Improved Barrier Properties Research Articles

Effect of Cold Plasma Treatment on the Packaging Properties of Biopolymer-Based Films: A Review

Biopolymers, like polysaccharides and proteins, are sustainable and green materials with excellent film-forming potential. Bio-based films have gained a lot of attention and are believed to be an alternative to plastics in next-generation food packaging. Compared to conventional plastics, biopolymers inherently have certain limitations like hydrophilicity, poor thermo-mechanical, and barrier properties. Therefore, the modification of biopolymers or their films provide an opportunity to develop packaging materials with desired characteristics. Among different modification approaches, the application of cold plasma has been a very efficient technology to enhance the functionality and interfacial characteristics of biopolymers. Cold plasma is biocompatible, shows uniformity in treatment, and is suitable for heat-sensitive components. This review provides information on different plasma generating equipment used for the modification of films and critically analyses the impact of cold plasma on packaging properties of films prepared from protein, polysaccharides, and their combinations. Most studies to date have shown that plasma treatment effectively enhances surface characteristics, mechanical, and thermal properties, while its impact on the improvement of barrier properties is limited. Plasma treatment increases surface roughness that enables surface adhesion, ink printability, and reduces the contact angle. Plasma-treated films loaded with antimicrobial compounds demonstrate strong antimicrobial efficacy, mainly due to the increase in their diffusion rate and the non-thermal nature of cold plasma that protects the functionality of bioactive compounds. This review also elaborates on the existing challenges and future needs. Overall, it can be concluded that the application of cold plasma is an effective strategy to modify the inherent limitations of biopolymer-based packaging materials for food packaging applications.

Layer-by-layer assembly of lysozyme with iota-carrageenan and gum Arabic for surface modification of food packaging materials with improved barrier properties

The study aimed to investigate the surface modification of biaxially oriented polypropylene (BOPP) by layer-by-layer (LbL) assembly of lysozyme (LZ) with two different polysaccharides, iota-carrageenan (IC) and gum arabic (GA), for food packaging applications. The effects of solution pH, adsorption time, elimination of intermediate drying steps were investigated. The LbL film growth was monitored up to 10 deposition steps by UV–Vis spectroscopy and in situ surface plasmon resonance (SPR). The most successful processing conditions for both types of coatings were pH 7–7 combination with intermediate drying and 20 min adsorption time. SPR pointed out a ‘dissolution/reconstruction’ mechanism in film formation. The thickness and surface morphology of the coatings were characterized by Atomic force microscopy (AFM). The surface roughnesses of LZ/IC coatings were higher than that of LZ/GA coatings indicating a denser matrix in the latter. Deposition of 5 bilayers of LZ/IC and LZ/GA on BOPP resulted in 66.15% and 56.89% reduction in oxygen transmission rate (OTR) of the film, respectively. The corresponding reductions in water vapor transmission rate (WVTR) were 28% and 33.52%, respectively. Elimination of intermediate drying steps resulted in less overall deposition, rougher surfaces, diminished oxygen and water barrier properties. The edible LbL coatings obtained in this study possess good gas barrier properties, which is very promising for their use in the preservation of fresh/fresh-cut produce in combination with modified atmosphere packaging applications. The results promise reduced use of plastic films in food packaging.

Sustainable nanocomposite films of improved barrier properties for food packaging applications

Environmentally benign, biodegradable materials derived from renewable resources are gaining great consideration in recent times. Food packaging requires FDA approved, lightweight and low cost materials with superior barrier properties for extended shelf life and good flavor/aroma retention. In the present study, polylactic acid (PLA) modified with triethyl citrate (TEC) as a bioplasticizer was reinforced with copper nanoparticles and tested for possible improvement in mechanical and barrier properties. The increase in TEC content upto 8 wt% improved the toughness, beyond 8 wt% there was a decrease in tensile strength and modulus. A nanocomposite film of PLA/TEC/copper nanoparticle (92/8/3 wt%) displayed better barrier properties and optimum mechanical strength. The water vapor permeability and oxygen permeability rate was drastically decreased upon addition of nanocopper.

Eco-friendly functionalization of hexagonal boron nitride nanosheets with carbon dots towards reinforcement of the protective performance of water-borne epoxy coatings

A h-BN@CDs/WEP coating shows superior corrosion protection under intact or damaged status owing to the improved barrier properties and interfacial bonding of the coating.

