Effect of Cellulose Nanocrystals and Lignin Nanoparticles on Mechanical, Antioxidant and Water Vapour Barrier Properties of Glutaraldehyde Crosslinked PVA Films

Glutaraldehyde cross-linking for improving the techno-functional properties of biopolymeric food packaging films; a comprehensive review

Biodegradable and/or edible films made from polysaccharides and proteins have gained attention for their potential to replace some traditional packaging materials in the food industry due to their abundance, biodegradability, and nutritional value. Glutaraldehyde (GLA), rapidly reacts with free deprotonated ε-amino groups in proteins, leading to crosslinking (CL) reactions. This review delves into the chemistry of GLA and explores the various biopolymeric food packaging materials crosslinked by GLA. Furthermore, it summarizes recent applications of active and intelligent food packaging based on GLA-CL of biopolymers for food preservation. The comprehensive enhancement of biopolymeric films through GLACL is evident, with the impact on their properties depending on the concentration of GLA and reaction state. GLACL with biopolymer molecules enhances the cohesion of the polymer network, with physical and chemical covalent CL being the primary phenomena. Notably, biopolymeric food packaging films/coatings fabricated by GLACL have proven highly effectiveness in preserving fresh foods.

The multifunctional polyvinyl alcohol based diethyl ferulate nano silver film with UV-blocking and antibacterial properties

Food is prone to spoilage due to light and microbial exposure. To address this issue, Polystyrene microspheres @ Polydopamine / Diethyl ferulate / AgNPs (PS@PDA/DEF/Ag) was synthesized via copper-catalyzed azide/alkynyl cycloaddition reaction (CuAAC) and in-situ reduction. Subsequently, it was incorporated into a polyvinyl alcohol (PVA) matrix to fabricate PS@PDA/DEF/Ag/PVA multifunctional films. Derivative thermogravimetric (DTGA) analysis showed the exothermic peak of PS@PDA/DEF/Ag/PVA-4 wt% increased from 265.3 °C to 334.5 °C compared with PVA film. At concentrations exceeding 0.5 wt%, the UV shielding rate of the composite films reached at least 94.0%. The antibacterial experiments revealed that PS@PDA/DEF/Ag/PVA-4 wt% exhibited inhibition zone diameters of 3.8 ± 0.3 mm and 3.2 ± 0.3 mm against E. coli O157:H7 and S. aureus. Furthermore, the multifunctional films significantly prevented milk photooxidation for 3 days, jujubes brownish and strawberries decay for 7 days, demonstrating their effectiveness in antibacterial and UV-blocking food packaging.

Optimization of a novel antimicrobial nanocomposite films based on starch saffron corm incorporating nanoclay/lignin/extract using response surface methodology

This study aimed to develop and optimize nanocomposite films for food packaging using starch saffron corm starch (SCS) combined with nanoclay and either lignin or saffron corm extract (SCE). Response surface methodology (RSM) with a face-centered central design was used to optimize clay, lignin, and SCE concentrations. The effects of these variables on the films' physical (thickness, water vapor permeability, color, and solubility), mechanical, and phenolic compound migration properties were evaluated. The microstructure and antifungal properties of the optimized films were also analyzed. Results showed that all parameters significantly influenced the films' physical, mechanical, and migration properties, except for thickness. Optimal formulations were determined as 15.6 % clay with 0.3 % lignin and 16.9 % clay with 0.3 % SCE. FT-IR and SEM analyses confirmed strong compatibility among components and a homogeneous polymer matrix. The films exhibited at least 67 % biodegradability in α-amylase enzyme solution. Lignin was more effective than SCE in inhibiting fungal growth against aspergillus parasiticus and aspergillus flavus. These findings highlight the potential of SCS-based nanocomposite films for extending the shelf life of fruits and vegetables while offering sustainable and biodegradable packaging solutions for the food industry.

Preparation of biodegradable succinic anhydride esterified lignin-based polyvinyl alcohol film with improved mechanical and thermal properties

In this study, a biodegradable SA esterified lignin-based PVA (SELP) film was created from the purified lignin, polyvinyl alcohol (PVA) and succinic anhydride (SA) under the catalysis of N,N-dimethylbenzylamine through three-step process. The chemical and crystalline characterization of SELP film was implemented to analyze the esterification of SA on the lignin macromolecule and PVA backbone. The research results confirmed the double esterification of lignin and PVA with SA. It was found that the introduction of lignin not only effectively regulated the surface morphologies of SELP films, but also greatly elevated their mechanical strength and thermal stability. Compared with SEP film, the elongation at break and toughness of SEL50P film were raised by 803.4 % and 2130.8 % to 1216.05 ± 5.97 % and 23.2 ± 2.04 MJ/m3, respectively. The largest increase in the tensile strength (5829.4 ± 5.34 kPa) was acquired for the SEL20P film having 20 % lignin dosage. Although in high humidity conditions, SEL50P film also displayed prominent tensile strength (8.12 ± 0.92 MPa) and satisfactory toughness (21.53 ± 2.01 MJ/m3). Meanwhile, even after soaking in water for 24 h, SEL50P film still showed excellent tensile resilience performance. More importantly, SEL50P film has good biodegradability, which can be completely degraded into CO2 and H2O by natural microorganisms within 3 months.

Rapid Fabrication of Tendon-inspired Ultrastrong, Water-rich Hydrogel Fibers: Synergistic Engineering of Cyano-p-aramid Nanofibers and Poly(vinyl alcohol)

Load-bearing fibrous tissues, like tendons, have remarkable strength with high water content (∼60%) due to the anisotropic network of collagen fibers. However, the scalability of biomimetic anisotropic hydrogels is limited by time-intensive fabrication processes involving cross-linking and stretching, often spanning several hours to days. Here, we present a rapid, scalable approach for fabricating tendon-mimetic hydrogel fibers within 1 min using the synergistic engineering of cyano-p-aramid nanofibers (CY-ANFs) and poly(vinyl alcohol) (PVA). Through continuous air-gap spinning, the formation of the anisotropic CY-ANF network drives instant gelation, producing hundreds of meters of hydrogel fibers without additional gelation treatment. From the perspective of properties, the hydrophilic PVA matrix affords flexibility, while the hydrophobic CY-ANF network provides a nonswelling feature and load-bearing ability, resulting in ultrastrong, water-rich hydrogel fibers. These hydrogel fibers exhibit a water content exceeding 80 wt %, along with exceptional strength (∼17.9 MPa), surpassing the mechanical properties of natural tendons (strength and modulus of approximately 10 and 100 MPa, respectively). Lengthy hydrogel fibers are integrated into larger-sized fabrics by knitting or weaving while also possessing strain-sensing capabilities. With excellent biocompatibility, these hydrogel fibers are promising candidates for artificial fibrous tissues and various biotechnological applications.

