Transparent and Homogenous Cellulose Nanocrystal/Lignin UV-Protection Films

Preparation and properties of lignin-based composite membranes

Composite membranes were prepared from lignin alkali (LA), polyvinyl alcohol (PVA), and cellulose nanofibrils (CNF) using a simple, low-cost, and environmentally friendly method. The deodorization performances and structures of these membranes were also characterized. The sample referred to as L3C3P5 prepared with a solution containing 35.7 wt% LA, 53.6 wt% PVA, and 10.7 wt% CNF showed the best deodorization properties, and the H2S adsorption time reached 36 min. The adsorption performance was further improved by adding nano-CuO to the membrane, and the H2S adsorption time of the doped membrane L3C3P5C4 reached 60 min. While the H2S adsorption performance improved, structural analysis revealed that the addition of nano-CuO reduced the crystallinity in the membrane, caused the membrane to crack, and led to a decrease in the mechanical properties. The surface oxygens in the L3C3P5C4 membrane were primarily C-O bonds and lattice oxygens in CuO. After the H2S adsorption reaction, the lattice oxygen disappeared, and CuS products appeared.

Characterization and applications of biomacromolecule structurally similar to glycogen as a dispersion aid and skin protection agent

Glycogen is a naturally occurring or metabolically synthesized biological macromolecule found in a wide range of living organisms, including animals, microorganisms, and even plants. However, naturally sourced glycogen poses challenges for industrial use. This study focused on a biological macromolecule referred to as glycogen-like particles (GLPs), detailing the production methods and biological properties of these particles. In vitro enzymatic production of GLPs was successfully achieved. GLPs synthesized through a simultaneous enzymatic reaction using sucrose had significant changes in their structure and functionality based on the branching enzyme (BE) to amylosucrase (ASase) ratio. As this ratio increased, the GLPs developed higher molecular weights and greater density, solubility, and branching degree while reducing size and turbidity. Structural changes in these enzymes were not observed beyond a critical BE/ASase ratio. Uniformly dispersed curcumin powder was generated in 50 % (w/v) aqueous GLP solution, and the GLPs were non-toxic to human skin keratinocytes at a concentration of 2.5 mg/mL. GLPs with lower branching inhibited tyrosinase activity and melanin synthesis, while those with more long chains displayed effective UV-blocking. By manipulating the BE/ASase ratio, GLPs were shown to display diverse chemical structures and physical characteristics, suggesting their potential application in the food and cosmetics industries.

Fundamental investigation of micro-nano cellulose and lignin interaction for transparent paper: Experiment and electrostatic potential calculation

Plastic has significant negative consequences for the environment and human health, demanding greener alternatives. Lignocellulose is a sustainable biomass material, and its paper has been considered as a potential material to replace plastics. Micro-nano lignocellulose, derived from natural plants, possesses a small size and abundant hydrogen bonding capacity. However, there is no clear explanation for the interactions between lignin and micro-nano cellulose, and little understanding of how the interaction can affect the papers' structure and optical properties. Electrostatic potential calculation is a reliable tool to explain non-covalent interactions, and can explore the binding between lignin and micro-nano cellulose. In this paper, kenaf - a non-wood fiber raw material - was employed to prepare micro-nano lignocellulose. The resulting slurry facilitated the production of transparent paper via a simple casting method. The prepared transparent micro-nano paper exhibited high transparency (~90 %), UVA resistance (~80 %), and hydrophobicity (~114°). More importantly, the electrostatic potential calculation demonstrates the inherent relationship between structure and performance, providing practical knowledge for constructing film materials.

Photocrosslinkable and hydroplasicable UV-shielding nanocellulose films facilitated by hydroxyl-yne click reaction

Sustainably-sourced functional nanocellulose materials are vitally important for the green and sustainable development. Herein, we reported photocrosslinkable and hydroplasticable TEMPO-oxidized cellulose nanofiber phenyl propylene ketone ethers (TOCNPPK) films with excellent ultraviolet (UV) shielding, highly reversible processability, and extended mechanical properties, which were facilitated by green hydroxyl-yne click reaction. The introduction of conjugated aromatic ring and vinyl bonds (-C=C-) had been demonstrated the key for the improved overall performance of resultant TOCNPPK, which not only endowed the TOCNPPK with nearly 100 % UV shielding, but also enabled it to be formed into diverse 3D shapes (helix, ring and letters "N, F, U") via the facile hydrosetting method. The photocrosslinkable-enhanced mechanical performance of TOCNPPK films was also attributed to -C=C- which could crosslink via [2π + 2π] cycloaddition reactions under UV-irradiation. The ultimate stress of TOCNPPK films was as high as 210.0 ± 22.8 MPa and the Young's modulus was 11.5 ± 0.7 GPa, much superior to those of 128.6 ± 8.5 MPa and 9.2 ± 0.6 GPa for pristine TOCN films. Furthermore, the TOCNPPK had been demonstrated as efficient nanofillers for both hydrophilic polyvinyl alcohol and lipophilic polycaprolactone to develop advanced biodegradable composite films with the integration of good water-wetting resistance, excellent UV blocking, and photo-enhanced mechanical performance.

