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Almond shells (ASs) are a potential source of cellulose that could be obtained through sustainable methods for their valorisation. Biocomposites (BCs) from polyvinyl alcohol (PVA) and cellulose are interesting materials for developing sustainable packaging materials. BC based on PVA and AS cellulose were obtained by melt blending and compression moulding, by using subcritical water extraction at 160 or 180 °C, and subsequent bleaching with sodium chlorite (C) or hydrogen peroxide (P) to purify cellulose. The influence of the purification method on the properties of BC was analysed. Fibres treated with C were better dispersed in composites than those bleached with P. Residual phenolic compounds in the fibres provide the composite with ABTS∙+ scavenging capacity in line with the residual lignin content of the fibres. Both the presence of phenols and dispersed fibres reduced the film transparency, mainly in the UV range. Fibres enhanced the oxygen barrier capacity of composites, and those treated with HP also improved the water vapour barrier capacity. Fibres treated with C better promoted the increase in the elastic modulus of the composites, due to their highest crystallinity and dispersibility, while favoured the PVA crystallisation. Therefore, the obtained AS cellulose fibres could be used to obtain thermoprocessed PVA biocomposites for food packaging applications. [ABSTRACT FROM AUTHOR]

Cellulose nanomaterials (CNMs) have potential utilization as oxygen barrier layers when applied as the primary component of a single layer in multilayer packaging systems. One limitation of dense CNM films is their lack of durability due to their brittle nature. The durability of cellulose nanofibril (CNF) films was examined through the lens of understanding the residual stress that formed within the films during drying. A beam bending method consisting of drying CNF films on top of a flexible substrate was used to quantify residual stress. It was determined that for two common variations of CNFs (TEMPO-oxidized vs mechanically refined), the residual drying stress was on the order of 50% of the yield strength of the material at a given humidity. Larger residual stress formed within the TEMPO-oxidized CNFs as compared to the mechanically refined CNFs due to the smaller fibril diameters resultant of the TEMPO oxidation production process. The residual stress in the TEMPO-oxidized material was also more sensitive to moisture (humidity) than the mechanically refined material. Various plasticizers were examined for their efficacy in reducing residual drying stress. Triethyl citrate appears more effective in reducing residual stress than common polyols (glycerol/sorbitol), especially when subjecting the films to low humidity. Triethyl citrate in combination with a small amount of polyvinyl alcohol at a total plasticizer content of 30% of the mass of the CNFs resulted in a 75% reduction in the residual stress from the unplasticized state. In this low-stress state, standalone films (10–15 µm) can withstand creasing operations that compromise unmodified (high residual stress) films in terms of their ability to prevent oxygen transmission. Additionally, the low-stress formulation was coated onto a paper substrate resulting in enhanced durability during creasing operations prior to oxygen barrier testing. [ABSTRACT FROM AUTHOR]

Polylactic acid (PLA) is a biodegradable polymer extensively used in packaging; however, its mechanical and barrier properties require enhancement for wider applications. Chitin-derived nanoflakes (CNFL), a two-dimensionally separated nanomaterial derived from α-chitin, possess high strength and toughness, making them ideal additives for improved PLA performance. This study investigated the effect of CNFL on the properties of PLA composite films. Incorporating CNFL significantly enhanced the mechanical properties of PLA, increasing its tensile strength and stiffness while preserving flexibility. This enhancement was attributed to the nucleating effect of CNFL, which increases crystallinity. Additionally, CNFL improved the thermal stability of the composite films by mitigating thermal deformation. Notably, the oxygen barrier properties of CNFL-filled PLA composites were also enhanced, demonstrating a significant reduction in oxygen permeability at optimal CNFL concentrations due to increased tortuosity of the oxygen diffusion path. Overall, CNFL-filled PLA composites exhibit great potential as renewable packaging materials, particularly for protecting sensitive products, such as food and pharmaceuticals, from oxidative degradation, thereby extending shelf life and maintaining quality. These findings suggest that CNFL-filled PLA composites are promising materials for advanced applications, offering a combination of enhanced mechanical performance, improved thermal stability, and superior oxygen barrier properties. [ABSTRACT FROM AUTHOR]

Copyright of Transactions of China Pulp & Paper is the property of China Pulp & Paper Magazines Publisher and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Objective: This paper investigates the critical role of material thickness in freeze-dried pellets for enhancing the storage stability of encapsulated bacteria. Freeze dried material of varying thicknesses obtained from different annealing durations is quantified using Scanning Electron Microscopy (SEM) and X-ray microtomography (μCT), the material thickness is then correlated to the storage stability of the encapsulated cells. Methods: A formulation comprising of sucrose, maltodextrin, and probiotic cells is quenched in liquid nitrogen to form pellets. The pellets undergo different durations of annealing before undergoing freeze-drying. The material thickness is quantified using SEM and μCT. Storage stability in both oxygen-rich and oxygen-poor environments is evaluated by measuring CFU counts and correlated with the pellet structure. Results: The varying annealing protocols produce a range of material thicknesses, with more extensive annealing resulting in thicker materials. Storage stability exhibits a positive correlation with material thickness, indicating improved stability with thicker materials. Non-annealed pellets exhibit structural irregularities and inconsistent storage stability, highlighting the impracticality of avoiding annealing in the freeze-drying process. Conclusions: Extensive annealing not only enhances the storage stability of probiotic products but also provides greater control over the freeze-drying process, ensuring homogeneous and reproducible products. This study underscores the importance of material thickness in freeze-dried pellets for optimizing storage stability for probiotic formulations, and emphasize the necessity of annealing as a critical step in freeze-drying quenched pellets to achieve desired structural and stability outcomes. [ABSTRACT FROM AUTHOR]

In 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. [ABSTRACT FROM AUTHOR]

