Oxygen Permeability Coefficient Research Articles

The Effect of Fibrillation, Semi-Dry Pressing, and Surface Treatment on the Barrier Properties of Water Molecules and Oxygen on Food Packaging Paper

The characteristics of fiber morphology and paper structure are critical to the barrier properties of food packaging paper. Herein, this study aimed to use pulp fibrillation, paper semi-dry pressing and carboxymethyl starch (CMS) coating to flatten the fibers, which were formed on the paper surface with good barrier properties due to the tight bond between fibers. The results showed that the permeability of paper was reduced by 87.56%, from 81.44 μm/Pa·s to 10.13 μm/Pa·s after the pulp fibrillation treatment (60 °SR). Moreover, semi-dry pressing treatment contributed to decreasing the water vapor transmission coefficient (WVP) by 50.98% to 2.74 × 10−10 g/m·s·Pa, and the oxygen permeation coefficient (OP) decreased by 98.04% to 1.93 × 10−14 cm3·cm/cm2·s·Pa. After coating the paper surface with titanium dioxide (TiO2) and CMS, the WVP of the paper was further reduced to 1.55 × 10−10 g/m·s·Pa, and OP was reduced to 0.19 × 10−14 cm3·cm/cm2·s·Pa. These values were 72.27% and 99.8% lower than those of the original paper, respectively. Therefore, through pulp fibrillation, semi-dry pressing of paper, TiO2 filling, and surface coating with CMS, there is no need to use synthetic polymer surface film-forming agents to achieve the high barrier properties that are required for low water and oxygen molecules permeation in food packaging paper.

Development of high barrier poly(l-actic acid)/chitosan/graphene oxide flexible films for meat packaging by layer-by-layer

An new high-barrier packaging films for meat preservation were obtained by depositing graphene oxide (GO) layer-by-layer (LbL) on poly(l-lactic acid)(PLLA)-poly (butylene itaconate) (PBI) copolymers (PLBI) with chitosan (CS) as bonding layer in this study. The 1H NMR results revealed that PLBI copolymer was successful synthesized. The introduction of PBI reduced the Tg and crystallization capacity of PLLA film, which made the copolymer films exhibit extremely high flexibility (up to 186.1% elongation at break). The film also exhibited high hydrophilicity, which was favorable for the effective attachment of CS. With CS as an intermediate layer, the FTIR and SEM results showed that the GO was evenly distributed onto the PLBI film surface due to the electrostatic interaction. The oxygen, water vapor and UV light barrier properties of PLBI/CS/(GO-CS)x films were improved and increased with the GO-CS layers. The PLBI/CS/(GO-CS)10 films, with extremely low oxygen permeability coefficients about 0.4 × 10−8 cm3 m/m2·h·Pa, delayed the increase in weight loss, hardness, pH, TVB-N, TBARS, and total viable counts of chilled meat during storage. It also decreased the discoloration, and loss of springness and cohesiveness of chilled meat caused by long-term refrigeration. The LbL films even showed better freshness-keeping effect than commercial PA/PE films due to its superior barrier and certain antibacterial properties, suggesting great potential application in fresh meat preservation.

Apple pectin-based active films to preserve oil: Effects of naturally branched phytoglycogen-curcumin host

Pectin has excellent film-forming properties, but its functional properties need to be enhanced. Therefore, we constructed naturally branched phytoglycogen (PG) nanoparticles to solubilize curcumin (CCM) and further enhance the properties of apple pectin-based active films. The size of the PG spherical particles ranged from 30 to 100 nm with some aggregates. The branch density of the PG was 6.02 %. These PG nanoparticles increased the solubility of CCM nearly 1742-fold and a nanosized phytoglycogen-curcumin (PG-CCM) host was formed via hydrogen bonding and hydrophobic interaction. This host promoted the formation of pectin-based films with a dense structure and increased their tensile strength to 23.51 MPa. The coefficient to water vapor permeability, oxygen permeability and carbon dioxide permeability were all decreased indicating their barrier performance were improved. Among them, the oxygen permeability coefficient decreased most, from 1.14 × 10−7 g·m−1·s−1 to 0.8 × 10−7 g·m−1·s−1. Also, the transmittance of the active film at 280 nm and 660 nm decreased to 0.65 % and 72.10 %. Antioxidant and antibacterial properties were significantly enhanced (P < 0.05). And the results showed this film was an excellent oil packaging material. The active film incorporating PG-CCM host can replace heat-sealed plastic bags/pouch made from polyethylene and polypropylene synthetic plastics, and solve the problem that plastic packaging is difficult to degrade and cannot be squeezed clean. This provides a new conceptual framework for developing pectin-based active films by incorporating of PG and CCM.