Controlled release fertilizer delivery system derived from rice straw cellulose nanofibres: a circular economy based solution for sustainable development

Recently, the development of sustainable and environmentally friendly biomaterials has gained the attention of researchers as potential alternatives to petroleum-based materials. Biomaterials are a promising candidate to mitigate sustainability issues due to their renewability, biodegradability, and cost-effectiveness. Thus, the purpose of this study is to explore a cost-effective biomaterial-based delivery system for delivering fertilizers to plants. To achieve this, rice straw (agro-waste) was selected as a raw material for the extraction of cellulose. The cellulose was extracted through alkali treatment (12% NaOH), followed by TEMPO-based oxidation. The cellulose nanofibers were characterized using Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy, and transmission electron microscopy. In scanning electron microscopy, a loosening of the fibrillar structure in cellulose nanofibers (CNFs) was observed with a diameter of 17 ± 4 nm. The CNFs were loaded with nitrogen-based fertilizer (ammonium chloride) in 1:1, 1:2, and 2:1 (w/w) proportions. The loading was estimated through surface charge variation; in the case of the 1:1 sample, maximum reductions in surface charge were seen from -42.0 mV to -12.8 mV due to the binding of positive ammonium ions. In the release kinetics study, a controlled release pattern was observed at 1:1, which showed a 58% cumulative release of ammonium ions within 8 days. Thus, the study paves the way for value-added uses of rice straw as an alternative to the current environmentally harmful practices.

Effect of the combined addition of ultrasonicated kraft lignin and montmorillonite on hydroxypropyl methylcellulose bionanocomposites

Although hydroxypropyl methylcellulose (HPMC) has been proposed as renewable substitute for traditional plastic, its barrier and active properties need to be improved. Thus, the combination of an organic residue such as kraft lignin (0-10% w/w) and a natural clay such as montmorillonite (3% w/w) by application of ultrasound can significantly improve HPMC properties. This is most likely due to the close interaction between lignin and montmorillonite, which leads to delamination of the clay and improves its dispersion within the HPMC matrix. Specifically, the addition of kraft lignin to the bionanocomposite films provided them with UV-shielding, antioxidant capacity and antibacterial activity. The incorporation of 3% montmorillonite resulted in reductions of 65.8% and 11.4% in oxygen (OP) and water vapor permeabilities (WVP), respectively. Moreover, a reduction of 43.8% in WVP was achieved when both lignin (1%) and montmorillonite (3%) were incorporated, observing a synergistic effect. Thus, the HPMC bionanocomposite with 1% lignin and 3% montmorillonite, presented good thermal stability and mechanical strength with significantly improved gas barrier permeability, as well as UV-shielding (maintaining a good transparency), antioxidant and antibacterial activities.

Kraft Lignin: A Valuable, Sustainable Resource, Opportunities and Challenges

Kraft lignin, a by-product from the production of pulp, is currently incinerated in the recovery boiler during the chemical recovery cycle, generating valuable bioenergy and recycling inorganic chemicals to the pulping process operation. Removing lignin from the black liquor or its gasification lowers the recovery boiler load enabling increased pulp production. During the past ten years, lignin separation technologies have emerged and the interest of the research community to valorize this underutilized resource has been invigorated. The aim of this Review is to give (1) a dedicated overview of the kraft process with a focus on the lignin, (2) an overview of applications that are being developed, and (3) a techno-economic and life cycle asseeements of value chains from black liquor to different products. Overall, it is anticipated that this effort will inspire further work for developing and using kraft lignin as a commodity raw material for new applications undeniably promoting pivotal global sustainability concerns.

