Low Oxygen Permeability Research Articles

Optimization of the Oxygen Permeability of Non-Silicone Hydrogel Contact Lenses Through Crosslinking Modifications

The main weakness of non-silicone hydrogel contact lenses is their low oxygen permeability (Dk). Hence, we have tried to optimize their Dk using various concentrations and lengths of the poly (ethylene glycol) dimethacrylate crosslinker in a mixture of N,N-Dimethylacrylamide and Cyclohexyl methacrylate monomers. After synthesizing the different contact lenses, we evaluated their chemical, optical, and mechanical properties. The resultant non-silicone hydrogel contact lenses presented similar high water contents (75.69–80.60%) and adequate optical (e.g., a transmittance ranging from 85.91% to 99.91% and a refractive index between 1.3630 and 1.3740) and elongation at break (178.95–356.05%) characteristics for clinical applications. Conversely, they presented high contact angles (81.00–100.00°) and a low Young’s modulus (0.066–0.167 MPa). Regarding the impact of the crosslinking modifications, the water content, contact angle, refractive index, transmittance, and Young’s modulus of the synthesized lenses were slightly affected by crosslinker conditions. In contrast, the elongation at break (178.95–356.05%) and, more importantly, the oxygen permeability, which reached values of up to 73.90 Fatt units, were considerably impacted by the crosslinker conditions. To our knowledge, this study demonstrates for the first time that, in addition to water, other usual hydrogel components, like crosslinkers, can modulate the Dk of non-silicone contact lenses. It also provides a simple and scalable method to fabricate more permeable non-silicone lenses.

Performance analysis of biodegradable composite using polyvinyl alcohol and pomegranate peel powder for sustainable dry packaging applications

This study focuses on the fabrication of a biodegradable dry packaging material for fruits, vegetables, and flowers, with an emphasis on affordability for street vendors. Approximately 55% of waste originates from packaging materials. To address this issue, a biodegradable Polyvinyl alcohol/Pomegranate peel powder (PVA/PPP) composite film was fabricated. The PVA, a water-soluble synthetic biodegradable polymer, served as the matrix, while PPP, an agro-waste product, was used as the filler. The PVA/PPP films were characterized through optical microscopy, FTIR, XRD, TGA, DSC, moisture absorption analysis, water vapour transmission rate (WVTR), water vapour permeability (WVP), and oxygen permeability testing. The inclusion of PPP enhanced the film’s properties via increasing moisture absorption by 85%, reducing PVA crystallinity index from 33.2 to 17.5%, percentage crystallinity reduced from 73.90 to 0.57%, lowering WVTR from 0.063 to 0.042 g/h.m2, low oxygen permeability and improving thermal stability up to 423 °C. Additionally, the pH of PPP (4.5) contributed to microbial resistance. The fabricated PVA/PPP films were fully biodegradable and produced via green synthesis without any hazardous chemicals. The use of PPP as a filler not only improved film performance but also reduced environmental hazard, demonstrating the material’s suitability for sustainable packaging applications.

Study on the Oxidation Behavior of TiB2-CeO2-Modified (Nb,Mo,Cr,W)Si2 Coating on the Surface of Niobium Alloy

A novel TiB2-CeO2-modified (Nb,Mo,Cr,W)Si2 coating was prepared on a Nb-5W-2Mo-1Zr alloy substrate using two-step slurry sintering and halide-activated pack cementation to address the limitations of a single NbSi2 coating in meeting the service requirements of niobium alloys at elevated temperatures. At 1700 °C, the static oxidation life of the coating exceeded 20 h, thus indicating excellent high-temperature oxidation resistance. This was due to the formation of a TiO2-SiO2-Cr2O3 composite oxide film on the coating surface, which, due to low oxygen permeability, effectively prevented the inward infiltration of oxygen. Additionally, the dense structure of the composite coating further enhanced this protective effect. The composite coating was able to withstand over 1600 thermal shock cycles from room temperature to 1700 °C, and its excellent thermal shock performance could be attributed to the formation of MoSi2, CrSi2, and WSi2 from elements such as Mo, Cr, and W, which were added during modification. In addition to adjusting the difference in thermal expansion coefficients between the layers of composite coatings to reduce the thermal stress generated by thermal shock cycles, the formation of silicide compounds also improved the overall fracture toughness of the coating and thereby improved its thermal shock resistance.

