Vapor Barrier Research Articles

Polyvinyl alcohol-based capsule shells manufactured by injection molding as ready-to-use moisture barriers for the development of delivery systems

In this work, feasibility of injection molding was demonstrated for manufacturing capsule shells. 600 µm-thick prototypes were successfully molded with pharmaceutical-grade low-viscosity polyvinyl alcohols (PVAs), possibly added with a range of different fillers. They showed reproducible weight and thickness (CV < 2 and 5, respectively), compliant behavior upon piercing (holes diameter analogous to the reference), tunable release performance (immediate and pulsatile), and moisture protection capability. To assess the latter, an on-line method relying on near infrared spectroscopy measurements was set-up and validated. Based on the data collected and considering the versatility IM would provide for product shape/thickness/composition, PVA-based molded shells could help widening the portfolio of ready-to-use capsules, representing an interesting alternative to those commercially available. Indeed, these capsules could be filled with various formulations, even those with stability issues, and intended either for oral administration or for pulmonary delivery via single-dose dry powder inhalers.

Ultrastrong and Thermo‐Remoldable Lignin‐Based Polyurethane Foam Insulation with Active‐Passive Fire Resistance

AbstractFoam thermal insulators are indispensable for prevailing energy‐saving engineering, however their widespread use brings intractability such as unsustainability, “white pollution”, and fire hazards. The emergence of bio‐based foams is highly appreciated, but the fabrication approaches are economically unattractive and/or the product properties are inferior, making their large‐scale implementation unviable. Herein, a versatile, thermally remoldable phosphate‐containing polyurethane composite foam (LPU‐G) is constructed from natural lignin and expanded graphite flakes via an atmospheric pressure and scalable one‐pot strategy. The optimal LPU‐G exhibits exceptional mechanical strength, capable of supporting over 6000 times its weight without significant deformation. Moreover, the LPU‐G demonstrates the desired multifunctionality in handling extreme circumstances, including humidity‐tolerant thermal insulation, superb water vapor barrier, and withstanding ≈1200 °C flame without ignition. Based on the “expansion‐conductivity” micro‐mechanism, LPU‐G is the first foam material to be constructed as a sensitive fire alarm system with an ultra‐long alarm time (&gt;1800 s). Surprisingly, LPU‐G can be rapidly upcycled into recyclable bulk composites for a second life through simple thermo‐molding processes rooted in the multi‐dynamic behavior of the phosphate, carbamate, and hydrogen bonds. The easy‐to‐scale LPU‐G represents a new generation of thermal insulators that address concerns regarding unsustainability, high cost, fire risk, and inferior mechanical properties.

Indicative bacterial cellulose films incorporated with curcumin-embedded Pickering emulsions: Preparation, antibacterial performance, and mechanism

Biodegradable, sustainable, and multifunctional intelligent food packaging has attracted extensive attention due to the concerns about the environmental pollution, the health hazard, and the food safety of plastic packaging. Herein, a multifunctional bacterial cellulose (BC)-based film (termed BC-PE-Cur) was fabricated for intelligent food packaging. The film was simply prepared by vacuum filtration and compression of a mixture of the BC and the curcumin (Cur)-embedded Pickering emulsion (PE) stabilized with the natural protein-polysaccharide hybrid nanoparticles (PPH NPs). The Pickering emulsion droplets containing Cur were uniformly distributed within the film and adhered to the film surface, resulting in a uniform dispersion of Cur in the film, and a thicker, rougher film with a laminated pore structure. The BC-PE-Cur film showed excellent antibacterial, antioxidant, UV-shielding, water vapor barrier, and mechanical properties. BC-PE-Cur film can extend the shelf life of basa fish by delaying the lipid peroxidation and inhibiting the growth of spoilage microorganisms. Moreover, during the storage of basa fish, BC-PE-Cur films underwent significant color change due to the production of alkaline substances, which could indicate the freshness of basa fish. This study provides an attractive strategy to construct multifunctional smart bio-based composite films containing non-water-soluble active ingredients for food packaging and freshness monitoring.