Utilization of structure-specific lignin extracted from coconut fiber via deep eutectic solvents to enhance the functional properties of PVA nanocomposite films

This study utilized deep eutectic solvents (DES) based on choline chloride/lactic acid (ChCl/LA) to deconstruct coconut fibers. The effects of DES with different temperatures and molar ratios on the yield of lignin, recovery rate of residues, structural changes in lignin and solid residues, and saccharification efficiency were investigated. The results showed that acidic DES treatment effectively deconstructed the coconut fibers, resulting in a high lignin yield of 68.51 % while enhancing the enzymatic saccharification of cellulose, reaching a glucose yield of 85.88 %. The structural characterization of lignin revealed that acidic DES primarily cleaved β-O-4 bonds, yielding coconut fiber lignin with lower molecular weight and higher phenolic hydroxyl groups. Uniform and smooth coconut fiber lignin nanoparticles (CFLNPs) with excellent antioxidant activity were finally obtained by antisolvent method. Furthermore, PVA/CFLNPs nanocomposite films were prepared based on acidic DES CFLNPs. The results of the structural and functional analysis showed that CFLNPs significantly improved the thermal stability, mechanical properties, hydrophobicity, antioxidant and antibacterial activity of the nanocomposite films. In general, this work achieved efficient deconstruction of coconut fibers, providing insights for biorefining in the future, and more importantly, the potential to use the CFLNPs as a choice for active food packaging.

Minimizing food oxidation using aromatic polymer: From lignin into nano-lignin

Food loss and waste caused by oxidation result in environmental and economic losses and health threats. Lignin is an abundant aromatic polymer with varied antioxidant capacity, which can reduce food oxidation caused by radical species exposure. The lignin antioxidant strength can be influenced by source, type, structure, processing, degradation products, chemical modifications, and particle size. Lignin in micro- or nano-particles has high reactivity and is associated with increased surface area to improve antioxidant capacity. Lignin can be used as a food additive to suppress lipid and protein oxidation, although its effect on fruit/vegetable oxidation needs to be discussed. The lignin antioxidant properties are promising to be applied in food industries, such as food additives, animal feed supplements, and antioxidant packaging designs. However, there are challenges and limitations to consider, such as the potential for toxicity reactions in some individuals and the need for further research to understand its effects on different food products fully. As a feed nutrition, lignin can improve meat quality. Meanwhile, loading lignin in the packaging matrix can extend the food shelf life through antioxidant and antimicrobial activities, and UV-block. Lignin also improves packaging properties (conventional and 3D-printing fabrication) to maintain food quality, e.g., changes in mechanical properties, hydrophobicity, water vapor permeability, and other influences. This article reviews lignin's role as a natural antioxidant in the food industry. Future directions and discussions relate to prooxidative mechanisms, toxicity, fruit and vegetable preservation mechanisms, inhibition of protein oxidation, activity to food enzymes (fruit ripening enzyme activators and inhibitors of cellulase and β-glucosidase enzyme), dispersity in packaging matrices, and material diversification for 3D printing.

Lignin nanoparticles enable and improve multiple functions of photonic films derived from cellulose nanocrystals

Flexible photonic materials derived from cellulose nanocrystals (CNCs) have attracted significant attention, particularly in multifunctional sensors, intelligent detection, and anti-counterfeiting applications. However, the major bottleneck with traditional CNC photonic materials is the provision of flexibility and multifunctional properties which often comes with compromises in optical properties. To address these challenges, we incorporated organosolv lignin nanoparticles (LNPs) and polyethylene glycol (PEG) into CNC films. LNPs were produced from sugarcane bagasse using various solvents, resulting in nanoparticles with distinct structural and chemical properties, such as different sizes and surface chemistries. The addition of LNPs and PEG to CNC films led to enhanced flexibility, strong iridescence, improved thermal stability and superior UV-blocking performance. Interestingly, the intercalation of LNPs significantly improved the strain at break by 89.6 % with slight increase of 7.7 % and 23.1 % in tensile strength and young's modulus respectively. Additionally, distinguished UV-blockage performance of up to 99.9 % in the UVB region and 94 % in the UVA region was also achieved in CNC-LNP-PEG films. The films exhibited varying responses to several organic solvents and HCl gas with reversible color changes. These responses were attributed to the distinct surface chemistries of the LNPs, which influenced their interactions with the CNC matrix through mechanisms such as hydrogen bonding and hydrophobic interactions. This study highlights the potential of CNC-LNP-PEG composite films for advanced applications in chemical safety and anti-counterfeiting measures, demonstrating the importance of composite formulation and processing conditions in achieving desirable properties.

Advancements of Biomacromolecular Hydrogel Applications in Food Nutrition and Health

Hydrogels exhibit remarkable degradability, biocompatibility and functionality, which position them as highly promising materials for applications within the food and pharmaceutical industries. Although many relevant studies on hydrogels have been reported in the chemical industry, materials, and other fields, there have been few reviews on their potential applications in food nutrition and human health. This study aims to address this gap by reviewing the functional properties of hydrogels and assessing their value in terms of food nutrition and human health. The use of hydrogels in preserving bioactive ingredients, food packaging and food distribution is delved into specifically in this review. Hydrogels can serve as cutting-edge materials for food packaging and delivery, ensuring the preservation of nutritional activity within food products, facilitating targeted delivery of bioactive compounds and regulating the digestion and absorption processes in the human body, thereby promoting human health. Moreover, hydrogels find applications in in vitro cell and tissue culture, human tissue repair, as well as chronic disease prevention and treatment. These broad applications have attracted great attention in the fields of human food nutrition and health. Ultimately, this paper serves as a valuable reference for further utilization and exploration of hydrogels in these respective fields.

Yellow emissive and high fluorescence quantum yield carbon dots from perylene-3,4,9,10-tetracarboxylic dianhydride for anticounterfeiting applications

Forged products are widespread in the market and there is an immediate need to counter this growing menace. Anti-counterfeit techniques using fluorescent materials with covert features that appear hidden under daylight and display characteristic fluorescence upon specific source irradiation have gained popularity. Carbon dots (CDs) that can be prepared through facile synthesis from various raw materials are a class of fluorescent materials that provide tremendous opportunities to combat counterfeiting. This work focuses on the fabrication of perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA) derived CDs via the solvothermal approach and their subsequent purification using column chromatography. The fifth fraction obtained exhibited remarkable yellow emission (λem = 540 nm) with a high fluorescence quantum yield of 53.22% and a lifetime of 4 ns. The CDs appeared quasi-spherical during TEM imaging with an average diameter of 1-3 nm and appeared polycrystalline from the SAED pattern. The XPS and TEM-EDS results suggested carbon as the major element along with oxygen and nitrogen as the other heteroatoms. The water-based ecofriendly ink formulated using the CDs was printed on UV dull paper using the flexography technique. The print-proof paper samples appeared pale pink under daylight and fluorescent yellow upon 365 nm UV illumination. Moreover, the stability of the print was confirmed upon exposure to strong UV radiation cycles and abrasion resistance. Besides, the fluorescence emission remained unaltered even after 5 months of storage under room temperature conditions. The ink was used to print on PVC sheets and FBB boards with good stability against scuffing, suggesting its applicability in the packaging industry. The CDs could also serve as fluorescent markers for identifying post-consumer plastic packaging for a circular economy.