Enhancement of thermo-oxidative stability of polyimide composites by functionalized polyimide film surface modification

Polyimide (PI) resin-based composites exhibit excellent high-temperature resistance, solvent resistance, and mechanical properties, making them have broad application prospects in various fields such as aviation, aerospace, and transportation. With the continuous development of new devices, the requirements for the service temperature and service life of materials are improved, so there is an urgent need to improve the thermo-oxidative stability of polyimide composites. In this work, PI films, aluminum-coated PI film, and copper-coated PI film with low oxygen permeability were used as surface oxygen barrier materials, and surface film modified polyimide composites were prepared. The results show that, compared with the unmodified composite materials, after aging at 350°C for 400 hours, the weight loss rates of the composites modified by three kinds of surface films all increased by more than 50%, and the bending strength retention rates of the composites respectively increased by 47%, 51%, 45%, and the interlaminar shear strength retention rates respectively increased by 107%, 82%, 78%, showing excellent thermo-oxidative stability.

Microstructural evolution and 1500 °C oxidation resistance of Mo(Al,Si)2 fabricated via an innovative two-step SHS-SPS technique

An innovative two-step approach of self-propagating high-temperature synthesis (SHS) and spark plasma sintering (SPS) was developed to rapidly fabricate MoSi2 and Mo(Al,Si)2 ceramics for high-temperature anti-oxidation applications. The SHS process predominantly promoted the synthesis of high-purity and high-yield MoSi2 and Mo(Si,Al)2 phases in the alloyed powders. Subsequently, dense and crack-free MoSi2 and Mo(Al,Si)2 ceramics were produced using SPS. 1500 °C oxidation tests of the ceramics (100 h) revealed the formation of a protective SiO2 oxide layer on the surface of MoSi2 ceramics, while an Al-Si-O composite glassy oxide layer formed on Mo(Si,Al)2 ceramics., which exhibited better thermal stability and lower oxygen permeability compared to the single SiO2 oxide layer. However, an excessive Al content (>0.05 at.%) compromised the oxidation resistance due to the emergence of a Si-depleted Mo5(Si,Al)3 layer with inferior oxidation resistance, which was caused by the high-temperature diffusion of Si. Therefore, via this novel two-step SHS-SPS technique compact and crack-free Mo(Si,Al)2 ceramics can be rapidly synthesized at high temperatures. When trace amount of Al was added (0.05 at.%), Mo(Si0.95,Al0.05)2 showed optimum high-temperature oxidation resistance.

Methods for Fabrication of Self/Free Standing Nanocellulose (NC)-Nano Montmorillonite (N-MMT) Composite Films/Sheets — A Review

Plastic pollution looms large as a formidable foe to the environment. Enter cellulose nanofibers, the shining stars in the quest for innovative, eco-friendly paper-based packaging that is not just renewable, but also recyclable and biodegradable. These cellulose wonders boast impressively low oxygen permeability, but when it comes to water vapor, they fall short compared to traditional packaging plastics like LDPE. To tackle this challenge, researchers have been crafting composites by blending cellulose nanofibers with inorganic nanoparticles, such as Montmorillonite clay, which helps to curb water vapor permeability. However, this clever addition comes with a catch — it further complicates the already tricky drainage process during layer formation via vacuum filtration. This review delves into the complex world of nano cellulose-nano-MMT (Montmorillonite) composites, examining their preparation processes, unique characteristics, wide-ranging uses, and their significant contribution to promoting circular economy principles. By combining cellulose nanomaterials with MMT, a synergistic approach is taken to develop a new composite material with improved mechanical, thermal, and barrier properties. Various fabrication techniques are explored, including solution blending, in-situ polymerization, and electrospinning, allowing for customized design and optimization of the composite material. The review discusses how the nano cellulose-MMT composite demonstrates enhanced mechanical strength, thermal stability, and barrier properties, positioning it as a sustainable option compared to traditional materials. The review also showcases the diverse applications of these nano-composites in fields like packaging, biomedical devices, and environmental cleanup, emphasizing their alignment with circular economy principles. By examining the entire life cycle of these composites, from production to use and eventual disposal or recycling, the review underscores their role in supporting a circular economy. In light of the ongoing efforts by the scientific community and various industries to identify environmentally sustainable solutions, it is imperative to comprehend the synthesis, properties, and applications of nano cellulose-MMT composites. This understanding is essential for advancing sustainable processing for green material development.