Design and analysis of biodegradable and potentially biobased multiphase systems from starch and co-polyesters

To develop tailored and performing biodegradable multilayer systems with polyester as cap layers and thermoplastic starch (TPS)/polyester blends in the core, several TPS-based blends, with varying formulations and several biodegradable and potentially biobased polyesters, were first elaborated. Poly(butylene adipate-co-terephthalate) (PBAT), poly(butylene succinate) (PBS) and poly(butylene succinate-co-adipate) (PBSA) were tested. The TPS-based blends for the core layer were compatibilized with a multifunctional epoxide styrene-acrylic reactive chain extender. As evidenced by tensile tests, the compatibilization was more effective with blends based on PBAT, probably due to its higher number of reactive chain ends. Multilayer films comprising neat PBAT cap layers and a TPS/PBAT blend, compatibilized or not, as a core layer were then elaborated by coextrusion. Thanks to the PBAT cap layers, the multilayer films had improved thermal stability and water vapor barrier properties, while TPS in the core layer added oxygen barrier properties to the global systems. In connection with the applications, the biocompatibility was also demonstrated through cell growth tests. The suitability of such multilayer films for biodegradable packaging linked to biomedical applications was thereby confirmed.

Carboxymethyl Cellulose-Blended Films from Rice Stubble as a New Potential Biopolymer Source to Reduce Agricultural Waste: A Mini Review

The vegetative part of the rice plant, Oryza sativa L., that remains after paddy fields have been cleared during harvest or afterward is known as rice stubble. Carboxymethyl Cellulose from Rice Stubble (CMCr) is a promising biopolymer source that can be made from rice stubble waste. Carboxymethyl cellulose was synthesized from rice stubble by a solvent-casting method. Various types of plasticizers (glycerol and olive oil) and the components they contain provide flexibility for use as a material for food packaging. The films' moisture barrier was enhanced by the olive oil content while their extensibility was enhanced by the glycerol content. Indonesia is known as a country with the majority of the population working as farmers. Along with the increase in rice harvested area each year, agricultural waste in the form of rice stubble is also increasing. In the future, the application of CMCr in food packaging has the potential to revolutionize sustainable practices in Indonesia's agricultural sector. By leveraging CMCr's unique properties, such as enhanced moisture barrier and increased extensibility, there is an opportunity to develop eco-friendly packaging solutions. This innovation not only addresses the challenge of rising rice stubble waste but also contributes to the reduction of environmental pollution, offering a greener and more sustainable approach to packaging in the country.

Chitosan film loaded with carbon dots and geraniol/hydroxypropyl-β-cyclodextrin inclusion complex: Simultaneous freshness preservation and quality monitoring of pork

Multi-functional film materials that enable monitoring and control of food safety are effective tools for addressing food safety issues. In this study, nitrogen-doped citric acid carbon dot (NCD) functionalized with surface potassium ions was incorporated into chitosan film to confer film pH-monitoring capability. The inclusion complex (HPCDGer) of hydroxypropyl cyclodextrin (HPCD) and geraniol (Ger) was prepared and added as antimicrobial material to the chitosan film. With the increase in pH, the fluorescence intensity of the composite film increased significantly. CS/NCD@HPCDGer exhibited excellent UV shielding, water vapor barrier, antioxidant (Scavenging activity of DPPH and ABTS were 74.01% and 92.48%, respectively), and antimicrobial effects. The inhibition rates against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) were 99.82% and 95.89%, respectively. The pH, weight loss, and total volatile alkaline nitrogen (TVB-N) of the pork packed in the composite film were significantly lower. Furthermore, the composite film is capable of showing orange fluorescence in response to biogenic amines from pork spoilage. These results indicate that the composite film has potential applications in the monitoring and control of food safety.