Nanocellulose materials have been widely used in biomedicine, food packaging, aerospace, composite material, and other fields. In this work, cellulose obtained from Camellia shells through alkali boiling and subbleaching was micro-dissolved and regenerated using the DMAc (N,N-Dimethylacetamide)/LiCl system, and TOCNs (TEMPO-oxidized cellulose nanofibers) with different degrees of oxidation. The membrane was prepared by filtration of polytetrafluoroethylene (pore size 0.1 μm), and the oxidized nanocellulose film was obtained after drying, Then, the crystallinity, mechanical properties and oxygen barrier properties of the TOCN film were investigated. Furthermore, based on TS (tea saponin) from Camellia oleifera seed cake and TOCNs, TS-TOCN film was prepared by the heterogeneous reaction. The TS-TOCN film not only shows excellent oxygen barrier properties (the oxygen permeability is 2.88 cc·m−2·d−1) but also has good antibacterial effects on both Gram-negative and Gram-positive bacteria. The antibacterial property is comparable to ZnO-TOCN with the same antibacterial content prepared by the in-situ deposition method. Antioxidant activity tests in vitro showed that TS-TOCN had a significant scavenging effect on DPPH (2,2-Diphenyl-1-picrylhydrazyl) radicals. This design strategy makes it possible for inexpensive and abundant Camellia oleifera remainders to be widely used in the field of biobased materials. [ABSTRACT FROM AUTHOR]

BACKGROUND: Encapsulation is commonly used to protect probiotics against harsh stresses. Thus, the fabrication of microcapsules with special structure is critical. In this work, microcapsules with the structure of S/O/W (solid-in-oil-in-water) emulsion were prepared for probiotics, with butterfat containing probiotics as the inner core and with whey protein isolate fibrils (WPIF) and antioxidants (epigallocatechin gallate, EGCG; glutathione, GSH) as the outer shell. RESULTS: Based on the high viscosity and good emulsifying ability of WPIF, dry well-dispersed microcapsules were successfully prepared via the stabilization of the butterfat emulsion during freeze-drying with 30-50 g L-1 WPIF. WPIF, WPIF + EGCG, and WPIF + GSH microcapsules with 50 g L-1 WPIF protected probiotics very well against different stresses and exhibited similar inactivation results, indicating that EGCG and GSH exerted neither harm or protection on probiotics. This significantly reduced the harmful effects of antioxidants on probiotics. Almost all the probiotics survived after pasteurization, which was critical for the use of probiotics in other foods. The inactivation values of probiotics in microcapsules were around 1 log in simulated gastric juice (SGJ), about 0.5 log in simulated intestinal juice (SIJ), and around 1 log after 40 days of ambient storage. CONCLUSION: Dry S/O/W microcapsule, with butterfat containing probiotics as the inner core and WPIF as the outer shell, significantly increased the resistance of probiotics to harsh environments. This work proposed a preparation method of dry S/O/W microcapsule with core/shell structure, which could be used in the encapsulation of probiotics and other bioactive ingredients. [ABSTRACT FROM AUTHOR]

Biodegradable polymers have become a topic of great scientific and industrial interest due to their environmentally friendly nature. For the benefit of the market economy and environment, biodegradable materials should play a more critical role in packaging materials, which currently account for more than 50% of plastic products. However, various challenges remain for biodegradable polymers for practical packaging applications. Particularly pertaining to the poor oxygen/moisture barrier issues, which greatly limit the application of current biodegradable polymers in food packaging. In this review, various strategies for barrier property improvement are summarized, such as chain architecture and crystallinity tailoring, melt blending, multi-layer co-extrusion, surface coating, and nanotechnology. These strategies have also been considered effective ways for overcoming the poor oxygen or water vapor barrier properties of representative biodegradable polymers in mainstream research. [ABSTRACT FROM AUTHOR]

Coronene emits phosphorescence only at cryogenic temperatures in the absence of oxygen. To achieve room‐temperature phosphorescence (RTP), coronene has been incorporated into various host materials to prevent non‐radiative deactivation of the incorporated molecules. Among host materials, crystalline porous materials homogeneously incorporate luminescent molecules and prevent their aggregation. Therefore, they have attracted attention as potential host materials. Although coronene incorporated into a crystalline porous material exhibited RTP in previous studies, the host material exhibited high affinity for oxygen, allowing the expression of RTP only under anoxic conditions. Therefore, RTP has not been achieved in air. Herein, we incorporate coronene into cage‐like sodalite‐type porous organic salts (s‐POSs) composed of tetrasulfonic acid with an adamantane core (4,4',4",4"'‐[adamantane‐1,3,5,7‐tetrayl]tetrabenzenesulfonic acid; AdPS) and triphenylmethylamines modified with substituents at the para‐position of the benzene rings (TPMA−X, X=methyl [Me], Br, I), which have low oxygen affinities and different degrees of heavy‐atom effects on incorporated coronene. The combination of the oxygen barrier due to the low affinity of s‐POSs for oxygen and the external heavy‐atom effect of bromine and iodine exposed on the pore surface enabled the incorporated coronene to exhibit RTP in air (phosphorescence lifetime with more than microseconds). [ABSTRACT FROM AUTHOR]

The frequent occurrence of building fires has triggered a compelling need for flame-retardant coatings. However, the existing flame-retardant coating technologies are high-cost, inefficient, and environmentally unfriendly. In this work, a silica-alumina sol has been developed as the substrate of the flame-retardant coatings. Boron nitride (h-BN) and glass powders with low melting temperature are employed as fillers to improve the flame retardancy. This kind of hybrid coatings can form a high-viscosity liquid-solid phase and be re-paired in high-temperature environments. The experimental results indicate that the as-prepared hybrid coating can act as an oxygen barrier to protect the substrates against fire. Besides, a carbonous layer has been formed on the coating surfaces when exposed to flames, which can stem the spread of the flame spread. Due to the low cost, high stability, self-repairing and easy preparation, the self-repairing hybrid coatings show great potential for application in the fields of fire-proof and flame retarding. Highlights: A silica-alumina sol is developed as the substrate of the flame-retardant coatings. Glass powders with low melting temperature are employed as fillers. The coating can form a high-viscosity liquid-solid phase at high temperatures. The coating can act as an oxygen barrier to protect the substrates against fire. [ABSTRACT FROM AUTHOR]