Optimized hybrid edible surface coating prepared with gelatin and cellulose nanofiber for cherry tomato preservation

The use of renewable bioresources and their nanoforms in developing edible coating materials is considered a promising approach for preserving food freshness. Herein, cellulose nanofibers (CNF) with different morphologies were combined with gelatin to prepare composite preservation film following by brushing over the surface of cherry tomatoes as an edible coating. The gelatin-based composite film containing 0.3 % CNF20 (GC2–0.3) exhibited the lowest water vapor permeability (WVP, 1.97 × 10−4 barrer), lower oxygen permeability (OP, 2.54 × 10−2 barrer), higher transparency (Tr = 85.28 %) and excellent mechanical properties (σ = 47.45 MPa, E = 1.84 GPa). When coated on cherry tomatoes, it maintained good luster and freshness, significantly reducing the water loss of cherry tomatoes. The weight loss was only 16 % after 14 days of storage at 25 °C and 30 % humidity, compared to >30 % for the uncoated cherry tomatoes. This work provides a viable strategy for developing sustainable, green fresh-keeping materials that can prolong the storage time of the putrescible food.

A new and easy-to-implement green packaging option with recycled paperboard and PBAT film

A commercial recycled paperboard was double coated with poly (butylene adipate-co-terephthalate) (PBAT) films by using hot pressing aiming the production of a laminated material compatible with food packaging. The proposed new approach allowed to smooth the paperboard surface and to obtain a material with low oxygen permeability, low wettability, and excellent resistance to grease (kit value of 12). The observations by scanning electron microscopy (SEM) showed a homogeneous surface with a high degree of coverage, suggesting good compatibility of the PBAT with the cellulose fibers. Some of the mechanical properties of the PBAT-coated paperboard were also greatly improved, such as ply-bonding, bending resistance and bursting strength, which are important for packaging applications. Remarkably, it was possible to firmly bond two pieces of paperboard coated with PBAT by simply hot-pressing at an appropriate temperature. This method created a reinforced coated paperboard that showed high potential to be used in the production of laminated food packaging with different structures without the need of adhesives.

Effects of TiB2 contents on the microstructure and oxidation behavior of Mo-Si-B composite coatings

A novel Mo-Si-B-TiB2 composite coating was prepared on Nb-Si based ultrahigh temperature alloy by slurry sintering. The effects of TiB2 contents (1, 3, 5 and 10 wt%) on the microstructure and oxidation behavior of Mo-Si-B composite coatings were revealed. The results show that TiB2 modified Mo-Si-B composite coatings display a bilayer structure, in which the outer layer is composed of MoSi2, Mo5Si3 and TiB2 phases, and the inner layer is composed of (Ti,Nb)5Si4, (Nb,X)5Si3 and (Nb,Ti)B2 phases. The added TiB2 particles are evenly distributed in the outer layer of the coatings. By introducing TiB2 into the coating, the service life of Mo-Si-B composite coatings is extended from 50 h to 100 h at 1250 ℃, the oxidation rate of the coating is reduced from 1.62 to 0.02 mg2 cm−4 h−1. This indicates that the addition of appropriate TiB2 effectively slows down the oxidation rate and significantly improves the oxidation resistance of Mo-Si-B composite coatings. The Mo-Si-B composite coating with 3 wt% TiB2 had the lowest mass gain (3.9 mg/cm2) after oxidation at 1250 ℃ for 100 h, and it exhibited the best oxidation resistance. This is attributed to the formation of composite oxide scale with crack-free, good healing ability, suitable levels of differential thermal expansion and low oxygen permeability.

Development of Functional Composite Edible Films or Coatings for Fruits Preservation with Addition of Pomace Oil-Based Nanoemulsion for Enhanced Barrier Properties and Caffeine for Enhanced Antioxidant Activity.

The aim of this study was to develop functional composite edible films or coatings for fruit preservation by the addition of bioactive components in combinations that have not yet been thoroughly studied, according to the relevant literature. Edible films were initially composed of (i) chitosan (CH), cellulose nanocrystals (CNC) and beta-cyclodextrin (CD) (50%-37.5%-12.5% ratio), and (ii) hydroxypropyl methylcellulose (HPMC), cellulose nanocrystals (CNC) and beta-cyclodextrin (CD) (50%-37.5%-12.5% ratio). The bioactive components incorporated (5, 10 and 15% v/v) were as follows: (i) pomace oil-based nanoemulsion (NE) aiming to enhance barrier properties, and (ii) caffeine (C), aiming to enhance the antioxidant activity of films, respectively. Indeed, NE addition led to very high barrier properties (low oxygen and water vapor permeability), increased flexibility and reduced color. Furthermore, the contribution of these coatings to fresh strawberries' preservation under cold storage was investigated, with very promising results concerning weight loss, color difference, and preservation of fruit moisture and quantity of O2 and CO2 inside the packages. Additionally, C addition led to very high antioxidant activity, reduced color and improved barrier properties. Finally, the contribution of these coatings to avocado's preservation under cold storage was investigated, with very encouraging results for color difference, hardness and peroxide value of the fruit samples.