Facile preparation of cellulose/lignosulfonate derivatives composite films with high UV-shielding and gas barrier properties

Herein, a serial of full cellulose and lignosulfonate derivatives (LS), including sodium lignosulfonate (LSS), calcium lignosulfonate (LSC), lignosulfonic acid (LSA), composite films were generated through dissolving cellulose in reversible carbon dioxide (CO₂) ionic liquids solvent system (TMG/EG/DMSO/CO₂ solvent system), followed by a facile solution-gelation transition and absorption strategy. The findings indicated that LS aggregated and embedded inside the cellulose matrix via H-bond interaction. The cellulose/LS derivatives composite films showed good mechanical properties which the tensile strength reaches the maximum value of 94.7 MPa in MCC3LSS film. While for the MCC1LSS film, the breaking strain increases to 11.6 %. The outstanding UV shielding effect and high transmittance in the visible region of composite films were also achieved and the shielding performance of the whole UV region (200-400 nm) tended to 100 % for MCC5LSS film. In addition, thiol-ene click reaction was selected as model reaction to verify the UV-shielding performance. It was also found that the oxygen and water vapor barrier performances of composite films were evidently associated with the intense H-bond interaction and tortuous path effect. The OP and WVP of MCC5LSS film were 0 and 6 × 10^-3 g·μm/m²·day·kPa, respectively. These outstanding properties make them with great potential for packaging field.

Improvement of UV stability of thermoplastic starch matrix by addition of selected lignin fraction - Photooxidative degradation

This paper examines the additivation of thermoplastic starch (TPS) matrix by selected fractions of kraft lignin (KL) and correlates its structure-performance when exposed to photooxidative degradation. KL from Eucalyptus urograndis wood was refined by a sequential fractionation process in ethyl acetate (EtOAc). Films were prepared by mixing lignin fractions as additive in TPS matrix by casting and pressing. The lignin employed were KL, fraction of KL insoluble in EtOAc (INS) and fraction of KL soluble in EtOAc (SOL). The samples were exposed to accelerated aging with Ultraviolet-C light (UV-C) for 432 h. Structural changes were measured by FTIR (Fourier-Transform Infrared) spectra. Thermal properties, such as melting enthalpy, glass transition temperature and thermal decomposition, were evaluated by DSC (Differential Scanning Calorimetry) and TG (Thermogravimetry). Morphology of the films was obtained by SEM (Scanning Electron Microscopy). Surface property of wettability was measured by contact angle. Mechanical properties were explored before and after exposure to UV-C light. It was observed that the least photodegraded films were those resulting from the addition of the lignin fraction with higher phenolic hydroxyl group content. According to structural and morphological observations, the soluble fraction (TSOL) presented the highest photoprotection and stabilizing effect as an UV-C light blocker additive on TPS matrix.

Lignin as a bioactive polymer and heavy metal absorber- an overview

As a pulping and bio-refinery by-product with phenolic chemical structure, lignin indicated high potential as natural antioxidant activity, UV blocker, antibacterial and toxic material absorbent properties. Presence of phenolic hydroxyl groups in lignin structure plays the main role of its antioxidant activity. However, lignin antioxidant power can change depending on its other structural features and functional groups like ortho-methoxy groups, -OCH₃ groups, the α-CH₂ groups, the aliphatic carbonyl groups, and the size of π-conjugated systems. Lignin in mixture with synthetic polymers, improved their thermal stability. Lignin has high UV light absorbing potential in broad-spectrum (UVA, UVB). Adding 1-5% of lignin into hand cream indicated excellent range of sun protection factor (SPF) with more than 95% UV light absorption. Lignin also indicated strong UV light protection when applied in different transparent film and protect paint, oil, and varnish from UV degradation. Lignosulfonate and other modified lignin including chemically modification, nano-particles and lignin hydrogel indicated high potential as heavy metal absorber.

Advanced cellulose nanocrystals (CNC) and cellulose nanofibrils (CNF) aerogels: Bottom-up assembly perspective for production of adsorbents

The most common and abundant polymer in nature is the linear polysaccharide cellulose, but processing it requires a new approach since cellulose degrades before melting and does not dissolve in ordinary organic solvents. Cellulose aerogels are exceptionally porous (>90 %), have a high specific surface area, and have low bulk density (0.0085 mg/cm³), making them suitable for a variety of sophisticated applications including but not limited to adsorbents. The production of materials with different qualities from the nanocellulose based aerogels is possible thanks to the ease with which other chemicals may be included into the structure of nanocellulose based aerogels; despite processing challenges, cellulose can nevertheless be formed into useful, value-added products using a variety of traditional and cutting-edge techniques. To improve the adsorption of these aerogels, rheology, 3-D printing, surface modification, employment of metal organic frameworks, freezing temperature, and freeze casting techniques were all investigated and included. In addition to exploring venues for creation of aerogels, their integration with CNC liquid crystal formation were also explored and examined to pursue "smart adsorbent aerogels". The objective of this endeavour is to provide a concise and in-depth evaluation of recent findings about the conception and understanding of nanocellulose aerogel employing a variety of technologies and examination of intricacies involved in enhancing adsorption properties of these aerogels.

