–4026, 2018     

Lithium phosphorus oxynitride thin films for rechargeable lithium batteries: Applications from thin-film batteries as micro batteries to surface modification for large-scale batteries

This article reviews the technological trends in lithium-phosphorous-oxynitride (LiPON)-film-based thin-film batteries. LiPON films have been actively used in thin-film batteries containing lithium anodes because of their excellent contact stability with lithium and the advantages offered for thin-film formation. In addition, studies that have focused on the use of LiPON films as protective layers to prevent surface deterioration of electrode materials are explored. Various studies have been conducted using LiPON films to improve the performance degradation of rechargeable lithium batteries due to a side reaction between the electrode material and the electrolyte. Finally, the technical tasks required for enhancing the utilization of LiPON films in the field of thin-film batteries or electrode surface modification are summarized.     

Robust SiO2 gate dielectric thin films prepared through plasma-enhanced atomic layer deposition involving di-sopropylamino silane (DIPAS) and oxygen plasma: Application to amorphous oxide thin film transistors

DIPAS (di-isopropylamino silane, H₃Si[N(C₃H₇)₂]) and O₂ plasma were employed, using plasma-enhanced atomic layer deposition (PEALD), to deposit silicon oxide to function as the gate dielectric at low temperature, i.e., below 200 °C. The superior amorphous SiO₂ thin films were deposited through the self-limiting reactions of atomic layer deposition with a deposition rate of 0.135 nm/cycle between 125 and 200 °C. PEALD-based SiO₂ thin layer films were applied to amorphous oxide thin film transistors constructed from amorphous In-Ga-Zn-O (IGZO) oxide layers, which functioned as channel layers in the bottom-gated thin film transistor (TFT) structure, with the aim of fabricating transparent electronics. The SiO₂ gate dielectric exhibited the highest TFT performance through the fabrication of heavily doped n-type Si substrates, with a saturation mobility of 16.42 cm²/V·s, threshold voltage of 2.95 V and large on/off current ratio of 3.69 × 10⁸. Ultimately, the highly doped Si was combined with the ALD-based SiO₂ gate dielectric layers, leading to a saturation mobility of 16.42 cm²/V·s, threshold voltage of 2.95 V, S-slope of 0.1944, and on/off current ratio of 3.69 × 10⁸. Semi-transparent and transparent TFTs were fabricated and provided saturation mobilities of 22.18 and 24.29 cm²/V·s, threshold voltages of 4.18 and 2.17 V, S-slopes of 0.1944 and 0.1945, and on/off current ratios of 9.63 × 10⁸ and 1.03 × 10⁷, respectively.