Good Gas Barrier Properties Research Articles

Shelf-Life Extension and Quality Changes of Fresh-Cut Apple via Sago and Soy-Oil-Based Edible Coatings

In-demand fresh-cut fruits are highly perishable and require shelf stability. Starch, such as sago, is a naturally available polysaccharide with good gas barrier properties. The study aimed to develop an edible coating and examine the effect of its application on the quality parameters of fresh-cut apples. The coating solution was prepared with sago and soy oil in concentrations of 3, 4, and 5% and 0, 0.25, and 0.50%, respectively. Lecithin (0.50%) was used as an emulsifier and glycerol (1.5%) as a plasticizer. Coated fresh-cut apples were evaluated for physicochemical properties (TSS, pH, non-enzymatic browning index, moisture content, weight loss, headspace gas, and color attributes) during a 12-day shelf-life study at 4 °C. Sensory analysis was also performed to assess consumer acceptability, and microbial analysis to investigate its inhibiting effect against yeast and mold. Compared to the control, developed coatings reduced browning, respiration rate, moisture, weight loss, and microbial load in fresh-cut apples. The study indicates that the blend of 5% sago and 0.5% soy oil produced the best coatings which were most effective for retaining the original quality attributes and in extending the shelf life of apple slices for 12 days in storage at 4 °C.

Preparation of biodegradable poly(lactic acid)/poly[(butylene diglycolate)‐co‐furandicarboxylate] blends with excellent toughness and gas barrier performance

AbstractPoly(lactic acid) (PLA) is known as one of the most promising biodegradable polyesters, while inherent brittleness and insufficient gas barrier performance limit its potential application as a film material. Herein, poly[(butylene diglycolate)‐co‐furandicarboxylate] (PBDF) with excellent flexibility and good gas barrier properties was synthesized and then melt‐blended with PLA. Compared with neat PLA, the elongation at break of the PLA/PBDF20 blend increased more than 40 times and reached over 176.7%. In addition, its O2, CO2 and H2O permeability coefficients decreased by 21.3%, 50.8% and 46.3%, respectively. Moreover, the PLA/PBDF20 blend also exhibited better biodegradability, with a weight loss rate increasing from 2.7% of neat PLA to 19.0% after 5 weeks of composting. Notably, incorporation of a multifunctional epoxy compatibilizer (Joncryl ADR®‐4368) into the PLA/PBDF blends further enhanced their toughness and gas barrier performance, which could be attributed to the improvement of the miscibility between PLA and PBDF. © 2024 Society of Chemical Industry.

Tetrazole-Containing Polyelectrolytes: A New Class of Ion-Solvating Membranes for Alkaline Water Electrolysis

Alkaline ion-solvating membranes, such as those based on polybenzimidazole (PBI), offer high ion conductivity and good gas barrier properties, making them promising for next-generation alkaline water electrolyzers.1 However, the stability of commonly used PBI derivatives is limited due to gradual backbone degradation. Consequently, alternative PBI chemistries and other polymer options like poly(vinyl alcohol),2 and carboxylate functionalized styrene-ethylene-butylene copolymers are being explored to address this inherent stability issue.3 In this study, we present the synthesis and characterization of a novel type of ion-solvating membranes for alkaline water electrolyzers. These membranes are based on tetrazole functionalized polymers derived from poly(styrene-co-acrylonitrile). A one-step click-type [3+2] cycloaddition reaction was utilized to introduce tetrazole pendants by converting acrylonitrile groups in poly(styrene-co-acrylonitrile). The degree of functionalization was controlled by adjusting the content of acrylonitrile units in the polymer. Subsequent treatment in aqueous KOH solution led to the formation of negatively charged tetrazolide pendants with high ionization degrees.The alkaline stability of the tetrazolides was evaluated using both DFT simulations and model compound studies, demonstrating remarkable stability with no degradation observed for over 3000 hours in 25 wt.% KOH at 80 °C. Physicochemical properties such as electrolyte uptake, swelling behavior, thermal stability, and ion conductivity were assessed for the synthesized polymers. The electrolyte-imbibed membranes exhibited high ion conductivity, reaching up to 90 mS cm-1 in 15 wt% KOH at 80 °C. Electrolysis operation using these membranes showed stable performance for 600 hours with no signs of degradation. 1 D. Aili, M. R. Kraglund, S. C. Rajappan, D. Serhiichuk, Y. Xia, V. Deimede, J. Kallitsis, C. Bae, P. Jannasch, D. Henkensmeier, J. O. Jensen, ACS Energy Letters, 2023, 1900–1910. 2 Y. Xia, S. C. Rajappan, D. Serhiichuk, M. R. Kraglund, J. O. Jensen, D. Aili, J Memb Sci 2023, 680, 121719. 3 D. Serhiichuk, D. Tian, M. R. Almind, Z. Ma, Y. Xia, M. R. Kraglund, C. Bae, J. O. Jensen, D. Aili ACS Applied Energy Materials 2024 7 (3), 1080-1091 Figure 1 Tetrazolation of poly(styrene-co-acrylonitrile) and formation of corresponding potassium tetrazolide following equilibration in aqueous KOH. Figure 1