Transparent Cellulose-based Film with High UV-blocking Performance Fabricated by Surface Modification using Biginelli Reaction

Efficient and sustainable ultraviolet (UV)-blocking materials are of great interest in many fields. Herein, novel cellulose-based UV-blocking films were developed via surface modification using Biginelli reaction. The resulting films exhibited excellent visible transparency (80%) at 550 nm and superhigh UV-blocking performance, which can shield almost 100% UVA and UVB. These features are very stable even the materials being subjected to solvents, UV irradiation, and thermal treatment. This work provides a novel and facile strategy to fabricate functional cellulose-based films with superhigh anti-ultraviolet performance. This article is protected by copyright. All rights reserved.

Facile adjustment on cellulose nanocrystals composite films with glycerol and benzyl acrylate copolymer for enhanced UV shielding property

In the present work, cellulose nanocrystals (CNCs) composite films with suitable applicable capabilities were prepared by facilely incorporating glycerol (Gly) and poly(benzyl acrylate) (PBA). Chemical and morphological variations during the fabrication of the films were systematically characterized. The properties of modified CNCs composite films including UV blocking ability, mechanical strength and thermal properties were characterized to assess their applicable potentials. As a result, the composite films have good UV shielding property in UVC (220-280 nm) region and UVB (280-320 nm) region. The shielding performance of the modified film in the ultraviolet absorption region reached 92.77% to 95.49% respectively, without damaging the original chiral nematic structure of the films. Along with the modification, BACNC film improved the mechanical properties, presenting the tensile strength 16 times higher compared to pure CNCs film. The nanocomposite films proposed in this work showed promising potentials in broad fields, such as food preservation, medical protection, and surface coating applications.

Plant-Based Structures as an Opportunity to Engineer Optical Functions in Next-Generation Light Management

This review addresses the reconstruction of structural plant components (cellulose, lignin, and hemicelluloses) into materials displaying advanced optical properties. The strategies to isolate the main building blocks are discussed, and the effects of fibrillation, fibril alignment, densification, self-assembly, surface-patterning, and compositing are presented considering their role in engineering optical performance. Then, key elements that enable lignocellulosic to be translated into materials that present optical functionality, such as transparency, haze, reflectance, UV-blocking, luminescence, and structural colors, are described. Mapping the optical landscape that is accessible from lignocellulosics is shown as an essential step toward their utilization in smart devices. Advanced materials built from sustainable resources, including those obtained from industrial or agricultural side streams, demonstrate enormous promise in optoelectronics due to their potentially lower cost, while meeting or even exceeding current demands in performance. The requirements are summarized for the production and application of plant-based optically functional materials in different smart material applications and the review is concluded with a perspective about this active field of knowledge.

Developing highly transparent yet ultraviolet blocking fully biocomposite films based on chitin and lignin using ethanol/water as processing solvents

Developing fully biobased products with functionality in a green fashion is highly desirable to meet the increasing demand for environmental sustainability and mitigate "white pollution" by petroleum-based counterparts. Here, chitin from shrimp shells was propionylated to obtain chitin propionate (CP) with significantly improved solubility in organic solvents, organosolv lignin (OSL) was extracted from the forest harvest residuals. The fully biobased composite consisting of CP as a matrix and OSL as a UV-blocker were successfully prepared using acidic ethanol/water as a green processing solvent. The results indicated that the 5% OSL addition enabled the CP film to block approximately 98% UV light while allowing 71% visible light transmittance; tensile and thermal properties were also retained. Nearly 100% UV light was blocked with 20% OSL addition, but visible light transmittance was moderately sacrificed. This study provides an alternative solution to produce novel fully biobased films with high transparency yet excellent UV protection for potential packaging applications.