Summary: Wheat bran extracts (WBE, mainly composed of feruloyl oligosaccharides (FOs)) have been approved by FDA in GRAS Notice. WBE was utilised in octenyl succinate anhydride‐modified starch (OSA‐starch)‐based microcapsules as wall materials to protect β‐carotene (BC) from oxygen. The storage retention and antioxidant indexes in vivo and in vitro of microcapsules were determined. The results showed that these characteristics were positively related to the proportion of WBE in the wall material. The in vivo antioxidant indexes in mouse serum and liver were positively regulated at gavage dose around content in wheat grain (normal dose), while at a higher dosage, the in vivo free oxidative stress fell into disorder. The results indicated that WBE was a good component of wall material, which can improve the antioxidant environment during both storage and consumption. This experiment provides a theoretical basis for the industrial application of WBE in the field of microcapsules. [ABSTRACT FROM AUTHOR]

Sustainable EHL/PHBH biocomposites were prepared by the addition of enzymatic hydrolyzed lignin (EHL) into poly (3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBH) via solution casting technique. The research comprehensively evaluated the effects of EHL contents on the morphological, thermostability, barrier and anti-ultraviolet properties of EHL/PHBH biocomposites. SEM and FT-IR analysis showed that the EHL filler had good dispersibility in PHBH matrix and the good interface binding was observed in biocomposites. Compared with neat PHBH, the tensile strength and Young's modulus of biocomposites with 3 ~ 5 wt% EHL increased by 46.1% and 130.4%, respectively, and the maximum degradation temperature (Tmax) increased by 50 °C. More notably, a 30.2% and 52.3% reduction of the moisture and oxygen permeability, which were much higher than conventional plastics. It was also found that the biocomposites exhibited excellent UV resistance, almost completely shielding UV-A (320–400 nm) and UV-B (280–320 nm), and good antioxidant activity with 76.6% DPPH scavenging rate. The above, EHL/PHBH were demonstrated a promising biocomposites for anti-oxidation, UV-blocking, oxygen barrier and moisture-proof packaging materials. [ABSTRACT FROM AUTHOR]

A series of polyethylene terephthalate‐polyethylene naphthalate (PETN) copolymer films with excellent oxygen barrier properties were prepared by introducing trace amounts of hydroxy‐terminated polybutadiene (HTPB) into PETN via in‐situ polymerization. The PETN‐HTPB copolymer films had strong oxygen scavengering capability. Due to the reaction of HTPB with oxygen, highly dense oxidized layers were formed. The introduction of HTPB also enhanced the nucleation of the PETN and increased crystallinity. The stronger oxygen scavenging capacity, the formation of the oxidized layer, and the increased crystallinity together greatly improved the oxygen barrier performance of the PETN‐HTPB films. When the HTPB content was only 1.0 wt%, the oxygen permeability of the films was as low as 18.2 cc mil m−2 day−1 0.1 MPa−1, which was about 7.5 times lower than that of the pure PETN film. The maximum oxygen scavenging amount of the samples was 8.3 ml g−1. The lowering of the diffusion coefficient instead of lowering of solubility was the main contributor to the decreasing permeability coefficient of the PETN‐HTPB films. This work provides a new idea for the preparation of high oxygen barrier polyester materials with oxygen scavenging capability. [ABSTRACT FROM AUTHOR]

The present study aimed at assessing the impact of addition of fumaric acid (0.5%), as an active agent, in a corn starch (2%) based edible coating, on the lipid quality and microbial shelf life of silver pomfret (Pampus argenteus) fish steaks stored at 4 °C. Treating fish steaks with FA resulted in a bacteriostatic effect leading to reduced counts of total mesophilic and psychrotrophic bacteria, H2S producing bacteria and Pseudomonas spp. The total mesophilic bacterial count of uncoated control sample exceeded the permissible limit of 7 log cfu g−1 on 6th day and had the lowest microbial shelf life. FA incorporation in the CS coating improved the microbial stability of fish steaks resulting in a shelf life of 15 days. The outcomes of the study suggest that CS based coating is beneficial in delaying lipid oxidation as displayed by the lower TBA and PV values while FA is an effective agent for further increasing the preservative action of CS coating by significantly inhibiting microbial growth as well as lipid quality deterioration, which could be exploited by the seafood industry as an active packaging component. [ABSTRACT FROM AUTHOR]

Polylactic acid (PLA) is widely known for its biocompatibility, biodegradability, and high transparency. However, it still has varied limitations such as flammability, UV sensitivity, and poor oxygen barrier properties. To address these issues, a bio-based compound, hexasubstituted cyclotriphosphazene (HVP), was synthesized by using vanillin and hexachlorocyclotriphosphazene to enhance the overall performance of PLA. The resulting PLA/HVP composites demonstrated improved mechanical strength and UV resistance. Specifically, PLA/3HVP, with a 3 wt% HVP loading, achieved a UL-94 V-0 rating and a high limiting oxygen index of 26.5 %. Cone calorimeter tests revealed that PLA/3HVP possessed a significantly longer ignition time and a lower peak heat release rate compared to pure PLA. These burning testing results indicated the enhanced fire resistance. Additionally, the oxygen transmission rate of PLA/3HVP was reduced by 81.1 % compared to pure PLA. When used as food packaging, the weight loss of mangoes covered with PLA/3HVP film was 2.2 % after 7 days, compared to 2.5 % with pure PLA film, highlighting its potential for food preservation applications. [Display omitted] • A bio-based multifunctional additive (HVP) was synthesized from vanillin and HCCP. • PLA/HVP composites showed improved mechanical and flame retardant properties. • PLA/HVP composites exhibited efficient anti-UV and high oxygen barrier performance. • PLA/HVP film was used as a packaging material to prolong the freshness of food. [ABSTRACT FROM AUTHOR]