High Barrier Nanocomposite Film with Accelerated Biodegradation by Clay Swelling Induced Fragmentation

AbstractConventional biodegradable polymers such as poly(lactic acid) (PLA) are an attractive alternative to replace traditional nondegradable food packaging films which plague the environment. However, PLA has shown to not be degradable in some environmentally relevant conditions, including within the freshwater systems. Additionally, PLA suffers from very poor barrier properties, which could result in food spoilage. Compositing with clay has been used to improve barrier properties according to tortuous path theory. Here a synthetic, large aspect ratio Na‐Hectorite is used that may be utterly delaminated in an organic solvent and composited with PLA by modification with 18‐crown‐6 (18C6Hec), yielding a castable, homogeneous nematic suspension. Upon drying, thermodynamics drive the suspension toward segregation into sublayers of PLA and partially restacked 18C6Hec in situ. This unique self‐assembled nanostructure combines the best of two worlds: The aspect ratio remains high and results in a 99.3% reduction in oxygen permeability. Additionally, the film shows surprisingly high resistance to swelling at elevated humidity, but once soaked in water, clay swelling is triggered, which fragments the film and drastically increases the surface area by 2500%. Accelerated degradation is observed under controlled enzymatic conditions and in an environmentally relevant wastewater medium during CO2 evolution testing.

Creation of Tortuosity in Unfilled Rubber via Heterogeneous Cross-Linking toward Improved Barrier Property

Creation of Tortuosity in Unfilled Rubber via Heterogeneous Cross-Linking toward Improved Barrier Property

Bio-based aliphatic/aromatic poly(trimethylene furanoate/sebacate) random copolymers: Correlation between mechanical, gas barrier performances and compostability and copolymer composition

Highly promising fully biobased random copolyesters, poly(trimethylene 2,5-furandicarboxylate-co-trimethylene sebacate) (PTFcoPTSeb), were synthesized by using bio derived 1,3-propanediol, dimethyl ester of 2,5- furandicarboxylic acid, and sebacic acid, through eco-friendly polycondensation in the melt. Copolymers with high molecular weight containing 5, 15, 25 mol % of PTSeb were obtained, and their chemical structure confirmed by 1H NMR and FTIR spectroscopy. The thermal, tensile and gas barrier properties and composability were studied in relation to the copolymer supramolecular structure. As expected, introduction of PTSeb co-units results in lowering of glass transition temperature of copolymers and improves their flexibility. Besides, all copolymers showed outstanding gas barrier properties to O2 and CO2, with copolymer containing 15 mol % of PTSeb showing exceptional gas barrier properties, better than those of PTF and comparable to those of EVOH, currently used in multilayer packaging films. The same copolymer exhibited temperature induced shape memory behaviour. It was found that low amounts (15-25 mol %) of PTSeb in copolymer significantly modifies PTF thermal, mechanical and barrier properties and renders the final material compostable. Copolyesters containing 15 and 25 mol % of PTSeb can compete in some applications with commercially available compostable Ecoflex® polymer, but with markedly improved barrier properties.

Development of multifunctional films based on chitosan, nano silica and hops extracts

• Hops extracts introduced into film with excellent properties. • The multifunctional film based on biopolymer. • The structural, physicochemical, and functional properties on films were investigated. • Multifunctional films process good biological activity and mechanical properties. Multifunctional films were developed by chitosan (CS) and nano silica (NS) with different concentrations (w/v, 0.05%, 0.10%, 0.15%, 0.20%) of hops extracts (HE). The effects of NS and/or HE on the structure, physicochemical and biological activities of CS membranes were studied. Multifunctional films were assessed by using Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). Structure analysis has proven successful incorporation of NS and HE into CS film. The physicochemical properties of the polymer matrix can be greatly changed by incorporating NS and/or HE. Obviously, the presence of NS could make the tensile strength show an upward trend (5.27–11.91 MPa), and the elongation at break also shows the same trend (42.23–68.98%). Furthermore, CS-NS film significantly improved barrier properties against water vapor permeability ( p < 0.05) and UV light. Bioactive analysis displayed that CS-HE and CS-NS-HE films both owned excellent antioxidant and antibacterial capability. Among these films, CS-NS-HE presented the lowest moisture content, water solubility and WVP, whereas the highest tensile strength and biological activity. This study suggests CS-NS-HE film would have broad application prospects in active food packaging materials that require strong water resistance and excellent mechanical properties.