Proton Transport, Electroosmotic Drag and Oxygen Permeation in Polytetrafluoroethylene Reinforced Ionomer Membranes and Their Effects on Fuel Cell Performance

Abstract With the increasing need for high power density of proton exchange membrane fuel cells, new composite membranes have been explored for superior proton transport and gas impermeability. These membranes’ physicochemical properties usually deviate from existing empirical formulas, which are poorly understood, especially when mechanical deformation occurs. This poor understanding hinders development of novelty membranes and their fuel cell applications. Here, using polytetrafluoroethylene reinforced ionomer membrane as an example, we conducted extensive water absorption experiments to determine hydration levels at different water activities. Molecular dynamics simulations and electrochemical impedance spectroscopy were used to investigate the impacts of hydration level, external electric field strength, and tensile deformation on proton transport and electroosmotic drag coefficient, as well as the impact of hydration level and free volume ratio on oxygen permeability. We proposed mathematical correlations for these impacts and incorporated them into a single-cell voltage model to analyze their effects on fuel cell performance. Results show that an increase in the electric field strength alters the proton transport pattern, but has minimal impact on the electro-osmosis coefficient. The oxygen permeability coefficient of a deformed membrane with a free volume ratio of 28.57% is more than two orders of magnitude higher than that of a non-deformed membrane. The electro-osmatic drag coefficient imposes a larger influence on fuel cell performance than oxygen permeability

Polyethylene terephthalate bottles with excellent oxygen, water vapor barrier and mechanical performances prepared by injection and blow molding

AbstractIn this work, the oxygen barrier property of polyethylene terephthalate (PET) films was enhanced by optimizing the “active” and “passive” synergistic barrier approaches, that is, integration of high barrier material polyethylene naphthalate (PEN) and oxygen scavengers along with catalyst with PET before biaxially stretching the PET blended films. When the PEN content in the PET blended films reached 50 wt%, the oxygen permeability coefficient was significantly reduced to 0.9687 cc·mil·m−2·day−1·0.1 MPa−1, showing an enhancement of 117.4 times compared to the pure PET film. Furthermore, the water vapor permeability coefficient was reduced to 8.0208 g·mil·m−2·day−1, representing a 45.5% reduction in comparison to the pristine PET film. It also maintained a higher transverse and longitudinal tensile strength (110.5 and 127.2 MPa) than PET film only with oxygen scavengers and catalyst (53.5 and 78.0 MPa). This work presents a viable and practical approach to endow PET materials with simultaneously enhanced oxygen, water barrier performance, and mechanical property.Highlights The OPC of PET film was as low as 0.9687 cc·mil·m−2·day−1·0.1 MPa−1. The “active” and “passive” barrier techniques together reduced the OPC of PET film.

Gas-permeable fluorine-substituted poly(diphenylacetylene)s: Effect of number and position of fluorine atoms on gas permeability

Poly(diphenylacetylene)s are ideal for fabricating gas-permeable membranes in gas separation systems. We previously reported the superior gas permeability of fluorine-substituted poly(diphenylacetylene)s compared to their fluorine-free counterparts. In this study, novel poly(diphenylacetylene)s were synthesized by varying the number of fluorine atoms from three to five in the repeating unit (2a, 2b, and 2c). Comparing the gas permeability for 2a–c, the highest value was achieved for poly(diphenylacetylene) with three fluorine atoms in a repeating unit (2a). The oxygen permeability coefficient was 8,100 barrers for 2a, remarkably higher than that of the previously reported poly(diphenylacetylene) with two fluorine atoms in the repeating unit. The density and X-ray diffraction analyses revealed a decrease in the free volume of the membranes with an increase in the number of fluorine atoms. Additionally, 2a–c did not show desilylation because the trimethyl silyl groups were substituted on the benzene ring possessing an electron-withdrawing fluorine atom.