Wood cellulose films with different foldabilities triggered by dissolution and regeneration from concentrated H2SO4 and NaOH/urea aqueous solutions

Forests are a major source of wealth for Canadians, and cellulose makes up the “skeleton” of wood fibers. Concentrated H2SO4 and NaOH/urea aqueous solutions are two efficient solvents that can rapidly dissolve cellulose. Our preliminary experiment obtained regenerated wood cellulose films with different mechanical properties from these two solvents. Therefore, herein, we aim to investigate the effects of aqueous solvents on the structure and properties of wood cellulose films. Regenerated cellulose (RC) films were produced by dissolving wood cellulose in either 64 wt% H2SO4 solution (RC-H4) or NaOH/urea aqueous solution (RC-N4). RC-H4 showed the higher tensile strength (109.78 ± 2.14 MPa), better folding endurance (20–28 times), and higher torsion angle (42°) than RC-N4 (62.90 ± 2.27 MPa, un-foldable, and 12°). The increased cellulose contents in the H2SO4 solutions from 3 to 5 wt% resulted in an improved tensile strength from 102.61 ± 1.99 to 132.93 ± 5.64 MPa and did not affect the foldability. RC-H4 also exhibited better water vapor barrier property (1.52 ± 0.04 × 10−7 g m−1 h−1 Pa−1), superior transparency (~90 % transmittance at 800 nm), but lower thermal stability compared to RC-N4. This work provides special insights into the regenerated wood cellulose from two aqueous solvents and is expected to facilitate the development of high-performance RC films from abundant forestry resources.

Effect of graphene nanoplatelets and nano zinc oxide on gas barrier and antibacterial properties of thermoplastic nanocomposites

AbstractGraphene‐loaded thermoplastic nanocomposite films must be evaluated for antibacterial activity, mechanical, and barrier properties before being utilized as food packaging. Herein, economically feasible linear low‐density polyethylene (LLDPE)‐based flexible packaging materials were developed via the melt compounding technique at 170°C temperature by taking advantage of both graphene nanoplatelets (GNP) and nano zinc oxide (ZnO) fillers. Morphological studies reveal that in composites loaded with GNP/ZnO hybrid fillers, ZnO nanoparticles form a network‐like structure throughout the polymer matrix. Simultaneously, GNPs are uniformly dispersed. The inclusion of hybrid nanofiller considerably reduces both the oxygen transmission rate and the water vapor transmission rate (WVTR) in LLDPE nanocomposites. A maximum decrease of 36% and 67%, respectively, in both oxygen transmission rate and WVTR is observed for 3 wt% of hybrid filler loading in a thermoplastic matrix containing 1 wt% of nano ZnO. The antibacterial efficacy of the derived nanocomposite films is obvious against gram‐positive (Bacillus subtilis) and gram‐negative (Escherichia coli) bacterial strains. These nanocomposite films have the potential to be successfully utilized as flexible packaging materials owing to their improved thermal, barrier, and antibacterial effectiveness.Highlights GNP/ZnO was used as a hybrid reinforcing filler in the LLDPE matrix. ZnO nanoparticles establish a network‐like morphology. LLDPE nanocomposite films exhibited excellent antibacterial activity. Oxygen and water vapor barrier properties were significantly improved. The thermoplastic composite films could be used as food packaging materials.

A study on tung oil-infused polyurea microcapsules: Prioritizing self-healing with bioassay-based toxicity and antibiofilm evaluations

This study presents a novel approach to enhancing the longevity and efficacy of dental materials through the incorporation of Tung oil into polyurea microcapsule coatings. Tung oil is renowned for its superior moisture barrier and antimicrobial properties, and when merged with the durable nature of polyurea, it creates a coating poised to substantially improve self-healing capabilities in dental applications. Focusing on the dual objectives of mechanical fortitude and biocompatibility, this research meticulously evaluates the coatings' proficiency in withstanding the rigors of the oral environment and their compatibility with oral tissues. Employing a suite of bioassays, we meticulously assess the toxicity and antibiofilm characteristics of these coatings, in addition to their self-healing efficiency. These evaluations measure the coatings’ ability to autonomously repair physical damage and counteract microbial colonization. The results reveal that tung oil significantly enhances the polyurea matrix's intrinsic self-repair features, which proves crucial in resisting the abrasive and microbial challenges prevalent in the oral cavity. The modified coatings demonstrate marked improvements in wear resistance and microbial interaction, heralding a significant advancement in dental material technology. This in-depth analysis corroborates the amplified capabilities of Tung oil-infused polyurea coatings and paves the way for future investigations into the integration of natural oils within medical-grade material design, opening a new chapter in the synthesis of biomaterials tailored for oral healthcare advancements.