Unfolding graphene nanosheets towards high barrier performance of epoxy/graphene nanocomposite coating

The improvement of barrier properties brought by graphene is severely restricted for graphene/polymer nanocomposites due to inevitable crumpling and folding of embedded graphene. Herein, graphene was sandwiched into mesoporous silica via a soft-template method, achieving unfolded graphene/SiO2 nanosheets (rGOSs). The barrier properties of the rGOSs-reinforced coatings (rGOSc) are evaluated. Experimental results reveal that, compared with conventional graphene/epoxy coating, the water vapor and oxygen transmission rate of rGOSc decreases by 65.2% and 62.3%, respectively, and corresponding corrosion resistance increases by ∼3–4 orders of magnitude. Numerical results further demonstrate that, comparing with conventional graphene with irregular crumpling and folding morphology, unfolded rGOSs perform better in prolonging and twisting the diffusion pathway of diffusing species in coating matrix.

Enhanced diffusion barrier property of nanolayered NbMoTaW/TiVCr high entropy alloy for copper metallization

In this work, the single-layered amorphous NbMoTaW and multilayered amorphous NbMoTaW/TiVCr high entropy alloys were prepared to investigate the diffusion barrier performance. The microstructure and thermal stability of these samples were analyzed by X-ray diffraction, transmission electron microscope, and four-point probe method after annealing at different temperatures. In the single-layered structure, Cu silicide formed after annealing at 600 °C. The reason is that the amorphous NbMoTaW layer crystallizes during annealing, which causes the interdiffusion between Cu and Si through grain boundaries (GBs). However, the multilayered structure still maintains effective barrier performance as the annealing temperature is below 800 °C. Amorphous structure without GBs diffusion path, severe lattice distortion, and the high dense layer interface are responsible for the improved barrier property in the multilayered system.

Optimization of biodegradable paper cup packaging coated with whey protein isolate and rice bran wax as potential popcorn package.

Biodegradable paper cups coated with rice bran wax and whey protein isolate were designed to package popcorn. Coatings with different concentrations of whey protein isolate (5.5, 7.75, and 10% w/v) and rice bran wax (0.2, 0.4, and 0.6% w/v) were applied on the outer surface of the paper cups. Thickness, color changes, Young's modulus and tensile strength, water vapor transmission rate (WVTR) of the coated and uncoated cups, and also popcorns properties (pH, texture, and sensory properties) were evaluated. Water vapor transmission rate, Young's modulus, thickness, total color change index, and tensile strength of coated cups with the optimal coating formulation was 19.785 (g/m2 day), 11.810 (MPa), 276.583 (µm), 1.839, and 11.222 (MPa), respectively. The results showed that paper cup coating increased thickness and yellowness and reduced the brightness, Young's modulus, and WVTR. Coating had a positive effect on the pH and texture of popcorns packaged in coated cups than samples packed in uncoated cups (p < .05). With increasing storage time due to moisture absorption, popcorn changes from crisp to viscoelastic and increases tissue firmness (p < .05). Popcorns’ taste in uncoated cups had gained significantly lower scores by panelists compared with the samples packed in coated cups. There was a significant decrease in the general acceptance of popcorn during storage and also the type of coating used in the packaging cup (p < .05). Storage time and type of coating showed no significant effect on the moisture content, odor, and appearance of popcorn. In sensory evaluation, the coated packaging increased the taste, no difference in odor and appearance, and increased the overall acceptance of popcorn compared to the sample in uncoated cups. In general, the results showed that paper cup coating could be a new approach for barrier property improvement in paper‐based food packaging and extending the shelf life of the products.

Physical, structural, and water barrier properties of emulsified blend film based on konjac glucomannan/agar/gum Arabic incorporating virgin coconut oil

This study aimed to develop a new emulsified film based on konjac glucomannan (KGM)/agar/gum Arabic (GA) incorporating virgin coconut oil (VCO). The effects of VCO on the physical, structural, and water barrier properties of the film were investigated. The values of the mechanical and water barrier properties were different with statistical significance (p < 0.05), with VCO contents ranging from 0.1% to 0.6% of the film solid weights. The addition of VCO decreased the tensile strength but effectively increased the elongation at the break of the films. Increased VCO concentrations resulted in decreased water vapor permeability, reduced water swelling, solubility, and adsorption, and increased water contact angle. Compared with cucumber without packaging, packed cucumber with emulsified film showed significantly lower weight loss and firmness reduction during storage up to 12 days at 7 ± 1 °C. Fourier transform infrared spectroscopy results indicated intermolecular hydrogen bonds between KGM, agar, and GA occurred, and X-ray diffraction results suggested that all the films were in the amorphous status. Combining all the above results, the mechanism of the water barrier property improvement was proposed. This study offers an alternative emulsion polysaccharide-based edible film with high potential to be used in cucumber packaging.