Nanocellulose as a Sustainable Polymer Electrolyte

Polymer electrolyte membranes in fuel cells and electrolyzers will play a key role in the hydrogen economy. These membranes are generally made of sulfonated fluoropolymers, which have excellent proton conductivity, impressive redox stability, and good gas barrier properties. However, the complex synthetic processes mean that they remain expensive. Their synthesis also involves ecologically damaging perfluorosulfonic acids (PFSAs), otherwise known as “forever chemicals” due to their persistence in the environment. More sustainable and lower cost hydrocarbon electrolytes should therefore be investigated.Cellulose is the most abundant biopolymer in nature, and is derived from plant matter. It is used at vast scale and low cost to make paper and cardboard. Cellulose can be chemically or mechanically treated to break up the fibers to form “nanocellulose”. Nanocellulose is a low-cost nanomaterial which can be formed into thin membranes which are much stronger than conventional cellulosic paper.We propose nanocellulose as an alternative electrolyte to replace sulfonated fluoropolymers in fuel cells. We confirmed that unmodified nanocellulose can conduct protons due to acidic hydroxyl groups. We also showed that nanocellulose membranes present a much better barrier to hydrogen compared to Nafion, and can successfully be used as an electrolyte in fuel cells. However, the current-voltage performance of unmodified nanocellulose was insufficient due to a high membrane resistance.We went on to improve the proton conductivity by introducing sulfonic acid groups and reduced the membrane resistance by using spray deposition to create thinner membranes, resulting in significantly improved fuel cell power density of 160 mW/cm2. We also implemented crosslinking with sulfosuccinic acid to simultaneously improve the ionic conductivity, increase strength, and reduce swelling in water. This work shows that nanocellulose is a promising new class of polymer electrolyte which could significantly reduce the cost and improve sustainability of fuel cell and electrolyser systems.1. Cellulose Nanocrystals Crosslinked with Sulfonic Acid as Sustainable Proton Exchange Membranes for Electrochemical Energy Applications, O. Selyanchyn, T. Bayer, D. Klotz, R. Selyanchyn, K. Sasaki, S. M. Lyth, Membranes 12 (7), 658 (2022)2. Spray Deposition of Sulfonated Cellulose Nanofibers as Proton Conducting Membranes for Fuel Cells, T. Bayer, B. Cunning, R. Selyanchyn, B. Smid, S. Fujikawa, K. Sasaki, S. M. Lyth, Cellulose, 28, 1355–1367 (2021)3. Proton Conductivity in Cellulosic Materials: A Review, O. Selyanchyn, R. Selyanchyn, S. M. Lyth, Frontiers in Energy Research: Fuel Cells, 8, 596164 (2020)4. High Temperature Proton Conductivity in Nanocellulose: Paper Fuel Cells, T. Bayer, R. Selyanchyn, S. Fujikawa, K. Sasaki, and S. M. Lyth, Chemistry of Materials, 28 (13), 4805–4814 (2016)