Stepwise reinforcement strategy for guar gum/sodium alginate based films: Introduction of carboxylated cellulose nanofibers by different methods and further calcium ion crosslinking

Insufficient mechanical, barrier and water resistance properties of guar gum (GG) films limit their application in food packaging field. Herein, the properties of GG films were enhanced by a stepwise modification strategy. The mechanical and water vapor barrier properties of GG films were initially reinforced by doping with a different type of polysaccharide (sodium alginate; SA). Next, carboxylated cellulose nanofibers (CCN) were introduced as a reinforcing agent to improve film properties via two methods (blending and layer-by-layer (LBL) assembly method). Finally, the water resistance of composite films was further enhanced by calcium ion cross-linking treatment. GG/SA composite films exhibited better mechanical strength and water vapor barrier capacity compared to pristine GG film. In addition, the introduction of CCN, either by blending or LBL method, improved the light barrier, water vapor barrier and tensile strength. The calcium ion cross-linking treatment further enhanced the water vapor barrier, thermal stability, tensile strength and water resistance capacity. The potential applications of GG/SA/CCN films in real food packaging were also explored. In short, this study presents a simple and feasible performance enhancement strategy for GG and other underperforming polysaccharide matrix films, with potential applications in the development of high-performance bio-based food packaging materials.

Multifunctional biopolymer poly (lactic acid)-based triboelectric nanogenerator via controlled construction of secondary electron path

Seeking sustainable energy solutions for bioelectronic devices, high-performance, multifunctional biopolymer-based triboelectric nanogenerators (TENGs) are proving to be essential for biomedical applications. This study presents an innovative fabrication method for establishing secondary electron transport paths, resulting in biopolymer-based nanocomposites (poly (lactic acid) (PLA)/carbon nanotube (CNT)@expanded graphite (EG)) with inherent electron pathways. By integrating conductive biopolymer nanocomposites with polytetrafluoroethylene (PTFE) films, we developed a contact-separation mode TENG (CS-TENG) that demonstrates outstanding energy-harvesting efficiency. The CS-TENG displays an impressive charge density of 280 μC/m2, accompanied by an open circuit voltage (Voc) of 100.5 V and short circuit current density (Isc) values of 47.25 mA/m2. Moreover, the essential conductive network guarantees the CS-TENG’s stability across different humidity levels and serves as a moisture barrier. In addition to energy harvesting, the fabricated biopolymer nanocomposite films exhibit effective electromagnetic interference (EMI) shielding and Joule heating capabilities, rendering the CS-TENG suitable for use in diverse application scenarios. Our results emphasize the crucial role of conductive network architecture in creating high-performance biopolymer PLA-based TENGs. The innovative fabrication method and our CS-TENG's capabilities reveal the significant potential of biopolymer-based composites to transform energy harvesting, thermal management, and EMI shielding in bioelectronics.

Biofilms from poly-vinyl alcohol/palmyra root sprout with Boswellia serrata, carbon dots and anthocyanin for sensing the freshness of sardine fish