NIR light-triggered self-healing waterborne polyurethane coatings with polydopamine-coated reduced graphene oxide nanoparticles

Self-healing coatings that are able to self-repair after being damaged represent an effective solution to provide a reliable and long-lasting protection of the underlying substrate. In this work, we developed self-healing waterborne polyurethane (PU) coatings through the introduction of Diels-Alder bonds in the polymer backbone. Although heat is typically used as trigger, here we exploited photothermal converters to allow also NIR light-induced self-healing. To this aim, we synthesized (3-aminopropyl)-triethoxysilane-modified graphene oxide nanosheets that were subsequently coated by nanometric polydopamine particles, which serve for imparting to the coating the NIR-responsive self-healing feature. Fourier transform infrared and X-ray photoelectron spectroscopy confirmed the successful synthesis of PDA-coated reduced graphene oxide nanoparticles, which were thus exploited to prepare nanocomposite PU coatings on bronze substrates on which they exhibited good adhesion. Once scratched, fast and effective self-healing was ensured upon irradiation with NIR light for only 30 s. In addition, electrochemical impedance spectroscopy analyses proved that the nanocomposite coatings exhibited improved barrier properties which resulted in an enhanced protection of the underlying metal from corrosion.

Siloxane-Starch-Based Hydrophobic Coating for Multiple Recyclable Cellulosic Materials.

The results of the application of a new hydrophobization agent based on a triethoxymethylsilane and standard starch aqueous mixture for mass-produced cellulosic materials—printing paper, paperboard, and sack paper—have been evaluated to examine whether such a mixture can be used in industrial practice. The application of this agent on laboratory sheets prepared in a repetitive recycling process was performed to investigate its influence on the formation and properties of the products, as well as the contamination of circulating water. Measurements of the water contact angle, Cobb tests, and water penetration dynamics (PDA) were performed to test the barrier properties of the resulting materials. The effects of the applied coatings and recycling process on the paper’s tensile strength, tear index, roughness, air permeance, and ISO brightness were studied. Studies have proven that this formulation imparts relatively high surface hydrophobicity to all materials tested (contact angles above 100°) and a significant improvement in barrier properties while maintaining good mechanical and optical performance. The agent also does not interfere with the pulping and re-forming processes during recycling and increases circulation water contamination to an acceptable degree. Attenuated total reflectance Fourier-transform infrared (FT-IR) spectra of the paper samples revealed the presence of a polysiloxane network on the surface.

Hybrid paper sheets with improved barrier properties.

Hybrid paper sheets were prepared by applying a thin coating layer of cross-linked polydimethylsiloxane (PDMS) and inorganic particles onto Whatman Grade 1 filter paper substrates. Several coatings with different inorganic particle contents and types were applied onto the paper substrates to investigate the effect of the variation in the coating formulation on the (i) wetting, (ii) water barrier properties, (iii) air barrier properties, (iv) surface roughness, and (v) mechanical properties of the samples. It was revealed that the superhydrophobic hybrid paper sheets with significantly low air permeability and high water barrier properties could be prepared which is an indication that the method proposed can be used for the preparation of packaging materials.

Sustainable coatings on paper for enhancing barrier properties based on hemicellulose

AbstractCoated paper with enhanced barrier properties was prepared via a simple layered self-assembly method using hemicellulose and starch as biobased coatings. Effect of the coating on properties of cellulose paper was investigated. Barrier properties of the paper was increasingly strengthened as the coating amount of hemicellulose rose. When the paper was coated with starch (10.7±0.3 g/m2\text{g}/{\text{m}^{2}}) and hemicellulose (6.9±0.2 g/m2\text{g}/{\text{m}^{2}}) successively, the oil resistance of the paper was increased from 0 to grade 7. Air permeability and water vapor transmittance was decreased by 93.8 % and 39.7 %, respectively. The water contact angle of the coated paper reached 91.7° when the amount of hemicellulose was 1.5±0.2 g/m2\text{g}/{\text{m}^{2}}. The hydrophobicity of the coated paper was superior to the original paper although it was negatively influenced by the increasing amount of hemicellulose. The improvement of barrier properties of the coated paper was mainly ascribed to the formation of a thin polymer network on paper surface through intermolecular interaction via hydrogen bonds as demonstrated in SEM and FTIR-ATR results. Moreover, tensile strength and rupture resistance of the coated paper was improved. The results offered an environmentally friendly and economical strategy for preparation of food packaging paper with good barrier properties using biobased coating materials.