Large-scale dispersion of the hierarchical (1D, 2D and 3D) carbonaceous nanofillers in thermoplastic polyurethane through supramolecular self-assembly and extrusion

ABSTRACT The hierarchical carbonaceous nanofillers viz. carboxylated multiwalled carbon nanotube (MWCNT-COOH as 1D), hydroxylated few-layer graphene (FLG-OH as 2D), and hybrid 3D i.e., MWCNT-COOH immobilized into FLG-OH were dispersed into segmented thermoplastic polyurethane (TPU) by twin-screw extrusion (TSE). The concentration of nanofillers was varied as 0.25, 0.5, 1.0, 2.0 and 5 wt%. To increase the level of dispersion, hybrid 3D nanofillers were also incorporated into TPU by producing cellular structures through supramolecular self-assembly route (SSAR). The cellular structure in which the nanofillers were found to be uniformly dispersed was then compounded by TSE technique. The large-scale uniform dispersion was observed at higher loading (2 wt%) by SSAR followed by TSE when compared with direct TSE. Uniform dispersion was found at 1 wt% loading by direct TSE. PU nanocomposite film reinforced with 2 wt% hybrid 3D nanofillers showed good gas barrier property with ~63% reduction of helium gas permeability to 472 cm3/m2/day from 1287 cm3/m2/day of neat PU film.

High toughness, UV & blue light shielding and antibacterial bio-based PEF/TiO2 nanowires composites for packaging application

As a candidate of fossil-based poly(ethylene terephthalate) (PET), bio-based poly(ethylene 2,5-furandicarboxylate) (PEF) that could be converted from renewable resources has attracted attention from academia and industry. Here, we prepare a series of new type of PEF/TiO2 NWs composites from 2,5-furandicarboxylic acid (FDCA), ethylene glycol (EG), titanium dioxide nanowire (TiO2 NWs, diameter∼100 nm, length∼20 µm) and dipentaerythritol (Di-PE) via in-situ polymerization. The TiO2 nanowires (0.5∼10 wt‰ based on PEF) and Di-PE (3 mol‰ based on FDCA) were added as fillers and extenders. TiO2 nanowires were distributed in the PEF uniformly, shown by SEM. Compared with pure PEF, the Tg and thermal stability of all nanocomposites got improved. And the impact strength of nanocomposites could reach 60 kJ/m2 in contrast to brittle pure PEF. The UV-A and blue-light shielding of nanocomposites increased from 53 % to 98 % and 28 % to 86 %, respectively, and the nanocomposites still maintained good gas barrier properties. Moreover, the antibacterial activity of nanocomposites against E. coli had increased to 98 %, better than that of the PEF/Ag NWs composites. By uniaxial pre-stretching, the tensile modulus and the elongation at break were improved obviously, from 1840 MPa to 5466 MPa and 4 % to 54 % respectively with pre-stretching ratio increasing. Compared to the PET/TiO2 NWs composites, the PEF/TiO2 NWs composites shows batter thermal property and mechanical property. The PEF/TiO2 NWs composites exhibit potential foreground in the packaging application.

Soy protein isolate/kappa-carrageenan/cellulose nanofibrils composite film incorporated with zenian essential oil-loaded MOFs for food packaging