Incorporation of Nano-Zinc Oxide as a Strategy to Improve the Barrier Properties of Biopolymer-Suberinic Acid Residues Films: A Preliminary Study

Finishing coatings in the wood-based composites industry not only influence the final appearance of the product but also serve to protect against fungi and molds and reduce the release of harmful substances, particularly formaldehyde and volatile organic compounds (VOCs). Carbon-rich materials, such as those derived from birch bark extraction, specifically suberin acids, can fulfill this role. Previous research has demonstrated that adding suberin acid residues (SAR) at 20% and 50% by weight significantly enhances the gas barrier properties of surface-finishing materials based on poly(lactide) (PLA) and polycaprolactone (PCL), particularly in terms of total VOC (TVOC) and formaldehyde emissions. This study aims to explore whether these properties can be further improved through the incorporation of nano-zinc oxide (nano-ZnO). Previous research has shown that these nanoparticles possess strong resistance to biological factors and can positively affect the characteristics of nanofilms applied as surface protection. The study employed PLA and PCL finishing layers blended with SAR powder at 10% w/w and included 2% and 4% nano-zinc oxide nanoparticles. The resulting blends were milled to create a powder, which was subsequently pressed into 1 mm-thick films. These films were then applied to raw particleboard surfaces. TVOC and formaldehyde emission tests were conducted. Additionally, the fungal resistance of the coated surfaces was assessed. The results showed that PLA/SAR and PCL/SAR composites with the addition of nano-zinc oxide nanoparticles exhibited significantly improved barrier properties, offering a promising avenue for developing biodegradable, formaldehyde-free coatings with enhanced features in the furniture industry. Furthermore, by utilizing SAR as a post-extraction residue, this project aligns perfectly with the concept of upcycling.

UV-blocking, antibacterial, corrosion resistance, antioxidant, and fruit packaging ability of lignin-rich alkaline black liquor composite film

The novel multifunctional active packaging composite film with antimicrobial, antioxidant, water-vapor and UV-barrier, and corrosion resistance properties was successfully prepared from waste biomass. In this study, waste poplar sawdust was pretreated using green liquor to extract black liquor (BL). BL was then mixed with polyvinyl alcohol (PVA) solution for synthesizing silver nanoparticles (AgNPs). PVA-BL-AgNPs film was fabricated by solution casting method, and the microstructure characterization and macroscopic performance testing of the composite film were conducted. The results revealed that PVA-BL-AgNPs film exhibited inhibitory effects against Staphylococcus aureus (inhibition zone: 33.6 mm), Pseudomonas aeruginosa (inhibition zone: 31.6 mm), and Escherichia coli (inhibition zone: 32.0 mm). It could eliminate over 99 % of 2,2-diazodi (3-ethyl-benzothiazol-6-sulfonic acid) (ABTS) free radicals and provided 100 % UV-blocking, reducing light-induced food damage. It exhibited the improvement of water-vapor barrier properties and corrosion resistance. In vitro cytotoxicity assays demonstrated that no significant impact occurred on cell proliferation, confirming the safety of the film. Packaging experiments showed that PVA-BL-AgNPs film effectively inhibited milk spoilage and prolonged the shelf-life of bread and bananas. Therefore, PVA-BL-AgNPs film might extend the shelf-life of food and offer significant opportunities in addressing the issues of low safety and environmental pollution associated with traditional packaging films.

Preparation of Vitamin-g-Lignin Nanohybrids with Excellent Biological Activity and Fluorescence Performance

As a natural renewable biomacromolecule, lignin has some inherently interesting properties such as fluorescence, antioxidation, and antibacterial performance. However, the unsatisfactory fluorescence and biological activities have greatly limited their value-added and large-scale applications. In this work, lignin nanoparticles (LNPs) grafted with vitamin B1 hybrid nanoparticles (LEVs) were obtained by using ethylenediamine and different contents of vitamin B1 through a simple hydrothermal method. The chemical structure, fluorescence properties, and bioactivity were characterized to assess the effects of ethylenediamine and vitamin B1 on the properties of LEVs. It was found that the fluorescence performance of synthesized LEV particles was improved with the increase in the amount of vitamin B1. The free radical scavenging rate (RSA, %) increased to 97.8%, while the antibacterial rates reached up to 99.9%. The antibacterial activity of LEV involved multiple combined mechanisms. The introduction of imine, amide groups, and positively charged VB1 of LEV will make it easier to interact with the negatively charged bacterial phospholipid membranes and cause bacterial lysis and death. Then, the PVA/LEV hydrogel composites were prepared by the freezing-thawing method, and the results showed that PVA/LEV hydrogels had more comprehensive performance such as improved mechanical properties and antioxidant and antibacterial activities, resulting in its great potential to be used as an efficient biomedical material.

Preparation and characterization of polyvinyl alcohol (PVA)-glycerol composite films incorporating nanosilica from municipal solid waste incinerator bottom ash

This study investigates the fabrication of a composite film composed of polyvinyl alcohol (PVA) and glycerol, incorporating nanosilica derived from municipal solid waste incinerator bottom ash (BA). The nanosilica is blended with a PVA film-forming solution containing glycerol as a plasticizer. The composite films are characterized using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and scanning electron microscopy (SEM). Additionally, thermogravimetric analysis (TGA) is conducted to evaluate the thermal properties, while the mechanical properties are assessed in terms of tensile strength (TS) and elongation at break (EAB). The results indicate that the presence of silica nanoparticles reduces transparency and increases film thickness in the presence of glycerol. Notably, the film containing 1% silica demonstrates a significant enhancement in tensile strength, exhibiting a 50% increase compared to the film without silica. However, higher silica loadings lead to a deterioration in mechanical properties due to silica agglomeration within the polymer matrix. As expected, the presence of silica in the films slightly elevates the degradation temperature.

Sustainable lignin nanoparticles from coconut fiber waste for enhancing multifunctional properties of macroalgae biofilms

Multifunctional and sustainable packaging biofilms felicitous to changeable conditions are in large demand as substitutes to petroleum-derived synthetic films. Macroalgae with noticeable film-formation, abundant, low-cost, and edible properties is a promising bioresource for sustainable and eco-friendly packaging materials. However, the poor hydrophobicity and mechanical properties of sustainable macroalgae biofilms seriously impede their practical applications. Herein, lignin nanoparticles (LNPs) produced by a sustainable approach from black liquor of coconut fiber waste were incorporated in the macroalgae matrix to improve the water tolerance and mechanical characteristics of the biofilms. The effect of different LNPs loadings on the performance of biofilms, such as physical, morphological, surface roughness, structural, water resistance, mechanical, and thermal behaviors, were systematically evaluated and found to be considerably improved. Biofilm with 6 % LNPs presented the optimum enhancement in most ultimate performances. The optimized biofilm exhibited great hydrophobic features with a water contact angle of over 100° and high enhancement in the tensile strength of >60 %. This study proposes a facile and sustainable approach for designing and developing LNPs-macroalgae biofilms with excellent and multifunctional properties for sustainable high-performance packaging materials.