Novel thermally regenerated flexible cellulose-based films

AbstractIn this work, cellulose powder obtained by acid hydrolysis of industrial Eucalyptus kraft pulp was dissolved in NaOH/Urea/H2O system (7/12/81 wt%) in a concentration of 6% (w/v). Cellulose films were prepared by spreading the dissolved cellulose over glass plates, followed by thermal regeneration – a novel approach reported here for the first time. To obtain final flexible films, plasticization was carried out by immersion in aqueous glycerol solutions of various concentrations (10 to 70 wt%) and hot-pressing (at 0.1 MPa and 105 ºC) was used to dry and compress the cellulose films. The resulting films were characterized by Attenuated Total Reflectance Fourier transform infrared spectroscopy, differential scanning calorimetry, thermogravimetric analysis, X-ray diffraction, contact angle measurements, transparency analysis, and gas permeabilities (oxygen and water vapor). Highly flexible films containing up to 50 wt% of glycerol were successfully obtained, exhibiting no glycerol release upon manual handling. Overall, the produced films demonstrated dense and compact structure, good transparency, flexibility and malleability, and very low oxygen permeability.

Nanocellulose@gallic Acid-Based MOFs: A Novel Material for Ecofriendly Food Packaging.

The development of an effective food packaging material is essential for safeguarding against infections and preventing chemical, physical, and biological changes during food storage and transportation. In the present study, we successfully synthesized an innovative food packaging material by combining chitosan (CH), nanocellulose (NC), and a gallic acid-based metal-organic framework (MOF). The CH films were prepared using different concentrations of NC (5 and 10%) and MOFs (1.5, 2.5, and 5%). Various properties of prepared films, including water solubility (WS), moisture content (MC), swelling degree, oxygen permeability, water vapor permeability (WVP), mechanical property, color analysis, and light transmittance, were studied. The chitosan film with a 5% NC and 1.5% MOF (CH-5% NC-1.5% MOF) exhibited the least water solubility, moisture content, and water vapor permeability, indicating the overall stability of the film. Additionally, this film demonstrated low oxygen permeability, as indicated by a peroxide value of 18.911 ± 4.009, ensuring the effective preservation of packaged contents. Notably, this synthesized film exhibited high antioxidant activity, resulting in an extended duration of 52 days. This antioxidant activity was further validated by the preservation of apple slices for 9 days in a CH-5% NC-1.5% MOF film. The findings of the study suggest that the developed films can provide a promising and environmentally friendly solution for active food packaging.

Flexible Cellulose Nanofiber (CNF)-Nano- Montmorillonite (MMT) Composite Sheet Structure and Water Vapor Barrier Performance

One of the newly developed nanomaterials for functioning as high-performance packaging materials to replace synthetic plastics such as low-density and high-density polyethylene (LDPE, HDPE) is cellulose nanofiber (CNF). These substances are biodegradable, recyclable, and renewable. While cellulose nanofiber-based films have substantially better water vapor permeability than traditional packaging polymers, they have extremely low oxygen permeability. Water vapor permeability (WVP) of the spray-coated composites was decreased via spraying nano-montmorillonite (MMT) content into CNF suspension and also high-pressure homogenization of CNF-MMT suspension. The process for spraying cellulose nanofiber (CNF)-nano-montmorillonite (MMT) suspension on the stainless-steel surface was developed to produce a high-barrier performance composite. The two types of composites were prepared via spraying of raw CNF with MMT and fibrillated CNF with MMT via high-pressure homogenization. The structure and barrier performance of these composites were investigated with SAXS and ASTM E96/E96M-05. Before homogenization, the MMT is agglomerated, while after homogenization it is more exfoliated, which is split up into individual sheets. The water vapor permeability could be reduced by adding up to 20 wt. % montmorillonite and dispersing montmorillonite with two passes in a high-pressure homogenizer. With montmorillonite addition above 20 wt. %, the water vapor permeability started to increase due to aggregation of the montmorillonite in the homogenized composite. At the optimal addition level, the best performance achieved with spraying was a water vapor permeability of 8.3 x 10-12 g/m.s.pa. The air permeability of the composite was evaluated to be less than 0.003 µm/Pa.s. This value confirms an impermeable composite for packaging applications. Considering the orientation of MMT in the composite, the composite’s structure can decide the barrier performance and can be altered by further fibrillation process of cellulose nanofibers via high-pressure homogenization.