Edible films applied in food packaging must possess excellent inhibitory and mechanical properties. Protein-based films exhibit a high capacity for film formation and offer good gas barrier properties. However, they have weak mechanical and water barrier characteristics. The objective of this research was to develop active composite films based on reinforced soy protein isolate (SPI)/Kappa-carrageenan (K) with varying concentrations of bacterial cellulose nanofibrils (BCN). Increasing the BCN concentration improved the morphological, structural, mechanical, water vapor barrier, and moisture content properties. In comparison to the pure SPI film (S), the film with a high BCN concentration demonstrated a significant decrease in WS (22.98 ± 0.78 %), MC (21.72 ± 0.68 %), WVP (1.22 ± 0.14 g mm-1 S-1 Pa-1 10-10), and EAB (57.77 ± 5.25 %) properties. It should be emphasized that there was no significant alteration in the physicomechanical properties of the optimal film (SKB0.75) containing Zenian-loaded metal-organic frameworks (ZM). However, it substantially enhanced the thermal stability of this film, which can be attributed to the strong interfacial interactions between polymer chains and ZM. Furthermore, the ZM films inhibited the growth of pathogenic bacteria and increased the DPPH antioxidant activity. Thus, SKB0.75-ZM2 films can be utilized as practical components in food packaging.

Development of chitosan/konjac glucomannan/tragacanth gum tri-layer food packaging films incorporated with tannic acid and ε-polylysine based on mussel-inspired strategy

Constructing biodegradable food packaging with good mechanics, gas barrier and antibacterial properties to maintain food quality is still challenge. In this work, mussel-inspired bio-interface emerged as a tool for constructing functional multilayer films. Konjac glucomannan (KGM) and tragacanth gum (TG) with physical entangled network are introduced in the core layer. Cationic polypeptide ε-polylysine (ε-PLL) and chitosan (CS) producing cationic-π interaction with adjacent aromatic residues in tannic acid (TA) are introduced in the two-sided outer layer. The triple-layer film mimics the mussel adhesive bio-interface, where cationic residues in outer layers interact with negatively charged TG in the core layer. Furthermore, a series of physical tests showed excellent performance of triple-layer film with great mechanical properties (tensile strength (TS): 21.4 MPa, elongation at break (EAB): 7.9 %), UV-shielding (almost 0 % UV transmittance), thermal stability, water, and oxygen barrier (oxygen permeability (OP): 1.14 × 10−3 g/m s Pa and water vapor permeability (WVP): 2.15 g mm/m2 day kPa). In addition, the triple-layer film demonstrated advanced degradability, antimicrobial functions, and presented good moisture-proof performance for crackers, which can be potentially applied as dry food packaging.

Stretchable Clay Nanocomposite Barrier Film for Flexible Packaging

The goal of reconciling all packaging requirements, e.g., mechanical resistance, transparency, flexibility, and gas barrier properties, is immensely challenging for packaging materials. Particularly, the combination of flexibility and good gas barrier properties poses a serious problem, especially when barrier requirements can only be met by lamination with a metal foil, metalization, or vapor-deposited ceramic layers, as all of these tend to be nonstretchable. In this work, we produced a stretchable nanocomposite barrier composed of one-dimensional (1D) crystalline (Bragg stack) barrier films composed of alternating layers of poly(ethylene glycol) (PEG) and synthetic sodium fluorohectorite (Hec) nanosheets. By sandwiching the Bragg stack type film between two plasticized poly(vinyl alcohol) (PVOH) layers, a waterborne laminate was obtained that outperforms commercial polymer materials in terms of water vapor permeability (WVP = 2.8 g mm m-2 day-1 bar-1 at 23 °C and 85% relative humidity), which is remarkable for an entirely water-soluble film. Moreover, no deterioration of barrier performance up to 10% elongation was observed, rendering the transparent self-standing laminate promising for thermoformed blister packaging, shrink wrap, or vacuum packaging. Besides the low WVP, the scalable and green processing method makes this technology auspicious for real-world applications.