One of the main issues that customers worldwide have is food adulteration. In commercial packages, freshness cannot always be determined visually. Here, we propose sensitive films for use in food packaging that could alter colour to indicate a change in freshness. Hybrid, multifunctional, and eco-friendly films were prepared from polyvinyl alcohol/palmyra root sprout (PVA/PRS), fused with soy protein isolate carbon dot (CD), Boswellia serrata (BS), and Clitoriaternatea anthocyanin (CTE). The films showed pH sensitivity, antioxidant, and UV barrier properties. By creating hydrogen bonds between PRS and the other fillers, adding these substances makes PVA less crystallized. These interactions were verified by infrared Fourier-transform analysis. When compared to PVA, PRS films had significantly lower moisture content and swelling ratios. The UV-blocking capabilities of the films were greatly improved by the addition of CD, BS, and CTE without compromising their mechanical, thermal, or water vapor barrier properties. The composite film PVA/PRS/CD/BS/CTE exhibited a maximum tensile strength value of 69.47 ± 1.49 MPa. The CT extract provides the film with superior antioxidant properties. The colorimetric films PVA/PRS/CTE and PVA/PRS/CD/BS/CTE showed distinct pH-responsive colour-change properties as well as good colour stability. The colorimetric films were used to test the freshness of sardine fish, and they revealed unique colour changes that indicated whether the fish sample was spoiled or not.

Pea-like inspired design: Lignin nanospheres-mediated PVA film with high strength, low water evaporation permeability, strong UV resistance and anti-oxidation properties for extending food freshness

The excessive utilization of petroleum-based plastic products has inflicted significant harm upon the ecological and health problems, compelling individuals to continually seek renewable and biodegradable polymer materials as alternatives. Drawing inspiration from the structure of a natural pea pod, a unique interlocking packaging material based on a pea-like structure is obtained via green electrospinning and mild glutaraldehyde (GA) cross-linking method. Herein, polyvinyl alcohol (PVA) serves as a green protective layer encompassing the active lignin nanospheres (LNP) pod, forming a packaging film that prevents LNP migration. The LNP within the fibers can effectively shorten the fiber spacing, and when exposed to the GA vapor, they promote the bonding between neighboring fibers to form a tight interlock structure. Benefiting from the interlocking pea-like structure, the film exhibits excellent tensile strength (3.53 ± 0.02 MPa), wetting strength (1.92 ± 0.05 MPa), and outstanding water vapor barrier properties (3.27 ± 0.3 10−10 gm−1 s−1 Pa−1). Furthermore, the inclusion of LNP endows exceptional water resistance, UV-blocking capabilities, antibacterial and antioxidant properties, which can effectively prolong the storage life of perishable fruits. This eco-logical sustainable design holds tremendous potential in mitigating the burden on the environment, thus making a novel avenue for exploring alternatives to petroleum-derived plastics.

Fabrication and Characterization of Chitosan and Gelatin-Based Antimicrobial Films Incorporated with Different Essential Oils.

This study was performed to check the effect of different essential oils on chitosan and gelatin-based antimicrobial films. Films prepared from biopolymers contain better mechanical strength but lack in moisture barrier properties. In order to increase the moisture barrier properties of chitosan and gelatin-based films in the current research work, different essential oils, i.e., thyme, cinnamon, basil, ginger, and cumin, at varying concentrations (1.0, 1.5, and 2.0%) were incorporated. Moreover, the concentrations of glycerol (plasticizer) and emulsifier (Tween 20) were kept constant to maintain homogeneity in the research. Antimicrobial films composed of gelatin and chitosan infused with essential oils were evaluated for their physicochemical (emulsion stability, particle size, and viscosity), FT-IR, microstructural (scanning electron microscopy), moisture barrier (water vapor permeability), and antimicrobial properties (E. coli, Salmonella, and S. aureus). Study outcomes elucidated significant variations (p < 0.05) as the concentration of essential oil was increased in the film solutions. An increased concentration of essential oil (2.0%) significantly enhanced the moisture barrier properties (1.12 ± 0.03 g.mm/kPa.h.m2). Nevertheless, the tensile strength decreased (38.60 ± 1.4 to 31.50 ± 1.5 MPa) from 1 to 2%. The increase in essential oil concentration in the emulsion-based films also influenced their physicochemical characteristics, such as droplet size, viscosity, and emulsion stability. At lower concentrations (1.0%), films exhibited a uniform microstructure but lacked moisture barrier properties. Antimicrobial properties against E. coli, Salmonella, and S. aureus showed an increased inhibition effect as the concentration of essential oil was increased. Of the essential oil-based films, ginger- and basil-based films showed greater inhibition effects as compared to the other essential oils. Overall, antimicrobial films containing a 1.5% concentration of ginger and basil oil showed better results as compared to the other treatments for mechanical, moisture barrier, and antimicrobial properties, while films with a 2.0% oil concentration showed better antimicrobial and moisture barrier properties but lacked in mechanical properties. Essential oil-based antimicrobial films have prospective applications in foods, specifically in fresh and processed food items such as seafood, meat, chicken, and sausages.