Thymol@Natural Zeolite Nanohybrids for Chitosan/Polyvinyl-Alcohol-Based Hydrogels Applied as Active Pads.

Currently, food saving, a circular economy, and zero environmental fingerprints are of major interest. Scientific efforts for enhanced food preservation using "green" methods have been intensified. Even though chemicals could achieve such targets effectively, the global trend against the "greenhouse effect" suggests the use of environmentally friendly biobased materials for this purpose. In this study, the promising biopolymer chitosan is incorporated with the promising biodegradable polymer polyvinyl alcohol to produce an improved biopolymeric matrix. This biodegradable biopolymer was further mixed homogeneously with 15% thymol/nano-zeolite nanohybrid material. The properties of the final developed film were improved compared to the relevant values of chitosan/polyvinyl alcohol film. The mechanical properties were enhanced significantly, i.e., there was a 34% increase in Young's modulus and a 4.5% increase in the ultimate tensile strength, while the antioxidant activity increased by 53.4%. The antibacterial activity increased by 134% for Escherichia coli, 87.5% for Staphylococcus aureus, 32% for Listeria monocytogenes, and 9% for Salmonella enterica. The water vapor diffusion coefficient and the oxygen permeability coefficient decreased to -51% and -74%, respectively, and thus, the water vapor and oxygen barrier increased significantly. The active pads were used in strawberries, and the antimicrobial activity evaluation against the mold of fungi was carried out. The visual evaluation shows that the active pads could extend the shelf life duration of strawberries.

Crystallization behavior analysis and reducing thermal shrinkage of poly(lactic acid) miscibilized with poly(butylene succinate) film for food packaging

AbstractPoly(lactic acid) (PLA) incorporated with poly(butylene succinate) (PBS) through in situ reactive blending is proposed to retard thermal shrinkage. Succinic anhydride (SA) with varied contents (0.01–0.5 phr) was used as a reactive compatibilizer to enhance miscibility between PLA and PBS phases. The success of PLA chemically bound with PBS chains through simple esterification to form PLA‐SA‐PBS phase is confirmed and quantified using an X‐ray photoelectron spectroscopy technique. The binding energy intensity ratio of ester and hydrocarbon in the PLA/PBS/SA blend with 0.5 phr SA increases for two‐fold, as compared to the PLA/PBS blend. The good interfacial adhesion of PLA and PBS phases is achievable with SA content up to 0.1 phr. In addition, the PLA‐SA‐PBS molecules preferentially support crystallization of PBS phase with increased degree of crystallinity (Xc,PBS) by ~15%. These enhanced homogeneity of PLA/PBS/SA blend and high Xc,PBS trigger the increased tensile strength to 50 MPa, and substantially reduced oxygen permeation coefficient approximately 10 times. Remarkably, the interpenetration of PLA‐SA‐PBS phase in amorphous PLA region coexisting with uniformly dispersed PBS crystals inhibits the PLA chain relaxation and deformation at elevated temperatures, leading to maintaining dimensional stability of PLA/PBS/SA films without shrinkage at 100°C.

Oxygen permeability of regenerated cellulose films with different water regains

The effect of water regain on the oxygen permeability coefficient (OP) of regenerated cellulose film was investigated. The OP of the dry film was extremely low, which was classified as a “very high” performance gas barrier; however, the OP increased with increasing water regain, and reached to the OP similar to that of low-density polyethylene film, which was categorized as a “poor” gas barrier. The film thickness increased with increasing water regain, and edge-view small-angle X-ray scattering revealed widening of the space between microcrystals in the thickness direction. Oxygen molecules likely passed through the space between cellulose molecules, which was widened with increasing water regain. The viscoelastic measurements indicated that regenerated cellulose existed in a rubbery state under wet conditions. Overall, the OP of regenerated cellulose was increased because of the widening and micro-Brownian motion of cellulose main chains caused by water.