Construction of multiple crosslinked networks for the preparation of high-performance lignin-containing cellulose nanofiber reinforced polyvinyl alcohol films

Polyvinyl alcohol (PVA) film, a promising alternative to non-biodegradable plastic packaging films for food and medical packaging, is limited by poor water resistance. In this work, a simple solvent evaporation self-assembly was used to construct a nanophase separation structure to establish dense interfacial hydrogen bonding, covalent bonding and iron metal ion coordination interactions between lignin-containing cellulose nanofibers (LCNFs) and PVA matrix to improve the interfacial force and solve the problem of poor compatibility of LCNFs in PVA. The iron ion (Fe3+) coordination tended to combine with the more active lignin phenolic hydroxyl group to construct the nanophase separation structure. Covalent crosslinking of glutaraldehyde (GA) improved the interfacial compatibility of PVA/LCNF films, enhanced the interfacial bonding and formed a homogeneous structure. The multi-nanophase structures improved the strength and elastic modulus of the PVA/LCNF film and provided the films with extremely low water absorption, water vapor transmission rate and excellent UV-shielding. Compared with pure PVA film, PVA-10L-5Fe-3GA film had about 106.9 % higher tensile strength, 93.9 % lower water absorption and 93.4 % lower mass loss, 69.8 % lower water vapor transmission coefficient, and was able to shield UV at 200-400 nm, which is highly expected to be used in packaging films.

Synthesis of Biodegradable and Antimicrobial Nanocomposite Films Reinforced for Coffee and Agri-Food Product Preservation

The antimicrobial activity of silver nanoparticles is widely known. However, their application to biodegradable polymeric materials is still limited. In this work, we report a strategy involving the green synthesis of nanocomposite films based on a natural biodegradable matrix. Nanometer-sized silver nanoparticles (C-AgNPs) were synthesized with the aid of ultrasound waves between the silver nitrate solution and the nanocurcumin solution. The green synthesized C-AgNPs were found to have particle sizes in the range of 5-25 nm and demonstrated good antimicrobial activity against Clostridium perfringens, Staphylococcus aureus, Bacillus subtilis, Macrophoma theicola, and Aspergillus flavus. Owing to their physical-chemical and mechanical properties and the excellent antimicrobial activities, the obtained AgNPs were used together with chitosan, cassava starch, and poly(vinyl alcohol) (PVA) to make nanocomposite films, which are suitable for the packaging requirements of various key agricultural and food products such as coffee beans, bamboo straws, and fruits. The nanocomposite films lost up to 85% of their weight after being buried in the soil for 120 days. This indicates that the films made with natural biodegradable materials are environmentally friendly.

Superhydrophobic, Magnetic Aerogels Based on Nanocellulose Fibers Derived from Harakeke for Oily Wastewater Remediation

Cellulose-based aerogels have been seen as a promising sorbent for oil and organic pollutant cleaning; however, their intrinsic hydrophilicity and difficulty of recycling has hindered their practical application. In this work, a superhydrophobic, magnetic cellulose-based aerogel was fabricated as a highly efficient sorbent for the adsorption of oils and organic solvents. The aerogel was prepared via a simple freeze-drying method, followed by chemical vapor deposition (CVD). The incorporation of Fe3O4 nanoparticles into the aerogel not only makes it responsive to external magnetic field, but also contributes to the better hydrophobicity of the aerogel, in which the water contact angle (WCA) was about 20° higher than the aerogel without loading with Fe3O4 nanoparticles. The adsorption test showed that the resultant aerogel can selectively adsorb a wide range of oils and organic solvents from oil/water mixtures with a high adsorption capacity (up to 113.49 g/g for silicone oil). It can retain about 50% of its adsorption capacity even after 10 adsorption-squeezing cycles, which indicates its outstanding reusability. Moreover, the aerogels can be easily controlled by an external magnet, which is preferred for the adsorption of oily contaminants in harsh environments and enhanced the recyclability of the aerogel. We believe that this study provides a green and convenient approach for the practical fabrication of cellulose-based oil sorbents.

Theta-Gel-Reinforced Hydrogel Composites for Potential Tensile Load-Bearing Soft Tissue Repair Applications

Engineering synthetic hydrogels for the repair and augmentation of load-bearing soft tissues with simultaneously high-water content and mechanical strength is a long-standing challenge. Prior formulations to enhance the strength have involved using chemical crosslinkers where residues remain a risk for implantation or complex processes such as freeze-casting and self-assembly, requiring specialised equipment and technical expertise to manufacture reliably. In this study, we report for the first time that the tensile strength of high-water content (>60 wt.%), biocompatible polyvinyl alcohol hydrogels can exceed 1.0 MPa through a combination of facile manufacturing strategies via physical crosslinking, mechanical drawing, post-fabrication freeze drying, and deliberate hierarchical design. It is anticipated that the findings in this paper can also be used in conjunction with other strategies to enhance the mechanical properties of hydrogel platforms in the design and construction of synthetic grafts for load-bearing soft tissues.

Opportunities and Challenges for Lignin Valorization in Food Packaging, Antimicrobial, and Agricultural Applications

The exploration of renewable resources is essential to help transition toward a more sustainable materials economy. The valorization of lignin can be a key component of this transition. Lignin is an aromatic polymer that constitutes approximately one-third of the total lignocellulosic biomass and is isolated in huge quantities as a waste material of biofuel and paper production. About 98% of the 100 million tons of lignin produced each year is simply burned as low-value fuel, so this renewable polymer is widely available at very low cost. Lignin has valuable properties that make it a promising material for numerous applications, but it is far from being fully exploited. The aim of this Perspective is to highlight opportunities and challenges for the use of lignin-based materials in food packaging, antimicrobial, and agricultural applications. In the first part, the ongoing research and the possible future developments for the use of lignin as an additive to improve mechanical, gas and UV barrier, and antioxidant properties of food packaging items will be treated. Second, the application of lignin as an antimicrobial agent will be discussed to elaborate on the activity of lignin against bacteria, fungi, and viruses. Finally, the use of lignin in agriculture will be presented by focusing on the application of lignin as fertilizer.

