Improved Water Barrier Properties Research Articles

Development of Plumeria alba extract supplemented biodegradable films containing chitosan and cellulose derived from bagasse and corn cob waste for antimicrobial food packaging

With the increase in global plastic pollution due to conventional plastic packaging (petroleum-derived), bioplastics have emerged as an alternative green source for practising a circular economy. This research aimed to extract cellulose from bagasse and corn cob waste and utilized in mixed form to prepare bioplastic film. The mixed cellulose was further reinforced with natural substances such as chitosan, bentonite, and P. alba extract. These newly developed bioplastics films were characterized by various physical tests like film thickness, moisture content, water solubility and spectroscopic techniques such as Fourier transform infrared (FTIR), scanning electron microscopy-energy dispersive spectroscopic (SEM-EDX), thermal gravimetric analysis (TGA), and ultraviolet-visible (UV–Vis) spectroscopy for opacity testing. The results revealed the enhanced bioplastic thermal and mechanical characteristics through robust interactions between cellulose and bentonite molecules. Moreover, incorporating chitosan solution as reinforcements in bio-composite films resulted in improved water barrier properties. The results indicated lower absorption in the UV range of 250–400 nm, attributed to the absence of UV-absorbing groups. Finally, their biodegradability was tested in soil, and 85.3 % weight loss of bioplastic films was observed after 50 days of the experiment which is the main task of this research. The antimicrobial properties of bioplastic films have been evaluated, and showed an inhibition zone of 16 mm against E. coli. After 12 days of incubation of sherbet berries, complete spoilage is identified in the control group compared to those covered with the bioplastic film. This outcome is attributed to the antioxidant and antimicrobial activities provided by chitosan and P. alba extract in the bioplastic film. The comprehensive outcomes of this study suggest the potential future adoption of these entirely bio-derived, environmentally sustainable and biodegradable bioplastic films as a viable substitute for the plastic packaging currently present in the market.

Engineering biodegradable controlled gelatin-zein bilayer film with improved mechanical strength and flexibility

Compiling hydrophobic and hydrophilic proteins to form mechanically reliable bilayer film with improved water barrier properties and hydrophobicity to replace petroleum-based standards is challenging because fabricating compatible surfaces and flexible film with interlinked interfaces is complex. The mechanical properties of gelatin and zein layers exhibited unique variations, and synergistic enhancement of bilayer properties reflected robust layer-by-layer (LBL) interactions. To overcome the problem of impaired integrated surface, viscously cross-linked zein film forming solution (FFS) by glyoxal (GX) introduced compact and closely entangled network formation with cross-linking of gelatin film. Zein surface compatibility and flexibility by GX and polyethylene glycol (PEG 400) synergized with the gelatin layer closed to compare flexible plastic materials such as PE and PP besides modulated color and transparency. Enhancing flexible formation was mechanized by acetic acid as solvent of zein solution after long-range repulsion during casting on well-manageable plasticized and cross-linked gelatin film with glutaraldehyde (GA) and PEG 400, respectively. Elongation (E%) was achieved by nearly 192% with modified tensile strength (TS) and Young's modulus (YM). Cross-linkers, especially GX, resulted in lower water solubility (WS), and joint layers resulted in controlled water vapor permeability (WVP) of bilayer films. Decreased surface roughness and WS increased water contact angle (WCA). FTIR spectroscopy, XRD analysis, DMTA, and SDS-PAGE analyzed cross-linking mode and intensity. Hence, gelatin-zein bilayer films showed significant potential for improving value-added functional properties.

Energy efficient out-of-oven manufacturing of natural fibre composites with integrated sensing capabilities and improved water barrier properties

Bio-based and eco-friendly materials have gained a great amount of attention, thanks to the increased awareness of sustainable development and global environments. The use of natural fibres in composites can reduce greenhouse gas emissions and the carbon footprint compared to many synthetic fibres. However, some challenges and concerns remain in natural fibre-reinforced plastics, such as the high moisture absorption and high energy consumption during their manufacturing stage. To tackle these challenges, this study developed an energy-efficient out-of-oven manufacturing method based on a conductive biopolymer nanocomposite film to fabricate natural fibre-reinforced composites with integrated multifunctionalities throughout their life cycle. The smart nanocomposite layer works as an autonomous self-regulating heating element to cure the laminates at the desired temperature without the risk of overheating. Extremely high energy efficiency has been achieved with a significantly reduced energy consumption (a 95% reduction compared with traditional oven curing), which has been attained through the direct heat conduction from the surface layer to the laminates. The embedded nanocomposite surface film on the cured laminate subsequently becomes an integrated multifunctional layer, providing integrated real-time deformation and damage sensing capabilities with enhanced water barrier properties to prolong the service life of natural fibre composites.