Hierarchical-design coating on C/C composite with excellent combination of autonomously self-healing ability and low oxygen permeability from 973 K to 1273 K

Antioxidant SiO2 coating exhibits low cost and great compatibility with existing uses, but is strongly limited by its poor fluidity and high oxygen permeability from 973 K to 1273 K. Therefore, the hierarchical-design Glass/MoSi2-B2O3@SiO2-SiC coating was fabricated on C/C composite by a simple embedding method, and followed by a hot dip process. This composite yielded excellent combination of long-term antioxidant abilities and thermal shock resistances. As oxidized at 973 K for 1500 h, its mass loss was 0.35 %, and only 0.66 % at 1073 K for 2600 h. After thermal shocks 270 times, the weight loss was only 0.56 %. Interestingly, the Glass/MoSi2 coating acted as a self-healing encapsulation shelter against oxygen, whilst the B2O3@SiO2 layer yielded stable healing effect. The B2O3@SiO2 microcapsule facilitated the activation of B2O3, SiO2 phases, and borosilicate glass sequentially as temperature rose, leveraging their unique advantages in defect healing. Through the synergistic effects of interface encapsulation and defect self-healing, the oxygen kept osmotic diffusion. This study underscores the significance of hierarchical designs in coatings, facilitating structure optimizations and enhancing antioxidant capabilities at multiple levels.

Development of multifunctional chitosan-based composite film loaded with tea polyphenol nanoparticles for strawberry preservation

Incorporating polysaccharide-based composite films with nanobiotechnology offers a new strategy for food preservation. This study initially focuses on the preparation of tea polyphenol nanoparticles (TPNP), novel and derived from natural antibacterial agents, which serve to improve stability. Afterwards chitosan-based composite films loaded with TPNP (CTN film) were developed using solution casting method. The incorporation of TPNP significantly improved the UV/water/oxygen barrier properties, mechanical properties and thermal stability, alongside notable physical properties including water contact angle (93.65 ± 0.04°), low water vapor permeability (33.72 ± 3.32 g/m2h) and oxygen permeability (0.11 ± 0.02 g/m2h), tensile strength (61.83 ± 0.70 %), and elongation at break (31.60 ± 6.12 %). The CTN film not only exhibited exceptional biodegradability and nontoxicity, but also demonstrated remarkable antimicrobial efficacy against Escherichia coli and Bacillus subtilis. Additionally, it showcased potent antioxidant activity, boasting DPPH and ABTS radical scavenging rates up to 89.25 ± 0.18 % and 93.84 ± 0.42 %. The CTN film was successfully formed on the surface of strawberries through dip-coating process and their shelf life was extended from 4 to 6 days at 20 °C without side-effect on the weight loss, harness, pH and total soluble solids, illustrating its potential for enhancing food preservation.

Ultra-high-molecular weight cyclic olefin copolymers with excellent all-round performance prepared via highly effective quasi-living copolymerization

Cyclic olefin copolymers (COCs) are a type of engineering thermoplastics that have excellent transparency, high heat deflection temperature, high tensile modulus, and rigidity, but low elongation (usually below 5 %). Achieving COCs with better mechanical performance, particularly toughness, while maintaining their other properties, is a critical goal that remains a significant challenge. Herein, COCs with an ultra-high-molecular weight (UHMW)—an average molecular weight of up to 2046 kDa—and a relatively narrow molecular weight distribution (Mw/Mn < 1.66), were prepared via a highly efficient, quasi-living catalytic system under mild polymerization conditions. The dependence of the tensile properties, impact properties, wear rate, mean friction coefficient, water vapor transmission rate, and oxygen permeability of the newly obtained COCs on their molecular weight was studied in-depth and compared with those of a commercial COC (Topas 6013, with a molecular weight of 144 kDa). As clearly shown, the obtained UHMW-COCs not only provided satisfactory heat resistance and excellent optical transparency but also demonstrated excellent mechanical performance, tribology behaviors, and barrier properties. Compared with the COCs with lower molecular weight but similar norbornene (NBE) incorporation and optical transmittance, these UHMW-COC samples possessed a higher glass transition temperature, higher tensile strength (up to 73.5 MPa), better elongation at break (6.8 %), better impact strength (4.0 kJ/m2), and a lower wear rate (2 × 10−5 mm3/mN), as well as a lower mean friction coefficient (0.48), lower water vapor transmission rate (0.68 g·mm·m−2·day−1), and lower oxygen permeability (1.60 Barrer). These all-round properties, together with their original advantages, make the UHMW-COCs promising for a broad range of high-end applications.