Fabrication and Properties of Gelatin/Dialdehyde Chitosan Films

Non-biodegradable petroleum-based packaging film waste has led to a severe environmental pollution and human health problems. Gelatin and chitosan are attractive biopolymers for biomedical and food packaging applications due to biocompatibility, biodegradability, renewability, nontoxicity, and good gas barrier properties. However, disadvantages of the gelatin and chitosan are their low physicochemical stability and poor mechanical properties. In this study, dialdehyde chitosan was synthesized by periodate oxidation to use as a cross-linking agent for gelatin. The effect of the incorporation of the dialdehyde chitosan with 10, 15 and 20 wt% on mechanical and swelling properties as well as wettability of the gelatin films was investigated. The results reveal that the mechanical strength and swelling properties of the gelatin films were improved as an increase in the dialdehyde chitosan content, whereas the addition of the dialdehyde chitosan led to a decrease in water swelling ability in the gelatin films. Moreover, the wettability of the gelatin/dialdehyde chitosan films showed hydrophobic behaviour. Thus, the obtained gelatin/dialdehyde chitosan films as green polymeric products have a potential for food packaging fields.

Multi-Block Copolymer Membranes Consisting of Sulfonated Poly(p-phenylene) and Naphthalene Containing Poly(arylene Ether Ketone) for Proton Exchange Membrane Water Electrolysis

Glassy hydrocarbon-based membranes are being researched as a replacement for perfluorosulfonic acid (PFSA) membranes in proton exchange membrane water electrolysis (PEMWE). Here, naphthalene containing Poly(arylene Ether Ketone) was introduced into the Poly(p-phenylene)-based multi-block copolymers through Ni(0)-catalyzed coupling reaction to enhance π-π interactions of the naphthalene units. It is discovered that there is an optimum input ratio of the hydrophilic monomer and NBP oligomer for the multi-block copolymers with high ion exchange capacity (IEC) and polymerization yield. With the optimum input ratio, the naphthalene containing copolymer exhibits good hydrogen gas barrier property, chemical stability, and mechanical toughness, even with its high IEC value over 2.4 meq g-1. The membrane shows 3.6 times higher proton selectivity to hydrogen gas than Nafion 212. The PEMWE single cells using the membrane performed better (5.5 A cm-2) than Nafion 212 (4.75 A cm-2) at 1.9 V and 80 °C. These findings suggest that naphthalene containing copolymer membranes are a promising replacement for PFSA membranes in PEMWE.

Priamine 1075 and catechol carbonate, a perfect match for ecofriendly production of a new renewable polyurea for sustainable flexible food packaging

New homopolyurea with enhanced functional properties was synthesized by combining a bio-based vegetable oil derived diamine, Priamine 1075, with catechol carbonate as carbonylating agent employing an ecofriendly synthetic strategy. The synthesis, carried out in catalyst-free and solventless conditions, allowed obtaining a transparent rubbery material soluble in chloroform and processable in form of film. The polyurea was firstly subjected to molecular characterization by 1H, 13C NMR, ATR-FTIR spectroscopy and GPC analysis, to check molecular structure and weight ensuring the good control of synthesis process. Afterwards, the film was subjected to thermal characterization, DSC analysis confirming the amorphous rubbery nature and TGA revealing the outstanding thermal stability.Tensile tests showed low elastic modulus and exceptional elongation at break together with shape-recovery capability.Permeability tests revealed good gas-barrier properties regardless the amorphous rubbery nature, in particular to CO2 molecules. The measured values were better than polyolefins ones, to date the most used materials in food packaging.

An Efficient Composite Modifier Prepared for Enhancing the Crystallization and Flame-Retardancy of Poly(m-xylylene adipamide)

Poly(m-xylylene adipamide) (MXD6) has good gas barrier properties and high mechanical strength. However, in nature, this resin has a low rate of crystallization. In order to overcome this obstacle in its applications, this study prepares a new, efficient modifier for MXD6 by combining the synthesized DOPO derivative (DT) and P22. It is found that the use of the binary modifier exhibits obvious effects on the crystallization of MXD6. When 11.0 wt.% DT is added together with 0.1 wt.% P22 (DT/P22), the crystallization temperature of MXD6 shifts to a higher temperature of 19.7 °C, and the crystallinity degree of MXD6 is significantly increased by 60%. Meanwhile, this modifier exhibits obviously intumescent flame-retardancy on MXD6 by increasing the limited oxygen index (LOI) from 26.4% to 33.4%. The results of the cone calorimeter test (CCT) reveal that the peak heat release rate (PHRR), total heat release (THR) and average effective heat release (av-EHC) are obviously suppressed due to the use of this modifier. Moreover, the influences of this modifier on the crystal structures, mechanical and rheological properties of MXD6 are analyzed in detail. This study can provide an efficient modifier for MXD6.