Morphological evolution ofTMB‐5/ethylene–vinyl alcohol copolymer blends under biaxial‐stretching field and its effect on the crystallization and gas barrier properties of isotactic polypropylene

AbstractThe morphological evolution of TMB‐5/ethylene–vinyl alcohol (EVOH) copolymer blends under biaxial‐stretching field and its effect on the crystallization and gas barrier properties of isotactic polypropylene (iPP) were investigated. iPP/TMB‐5/EVOH ternary blends with TBM‐5 selectively distributed in the EVOH phase were prepared through a multistage stretching extrusion, which combined an assembly of layer multiplying elements (LMEs) with an extruder. Scanning electron microscopy revealed that the biaxial‐stretching field in LMEs transformed the TMB‐5/EVOH phase into platelets along the extrusion direction. Differential scanning calorimetry and X‐ray diffraction results indicated that the TMB‐5 particles were distributed in the EVOH phase and noβcrystals formed in as‐extruded samples. Especially, the TMB‐5 was released from the EVOH phase into iPP in the annealing process and induced the formation ofβcrystals. Compared with that of pure iPP, the oxygen permeability coefficient of iPP containing aligned TMB‐5/EVOH platelets decreased more than three times. The enhanced barrier properties resulted from the increased tortuosity of the diffusion pathway caused by the orientated high‐aspect‐ratio platelets. © 2023 Society of Industrial Chemistry.

Novel edible films of pectins extracted from low-grade fruits and stalk wastes of sun-dried figs: Effects of pectin composition and molecular properties on film characteristics

This study aimed to explore the characteristics of novel fig pectin films. For this purpose, films of crude fig pectin (CFP) extracted from low-grade sun-dried fruits and films of crude (CSP) and purified (PSP) stalk pectins extracted from stalk waste of processed high-quality sun-dried figs were evaluated for their physicochemical properties. The properties of pristine (CFP, CSP, and PSP films) and CaCl 2 cross-linked films (CFP–Ca ++ , CSP-Ca ++ and PSP-Ca ++ films) of fig pectins were also compared with films of commercial citrus (CP and CP-Ca ++ ) and apple (AP, AP-Ca ++ ) pectins. The cross-linking improved the mechanical strength and barrier properties of most films. CP, CP-Ca ++ , PSP, and PSP-Ca ++ films showed greater mechanical strength and stiffness than other films. PSP-Ca ++ , PSP and CP-Ca ++ films showed the lowest water vapor permeability (6.28, 12.85, 14.96 g.mm.m −2 .day −1 .kPa −1 , respectively) while CSP-Ca ++ , CP-Ca ++ , CP, PSP-Ca ++ films showed the lowest oxygen permeability coefficients (5403, 8265, 10776, 11124 ml.μm.m −2 .24h −1 .atm −1 , respectively). All cross-linked fig pectin films showed 2–3 fold lower degree of swelling than CP-Ca ++ film. The CFP-Ca ++ film showed the highest surface hydrophobicity (contact angle = 101.8°) but the lowest water solubility (32.8%) and degree of swelling. Analysis of Pearson's correlations between pectin properties and film characteristics revealed that galacturonic acid (GA) content affects the mechanical properties, while GA content, degree of esterification (DE), and acetylation affect the moisture barrier performance; finally, GA content and DE affect the oxygen barrier performance of pectin films. Films of stalk waste pectins showed some properties beyond the limits of those obtained from commercial pectins. • Pectins were extracted from low-grade fruits and stalk wastes of sun-dried figs. • Mechanical and barrier properties of fig and commercial pectins were compared. • Cross-linking of films improved their mechanical and barrier properties. • Stalk waste pectin films showed the highest moisture and gas barrier properties. • Pectin composition was correlated with film properties for the first time.