Enhanced Functional Properties of Bioplastic Films Using Lignin Nanoparticles from Oil Palm-Processing Residue

The development of bioplastic materials that are biobased and/or degradable is commonly presented as an alleviating alternative, offering sustainable and eco-friendly properties over conventional petroleum-derived plastics. However, the hydrophobicity, water barrier, and antimicrobial properties of bioplastics have hindered their utilization in packaging applications. In this study, lignin nanoparticles (LNPs) with a purification process were used in different loadings as enhancements in a Kappaphycus alvarezii matrix to reduce the hydrophilic nature and improve antibacterial properties of the matrix and compared with unpurified LNPs. The influence of the incorporation of LNPs on functional properties of bioplastic films, such as morphology, surface roughness, structure, hydrophobicity, water barrier, antimicrobial, and biodegradability, was studied and found to be remarkably enhanced. Bioplastic film containing 5% purified LNPs showed the optimum enhancement in almost all of the ultimate performances. The enhancement is related to strong interfacial interaction between the LNPs and matrix, resulting in high compatibility of films. Bioplastic films could have additional advantages and provide breakthroughs in packaging materials for a wide range of applications.

Multicolor Emitting Carbon Dot-Reinforced PVA Composites as Edible Food Packaging Films and Coatings with Antimicrobial and UV-Blocking Properties

Active food packaging has become attractive because of the possibility to provide a longer shelf-life by loading functional agents into the packages to maintain the quality of food products. Herein, photoluminescent and transparent polyvinyl alcohol (PVA)-based composites embedding multicolor fluorescent carbon dots (CD/PVA) were prepared by the solvent casting method. The prepared CDs emit a strong and stable fluorescence in solution while the CD/PVA composite films were transparent, flexible, and showed UV-blocking activity with a strong fluorescence emission. Blue color-emitting CDs showed the highest UV blockage at UVA (87.04%), UVB (87.04%), and UVC (92.22%) regions while PVA alone absorbed only less than 25% of the light in all UV regions. UV blockage capacity was shown to be decreased by half, in line with the emission color shift from blue to red. Thermal properties of the PVA film were improved by the addition of CDs to the polymer, and in vitro cell viability tests showed that none of the CDs were cytotoxic against the human lung fibroblast healthy cell line (MRC-F cells) when integrated into the PVA. The antimicrobial activity of CD/PVA nanofilms was qualitatively determined. The prepared films exhibited good antimicrobial activity against both Gram-positive and Gram-negative bacteria with mild antioxidant and metal chelating activity, and significant inhibition of biofilm formation with a strong link with emitted color and the concentration of the composites. Green- and red-emitting CD/PVA with the highest antimicrobial activity were then analyzed and compared with the plane PVA employing their effect on the shelf-life of strawberries as a model for perishable foods. Fresh strawberries dip coated with CD/PVA and PVA were monitored over time, and virtual evaluations showed that CDs/PVA film coating resulted in reduced weight and moisture loss and significantly inhibited the fungal growth and spoiling for over 6 days at RT and 12 days at fridge conditions maintaining the visual appearance and natural color of the fruit. The findings in this work indicated the potential of reported CD as non-cytotoxic, UV-blocking antimicrobial additives for the development of edible coatings and packages for their use in the food industry, as well as pharmaceutical and healthcare applications.

Sustainable and Eco-Friendly Packaging Films Based on Poly (Vinyl Alcohol) and Glass Flakes

The majority of food packaging materials are petroleum-based polymers, which are neither easily recyclable nor ecologically friendly. Packaging films should preferably be transparent, light in weight, and easy to process, as well as mechanically flexible, and they should meet the criteria for food encapsulation. In this study, poly (vinyl alcohol) (PVA)-based films were developed by incorporating glass flakes into the films. The selection of PVA was based on its well-known biodegradability, whereas the selection of glass flakes was based on their natural impermeability to oxygen and moisture. The films were processed using the blade coating method and were characterized in terms of transparency, oxygen transmission rate, mechanical strength, and flexibility. We observed that the incorporation of glass flakes into the PVA matrix did not significantly change the transparency of the PVA films, and they exhibited a total transmittance of around 87% (at 550 nm). When the glass flakes were added to the PVA, a significant reduction in moisture permeation was observed. This reduction was also supported and proven by Bhardwaj’s permeability model. In addition, even after the addition of glass flakes to the PVA, the films remained flexible and showed no degradation in terms of the water vapor transmission rate (WVTR), even after bending cycles of 23,000. The PVA film with glass flakes had decent tensile characteristics, i.e., around >50 MPa. Increasing the concentration of glass flakes also increased the hardness of the films. Finally, a piece of bread was packaged in a well-characterized composite film. We observed that the bread packaged in the PVA film with glass flakes did not show any degradation at all, even after 10 days, whereas the bread piece packaged in a commercial polyethylene bag degraded completely. Based on these results, the developed packaging films are the perfect solution to replace commercial non-biodegradable films.

Comparative Preparation Method and Associated Cost of Lignin–Cellulose Nanocrystals

Lignin is a natural source of UV-shielding materials, though its recalcitrant and heterogeneous structure makes the extraction and purification processes complex. However, lignin’s functionality can be directly utilised when it stays as native with cellulose and hemicellulose in plant biomass, rather than being separated. The fabrication process of this native lignin is sustainable, as it consumes less energy and chemicals compared to purified lignin; thus, it is an economic and more straightforward approach. In this study, the properties of native and purified lignin–cellulose nanocrystals (L–CNCs) sourced from hemp hurd waste were compared to explore the differences in their morphology, UV-shielding properties and chemical structure affected by their distinct fabrication process. These two kinds of L–CNCs were further added into polyvinyl alcohol (PVA) to evaluate their reinforcement characteristics. The resulting native L–CNCs/PVA film showed stronger UV-shielding ability than purified L–CNCs. Moreover, the native L–CNCs showed better compatibility with PVA, while the purified L–CNCs/PVA interfaces showed phase separation. The phase separation in purified L–CNCs/PVA films reduced the films’ tensile strength and Young’s modulus and increased the water vapour transmission. The laboratory-scale cost of native L–CNCs production (~AUD 80/kg) was only 10% of purified L–CNCs (~AUD 850/kg), resulting in a comparatively lower cost for preparing native L–CNCs/PVA composite films. Overall, this study shows that the proposed method of production and use of native L–CNCs can be an economic approach to deliver UV-shielding properties for potential applications, such as food packaging.

Hemicellulose and Nano/Microfibrils Improving the Pliability and Hydrophobic Properties of Cellulose Film by Interstitial Filling and Forming Micro/Nanostructure

In this paper, nano/microfibrils were applied to enhance the mechanical and hydrophobic properties of the sugarcane bagasse fiber films. The successful preparation of nano/microfibrils was confirmed by scanning electron microscope (SEM), X-ray diffraction (XRD), fiber length analyzer (FLA), and ion chromatography (IC). The transparency, morphology, mechanical and hydrophobic properties of the cellulose films were evaluated. The results show that the nanoparticle was formed by the hemicellulose diffusing on the surface of the cellulose and agglomerating in the film-forming process at 40 °C. The elastic modulus of the cellulose film was as high as 4140.60 MPa, and the water contact angle was increased to 113°. The micro/nanostructures were formed due to hemicellulose adsorption on nano/microfilament surfaces. The hydrophobicity of the films was improved. The directional crystallization of nano/microfibrous molecules was found. Cellulose films with a high elastic modulus and high elasticity were obtained. It provides theoretical support for the preparation of high-performance cellulose film.