Chitosan films synthesized via thiol-ene click chemistry: Toward safe and versatile platforms for packaging, cosmetics and biomedical applications

The first synthesis of chitosan-based films using bio-based reticulating agents via Thiol-Michael addition click reaction was described, along with their successful application in packaging, cosmetics, and biomedical fields. The impact of chitosan (CS) concentration and the type of synthesized bio-sourced biacids (GD) and triacids (GT and TT) on the physicochemical properties of these films were assessed. Films prepared with dibasic and tribasic acids (4%-CS) demonstrated superior mechanical properties and lower solubility compared to those containing 2% CS. The incorporation of the bio-sourced GD, GT, and TT acids led to a reduction of 53%, 60% and 60.4%, respectively, in the water vapor permeability (WVP) of 4% CS-based films compared to the control film. Remarkably, CS-TT-4% films exhibited the highest mechanical strength (TS), elongation at break (%E), elasticity, water vapor, and light barrier properties. Cytotoxicity tests performed on the NIH 3T3 fibroblast cell line showed that CS-GD-4% films exhibited the highest compatibility. The efficiency of these films as drug carriers was tested with challenging anticancer and cosmetic molecules, particularly etoposide (ETP) caffeine (Caf), showing very high drug loading with a progressive release of less than 20% after 72h of incubation. Moreover, ex-vivo permeation studies in rat skin revealed that the percutaneous absorption of Caf is significantly increased by a factor of 5.5 compared to that of CS-GD-4%-Caf films with no significant histological alterations of skin layers. Altogether, this work evidences the most suitable casting solvent for developing safe chitosan films, promising their potential applications in the cosmetic and biomedical fields.

Mechanically robust carboxymethyl cellulose/graphene oxide composite cross-linked by polyetherimide for fruits packaging and preservation system

Modulating the interactions between biopolymer matrix and nanofillers highly determined the mechanical performances of composite packaging materials. Herein, we innovatively proposed a sort of eco-friendly and mechanically robust carboxymethyl cellulose/graphene oxide/tannic acid/polyetherimide (CMC/GO/TA/PEI, CGTP) composite by employing PEI as cross-linker and TA as proton donor. The amidation reaction between -NH2 and -COOH chemically connected the CMC/GO, CMC/CMC and GO/GO and the physical interaction (e.g. hydrogen bonds and molecular entanglements) was beneficial to form dense structures. The chemical/physical bonds among polymers and nanofillers contributed to dissipate the external energy. The toughness was effectively reinforced from 1.68 MJ/m3 for CGTP0 to 4.63 MJ/m3 for CGTP1.0. Furthermore, the CGTP1.0 composite film also delivered improved gas (moisture and oxygen) barriers, UV protection and antimicrobial features. Originating from these merits, the shelf life of fresh fruits (e.g. strawberries, blueberries and cherry tomatoes) was prolonged at least 5 days under ambient conditions when the packaging box was covered by the fabricated CGTP1.0 film. Our findings not only provided a facial strategy to reinforce the interactions between biopolymer matrix and nanofillers, but also boosted the development of eco-friendly packaging materials with robust structures in the area of food packaging.