Valorisation of fruit peel bioactive into green synthesized silver nanoparticles to modify cellulose wrapper for shelf-life extension of packaged bread

Fruit peels are rich source of bioactive compounds such as polyphenols, flavonoids, and antioxidants but are often discarded as waste due to limited pharmaceutical and nutraceutical applications. This study aimed to valorise pomegranate and citrus fruit peel into green synthesised silver nanoparticles (AgNPs) in order to modify cellulose-based wrapping material for prospective food packaging applications and propose an alternate and sustainable approach to replace polyethene based food packaging material. Four different concentrations of AgNO3 (0.5 mM, 1 mM, 2 mM, and 3 mM) were used for green synthesis of AgNPs from fruit peel bioactive, which were characterised followed by phytochemical analysis. Ultraviolet–Visible spectroscopy showed surface plasmon resonance at 420 nm, XRD analysis showed 2θ peak at 27.8°, 32.16°, 38.5°, 44.31°, 46.09°, 54.76°, 57.47°, 64.61° and 77.50° corresponding to (210), (122), (111), (200), (231), (142), (241), (220) and (311) plane of face centred cubic crystal structure of AgNPs. Fourier-transform infrared spectroscopy analysis of AgNPs green synthesised from pomegranate and kinnow peel extract showed a major peak at 3277, 1640 and 1250–1020 1/cm while a small peak at 2786 1/cm was observed in case of pomegranate peel extract which was negligible in AgNPs synthesized from kinnow peel extract. Particle sizes of AgNPs showed no statistically significant variance with p > 0.10 and thus, 2 mM was chosen for further experimentation and modification of cellulose based packaging material as it showed smallest average particle size. Zeta potential was observed to be nearly neutral with a partial negative strength due to presence of various phenolic compounds such as presence of gallic acid which was confirmed by ultrahigh performance liquid chromatography-photodiode array(UHPLC-PDA) detector. Thermal stability analysis of green synthesised AgNPs qualified the sterilisation conditions up to 100 °C. AgNPs green synthesized from both the peel extracts had higher polyphenolic content, antioxidant and radical scavenging activity as compared to peel extracts without treatment (p < 0.05). The cellulose based food grade packaging material was enrobed by green synthesised AgNPs. The characterisation of modified cellulose wrappers showed no significant difference in thickness of modified cellulose wrappers as compared with untreated cellulose wrapper (p > 0.42) while weight and grammage increased significantly in modified cellulose wrapper (p < 0.05). The colour values on CIE scale (L*, a* and b*) showed statistically significant increase in yellow and green colour (p < 0.05) for modified cellulose wrappers as compared to control wrapper. The oxygen permeability coefficient, water vapour permeability coefficient, water absorption capacity and water behaviour characteristics (water content, swelling degree and solubility) showed significant decrease (p < 0.05) for modified cellulose wrapper as compared to control wrapper. A uniform distribution and density of green synthesised AgNPs across cellulose wrapper matrix was observed through scanning electron microscopy (SEM) images with no significant aggregation, confirming successful enrobing and stable immobilisation of nanoparticles from cellulose matrix. A seven-day storage study of bread wrapped in modified and control cellulose wrappers showed delayed occurrence of microbial, yeast and mould count in bread packaged in modified cellulose wrappers and thus, resulting in shelf life extension of bread. The results are encouraging for the potential applications of modified cellulose wrappers to replace polyethene based food packaging.

High oxygen barrier materials from paper to regenerated cellulose films

AbstractA transparent, bendable, high oxygen barrier cellulose‐based film was prepared, which has far better oxygen barrier properties than conventional polyethylene, polypropylene and cellophane materials. A series of regenerated cellulose films (RCs) were prepared from filter paper lacking oxygen barrier properties under different cellulose concentrations and gelation times. It was shown that the cellulose concentration and gel time had a greater effect on the oxygen barrier properties of RCs. When the cellulose concentration was 4 wt% and the gel time was 3 h, the RCs obtained the lowest oxygen permeability coefficient (OPC) down to 2.21 × 10−17 cm3 cm cm−2 s−1 Pa−1. The films have a tensile strength of 109.5 MPa, an elongation at break of 27.3% and a light transmission rate of 89%. In further, molecular dynamics simulations showed that when the filter paper was converted to RCs, the increase in hydrogen bonding and the decrease in free volume between cellulose chains caused a decrease in the diffusion coefficient of oxygen. As a novel biobased high oxygen barrier material, the film has broad application prospect in packaging and chemical industry.