Design, Synthesis and Adsorption Evaluation of Bio-Based Lignin/Chitosan Beads for Congo Red Removal

The morphology and intermolecular interaction are two of the most important factors in the design of highly efficient dye adsorbent in the industry. Millimeter-sized, bead-type, bio-based lignin/chitosan (Lig/CS) adsorbent was designed for the removal of Congo red (CR), based on the electrostatic attraction, π-π stacking, and hydrogen bonding, which were synthesized through the emulsification of the chitosan/lignin mixture followed by chemical cross-linking. The effects of the lignin/chitosan mass ratio, initial pH, temperature, concentration, and contact time on the adsorption were thoroughly investigated. The highest adsorption capacity (173 mg/g) was obtained for the 20 wt% Lig/CS beads, with a removal rate of 86.5%. To investigate the adsorption mechanism and recyclability, an evaluation of the kinetic model and an adsorption/desorption experiment were conducted. The adsorption of CR on Lig/CS beads followed the type 1 pseudo-second-order model, and the removal rate for CR was still above 90% at five cycles.

Kinetics and Adsorption Equilibrium in the Removal of Azo-Anionic Dyes by Modified Cellulose

This study introduces a new and bio-friendly adsorbent based on natural and cetyltrimethylammonium chloride (CTAC)-modified adsorbent prepared from wheat straw residues for the removal of Congo red (CR) and tartrazine azo-anionic dyes from aqueous solution. The adsorbent was characterized by thermogravimetric analysis (TGA), calorimetric differential (DSC), scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM/EDX), and pH point of zero charge (pHPZC) techniques. It was found that decreasing the adsorbent dose and increasing the initial concentration favors the removal of tartrazine and Congo red. Tartrazine adsorption capacities were 2.31 mg/g for the cellulose extracted from wheat residues (WC) and 18.85 mg/g for the modified wheat residue cellulose (MWC) for tartrazine as well as 18.5 mg/g for WC and 19.92 for MWC during Congo red (CR) adsorption, respectively. Increasing the initial and decreasing the adsorbent dose concentration favored the adsorption process. From time effect analysis, it was found that the equilibrium time was reached at 120 min when modified wheat cellulose was used and at 480 min when wheat cellulose was used. The kinetics of adsorption were described by pseudo-second-order in all cases with R2 > 0.95. The obtained data equilibrium from this research was well-fitted by the Freundlich isotherm model.

Swelling-Resistant, Crosslinked Polyvinyl Alcohol Membranes with High ZIF-8 Nanofiller Loadings as Effective Solid Electrolytes for Alkaline Fuel Cells

The present work investigates the direct mixing of aqueous zeolitic imidazolate framework-8 (ZIF-8) suspension into a polyvinyl alcohol (PVA) and crosslinked with glutaraldehyde (GA) to form swelling-resistant, mechanically robust and conductivity retentive composite membranes. This drying-free nanofiller incorporation method enhances the homogeneous ZIF-8 distributions in the PVA/ZIF-8/GA composites to overcome the nanofiller aggregation problem in the mixed matrix membranes. Various ZIF-8 concentrations (25.4, 40.5 and 45.4 wt.%) are used to study the suitability of the resulting GA-crosslinked composites for direct alkaline methanol fuel cell (DAMFC). Surface morphological analysis confirmed homogeneous ZIF-8 particle distribution in the GA-crosslinked composites with a defect- and crack-free structure. The increased ionic conductivity (21% higher than the ZIF-free base material) and suppressed alcohol permeability (94% lower from the base material) of PVA/40.5%ZIF-8/GA resulted in the highest selectivity among the prepared composites. In addition, the GA-crosslinked composites’ selectivity increased to 1.5−2 times that of those without crosslink. Moreover, the ZIF-8 nanofillers improved the mechanical strength and alkaline stability of the composites. This was due to the negligible volume swelling ratio (<1.4%) of high (>40%) ZIF-8-loaded composites. After 168 h of alkaline treatment, the PVA/40.5%ZIF-8/GA composite had almost negligible ionic conductivity loss (0.19%) compared with the initial material. The maximum power density (Pmax) of PVA/40.5%ZIF-8/GA composite was 190.5 mW cm−2 at 60 °C, an increase of 181% from the PVA/GA membrane. Moreover, the Pmax of PVA/40.5%ZIF-8/GA was 10% higher than that without GA crosslinking. These swelling-resistant and stable solid electrolytes are promising in alkaline fuel cell applications.

High-Performance and Water Resistant PVA-Based Films Modified by Air Plasma Treatment

Plasma treatment is considered a straightforward, cost-effective, and environmental-friendly technique for surface modification of film materials. In this study, air plasma treatment was applied for performance improvement of pure PVA, cellulose nanocrystal (CNC)/PVA, and CNC/oxalic acid (OA)/PVA films. Compared with the original performance of pure PVA, the mechanical properties and water resistance of air plasma treated films were greatly improved. Among them, the CNC/OA/PVA film treated by three minutes of air plasma irradiation exhibits the most remarkable performance in mechanical properties (tensile strength: 132.7 MPa; Young’s modulus: 5379.9 MPa) and water resistance (degree of swelling: 47.5%; solubility: 6.0%). By means of various modern characterization methods, the wettability, surface chemical structure, surface roughness, and thermal stability of different films before and after air plasma treatment were further revealed. Based on the results obtained, the air plasma treatment only changed the surface chemical structure, surface roughness, and hydrophobicity, while keeping the inner structure of films intact.

Flame Retardancy, Thermal and Mechanical Properties of Novel Intumescent Flame Retardant/MXene/Poly(Vinyl Alcohol) Nanocomposites

Poly(vinylphosphonic acid) (PVPA) and polyethylenepolyamine (PEPA) are used as novel intumescent flame retardants to improve the properties of MXene (2D Ti3C2Tx)/poly(vinyl alcohol) (PVA) nanocomposites. We investigated the flame-retardant properties, thermal stability, and mechanical properties of MXene/PVA nanocomposites. The results show that MXene was homogeneously dispersed in the PVA matrix containing PVPA and PEPA. PVPA and PEPA effectively improved the flame-retardant properties of MXene/PVA nanocomposites and they did not obviously change the thermal degradation of the MXene/PVA nanocomposites. Moreover, MXene improved the thermal stability of the PVA matrix. The elongation at break of MXene/PVA nanocomposites reached its maximum when the MXene mass fraction was 1.0 wt.%, regardless of whether PVPA and PEPA were present in the PVA matrix, whereas the tensile strength and Young’s modulus of MXene/PVA nanocomposites increased with the increase in MXene content in the PVA matrix.