Tung oil-based coatings towards sustainable paper packaging materials

Nowadays, the dependence on synthetic plastic-based materials for the preservation and transport of different types of products is very high, leading to major environmental and human health concerns, which highlights the importance of investigating sustainable options. Paper is a widely used bio-based material for packaging however, the development of newer and straightforward approaches to produce paper-based materials with increased functionalities and performance is still highly desired. In this work, we report the use of a bio-based photopolymerizable coating formulation, composed of tung oil, and using Darocur 1173 as photoinitiator, to develop functional papers with hydrophobic and improved water barrier properties, without compromising other properties. Coated paper samples were prepared, using different irradiation times (0, 15, 30, 60, and 300 s), to study the effect of this parameter on the properties of the coated papers. The ensuing coated papers presented pick-up values between 6 and 7 g/m2. Their hydrophobicity was significantly improved as evidenced by the increase in the contact angle values from about 71° to 127° and the significant decrease in the water absorption, measured by the Cobb test, from 108 down to 17 g/m2, upon a curing time of only 15 s. Furthermore, with this time of curing, the optical (viz. whiteness, brightness, and opacity) and mechanical properties (viz. tensile and burst strength) of paper were not affected. These results highlight the great potential of tung oil photopolymerizable coating formulations as a simple and promising alternative for the fabrication of more sustainable and functional paper packaging materials.

Water-resistant nanopaper with tunable water barrier and mechanical properties from assembled complexes of oppositely charged cellulosic nanomaterials

Owing to the intrinsic hydrophilicity of nanocellulose, films and nanopapers prepared from cellulosic nanomaterials exhibit weak mechanical strength when exposed to high-moisture conditions. In this study, an approach for designing a water resistant, assembled nanopaper through controlled and irreversible aqueous complexation of oppositely charged cellulose nanoconstituents, i.e., cationic cellulose nanocrystals (AH-CNC) and anionic cellulose nanofibers (TO-CNF), is proposed. The fabrication process and features of the nanopaper can be adjusted by altering of the AH-CNC/TO-CNF ratio. For example, the draining time during the filtration of a nanopaper decreased dramatically (480–10 min) when the dosage of nanocelluloses resulted in charge compensation. This dosage also reduced the swelling of the nanopaper. After all charged groups were neutralized, a nanopaper with a wet strength of 11 ± 3 MPa was obtained when immersed in water for 24 h. Furthermore, the electrostatic interaction between the charged nano-entities enhanced the mechanical properties of the nanopaper in dry state (the maximum of tensile strength was 174 ± 3 MPa) and resulted in improved water barrier properties (water vapor transmission rate of 1683 g μm m−2 d−1). This straightforward method based on simply aqueous mixing of two oppositely charged nanomaterials may provide a new pathway for the fabrication of various functionalized films and sheets with advanced characteristics from different type of charged nanoparticles and colloids.

Hygrothermal ageing behavior and mechanism of carbon nanofibers modified flax fiber-reinforced epoxy laminates

This study investigated the effects of carbon nanofibers (CNFs) content on hygrothermal ageing behaviors and mechanisms of flax fiber-reinforced epoxy (FFRE) laminates. CNFs/FFRE laminates containing 0.25–2.0 wt% CNFs were fabricated and immersed in distilled water for 180 days. Water absorption and tensile as well as thermodynamic properties were investigated. The research results showed that CNFs played a significant role in the improvement of hygrothermal properties of FFRE laminates. The water uptake of CNFs/FFRE laminates was significantly decreased because CNFs improved water barrier properties of the laminates. The improvements of tensile and thermodynamic properties of CNFs/FFRE laminates were attributed to the fact that CNFs strengthened the interface bonding and enhanced the matrix’s stability. This study demonstrates that adding appropriate amount of CNFs into FFRE laminates is beneficial to improving the hygrothermal durability of FFRE laminates.