Photodegradation and oxidation are major causes of the deterioration of food, resulting in darkening, off-flavors, and nutrient deficiency. To reduce this problem, novel functional polymeric materials are being developed to retain food's light sensitivity. Nanofillers are also used in a polymeric film to produce effective UV blockings and oxygen barrier coatings so that the degradation of the food can be delayed, thereby increasing the shelf life. For this purpose, polyvinyl alcohol coatings were prepared by the incorporation of ZnO nanoparticles. Polyvinyl alcohol is a naturally excellent barrier against oxygen, and the addition of ZnO particles at the nanoscale size has demonstrated effective UV blocking capabilities. In this work, the hydrothermal technique is used to produce ZnO nanoparticles, and these produced particles are then incorporated into the polyvinyl alcohol to produce thin films. These films are characterized in terms of the compositional, macroscopic, microscopic, and optical properties via X-ray diffraction (XRD), FTIR, scanning electron microscopy (SEM), and thermogravimetric analysis (TGA), as well as UV–VIS spectroscopy. ZnO nanoparticles at different concentrations were incorporated into the PVA solution, and the films were processed via the blade coating method. With the addition of ZnO, the oxygen transmission rate (OTR) of pure PVA was not altered and remained stable, and the lowest OTR was recorded as 0.65 cm3/m2·day·bar. Furthermore, the addition of ZnO increased the water contact angle (WCA) of PVA, and the highest WCA was recorded to be around more than 70°. Due to this, water permeability decreased. Additionally, PVA/ZnO films were highly flexible and bendable and maintained the OTR even after going through bending cycles of 20K. Furthermore, the addition of ZnO showed a significant UV blocking effect and blocked the rays below a wavelength of 380 nm. Finally, the optimized films were used for packaging applications, and it was observed that the packaged apple remained fresh and unoxidized for a longer period as compared with the piece of apple without packaging. Thus, based on these results, the PVA/ZnO films are ideally suited for packaging purposes and can effectively enhance the shelf life of food. [ABSTRACT FROM AUTHOR]

Copyright of China Pulp & Paper is the property of China Pulp & Paper Magazines Publisher and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Different types of impermeable fillers are usually incorporated into polymeric coating film to enhance the gas barrier properties. For instance, impermeable fillers are commonly used in barrier coating due to their larger surface, which in turn serve as barrier inclusions restricting the penetrant gas to diffuse through a longer tortuous pathway. Modeling gas transport in barrier coating can help determine the shelf-life of packaged food and reduce product development resources and time. In this paper, related tortuosity-based models corresponding to different filler geometries are outlined. This review emphasizes the emerging trends in modeling the tortuous pathway and the respective relative permeability model to predict the gas barrier performance in composite films used for barrier coating applications. We review models incorporating a range of factors, including different shapes, geometries, angular orientations, alignments, randomness in distribution, stacking, interspacing, and the polydispersity of fillers. The approaches employed to develop the tortuosity-based phenomenological models starting with simplified filler geometry and orientations to more complex morphological features of the composite films are elaborated. [ABSTRACT FROM AUTHOR]

Biopolymers, e.g., polysaccharides and protein, have been employed as edible coatings for the preservation of fruits for many years and are the promising candidates for resolving the problems caused by the extensive using of synthesized polymers in recent years. Chitosan, a kind of polysaccharide with excellent antibacterial and coatings forming properties, has attracted a lot of research interests in being applied as an edible coating for the preservation of postharvest fruits. However, the applying of chitosan is restricted by its poor stability. In this study, we introduce the water-soluble dialdehyde cellulose (DAC) as the crosslinking agent for chitosan to enhance its stability. Fourier transform-infrared spectroscopy is applied to prove the happening of crosslinking and the detection of swelling ratio in water and mechanical properties of DAC-crosslinked chitosan (DAC/CS) confirms the enhanced stability. Furthermore, scanning electron microscope, thermogravimetric analysis, water contact angle, mechanical and gas barrier properties are performed to characterize DAC/CS films with different DAC contents. Finally, DAC/CS is employed as a coating agent to study the effect on the storage of mandarin fruit at room temperature. Chitosan, with enhanced stability by biopolymer, would be a promising candidate applied as a green edible coating in the preservation of fruits. [ABSTRACT FROM AUTHOR]

Environmental barrier coatings (EBCs) with great oxidation-resistant performance in steam are needed for efficient protection of silicon carbide-based composites in future advanced gas turbine engines. Besides a dense structure without rapid penetration paths for oxidants and other corrosives, refractory components such as alumina oxide or oxide-containing compounds also help to repel oxygen through coatings, which can ensure a long service life of EBC when used to infiltrate and block pores. However, due to their melting temperature up to nearly 2000 °C, melting and infiltration will damage EBC and matrix. In this work, metallic aluminum first infiltrates into open pores and microcracks at a low temperature of 750 °C, forming a dense structure, and then reacts in situ to form the refractory phases during heat treatment at 1100 °C, which is far below the melting point of refractory components of nearly 2000 °C. The results demonstrate that the structure remained dense after heat treatment. An intermedia layer composed of alumina and ytterbium aluminum garnet was observed due to the diffusion and reaction of oxygen and aluminum. The dense and refractory diffusion-reaction layer prevents the rapid infiltration and diffusion of oxidants in the engine environment to coating and matrix. [Display omitted] [ABSTRACT FROM AUTHOR]