Poly(3-hydroxybutyrate) Nanocomposites with Cellulose Nanocrystals.

Poly(3-hydroxybutyrate) (PHB) is one of the most promising substitutes for the petroleum-based polymers used in the packaging and biomedical fields due to its biodegradability, biocompatibility, good stiffness, and strength, along with its good gas-barrier properties. One route to overcome some of the PHB’s weaknesses, such as its slow crystallization, brittleness, modest thermal stability, and low melt strength is the addition of cellulose nanocrystals (CNCs) and the production of PHB/CNCs nanocomposites. Choosing the adequate processing technology for the fabrication of the PHB/CNCs nanocomposites and a suitable surface treatment for the CNCs are key factors in obtaining a good interfacial adhesion, superior thermal stability, and mechanical performances for the resulting nanocomposites. The information provided in this review related to the preparation routes, thermal, mechanical, and barrier properties of the PHB/CNCs nanocomposites may represent a starting point in finding new strategies to reduce the manufacturing costs or to design better technological solutions for the production of these materials at industrial scale. It is outlined in this review that the use of low-value biomass resources in the obtaining of both PHB and CNCs might be a safe track for a circular and bio-based economy. Undoubtedly, the PHB/CNCs nanocomposites will be an important part of a greener future in terms of successful replacement of the conventional plastic materials in many engineering and biomedical applications.

PHB/PLA plasticized by olive oil and carvacrol solvent-cast films with optimised ductility and physical ageing stability

Polylactic acid (PLA) is a bio-based polyester, widely used in various compostable food packaging film applications. Polyhydroxybutyrate (PHB), the most commercialised polymer of the PHA polyesters family, is one of the preferred bio-based polymers for food packaging, mainly because of its biodegradability in natural and controlled environments, and its good gas barrier properties. PHB, being a rather brittle polymer, is suitable for rigid packaging applications, mainly through injection molding processes. PHB may also be used for manufacturing flexible packaging by film casting and film blowing extrusion, through blending or co-extrusion with selected bio-based polymers such as PLA and additives. The potential development of blends of PHB with selected bio-based polymers that may be used for food packaging film applications was investigated in this work. Films made of various blends of PHB with other bio-based biodegradable polymers and additives were produced by the solvent casting method at laboratory scale and evaluated in terms of their mechanical properties and stability, used as “pass-fail” selection criteria. Following the development and evaluation of a second series of selected PHB/PLA blends suitable for films production, it was possible to achieve optimised compositions of PHB/PLA (10/90) blends with olive oil (OO) and carvacrol (CAR) as plasticizing and stabilising additives. The excellent mechanical performance of the selected blends with high ductility and stability against physical ageing, was analysed in depth in terms of their chemical structure and thermal behaviour.

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.

A review on specialty elastomers based potential inflatable structures and applications

With the escalation in continuous human curiosity, massive research work is going on in the field of inflatable structures and inflatable systems. These inflatable structures offer a great advantage for the building of emergency air shelters for civilian and military, industrial fuel and gas storage tanks, life rafts, lifeboats, etc. Even, more advanced inflatables like hull structure for lighter-than-air systems (LTA) and inflated radomes are employed in the defence sector. The advantage of inflatable structures lies on their excellent mechanical strength, lightweight, durability and they can be stored in a small volume. Specialty elastomers play an important role in developing inflatable structures because of their excellent properties towards weather resistance, UV and ozone resistance, stability against aging, and oxidation. In addition, they show good gas and vapour barrier properties. In the beginning of this review article, the structure and properties of specialty elastomers selected in this study have been discussed and then the gas transport mechanism through polymeric material is described. In the last part, the development of diverse types of inflatable systems used in industry, defence, and marine applications have been highlighted. More attention is given to the advanced application of inflatables in the defence sector. Throughout this review work, various literature and published work related to specialty elastomers application in inflatable systems have been reviewed. The main emphasis of this study is on the structure, properties and application of specialty elastomers in the advancement of inflatable structures.