Effects of freeze–thaw cycles on the properties of polyethylene geomembranes

High-density polyethylene (HDPE) geomembranes (GMs) are frequently used as fluid barrier components of cover systems for mine site reclamation in regions that are prone to freeze–thaw cycles (FTCs). However, HDPE GMs are more susceptible to stress cracking than linear low-density polyethylene (LLDPE) GMs. Hence, LLDPE GMs are increasingly considered as alternatives to HDPE GMs in cover systems. Nevertheless, little information is available on LLDPE compared to HDPE GMs. Moreover, little is known about the changes in the fluid barrier properties (the equivalent hydraulic conductivity and the oxygen sorption and diffusion coefficients) for these two materials with FTCs. The purpose of this study is therefore to compare the effects of FTCs on the tensile, hydraulic, and oxygen sorption and diffusion properties of HDPE and LLDPE GMs. To do so, GM sheets were subjected up to 300 FTCs. Mechanically, both GMs got stiffer and their tensile break properties increased with increasing number of FTCs. However, although the GM fluid barrier properties changed with FTCs, the equivalent hydraulic conductivity and the oxygen permeation coefficient remained within an order of magnitude of 10−14 m/s and 10−13 m2/s, respectively. Up to 300 FTCs would therefore have no adverse effects on HDPE and LLDPE GMs.

Effect of methyl group on gas permeability of trimethylsilyl-containing poly(diphenylacetylene)s

Novel highly gas-permeable diphenylacetylene polymers ( P1 – P4 ) were synthesized via polymerization of diphenylacetylenes bearing a methyl group directly beside the trimethylsilyl group ( p -Me 3 Si- m -MeC 6 H 3 C CC 6 H 4 R; R = H ( 1 ), p -SiMe 3 ( 2 ), p - t -Bu ( 3 ), and m -SiMe 3 ( 4 )). The corresponding polymers P1 and P4 were completely soluble in various organic solvents, whereas polymers P2 and P3 were insoluble. Polymer P1 exhibited a very high oxygen permeability coefficient ( P O2 ) of 3960 barrers, indicating that the methyl groups had a profound effect on the gas permeability. Polymer DP1 , obtained by the desilylation of P1 , exhibited even higher gas permeability. The copolymerization of 2 and 3 with 1 yielded solvent-soluble high-molecular-weight copolymers ( P12 and P13 ) with very high gas permeabilities. The methyl groups were found to broaden polymer chain distance. The gas permeabilities of P12 and P13 increased and decreased, respectively after desilylation. Although the oxygen permeability of the polymers/copolymers gradually decreased with storage time, their P O2 remained high (2220–4140 barrers) even after 90 days. • Novel highly gas-permeable methyl group-bearing poly (diphenylacetylene) polymers. • Inclusion of methyl group at meta position increased the gas permeability. • Highest P O2 = 3960 barrers for hompolymer and P O2 = 5540 barrers for copolymer. • Desilylation further enhanced the gas permeability ( P O2 ≤ 7830 barrers). • High gas permeability ( P O2 = 2220–4140 barrers) even after 90 days.

Enhanced Barrier Property for Polyethylene Terephthalate–Polyethylene Naphthalate Copolymer by In Situ Polymerization with Graphene Oxide Nanosheets

AbstractIn this paper, a series of polyethylene terephthalate‐polyethylene naphthalate copolymer (PETN) composites with high oxygen barrier properties are prepared by introducing trace of graphene oxide (GO) during the in situ polymerization. The single‐layer GO nanosheets with large lateral size (≈1.8 µm) and abundant functional groups are prepared by a combination of chemical exfoliation and solvent exchange. During the in situ polymerization process, some surface region of GO is grafted by PETN molecular chains with the grafting rate being 80%, which enhanced the interfacial interaction between GO and PETN matrix. Furthermore, the ungrafting surface region of GO is thermally reduced to the complete graphene. Due to the in‐plane stacking of grafted GO and reduced GO, and the increased crystallinity of PETN matrix, the oxygen transport path of the PETN film is greatly prolonged, which endowed the PETN nanocomposite films with highly improved oxygen barrier performance. When the GO content is only 0.1 wt%, the oxygen permeability coefficient of the nanocomposite films is as low as 38.9 cc mil m−2 d−1 0.1 MPa−1, which is ≈4.5 times lower than that of the pure PETN film. This work provides a new idea for the preparation of polyester materials with high oxygen barrier performance.