Renewable thermoplastic starch (TPS) was modified by poly (vinyl alcohol) (PVA) with varying degrees of polymerization (DPs) or scCO2-assisted processing to prepare TPSxPVAyz or scCO2TPSxPVAyz fully biodegradable blends. The TPSxPVAyz (or scCO2TPSxPVAyz) films showed the smallest free volume characteristics and oxygen transmission rates (OTRs), as their PVA loadings approached an optimum value. The smallest free volume characteristics and OTRs evaluated for each optimal TPSxPVAyz (or scCO2TPSxPVAyz) films reduced noticeably as their DPs reduced from 2400 to 300. Considerably smaller OTRs and free volume characteristics were acquired for scCO2TPSxPVAyz films than those of corresponding TPSxPVAyz films prepared without the assistance of scCO2. An essential result is that the OTR of the optimal scCO2TPSxPVAyz film with a moisture content of 4wt% was merely 4.6 cm3/m2∙day∙atm. This OTR is as good as that of the polyvinylidene chloride oxygen barrier packaging. Dynamic mechanical relaxations and WAXD characterizations revealed that TPS and PVA are miscible, as PVA loadings were ≤ the optimum values. The enhanced oxygen barrier resistance and reduced free volume characteristics for optimal TPSxPVAyz and scCO2TPSxPVAyz films are partly ascribed to the strengthened molecular interactions between O–H groups of TPS and PVA, as they were processed with the assistance of scCO2, optimum PVA loadings or diminished DPs. [ABSTRACT FROM AUTHOR]

Since the inception of research on hollow silica, the use of hollow nanosilica (HNS) as additives in barrier materials has not been reported. In this study, we evaluated the capacity of HNS as an additive in modified polypropylene (MPP). According to X-ray diffraction (XRD), the crystallinity, tensile strength, and thermal stability of MPP/HNS nanocomposite containing 0.1 phr HNS approached maximum values. Moreover, the nanocomposite had the best performance in terms of water vapor barrier and oxygen resistance. The reasons for the improvement in barrier performance were discussed. Scanning electron microscopy revealed that HNS at a low content dispersed well in MPP. In conclusion, the synthesized HNS can be used as an additive in barrier materials, and it would have potential applications in the fields of food packaging films and storage containers or materials. Hollow nanosilica was synthesized, and then it was used as an additive in modified polypropylene to prepare nanocomposites. These new nanocomposites show excellent properties, such as tensile strength, barrier performances and thermostability. The new nanocomposites could be widely used in packaging materials. [ABSTRACT FROM AUTHOR]

[Display omitted] • A cost‐effective copolymerization strategy simultaneously achieves high‐temperature transparency and oxygen barrier properties. • Copolymers have superior activation energy of pyrolysis and lifetime. • The transparency of films (92%) is unaffected by thermal crystallization. • The oxygen‐barrier performance of copolymer films is increased by 32% compared to MXD6. Semi-aromatic polyamides have long been recognized for their exceptional comprehensive properties in numerous demanding applications. Among them, poly(m-xylylene adipamide) (MXD6) was commonly used in oxygen-barrier packaging but suffered diminished transparency due to thermal crystallization. Herein, we introduced terephthalic acid (PTA) as rigid monomer units into the chain of MXD6 to prepare amorphous copolyamides PA MXDT-MXD6 via one-pot polycondensation, guided by thermal analysis. The chemical structure of copolyamides was confirmed using 1H NMR and FTIR spectra. Thermal analysis revealed that the copolyamides exhibited high thermal stability, amorphous characteristics, and improved glass transition temperatures (110.9–136.5 °C). Pyrolysis kinetics further demonstrated that copolyamides have enhanced thermal stability and lifetime. Furthermore, copolymerization resulted in numerous amide bonds conjugated with benzene rings, leading to superior high-temperature transparency, oxygen-barrier, and mechanical properties compared to MXD6 and other reference polyamides. These characteristics indicate the potential suitability of copolyamides as transparent and heat-resistant barrier materials. [ABSTRACT FROM AUTHOR]

Barrier materials are crucial in preserving product quality, safety and longevity across numerous applications, thereby contributing to sustainability, reducing waste and advancing technology. Among these materials, cellulose nanomaterials (CNs) have emerged as promising alternatives for traditional petroleum-based polymers. However, the wide range of sources and the different methods used to isolate and process CN-based materials can result in significant variations in moisture and oxygen barrier performance. In this review, we provide an in-depth discussion on the latest advancements in CN-based green barrier materials. We begin by offering a critical assessment of the barrier performance of CNs, both in their isolated form and when combined as hybrid materials. This includes their applications as standalone films, fillers and coatings in nanocomposites. This review also covers the influence of the isolation process and the stages of film formation on barrier efficacy. We further discuss the implications of the recycling process on barrier properties of CN-based materials, drawing a connection between barrier characteristics and the product's end-of-life. We conclude by highlighting the significant developments over the past five years, the present challenges, and the prospective future of CN-based materials in barrier applications. [Display omitted] [ABSTRACT FROM AUTHOR]

Poly(lactic acid) (PLA) films with significantly enhanced mechanical and oxygen barrier properties were obtained via oxygen scavenging strategy combining with uniaxial stretching. In this study, PLA was melt blended with 3 phr of hydroxy-terminated polybutadiene (HTPB) and different contents of acetyl(tributyl citrate) (ATBC) and cobalt neodecanoate. It was then followed by compression molding and uniaxial stretching. After uniaxial stretching, the crystallinity of all films was significantly improved, which contributed to the enhancement in the oxygen barrier performance of composite materials. The morphological analysis carried out using scanning electron microscopy (SEM) revealed that ATBC could obviously promote the dispersion of HTPB in PLA. Overall, the blend films showed a decrease in the oxygen permeability coefficient as compared with the neat PLA film, which reached a similar level to oriented PET film. The optical and mechanical properties of the blend films with ATBC also improved considerably. This work provides a method to prepare high-crystalline polymers with superior gas-barrier properties having great potential for use in high-barrier applications, such as polymers for oxygen-sensitive food packaging. • PLA films with significantly enhanced mechanical and oxygen barrier properties were obtained by uniaxial stretching. • Increased crystallinity and HTPB/cobalt catalyst both played important roles in improving oxygen barrier property of PLA films. • The dispersion of HTPB was improved with ATBC to further enhance oxygen barrier property of PLA films. • Modified PLA film displayed a similar level of oxygen barrier property to oriented PET film. [ABSTRACT FROM AUTHOR]