Preparation and Characterization of Whey Protein Isolate-based Coating Solutions and Coated Papers with Different Plasticizers

Whey protein isolates (WPIs) are a byproduct of cheese and milk processing. WPI-based films offer transparency and good gas barrier properties at a low relative humidity, along with numerous different functional groups. However, they are hydrophilic, which restricts their use, and feature poor mechanical properties like brittleness. In this study, we explored the properties of WPI based coating materials depending on the type and contents of plasticizers, to use as a barrier coating materials for paper. Coating materials of WPI/glycerol (GY) and WPI/sorbitol (SO) with different plasticizer contents were prepared by solution blending. These materials were then coated on the surface of paper. The morphological structure, burst strength, tensile index, elongation at break, air permeability, and surface properties of the WPI/GY and WPI/SO-coated papers were investigated and compared based on the type and content of plasticizer. Compared to the WPI/GY-coated papers, the cracking of coating layers on the WPI/SO-coated papers was mitigated with increasing SO content in the WPI matrix. The WPI/SO-coated papers exhibited a higher tensile index, elongation at break, and air barrier than the WPI/GO-coated papers. Surface property analysis revealed that the hydrophilicity of both coated papers increased with increasing plasticizer content. However, further research is needed to reduce the hydrophilicity in WPI-coated papers and improve the compatibility between WPI and the plasticizer to enable their application in packaging.

Mechanically Reinforced, Flexible, Hydrophobic and UV Impermeable Starch-Cellulose Nanofibers (CNF)-Lignin Composites with Good Barrier and Thermal Properties

Bio-based composite films have been widely studied as potential substitutes for conventional plastics in food packaging. The aim of this study was to develop multifunctional composite films by introducing cellulose nanofibers (CNF) and lignin into starch-based films. Instead of costly and complicated chemical modification or covalent coupling, this study optimized the performance of the composite films by simply tuning the formulation. We found that starch films were mechanically reinforced by CNF, with lignin dispersing as nanoparticles embedded in the matrix. The newly built-up hydrogen bonding between these three components improves the integration of the films, while the introduction of CNF and lignin improved the thermal stability of the starch-based films. Lignin, as a functional additive, improved hydrophobicity and blocked UV transmission. The inherent barrier property of CNF and the dense starch matrix provided the composite films with good gas barrier properties. The prepared flexible films were optically transparent, and exhibited UV blocking ability, good oxygen-barrier properties, high hydrophobicity, appreciable mechanical strength and good thermal stability. These characteristics indicate potential utilization as a green alternative to synthetic plastics especially for food packaging applications.

Functionalised graphene oxide-bromobutyl rubber composites with segregated structure for enhanced gas barrier properties

ABSTRACT Graphene-based elastomer composites with a segregated structure were prepared by electrostatic self-assembly. The morphology and microstructures of the composites were characterised by scanning electron microscope (SEM) and transmission electrical microscope (TEM). The segregated network leads to a low gas permeability coefficient for BIIR composites. With the incorporation as low as 0.4 wt-% GTA-GO, the helium permeability coefficient decreased about 63% when compared with that of neat BIIR. The tensile strength and percentage elongation increased with an increase in the GTA-GO content. This is attributed to the complete exfoliation, uniform dispersion and the segregated structure of GTA-GO in the BIIR matrix. These results demonstrate that such electrostatic self-assembly method between latex and sheet-fillers is an effective strategy to design and produce polymeric nanocomposites with good gas barrier properties. The results will effectively promote the application of barrier polymer in the production of protective clothing, gas storage devices and coatings.