Multifunctional poly(vinyl alcohol) films using cellulose nanocrystals/oregano and cellulose nanocrystals/cinnamon Pickering emulsions: Effect of oil type and concentration

Poly (vinyl alcohol) (PVA) films with high transparency, UV-barrier, antioxidant, and antimicrobial properties were prepared using oregano essential oil (OEO) and cinnamon essential oil (CEO) Pickering emulsions. The effect of Pickering emulsion type and concentration on the PVA film properties was studied. Cellulose nanocrystals (CNCs) were used as a natural stabilizer to prepare OEO and CEO Pickering emulsions. Both emulsions showed spherical droplets with diameters of 155-291 nm, zeta potential of -36.2 to -49.6 mV, minimum inhibition concentration of 6.25-12.5 μL/mL, and inhibition zone of 40-65 mm, depending on oil type. Morphology and FTIR analysis showed that OEO and CEO Pickering emulsions were compatible with the PVA matrix. The UV-transmittance of PVA films decreased from 77.3% to 30.4% and 2.0% without sacrificing the transparency after adding OEO and CEO Pickering emulsions, respectively. Antimicrobial results showed that E. coli was more sensitive to CEO, while S. aureus was sensitive to OEO Pickering emulsion. PVA/CEO film displayed higher properties than PVA/OEO film.

A Review on Synthesis Methods of Phyllosilicate- and Graphene-Filled Composite Hydrogels

This review discusses, in brief, the various synthetic methods of two widely-used nanofillers; phyllosilicate and graphene. Both are 2D fillers introduced into hydrogel matrices to achieve mechanical robustness and water uptake behavior. Both the fillers are inserted by physical and chemical gelation methods where most of the chemical gelation, i.e., covalent approaches, results in better physical properties compared to their physical gels. Physical gels occur due to supramolecular assembly, van der Waals interactions, electrostatic interactions, hydrophobic associations, and H-bonding. For chemical gelation, in situ radical triggered gelation mostly occurs.

Facile Preparation of Drug-Releasing Supramolecular Hydrogel for Preventing Postoperative Peritoneal Adhesion

Hydrogels have attracted widespread attention for breaking the bottlenecks faced during facile drug delivery. To date, the preparation of jelly carriers for hydrophobic drugs remains challenging. In this study, by evaporating ethanol to drive the formation of hydrogen bonds, hydrophilic poly(vinyl alcohol) (PVA) and certain hydrophobic compounds [luteolin (LUT), quercetin (QUE), and myricetin (MYR)] were rapidly prepared into supramolecular hydrogel within 10 min. The gelation performance of these three hydrogels changed regularly with the changing sequence of LUT, QUE, and MYR. An investigation of the gelation pathway of these hybrid gels reveals that the formation of this type of gel follows a simple supramolecular self-assembly process, called "hydrophobe-hydrophile crosslinked gelation". Because the hydrogen bond between PVA and the drug is noncovalent and reversible, the hydrogel has good plasticity and self-healing properties, while the drugs can be controllably released by tuning the output stimuli. Using a rat sidewall-cecum abrasion adhesion model, the as-prepared hydrogel was highly efficient and safe in preventing postsurgical adhesion. This work provides a useful archetypical template for researchers interested in the efficient delivery and controllable release of hydrophobic drugs.

Supercritical Carbon Dioxide Isolation of Cellulose Nanofibre and Enhancement Properties in Biopolymer Composites

The physical properties, such as the fibre dimension and crystallinity, of cellulose nanofibre (CNF) are significant to its functional reinforcement ability in composites. This study used supercritical carbon dioxide as a fibre bundle defibrillation pretreatment for the isolation of CNF from bamboo, in order to enhance its physical properties. The isolated CNF was characterised through zeta potential, TEM, XRD, and FT-IR analysis. Commercial CNF was used as a reference to evaluate the effectiveness of the method. The physical, mechanical, thermal, and wettability properties of the bamboo and commercial CNF-reinforced PLA/chitin were also analysed. The TEM and FT-IR results showed the successful isolation of CNF from bamboo using this method, with good colloidal stability shown by the zeta potential results. The properties of the isolated bamboo CNF were similar to the commercial type. However, the fibre diameter distribution and the crystallinity index significantly differed between the bamboo and the commercial CNF. The bamboo CNF had a smaller fibre size and a higher crystallinity index than the commercial CNF. The results from the CNF-reinforced biocomposite showed that the physical, mechanical, thermal, and wettability properties were significantly different due to the variations in their fibre sizes and crystallinity indices. The properties of bamboo CNF biocomposites were significantly better than those of commercial CNF biocomposites. This indicates that the physical properties (fibre size and crystallinity) of an isolated CNF significantly affect its reinforcement ability in biocomposites. The physical properties of isolated CNFs are partly dependent on their source and production method, among other factors. These composites can be used for various industrial applications, including packaging.

Preparation and properties of poly (vinyl alcohol)/sodium caseinate blend films crosslinked with glutaraldehyde and glyoxal

Bio-based films containing poly (vinyl alcohol)/casein have poor mechanical and water vapor barrier properties that limit their use in packaging application. Some properties such as water resistance and tensile strength can be increased by the cross-linking process. For this reason, poly(vinyl alcohol)/sodium caseinate (PVA/SC) blends were crosslinked by adding glutaraldehyde (GLA) and glyoxal (GL) at different ratios in this work. The films were prepared by solution casting technique. Fourier transform infrared analysis (FTIR) confirmed the crosslinking reaction between the components. As a result of the crosslinking, the thicknesses, water vapor barrier properties and water contact angle values of the films have increased. The total soluble matters (TSM) of PVA/SC film decreased with increasing amounts of crosslinkers and GLA crosslinked films exhibited lower TSM. The addition of GLA and GL resulted in more strengthened films as verified by the tensile test. On the other hand, GLA crosslinked films were more flexible than un-crosslinked and GL crosslinked PVA/SC films. The hydrophilic PVA/SC film became more hydrophobic with the increasing amounts of crosslinkers. With the crosslinking, the PVA/SC film became more thermally stable. In conclusion, the crosslinked PVA/SC films were obtained with suitable properties for packaging applications.