Developing the bio-based barrier material to substitute the petroleum-based one is the trend in functional packaging applications. Utilization of the abundantly underappreciated bark biomass is attractive from the sustainability point of view; however, an upgraded approach is required to maximize the performances of the lignin-containing cellulose nanofibril (LCNF) films from willow bark. Herein, hot water extraction (HWE) and microfluidization were studied for their effect on the yield of LCNF and its film performance after treatment of aqueous p-toluenesulfonic acid. The resultant HWE films were superior to the nontreated ones regarding yield, moisture, and oxygen barrier properties. In particular, the HWE films achieved an oxygen permeability of 3 cm3·μm/m2·kPa·day at 50% relative humidity, which is among the lowest achieved for single bio-based materials and comparable to commercially available synthetic barrier films. The LCNF films attained complete blocking of UV light transmission within the wavelength range of 290–400 nm. Overall, this study shows that HWE pretreatment not only allows the recovery of high-value extracts, but also significantly improves the yield of LCNF and its barrier performances. The biocompatible, lignin-containing, and self-standing hydrophobic nanocellulose films show promise as a barrier layer against UV radiation and oxygen permeation in food packaging and other applications. [ABSTRACT FROM AUTHOR]

To realize the application of xylan based film in food and drug packaging, the poor mechanical property and film-forming property of xylan based film must be overcome. Herein, a good oxygen barrier composite film with desired mechanical properties was prepared based on carboxymethly xylan (CMX), chitosan (CS), and graphene oxide (GO). The results of scanning electron microscope revealed the composite film had a dense and continuous structure, which will endow the composite film with excellent mechanical property. As expected, the composite film with the 0.5% mass fraction of GO exhibited best mechanical property, among which the tensile stress, tensile strain, and Young's modulus of the composite film reached 50.81 MPa, 47.61%, and 1.39 GPa, respectively. The oxygen barrier properties of the composite films significantly increased with the addition of graphene oxide due to the dense, stacked multilayer structure. In addition, these composite films exhibited good antibacterial properties. Therefore, these films show great promise in the field of food packaging and wound dressing due to their excellent mechanical, oxygen barrier and antibacterial properties. • Flexible composite films based on CMX, CS, and GO prepared by casting method. • Desired mechanical properties of the composite films were obtained by adding GO. • The composite films exhibit good oxygen barrier and antibacterial properties. [ABSTRACT FROM AUTHOR]

Food packaging is one of the most important parts of the food industry, and polyethylene‐based polymers have been widely used as food packaging films. In this study, corona‐treated polyethylene terephthalate (PET) films were used to increase adhesion to the barrier coating solution for multilayered film formation and various concentrations of montmorillonite (MMT; 0, 1, 3, and 5 wt.%) were used to improve the barrier properties of PET films for food packaging after different treatments of MMT including ultrasonication with bath or probe and 100‐W or 300‐W microwave to evenly disperse MMT. Among them, a 300‐W microwave treatment was most effective for size reduction of MMT particles. Even though 5 wt.% MMT was used to coat PET films with polyacrylic acid (PAA), good transmittance in the visible region (500 nm) was obtained, with a value similar to that of the neat PET film. The dispersion of MMT and binding of PAA/MMT nanocomposites were confirmed by field‐emission scanning electron microscopy, X‐ray diffraction, and Fourier transform infrared spectroscopy analyses. The water vapor and oxygen barrier properties of PET films were enhanced by PAA coating. Moreover, the oxygen permeability of PET films decreased via coating by PAA blended with 1 and 3 wt.% MMT. Based on these results, the PET film coated with PAA/MMT nanocomposites could be applied as food packaging films that require high gas barrier properties for oxygen‐sensitive food. [ABSTRACT FROM AUTHOR]

The current level of packaging consumption imposes a need to fabricate single-use food packaging with renewable and compostable materials, such as bio-polyesters (e.g., polylactic acid, PLA and polybutylene succinate, PBS) or cellulose, but their use is still problematic. Fabrication of bio-compostable composites can specifically address impeding challenges, and adhesive lamination, achieved with compostable glue, is becoming more and more popular with respect to the less versatile hot lamination. In this context, plasma activation, a chemical-free oxidation technique of a material's surface, is used to increase the affinity of three different biomaterials (cellulose, PLA and PBS) toward a compostable polyurethane adhesive to decrease its amount by gluing bio-polyesters to cellulose. Optical Microscopy reveals activation conditions that do not affect the integrity of the materials, while Water Contact Analyses confirm the activation of the surfaces, with contact angles decreased to roughly 50 deg in all cases. Unexpectedly, ζ-potential analyses and subtractive infrared spectroscopy highlight how the activation performed superficially etches cellulose, while for both PLA and PBS, a general decrease in surface potential and an increase in superficial hydroxyl group populations confirm the achievement of the desired oxidation. Thus, we rationalize continuous activation conditions to treat PLA and PBS and to glue them to neat cellulose. While no beneficial effect is observed with activated PLA, bi-laminate composites fabricated with activated PBS fulfill the benchmark for adhesion strength using less than before, while oxygen permeation analyses exclude plasma-induced etching even at a nanoscale.

Transparent polymeric thin films with high oxygen barrier are important for extending the shelf life of food and protecting flexible organic electronic devices. Polyelectrolyte/clay multilayer nanocoatings are shown to exhibit super gas barrier performance, but the layer‐by‐layer assembly process requires numerous deposition steps. In an effort to more quickly fabricate this type of barrier, a polyelectrolyte/clay coacervate composed of branched polyethyleneimine (PEI), poly(acrylic acid) (PAA), and kaolinite (KAO) clay is prepared and deposited in a single step, followed by humidity and thermal post‐treatments. When deposited onto a 179 µm poly(ethylene terephthalate) (PET) film, a 4 µm coacervate coating reduces the oxygen transmission rate (OTR) by more than three orders of magnitude, while maintaining high transparency. This single‐step deposition process uses only low‐cost, water‐based components and ambient conditions, which can be used to for sensitive food and electronics packaging. [ABSTRACT FROM AUTHOR]