Synthesis, Characterization and Properties of Soybean Oil-Based Polyurethane.

At present, the consumption of polyurethane is huge in various industries. As a result, it has become a research hotspot to use environmentally friendly and renewable bio-based raw materials (instead of petroleum-based raw materials) to prepare polyurethane. In this paper, epoxy soybean oil (ESO) was used as raw material, and polyethylene glycol (PEG-600) was used for ring opening. Fourier transform infrared (FT-IR) and proton nuclear magnetic resonance (1H NMR) analysis proved that soybean oil-based polyester polyols was prepared. Soybean oil-based polyurethane (SPU) was synthesized by the reaction of the soybean oil-based polyol with isophorone diisocyanate (IPDI), so as to save energy and protect the environment. The properties of SPU films were adjusted by changing the R value (the molar ration of -NCO/-OH) and the film forming temperature. The chemical structure and properties of the SPU were characterized by FTIR, 1H NMR, gel permeation chromatography (GPC), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). The results show that the mechanical strength, water contact angle, microphase separation degree, barrier property, and thermal stability of SPU films gradually increase, while the transparency, oxygen permeability coefficient and moisture permeability coefficient of SPU films gradually decrease with the increase of R value and film forming temperature.

Ultra-high temperature oxidation resistance of a novel (Mo, Hf, W, Ti)Si2 ceramic coating with Nb interlayer on Ta substrate

In order to solve the challenge of recyclability of tantalum substrates in high temperature oxidation environments, a novel MoSi2-WSi2-HfSi2-TiSi2 composite ceramic coating containing an Nb interlayer was prepared on the surface of tantalum substrate by a three-step method. The mix ceramic silicide coating exhibited superior performance and effective protection for 10.2 h at 1800 °C, possibly due to the formation of an outer SiO2-HfO2-HfSiO4 composite oxide film with low oxygen permeability, moderate viscosity and thermal expansion coefficient, as well as good self-healing ability. Furthermore, the coating successfully passed 537 thermal cycles from room temperature to 1800 °C. The presence of Nb interlayer significantly mitigated the thermal mismatch between the ceramic coating and the tantalum substrate, and the bidirectional diffusion of Nb element during the high temperature oxidation and thermal shock process further reduced the tendency of the coating to crack.

An Experimental Study of the Oxygen Permeability of a PET Film With a Nanosized Aluminum Oxide Layer

Results of an experimental study of the oxygen permeability of a PET film with nanosized aluminum oxide layers formed by reactive magnetron sputtering have been described. An experimental dependence of the oxygen permeability coefficient of PET film with the aluminum oxide layer in the range of 20 &amp;divide; 80 nm, providing its value up to 1 cm3/(m2∙24h∙0.1MPa), have been determined. The effect of various factors on the formation of a high-quality reproducible oxide PET film and the characteristics of a nanosized aluminum oxide layer and the specific electric energy consumption for the magnetron deposition of the layer has been defined. The planar surface structures and surface roughness parameters of PET and oxide films with layers of different thicknesses have been determined. A qualitative interpretation of the results has been given.

Synergistically Improved Oxygen Barrier Properties of Polyethylene Terephthalate by Combining “Active” and “Passive” Barrier Techniques

AbstractThe relatively poor oxygen barrier properties of polyethylene terephthalate (PET) limit its high‐end use in flexible electronic substrates. In this work, the oxygen barrier properties of PET films are highly improved by biaxially stretching PET films containing oxygen scavengers. The “active” oxygen scavengers result in a higher crystallinity of biaxially stretched PET films, improving the “passive” barrier properties. Biaxial stretching processing increases the surface area of oxygen scavengers’ domain, which consumes the oxygen molecules more effectively, thus improving the “active” barrier properties. More importantly, the enhanced “passive” barrier path prolongs the residence time of oxygen molecules in the films, allowing the oxygen scavenges to have enough time to sufficiently react with oxygen molecules. As a result, the oxygen permeability coefficient of biaxially stretching PET films containing oxygen scavengers is as low as 14.5792 cc mil m−2 day−1 0.1 MPa−1, synergistically improved by a factor of 11.99 compared to pristine PET films.