Characterization of chitosan based polyelectrolyte films incorporated with OSA-modified gum arabic-stabilized cinnamon essential oil emulsions

Octenyl succinic anhydride (OSA) modified gum arabic (GA) was synthesized and used as an emulsifier to stabilize cinnamon essential oil (CEO) emulsions. The structure and properties of chitosan based polyelectrolyte films incorporated with above OSA-GA stabilized CEO emulsions were investigated. Results showed that OSA modification introduced the hydrophobic groups, which greatly influenced the emulsification capability of GA. The antimicrobial activities of CEO emulsions were significantly enhanced by the synergistic effect of GA modification and ultrasonic treatment. When the proportions of CEO emulsion increased, the improved water barrier properties but deteriorated tensile properties of films were observed. The retention of CEO during storage was prolonged to 20 days and the release of CEO in food simulant was effectively inhibited as emulsion ratios increased to 20%, indicating the effectiveness of the system for CEO delivery. As a result, the antimicrobial activities of films significantly enhanced with the innovative incorporation of OSA-GA stabilized CEO emulsions.

Highly dispersed graphene oxide–zinc oxide nanohybrids in epoxy coating with improved water barrier properties and corrosion resistance

Epoxy resin (EP) coating that prevents corrosion is subject to premature failure as its crosslinking network appears to be porous due to the presence of hollow spaces across the network, which leads to poor water barrier. This study introduces a novel approach of utilizing the stable surface property of zinc oxide (ZnO) to facilitate the dispersion of graphene oxide (GO) sheets in epoxy coating to improve water barrier and corrosion resistance properties. The ZnO nanoparticles (ZnO NPs) were decorated on GO sheets by using (3-aminopropyl)triethoxysilane as coupling agent. The GO-ZnO nanohybrids were successfully formed, as demonstrated in Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy analyses. The GO-ZnO sheets were well dispersed in epoxy matrix with no significant agglomeration, as verified via field emission scanning electron microscopy with energy-dispersive X-ray spectroscopy. The decoration of GO with ZnO NPs expanded the spacing between GO sheets, as observed from the outcomes of X-ray diffraction analysis, which improved exfoliation and compatibility in epoxy matrix. Based on the investigations and characterization outputs, the well-dispersed GO-ZnO nanohybrids in the epoxy coatings had effectively improved water barrier properties, as well as adhesion and corrosion protection, in comparison with neat epoxy (EP) and GO–epoxy coatings.

Functional characterization of biopolymer based composite film: Incorporation of natural essential oils and antimicrobial agents

Rosemary (REO), mint essential oil (MEO), nisin and lactic acid were incorporated at 0.5% to develop a novel functional packaging film including chitosan pectin and starch polymers (0.75:1.5:0.75 w/w). Inclusion of REO and nisin significantly (p ≤ 0.05) improved water barrier properties (0.014 g.mm/m224h), tensile strength (25.95 MPa) and thermal stability as compared to control. ATR-FTIR spectra and XRD pattern elucidated structural interaction between EO's and biocomposite films. Addition of REO of and nisin increased microsctructural heterogeneity and opacity (2.78). Incorporation of REO and nisin exhibited the highest inhibitory activity against all tested pathogenic strains (Bacillus subtilis, Escherichia coli, and Listeria monocytogenes). The antioxidant properties of biocomposite films were analyzed using reducing power, metal chelation, DPPH and ABTS radical scavenging assays, which enhanced significantly (p ≤ 0.05) with the addition of MEO and REO. This study validated that incorporation of natural additives in active biocomposite films offers promising functional ingredients for packaging materials for various food applications.

Mechanical Properties and Failure Analysis of Short Kenaf Fibre Reinforced Composites Processed by Resin Casting and Vacuum Infusion Methods

Modified and unmodified short kenaf fibre reinforced epoxy composites were processed with different short fibre lengths and fibre concentrations by resin casting (RC) and vacuum-assisted resin infusion (VARIM) methods. Three types of kenaf fibres were reinforced in epoxy polymer, namely, untreated kenaf fibre, mercerised and nanoclay-infused kenaf fibres. The mechanical properties such as tensile, flexural and impact properties of composites were studied. Nanoclay infused kenaf fibres have shown better tensile, flexural and impact properties than those of untreated and mercerised fibres. The composites processed by VARIM possess improved tensile and flexural properties when compared with RC composites, whereas the impact properties were better in RC composites than those of VARIM processed composites. The results showed that the mechanical properties of composites depend on the short fibre length and fibre concentration, irrespective of the processing conditions. Improved water barrier properties were also obtained in nanoclay-treated banana fibre composites.