Active oxygen barrier films of chitosan/gallic acid/sodium carbonate (CH/GA/SC) were prepared by solution casting method. The effect of gallic acid on physical, mechanical, structural, and oxygen scavenging properties of films was investigated. As compared with neat CH film, CH/GA/SC films displayed higher thicknesses and water solubility. Tensile strength and elongation at break were affected by the addition of gallic acid and sodium carbonate. The chemical interaction evaluated by Fourier-transform infrared spectroscopy and morphology evaluated by scanning electron microscopy, and it is noticed that sodium carbonate and gallic acid were distributed homogeneously in the film structure. The X-ray diffraction confirmed that gallic acid, sodium carbonate, and chitosan had excellent compatibility. The addition of gallic acid in the chitosan matrix caused low water and oxygen permeability. The lowest oxygen transmission rate of the film was 4.10 ± 1.07 cm3/μm/m2 day kpa. The CH/GA/SC 20 film displayed the maximum oxygen-absorbing rate and capacity of 2.66 mL O2/g. day and 19.55 mL O2/g respectively, at 23 ± 2 °C. Moisture inside the package was utilized as a catalyst to begin the oxygen scavenging reaction. The results suggest that the combination of gallic acid and the sodium carbonate in chitosan film is a promising oxygen scavenging material for active oxygen barrier films. [ABSTRACT FROM AUTHOR]

Organic montmorillonite (OMMT) nano‐platelets were exfoliated and well dispersed in fully bio‐based polyamide 11/Poly(vinyl alcohol) (PA11/PVA) blends. Significantly lower oxygen permeation rates (OTR) were detected for the PA1172.5PVA27.5OMMTx films than those of PA11 and PA1172.5PVA27.5 films. An extremely low OTR of 0.218 cm3/m2·day·atm was found for PA1172.5PVA27.5OMMT1 film modified with 1 PHR optimum concentration of well dispersed OMMT nano‐platelets. Similarly, the free volume characteristics evaluated for PA1172.5PVA27.5OMMTx film series reduced to a minimum as the OMMT concentration reached the optimum value. As revealed by dynamic mechanical and differential scanning calorimetric analyses of PA1172.5PVA27.5OMMTx film series, all dynamic glass transition temperature (Tg), melting temperature (Tm) and percentage crystallinity (Wc) values of PA1172.5PVA27.5OMMTx films were noticeably higher than those of PA1172.5PVA27.5 film without addition of OMMT. In fact, Tgs, Tms and Wcs evaluated for PA1172.5PVA27.5OMMTx films increased to a maximum, as their OMMT reached the optimum concentration. The considerably enhanced oxygen barrier resistance found for PA1172.5PVA27.5OMMTx films was ascribed to the considerably reduced free volume characteristics and much longer permeation path caused by impermeably OMMT nano‐platelets well dispersed in PA1172.5PVA27.5OMMTx films. [ABSTRACT FROM AUTHOR]

Early transition metal carbides are considered to be superior candidate materials for oxidizing environments at temperatures exceeding 2000°C. Generally, the remarkable oxidation resistance is largely attributed to a carbonaceous oxide interlayer (eg, Hf–O–C, Zr–O–C, and Ta–O–C), located at the interface between the external oxide layer and internal carbide (eg, HfC, ZrC, and TaC), acting as the primary oxygen barrier. However, the oxygen barrier mechanism of the carbonaceous oxide interlayer remains unclear. Herein, through studying the oxidation behavior of a novel multicomponent carbide Hf0.5Zr0.3Ti0.2C in oxidizing environments up to 2500°C, the oxygen barrier mechanism of the carbonaceous oxide was recently revealed. We found that the oxygen barrier resulted from the slow oxygen diffusion through the inner grains of Hf‐Zr–Ti–O due to the presence of carbon formed at the grain boundaries because of the existence of compact external oxide layer, beneath which the Hf–Zr–Ti–O–C interlayer possesses much lower oxygen activity and temperature that allow carbon to exist stably. This as‐formed carbon strongly retarded the fast diffusion of oxygen along the grain boundaries of oxides. Additionally, desirable synergisms of the designed multicomponent system, particularly, the outward short‐circuit diffusion of Ti, lead to the self‐healing of the external oxide layer, evidently enhancing integral protection performance against oxidizing environments. [ABSTRACT FROM AUTHOR]

Hydroxy‐terminated polybutadiene (HTPB) was grafted onto nanosilica via two steps, and then melt extruded with PET and transition metal catalyst. Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA) results showed that HTPB successfully bridged to the surface of nanosilica through toluene‐2,4‐diisocyanate (TDI), and the grafting amount of HTPB accounted for about 11.2% of the total mass of nanosilica. The PET composite samples were also uniaxially stretched into films. Tensile results showed that the tensile strength of composite films was generally higher than that of composite sheets, especially the tensile strength of PET/SiO2‐HTPB composite film reached 139.8 MPa. After uniaxial stretching, the crystallinity of all films were significantly improved, and fillers accelerated the crystallization rate of PET, which greatly improved the crystallinity of composite materials, thereby contributing to the improvement of the oxygen barrier performance of composite materials. After adding the catalyst, the PET/SiO2‐HTPB/Co composite film has the lowest oxygen permeability coefficient of 1.05 × 10−15 (cm3·cm/cm2·s·pa), which was 87.6% lower than that of pure PET sheet. SEM showed that the compatibility between filler and matrix was improved. This study demonstrated that nanosilica grafted with HTPB played a synergistic role in improving the crystallinity of materials and exerting the active oxygen scavenging of HTPB, and uniaxial stretching was helpful for improving the comprehensive properties of composites. [ABSTRACT FROM AUTHOR]

Flexible and transparent polymeric and bio-polymeric "super barrier" packaging materials have become increasingly important in recent years especially for oxygen-sensitive foods packaging. Different approaches and emerging technologies have been applied in order to improve oxygen barrier properties which can extend the shelf life and maintain the quality and freshness of food products during their determined shelf life. In this review, we summarize the diverse strategies for manufacturing improved oxygen barrier materials including: incorporation of nanoparticles into polymer matrix, fabrication of multilayer polymer, creation of new barrier methods such as development of crystals in polymer matrix, and cross-linking technique. The structure, preparation, and gas barrier properties of obtained polymers via mentioned approaches are discussed in general along with detailed examples drawn from the scientific literature. [ABSTRACT FROM AUTHOR]