Effect of Layered Double Hydroxide and Its Localization on the Structure and Properties of PBAT/PPC Composites

AbstractThe blends of poly(butylene adipate‐co‐terephthalate) (PBAT), poly(propylene carbonate) (PPC), chain extender (ADR) and layered double hydroxides (LDH) are prepared by different extrusion methods. Effects of LDH and its distribution on rheology, phase morphology, mechanical properties, water vapor barrier properties and food preservation properties are investigated. Results show that when PBAT, PPC, and LDH are mixed directly, LDH is preferentially distributed in the PBAT phase. When LDH are mixed with PPC firstly and then further with PBAT, LDH mostly migrates to the interface of PBAT and PPC. The epoxy groups of ADR react with the terminal groups of the polymers to improve the interfacial compatibility. Adding LDH, the mechanical properties and barrier properties of the materials are improved and by premixing of PPC and LDH, properties of composites are further improved. Compared with PBAT/PPC blends, the tensile strength and elongation at break of PBAT/PPC(LDH‐0.5)/ADR increased by 25.2% and 15.3%, respectively. The banana packaged in PBAT/PPC/LDH films maintains good freshness. It illustrates that PBAT/PPC(LDH)/ADR composites have a good application prospect in the field of barrier and food packaging based on their excellent mechanical, barrier, and preservation properties.

Fabrication of smart vapor barrier membranes from polyhydroxyalkanoate and cellulose filaments for building envelope applications

Fabrication of smart vapor barrier membranes from polyhydroxyalkanoate and cellulose filaments for building envelope applications

Stability and Composting Behaviour of PLA-Starch Laminates Containing Active Extracts and Cellulose Fibres from Rice Straw.

The stability and composting behaviour of monolayers and laminates of poly (lactic acid) (PLA) and starch with and without active extracts and cellulose fibres from rice straw (RS) were evaluated. The retrogradation of the starch throughout storage (1, 5, and 10 weeks) gave rise to stiffer and less extensible monolayers with lower water vapour barrier capacity. In contrast, the PLA monolayers, with or without extract, did not show marked changes with storage. However, these changes were more attenuated in the bilayers that gained water vapour and oxygen barrier capacity during storage, maintaining the values of the different properties close to the initial range. The bioactivity of the active films exhibited a slight decrease during storage, so the antioxidant capacity is better preserved in the bilayers. All monolayer and bilayer films were fully composted within 90 days but with different behaviour. The bilayer assembly enhanced the biodegradation of PLA, whose monolayer exhibited a lag period of about 35 days. The active extract reduced the biodegradation rate of both mono- and bilayers but did not limit the material biodegradation within the time established in the Standard. Therefore, PLA-starch laminates, with or without the valorised fractions from RS, can be considered as biodegradable and stable materials for food packaging applications.

Spatial atomic layer deposition of nitrogen-doped alumina thin films for high-performance perovskite solar cell encapsulation

An atmospheric-pressure spatial atomic layer deposition (AP-SALD) system is used to deposit nitrogen-doped alumina (N-AlOx) thin-film-encapsulation layers. The rapid nature of the AP-SALD process facilitates deposition of 60-nm layers directly on perovskite solar cells at 130 °C with no damage to the temperature-sensitive perovskite and organic materials. Varying the bubbling of a NH4OH precursor varied the nitrogen concentration from 0.08 to 0.68 at%. These small concentrations were found to have a significant impact on the structural properties of the films and their moisture barrier performance. The N-AlOx thin films had slightly higher growth rates than undoped AlOx, less unwanted hydroxyl and carbon content, and were smoother and more compact, which was attributed to a higher flux of reactive species from the volatile NH4OH. Optical calcium tests showed that the N-AlOx films had lower water-vapor-transmission rates (∼10-5 g/m2/day) than undoped AlOx films and the transmission was minimized for 0.28% nitrogen. The increased compactness of the N-AlOx films is expected to minimize nanoscale percolation pathways, whereas higher nitrogen-defect concentrations may facilitate water permeation through these pathways. The stability of n-i-p and p-i-n perovskite solar cells under standard ISOS-D-1 and ISOS-D-3 testing conditions was significantly enhanced by the encapsulation layers. An N-AlOx encapsulation layer with 0.28% nitrogen improved the T80 value of a p-i-n formamidinium methylammonium lead iodide solar cell from 144 hrs to 855 hrs (ISOS-D-1) and 52 hrs to 300 hrs (ISOS-D-3).