Fabrication of Cationic Poly(vinyl alcohol) Films Cross-Linked Using Copolymers Containing Quaternary Ammonium Cations, Benzoxaborole, and Carboxy Groups

Water-insoluble cationic poly(vinyl alcohol) (PVA) films were fabricated using a mixed aqueous solution of PVA and poly([2-(methacryloyloxy)ethyl]trimethylammonium chloride (METAC)-co-methacrylic acid (MAAc)-co-5-methacrylamido-1,2-benzoxaborole (MAAmBO)) copolymer (3D). The surface of the PVA film is typically negatively charged, and simple fabrication methods for water-insoluble PVA films with cationic surface charges are required to expand their application fields. METAC, which has a permanent positive charge owing to the presence of a quaternary ammonium cation, was selected as the cationic unit. The MAAc and MAAmBO units were used as two types of cross-linking structures for the thermal cross-linking of the hydroxy and carboxy groups of the MAAc unit (covalent bonding) as well as the diol and benzoxaborole groups of the MAAmBO unit (dynamic covalent bonding). The films were thermally cross-linked at 135 °C for 4 h without the addition of materials. After immersion in surplus water at 80 °C for 3 h, the cross-linked PVA/3D films retained almost 100% of their weights. The ζ-potential of the water-insoluble PVA/3D film was 9.4 ± 0.8 mV. The PVA/3D film was strongly dyed using anionic acid red 1 (AR1) because of its positively charged surface. Interestingly, it could also be slightly dyed using cationic methylene blue (MB) and became transparent (original state) after immersion in water for 2 days. These results suggested that positive and negative charges coexisted in the PVA/3D film, and the surface properties were positively inclined. Moreover, the degree of hemolysis of the PVA/3D films was similar to that of the negative control, which showed high blood compatibility. To our knowledge, this is the first report on the fabrication of water-insoluble cationic PVA films using two types of cross-linking structures containing carboxy and benzoxaborole groups. The cross-linked PVA films were analyzed using Fourier transform infrared (FT-IR) spectroscopy, differential scanning calorimetry (DSC), and contact angle (CA) and ζ-potential measurement, as well as by determining the mechanical properties, adsorption of charged molecules, and biocompatibility. These readily fabricated water-insoluble PVA films with positive charges can show potential applications in sensors, adsorption systems, and antimicrobial materials.

Development and Characterization of Electrospun Fiber-Based Poly(ethylene-co-vinyl Alcohol) Films of Application Interest as High-Gas-Barrier Interlayers in Food Packaging

In the present study, poly(ethylene-co-vinyl alcohol) with 44 mol % ethylene content (EVOH44) was managed to be processed, for the first time, by electrospinning assisted by the coaxial technology of solvent jacket. In addition to this, different suspensions of cellulose nanocrystals (CNCs), with contents ranging from 0.1 to 1.0 wt %, were also electrospun to obtain hybrid bio-/non-bio nanocomposites. The resultant fiber mats were thereafter optimally annealed to promote interfiber coalescence at 145 °C, below the EVOH44 melting point, leading to continuous transparent fiber-based films. The morphological analysis revealed the successful distribution of CNCs into EVOH44 up to contents of 0.5 wt %. The incorporation of CNCs into the ethylene-vinyl alcohol copolymer caused a decrease in the crystallization and melting temperatures (TC and Tm) of about 12 and 7 °C, respectively, and also crystallinity. However, the incorporation of CNCs led to enhanced thermal stability of the copolymer matrix for a nanofiller content of 1.0 wt %. Furthermore, the incorporation of 0.1 and 0.5 wt % CNCs produced increases in the tensile modulus (E) of ca. 38% and 28%, respectively, but also yielded a reduction in the elongation at break and toughness. The oxygen barrier of the hybrid nanocomposite fiber-based films decreased with increasing the CNCs content, but they were seen to remain high barrier, especially in the low relative humidity (RH) regime, i.e., at 20% RH, showing permeability values lower than 0.6 × 10-20 m3·m·m-2·Pa-1·s-1. In general terms, an optimal balance in physical properties was found for the hybrid copolymer composite with a CNC loading of 0.1 wt %. On the overall, the present study demonstrates the potential of annealed electrospun fiber-based high-barrier polymers, with or without CNCs, to develop novel barrier interlayers to be used as food packaging constituents.

Functional Properties of Antimicrobial Neem Leaves Extract Based Macroalgae Biofilms for Potential Use as Active Dry Packaging Applications

Antimicrobial irradiated seaweed–neem biocomposite films were synthesized in this study. The storage functional properties of the films were investigated. Characterization of the prepared films was conducted using SEM, FT-IR, contact angle, and antimicrobial test. The macroscopic and microscopic including the analysis of the functional group and the gas chromatography-mass spectrometry test revealed the main active constituents present in the neem extract, which was used an essential component of the fabricated films. Neem leaves’ extracts with 5% w/w concentration were incorporated into the matrix of seaweed biopolymer and the seaweed–neem bio-composite film were irradiated with different dosages of gamma radiation (0.5, 1, 1.5, and 2 kGy). The tensile, thermal, and the antimicrobial properties of the films were studied. The results revealed that the irradiated films exhibited improved functional properties compared to the control film at 1.5 kGy radiation dosage. The tensile strength, tensile modulus, and toughness exhibited by the films increased, while the elongation of the irradiated bio-composite film decreased compared to the control film. The morphology of the irradiated films demonstrated a smoother surface compared to the control and provided surface intermolecular interaction of the neem–seaweed matrix. The film indicated an optimum storage stability under ambient conditions and demonstrated no significant changes in the visual appearance. However, an increase in the moisture content was exhibited by the film, and the hydrophobic properties was retained until nine months of the storage period. The study of the films antimicrobial activities against Staphylococcus aureus (SA), and Bacillus subtilis (BS) indicated improved resistance to bacterial activities after the incorporation of neem leaves extract and gamma irradiation. The fabricated irradiated seaweed–neem bio-composite film could be used as an excellent sustainable packaging material due to its effective storage stability.

Properties and Characterization of Lignin Nanoparticles Functionalized in Macroalgae Biopolymer Films

The demand for bioplastic material for industrial applications is increasing. However, moisture absorption and low mechanical strength have limited the use of bioplastic in commercial-scale applications. Macroalgae is no exception to these challenges of bioplastics. In this study, Kappaphycus alvarezii macroalgae were reinforced with lignin nanoparticles. Lignin nanoparticles (LNPs) were used as a filler to reduce the brittleness and hydrophilic nature of macroalgae (matrix). Lignin nanofiller was produced using a green approach from black liquor of soda pulping waste and purified. The physical, mechanical, morphological, structural, thermal, and water barrier properties of LNPs with and without the purification process in macroalgae films were studied. The bioplastic films’ functional properties, such as physical, mechanical, thermal, and water barrier properties, were significantly improved by incorporating purified and unpurified LNPs. However, the purified LNPs have a greater reinforcement effect on the macroalgae than unpurified LNPs. In this study, bioplastic film with 5% purified LNPs presented the optimum enhancement on almost all the functional properties. The enhancement is attributed to high compatibility due to strong interfacial interaction between the nanofiller and matrix. The developed LNPs/macroalgae bioplastic films can provide additional benefits and solutions to various industrial applications, especially packaging material.