The biocompatible, biodegradable and strong polyvinyl alcohol-based films have been widely investigated and used in the field of active packaging. To endow with diverse function, this paper firstly prepared lignin nanoparticles loaded with potassium sorbate (LNP@PS) as additives to exploit additional antibacterial, UV blocking, oxygen barrier, and water barrier properties. Besides, tannin acid (TA) was incorporated for compensating and further enhancing mechanical properties. Results showed that the PVA-based composite films containing 3 % LNP@PS and 5 % TA could achieve the optimal tensile strength at 74.51 MPa, water vapor permeability at 7.015·10−13·g·cm/cm2·s·Pa and oxygen permeability at 1.93 cm3/m2·24 h MPa, which was an 165 % of increase, 47 % and 112 % of reduction respectively compared to pure PVA films. Additionally, the composite films exhibited apparently superior bacteria and oxygen resistance properties evidenced by microbial infection and free radical scavenging performance. In addition, the slow-release effect of PS assisted the strawberry preservation with an extension of 3 days, which provided a promising novel route to prepare active food packaging material. [ABSTRACT FROM AUTHOR]

We have investigated the ability of multilayered hybrid thin films of cellulose nanocrystals (CNCs) and gibbsite nanoplatelets (GNPs) to be built by the layer-by-layer (LbL) technique onto substrates selected for packaging applications, and to improve the oxygen barrier properties. Using complementary structural characterization techniques, namely atomic force microscopy, ellipsometry, and spectral reflectance, we show that when deposited onto model silicon substrates these hybrid films were homogenous and of reduced porosity, and were comprised of alternately deposited monolayers of GNPs and CNCs. The successful deposition of such homogeneous and dense hybrid thin films onto various types of flexible substrates showing different chemical compositions, hydrophilicity, and surface morphology, ranging from cardboard to smart paper, polyethylene (PE) films, and PE-coated cardboard was also confirmed by scanning electron microscopy observations. In view of the diversity of these substrates we could confirm the remarkable robustness of such a deposition process, likely due to (i) the adaptability of the LbL assembling technique and (ii) the strong electrostatic and hydrogen bonding interactions between GNPs and CNCs. The measurement of the oxygen transmission rate (OTR) at 23°C and 50% RH showed that the oxygen barrier properties of the bare substrates could be significantly improved (e.g., 75% decrease of the OTR) after the deposition of such thin (

Binary blends based on polylactic acid (PLA) and other biodegradable polyesters from renewable sources (namely, polybutylene succinate (PBS) and poly-3-hydroxybutyrate (PHB)) were prepared by reactive compounding extrusion. The achieved polymeric compounds were reprocessed by cast extrusion to manufacture the corresponding bioplastic sheets. Three different binary blends, one of which also including tocopherol, an oxygen scavenger, were investigated to ensure high-barrier of the bioplastic sheets to oxygen permeation. Physical, mechanical and chemical properties of the bioplastic sheets were, therefore, comparatively evaluated by differential scanning calorimetry, infrared spectroscopy, tensile tests and gas permeability. The experimental results showed a remarkable improvement in the oxygen barrier properties, especially on sheets manufactured in the PLA/PHB binary blend, without negatively affecting their thermo-mechanical response. Based on experimental evidences, the PLA/PHB binary blend is found to be extremely promising for the development of bio-based and biodegradable polymeric materials with low oxygen permeation, that is, for the development of suitable alternatives to conventional and highly pollutant oil-based plastics. [ABSTRACT FROM AUTHOR]

Herein, polymethylmethacrylate (PMMA)/dextran(D) hybrid composites are prepared by reinforcement of various concentrations of in situ reduced gold nanoparticles (Au NPs). As-synthesised PMMA/D-Au nanocomposites are characterized by Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction(XRD), field emission scanning electron microscopy(FESEM), high resolution transmission electron microscopy(HRTEM) and atomic force microscopy(AFM). It is found that, the average size of Au NPs is 30 nm. The size distributions of Au NPs are studied from dynamics light scattering studies (DLS). The incorporation of Au NPs enhances the oxygen barrier, thermal, and antimicrobial properties of the PMMA/D matrix, by which, the hybrid composites are suitable for packaging applications. [ABSTRACT FROM AUTHOR]

Bacterial cellulose nanocrystals (BCNCs) obtained by enzymatic hydrolysis have been loaded in pullulan biopolymer for use as nanoparticles in the generation of high-oxygen barrier coatings intended for food packaging applications. Bacterial cellulose (BC) produced by Komagataeibacter sucrofermentans was hydrolyzed by two different enzymatic treatments, i.e., using endo-1,4-β-glucanases (EGs) from Thermobifida halotolerans and cellulase from Trichoderma reesei. The hydrolytic activity was compared by means of turbidity experiments over a period of 145 h, whereas BCNCs in their final state were compared, in terms of size and morphology, by atomic force microscopy (AFM) and dynamic light scattering (DLS). Though both treatments led to particles of similar size, a greater amount of nano-sized particles (≈250 nm) were observed in the system that also included cellulase enzymes. Unexpectedly, transmission electron microscopy (TEM) revealed that cellulose nanoparticles were round-shaped and made of 4–5 short (150–180 nm) piled whiskers. Pullulan/BCNCs nanocomposite coatings allowed an increase in the overall oxygen barrier performance, of more than two and one orders of magnitude (≈0.7 mL·m−2·24 h−1), of pure polyethylene terephthalate (PET) (≈120 mL·m−2·24 h−1) as well as pullulan/coated PET (≈6 mL·m−2·24 h−1), with no significant difference between treatments (hydrolysis mediated by EGs or with the addition of cellulase). BCNCs obtained by enzymatic hydrolysis have the potential to generate high oxygen barrier coatings for the food packaging industry.