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.

Regio- and Stereoregular EVOH Copolymers from ROMP as Designer Barrier Materials.

This work aimed to decrease the water permeability (P H2O) while simultaneously maintaining low oxygen permeability (P O2) in ethylene vinyl alcohol (EVOH)-based copolymers by introducing high levels of backbone regioregularity and stereoregularity. Both regioregular atactic and isotactic EVOH samples with 75 mol % ethylene were prepared by a ring-opening metathesis polymerization (ROMP)-hydrogenation-deprotection approach and then compared to commercial EVOH(44) (containing 44 mol % ethylene) as a low P O2 standard with poor water barrier characteristics (i.e., high P H2O). The high levels of regioregularity and stereoregularity in these copolymers increased the melting temperature (T m), degree of crystallinity (χc), and glass-transition temperature (T g) compared to less regular structures. EVOH(44) demonstrated the highest T m but lower χc and T g values as compared to that of the isotactic polymer. Wide-angle X-ray scattering showed that semicrystalline EVOH(44) exhibited a monoclinic structure characteristic of commercial materials, while ROMP-derived polymers displayed an intermediate structure between monoclinic and orthorhombic. Tensile testing showed that isotacticity resulted in brittle mechanical behavior, while the atactic and commercial EVOH(44) samples had higher tensile toughness values. Although EVOH(44) had the lowest P O2 of the samples explored, the atactic and tough ROMP-derived polymer approached this value of P O2 while having a P H2O over 3 times lower than that of commercial EVOH(44).

Flexible cellulose nanofibers/MXene composite films for UV-shielding packaging

Cellulose nanofibers (CNF) based films are promising packaging materials, but the lack of special functions (especially UV-shielding property) usually restrict their further applications. In this work, MXene was incorporated into the CNF film by a direct solvent volatilization induced film forming method to study its UV-shielding property for the first time, which avoided the using of a vacuum filtration equipment. The composite films containing glycerin could be folded repeatedly without breaking, showing good flexibility. The structure and properties of MXene/CNF composite films (CMF) were characterized systematically. The results showed that MXene distributed uniformly in the CNF film matrix and there was strong hydrogen bonding interaction between CNF and MXene. The tensile strength and Young's modulus of the composite films could reach 117.5 MPa and 2.23 GPa, which was 54.1 % and 59.2 % higher than those of pure CNF film, respectively. With the increase of MXene content, both the UVA and UVB shielding percentages increased significantly from 17.2 % and 25.5 % to 100.0 %, showing excellent UV-shielding property. Moreover, CMF exhibited a low oxygen permeability (OP) value of 0.39 cc μm d−1 m−2 kPa−1, a low water vapor permeability (WVP) value of 5.13 × 10−11 g−1s−1Pa−1 and a high antibacterial rate against E. coli (94.1 % at 24 h), showing potential application in the packaging field.

Tailoring Pectin-PLA Bilayer Film for Optimal Properties as a Food Pouch Material.

This study focuses on developing a biodegradable film using a novel hybrid citrus peel pectin. A bilayer approach with PLA was proposed and optimized using Response Surface Methodology (RSM) to complement pectin films' mechanical and barrier property limitations. The optimized film composition (2.90 g PLA and 1.96 g pectin) showed enhanced mechanical strength with a tensile strength (TS) of 7.04 MPa and an elongation at break (EAB) of 462.63%. In addition, it demonstrated lower water vapor (1.45 × 10-10 g/msPa), oxygen (2.79 × 10-7 g/ms) permeability, and solubility (23.53%). Compared to single-layer pectin films, the optimized bilayer film had a 25% increased thickness, significantly improved water barrier (3806 times lower) and oxygen barrier (3.68 times lower) properties, and 22.38 times higher stretchability, attributed to hydrogen bond formation, as confirmed by FTIR analysis. The bilayer film, effectively protected against UV and visible light, could be a barrier against light-induced lipid oxidation. Moreover, it demonstrated superior seal efficiency, ensuring secure sealing in practical applications. The bilayer pouch containing mustard dressing exhibited stable sealing with no leakage after immersion in hot water and ethanol, making it suitable for secure food pouch packaging.