Synthesis and characterization of fatty acid modified amines with improved water barrier properties

Fundamental studies aimed at elucidating the key contributions to corrosion performance are needed to make progress toward effective and environmentally compliant corrosion control. Epoxy/amine systems are typically employed as barrier coatings for corrosion control, however, the curing agents used for coating applications can be very complex, making fundamental studies of water and oxygen permeability challenging to carry out. Creating model building blocks for epoxy/amine coatings is the first step in carrying out these studies. This work demonstrates the synthesis and characterization of model amine building blocks from saturated fatty acids and diethylenetriamine (DETA) with tunable hydrophobicity. The glass transition temperature (Tg) of modified amine samples suffered a 45–50°C Tg reduction, which has been attributed to a loss of labile hydrogens available for crosslinking in these samples. It was observed that the fatty acid modified amines exhibited a reduced diffusivity to water of up to 50%. This has been attributed to the increased tortuosity of samples with a pendant aliphatic chain in the network. Samples with modified amines were observed to have lower solubility of water (S) of up to 30%. We propose that the reduction in S can be caused by a dilution of oxygen in the polymer network due to the addition of aliphatic pendant chains.

Improved water barrier properties of polylactic acid films with an amorphous hydrogenated carbon (a-C:H) coating

For the first time a 120 nm thick layer of amorphous hydrogenated carbon (a-C:H) deposited on top of 50 μm thick polylactic acid (PLA) films with radio-frequency plasma-enhanced chemical vapor deposition has been used as barrier to impede water diffusion through free-standing PLA films. Surface structures were examined by AFM and the water uptake was measured with Fourier transform infrared attenuated total reflection (FTIR-ATR) spectroscopy, a powerful technique for studying the diffusion of water through polymeric membranes. We have compared the water uptake of uncoated and a-C:H coated PLA films by placing the initially dry films in contact with deionized water for 24 h and monitoring the time-dependent absorbance changes in the FTIR spectra of the OH stretching bands of water in the wavenumber region of 2960–3750 cm−1. Mathematical modeling revealed that the water uptake was best described with a model consisting of three diffusion coefficients ascribed to monomeric and dimeric, clustered and bulk water having values between 1.1 × 10−8 and 2.6 × 10−10 cm2s−1. We show that the thin a-C:H layer effectively decreased the water uptake of PLA with 55% after a contact time of 24 h and even more at shorter times.

A novel active packaging material based on starch-halloysite nanocomposites incorporating antimicrobial peptides

Corn starch was used as a polymeric matrix for development of new antimicrobial packaging prepared by casting method and using nisin or pediocin for food preservation. Halloysite clay was selected as nanofiller to promote film reinforcement and a novel approach was tested using bacteriocins adsorbed on nanoclay before incorporation into film forming solutions. Active films against Listeria monocytogenes and Clostridium perfringens were obtained, but halloysite retained antimicrobial activity when comparing to films without nanofiller addition. Results from XRD showed that the addition of bacteriocins affected the crystallinity of starch matrix, whereas SEM images showed that peptides provoked surface irregularities. Adsorption approach proved to be a promise strategy to maintain a certain crystallinity and homogeneous morphology of films and consequently influencing other properties, like improving thermal performance. In the case of nanocomposite with nisin, adsorption procedure also improved water barrier properties. Increased mechanical resistance of films containing halloysite was observed. Elongation at break (EB) increased significantly for samples with nisin or pediocin, and those containing nisin plus halloysite. Physical interactions between additives and starch matrix via hydrogen bonding were evidenced by FTIR. Color parameters L*, a* and b* were close to those obtained for control films, although higher b* values were observed for pediocin samples. These results indicate the potential of such antimicrobial nanocomposite films as food packaging material.