Potential Application of Peppermint (Mentha piperita L.), German Chamomile (Matricaria chamomilla L.) and Yarrow (Achillea millefolium L.) as Active Fillers in Natural Rubber Biocomposites

In this study, peppermint (Mentha piperita L.), German chamomile (Matricaria chamomilla L.) and yarrow (Achillea millefolium L.) were applied as natural fibrous fillers to create biocomposites containing substances of plant origin. The purpose of the work was to investigate the activity and effectiveness of selected plants as a material for the modification of natural rubber composites. This research was the first approach to examine the usefulness of peppermint, German chamomile and yarrow in the field of polymer technology. Dried and ground plant particles were subjected to Fourier transmission infrared spectroscopy (FTIR) and UV–Vis spectroscopy, thermogravimetric analysis (TGA), goniometric measurements (contact angle) and scanning electron microscopy (SEM). The characterization of natural rubber composites filled with bio-additives was performed including rheometric measurements, FTIR, TGA, cross-linking density, mechanical properties and colour change after simulated aging processes. Composites filled with natural fillers showed improved barrier properties and mechanical strength. Moreover, an increase in the cross-linking density of the materials before and after the simulated aging processes, compared to the reference sample, was observed.

Cellulose Nanofibers from Olive Tree Pruning as Food Packaging Additive of a Biodegradable Film.

A biodegradable packaging film containing cellulose nanofibers from olive tree pruning, a by-product of olives production, was obtained using a solvent casting method. Nanocellulose was added to polyvinyl alcohol (PVA) to enhance the technological properties of the composite film as food packaging material. Nanocellulose was obtained from unbleached and bleached pulp through a mechanical and TEMPO pretreatment. Crystalline and chemical structure, surface microstructure, UV and gas barrier, optical, mechanical and antioxidant properties, as well as thermal stability were evaluated. Regarding optical properties, the UV barrier was increased from 6% for the pure PVA film to 50% and 24% for unbleached and bleached nanocellulose, respectively. The antioxidant capacity increased significantly in unbleached mechanical nanocellulose-films (5.3%) compared to pure PVA film (1.7%). In terms of mechanical properties, the tensile strength of the 5% unbleached mechanical nanocellulose films was significantly improved compared to the pure PVA film. Similarly, the 5% nanocellulose films had increased the thermal stability and improved barrier properties, reducing water vapor permeability by 38–59% and presenting an oxygen barrier comparable to aluminum layer and plastic films. Our results support the use of the developed films as a green alternative material for food packaging.

Engineering cellulose nanopaper with water resistant, antibacterial, and improved barrier properties by impregnation of chitosan and the followed halogenation

This work demonstrated a facile and sustainable approach to functionalize cellulose nanopaper (CNP) by impregnation of chitosan (CS) and the followed halogenation. It was found that the tensile strength of the functionalized CNP (CNP/CS-Cl) was enhanced by 38.3% and 512.6% at dry and wet conditions, respectively. Meanwhile, the total transmittance (at 550 nm) of CNP/CS-Cl was increased from 75% of pure CNP to 85%, with 35% decrease in optical haze. Moreover, the CNP/CS-Cl exhibited significant enhancement in barrier properties. Importantly, part of the amino groups on CS were transformed into N-halamines during the halogenation process, which endowed the CNP/CS-Cl with excellent antibacterial performance against both S. aureus and E. coli with 100% bacterial reduction after 10 min of contact. Thus, this work provides a simple and efficient approach to functionalize CNP with water resistance, high transparency, excellent antibacterial and barrier properties, which will expand the potential applications of CNP.

Mechanical and Barrier Properties of Bromo–Butyl Elastomers Filled with Electrochemically Exfoliated Graphene

AbstractIn this paper, the effects of graphene loading and processing technique on the morphological, mechanical, thermal, rheological, and barrier properties of bromo–butyl rubber, are explored. Bromo–butyl rubber composites with electrochemically exfoliated graphene (EEG) nanosheet filler are prepared via solvent casting and/or melt blending techniques, and their properties are compared against a carbon black control sample. Even though analysis of the EEG composites via microscopy reveals agglomeration problems not present in the carbon black controls, EEG composite samples are observed to have improved barrier properties over carbon black samples in exchange for slightly reduced stress and strain at break. Extensional rheological analysis of the bromo–butyl rubber composites reveals strain hardening phenomena in all the samples and higher extensional modulus in solvent casted‐melt blended (SCM) samples. As a result of better dispersion over the solely melt‐blended samples, the SCM rubber composites exhibit superior tensile modulus and extensional modulus compared to the samples that are solely melt‐blended.