Improved Water Barrier Properties of Calcium Alginate Capsules Modified by Silicone Oil

Calcium alginate films generally offer poor diffusion resistance to water. In this study, we present a technique for encapsulating aqueous drops in a modified calcium alginate membrane made from an emulsion of silicone oil and aqueous alginate solution and explore its effect on the loss of water from the capsule cores. The capsule membrane storage modulus increases as the initial concentration of oil in the emulsion is increased. The water barrier properties of the fabricated capsules were determined by observing the mass loss of capsules in a controlled environment. It was found that capsules made with emulsions containing 50 wt% silicone oil were robust while taking at least twice the time to dry completely as compared to capsules made from only an aqueous alginate solution. The size of the oil droplets in the emulsion also has an effect on the water barrier properties of the fabricated capsules. This study demonstrates a facile method of producing aqueous core alginate capsules with a modified membrane that improves the diffusion resistance to water and can have a wide range of applications.

Facile Preparation of Water-Dispersible Graphene Sheets Stabilized by Carboxylated Oligoanilines and Their Anticorrosion Coatings.

Dispersion of graphene in solvents is of crucial importance toward its practical applications. In this study, using a water-soluble carboxylated aniline trimer derivative (CAT(-)) as a stabilizer, the commercial graphene can be stably dispersed in water at high concentration (>1 mg/mL) via strong π-π interaction that was proved by Raman and UV-vis spectra. Moreover, the CAT(-)-functionalized graphene sheets (G-CAT(-) hybrid) exhibited high conductivity (∼1.5 S/cm), good electroactivity and improved electrochemical stability. The addition of well-dispersed graphene into waterborne epoxy system (G-CAT(-)/epoxy) remarkably improved corrosion protection compared with pure waterborne epoxy coating, based on a series of electrochemical measurements performed under 3.5% NaCl solution. This significantly enhanced anticorrosion performance is mainly due to the improved water barrier properties derived from highly dispersed graphene nanosheets in the epoxy coating.

Physical properties and stability of starch-gelatin based films as affected by the addition of esters of fatty acids

Cassava starch films containing 25 and 50% (in the polymer blend) of bovine gelatin were obtained using glycerol (30%) as plasticizer. Film formulations were also obtained with 15% of lipid (blend of fatty acid-glycerol esters). Microstructural and physical (optical, barrier and mechanical) properties were analyzed in order to compare blend films with neat starch or gelatin films. The incorporation of gelatin and lipids to glycerol-plasticized cassava starch films notably affected their physical properties, while they showed polymer-phase separation and a lipid-dispersed phase. Gelatine incorporation gave rise to harder films with greater resistance to break and extensibility, while the lipids decreased film hardness and resistance but enhanced the stretchability, especially in films with 50% gelatin content. Likewise, lipids improved water barrier properties of the films, but they impaired the oxygen permeability at the same time as they decreased the film gloss and transparency. After 5 weeks of storage, all the films became harder and more resistant to break, especially those which did not contain lipids, which enhanced the films' extensibility during storage. Cassava starch films with 50% gelatine, both with and without lipids, exhibited very adequate properties for food coating or packaging.

Properties and ageing behaviour of pea starch films as affected by blend with poly(vinyl alcohol)

Pea starch (S) and poly(vinyl alcohol) (PVA) blends with different ratios were produced in order to elucidate the possible advantages of blend films to overcome the common drawbacks of starch films. Starch, poly(vinyl alcohol) and blends (S:PVA ratios of 2:1, 1:1 and 1:2) were obtained by casting and microstructure and thermal behaviour were characterized. Moreover, barrier, mechanical and optical properties were evaluated after 1 and 5 storage weeks at 25 °C and 53% relative humidity in order to study the effect of poly(vinyl alcohol) on the ageing process of starch. The incorporation of PVA into pea starch films implied the formation of interpenetrated networks of both incompatible polymers with partial solubilisation. S-PVA blend films were much more extensible and stable during storage, with improved water barrier properties and reduced water sorption capacity especially when the S:PVA ratio were 1:1 and 1:2. Starch-poly(vinyl alcohol) blend films are environmentally friendly, low cost materials, with good functional properties.

The improvement of thin film barrier performances of organic–inorganic hybrid nanolaminates employing a low-temperature MLD/ALD method

The investigations reported in this study were carried out to determine the feasibility and properties of alucone/Al2O3 hybrid nanolaminate films for thin film encapsulation (TFE) at low temperature, using an integrated molecular layer deposition (MLD) and atomic layer deposition (ALD) process. The combination of alucone (MLD) and Al2O3 (ALD), with O3 serving as the oxidant in place of conventional H2O, has been evaluated experimentally. In our studies, O3-based encapsulation layers were observed to be smoother, displaying an average roughness of 0.342 ± 0.016 nm with three laminate layers. However, H2O-based laminates showed a much higher roughness of 0.843 ± 0.024 nm under identical conditions. Estimates of water vapor transmission rate (WVTR) yielded significantly better results for O3-based laminates, with values decreasing linearly from 3.22 × 10−3 g m−2 per day to 2.37 × 10−5 g m−2 per day as the number of laminate layers increased from one to three, while a gentle decline trend from 1.83 × 10−3 g m−2 per day to 5.92 × 10−4 g m−2 per day was obtained for the H2O-based laminate. This indicates that the hybrid nanolaminates exhibited improved water barrier properties when O3 was used as the oxidant instead of H2O. In particular, the O3-based films did not decrease the performance of organic light-emitting diodes (OLEDs). In fact, the lifetime of OLEDs with O3-based encapsulation was approximately two-fold longer than the H2O-based encapsulation. Thus, we believe that the alucone/Al2O3 hybrid encapsulation film, in which O3 serves as the oxidant, is a promising candidate for use in future OLED applications.

Development of Novel Zein-Sodium Caseinate Nanoparticle (ZP)-Stabilized Emulsion Films for Improved Water Barrier Properties via Emulsion/Solvent Evaporation

This work attempted to develop novel high barrier zein/SC nanoparticle (ZP)-stabilized emulsion films through microfluidic emulsification (ZPE films) or in combination with solvent (ethyl acetate) evaporation techniques (ZPE-EA films). Some physical properties, including tensile and optical properties, water vapor permeability (WVP), and surface hydrophobicity, as well as the microstructure of ZP-stabilized emulsion films were evaluated and compared with SC emulsion (SCE) films. The emulsion/solvent evaporation approach reduced lipid droplets of ZP-stabilized emulsions, and lipid droplets of ZP-stabilized emulsions were similar to or slightly lower than that of SC emulsions. However, ZP- and SC-stabilized emulsion films exhibited a completely different microstructure, nanoscalar lipid droplets were homogeneously distributed in the ZPE film matrix and interpenetrating protein-oil complex networks occurred within ZPE-EA films, whereas SCE films presented a heterogeneous microstructure. The different stabilization mechanisms against creaming or coalescence during film formation accounted for the preceding discrepancy of the microstructures between ZP-and SC-stabilized emulsion films. Interestingly, ZP-stabilized emulsion films exhibited a better water barrier efficiency, and the WVP values were only 40-50% of SCE films. A schematic representation for the formation of ZP-stabilized emulsion films was proposed to relate the physical performance of the films with their microstructure and to elucidate the possible forming mechanism of the films.

Use of alginate- and gellan-based coatings for improving barrier, texture and nutritional properties of fresh-cut papaya

The use of alginate- (2% w/v) or gellan-based (0.5% w/v) coating formulations on fresh-cut papaya pieces was investigated in order to determine their ability to improve water vapor resistance (WVR), to affect gas exchange and to carry agents that help to maintain the overall quality of the minimally processed fruit. Formulations containing 2% (w/v) glycerol+1% ascorbic acid or 1% glycerol+1% ascorbic acid exhibited slightly improved water barrier properties for both types of coatings, as compared to the uncoated samples. The incorporation of 0.025% (w/w) sunflower oil into the alginate or the gellan-based formulations resulted in a 16% and 66% increase in the WVR of the coated samples, respectively. In general, coatings improved firmness of the fresh-cut product during the period studied. Furthermore, the addition of ascorbic acid as antioxidant in the coatings aided to preserve the natural ascorbic acid content of the fresh-cut papaya, helping to maintain its nutritional quality throughout storage. The gas barrier properties of the formulated coatings were not modified to allow substantial changes on respiratory rate and ethylene production of the coated papayas.