Antisolvent versus ultrasonication: Bottom-up and top-down approaches to produce lignin nanoparticles (LNPs) with tailored properties

In spite of the increasing amount of literature on the production and application of lignin nanoparticles (LNPs), little or no attention has been paid so far to the influence of different production methods on the properties of these nanostructures. Herein, we propose a comprehensive study to assess the impact of several factors on the color, morphology, colloidal stability, antioxidant capacity, and UV-shielding performance of LNPs. LNPs were obtained by two different routes: a bottom-up approach based on the self-assembly in a solvent-antisolvent system with acetone/lignin/water; or a top-down approach based on the ultrasonication of never-dried lignin aqueous suspensions. The starting lignin was extracted from elephant grass leaves or stems, so that the influence of anatomical origin and molecular weight could also be investigated. Moreover, lignin was oxidized prior to being converted into LNPs, allowing for comparisons between different oxidation degrees. This study showed that interesting properties of LNPs can be easily tailored and combined focusing on the various applications of these versatile nanostructures. In a model application, different types of LNPs were incorporated into poly(vinyl alcohol)-based nanocomposites, modulating the UV-protection capability of the polymer matrix.

Lignin and Xylan as Interface Engineering Additives for Improved Environmental Durability of Sustainable Cellulose Nanopapers

Cellulose materials and products are frequently affected by environmental factors such as light, temperature, and humidity. Simulated UV irradiation, heat, and moisture exposure were comprehensively used to characterize changes in cellulose nanopaper (NP) tensile properties. For the preparation of NP, high-purity cellulose from old, unused filter paper waste was used. Lignin and xylan were used as sustainable green interface engineering modifiers for NP due to their structural compatibility, low price, nontoxic nature, and abundance as a by-product of biomass processing, as well as their ability to protect cellulose fibers from UV irradiation. Nanofibrillated cellulose (NFC) suspension was obtained by microfluidizing cellulose suspension, and NP was produced by casting films from water suspensions. The use of filler from 1 to 30 wt% significantly altered NP properties. All nanopapers were tested for their sensitivity to water humidity, which reduced mechanical properties from 10 to 40% depending on the saturation level. Xylan addition showed a significant increase in the specific elastic modulus and specific strength by 1.4- and 2.8-fold, respectively. Xylan-containing NPs had remarkable resistance to UV irradiation, retaining 50 to 90% of their initial properties. Lignin-modified NPs resulted in a decreased mechanical performance due to the particle structure of the filler and the agglomeration process, but it was compensated by good property retention and enhanced elongation. The UV oxidation process of the NP interface was studied with UV-Vis and FTIR spectroscopy, which showed that the degradation of lignin and xylan preserves a cellulose fiber structure. Scanning electron microscopy images revealed the structural formation of the interface and supplemented understanding of UV aging impact on the surface and penetration depth in the cross-section. The ability to overcome premature aging in environmental factors can significantly benefit the wide adaption of NP in food packaging and functional applications.

Sustainable and Superhydrophobic Lignocellulose-Based Transparent Films with Efficient Light Management and Self-Cleaning

Light-management (LM) films that can regulate transmitted light are significant to diverse fields, such as optoelectronics and energy-efficient buildings. However, for conventional LM films made from petroleum-based polymers, the nonbiodegradability and complicated fabrication process remain a challenge. Herein, we prepare sustainable lignocellulose-based films with excellent light-management capability by facile dissolution and regeneration of wood pulp and the corncob residue from xylitol production (CRXP). The obtained films exhibit high transparency (78%), high haze (61%), and especially remarkable UV-blocking performance (99.94% for UVB and 98.04% for UVA). They achieve consistent indoor light distribution and UV radiation shielding by light management for the application of smart buildings. Furthermore, by spray-coating with SiO₂ nanoparticles to construct hierarchical networks, the films are endowed with a superhydrophobic surface with a self-cleaning function to mitigate dust accumulation. Our work provides novel insights into the conversion of lignocellulosic waste to desirable and sustainable functional materials.

Multifunctional lignin-based nanocomposites and nanohybrids

Significant progress in lignins valorization and development of high-performance sustainable materials have been achieved in recent years. Reports related to lignin utilization indicate excellent prospects considering green chemistry, chemical engineering, energy, materials and polymer science, physical chemistry, biochemistry, among others. To fully realize such potential, one of the most promising routes involves lignin uses in nanocomposites and nanohybrid assemblies, where synergistic interactions are highly beneficial. This review first discusses the interfacial assembly of lignins with polysaccharides, proteins and other biopolymers, for instance, in the synthesis of nanocomposites. To give a wide perspective, we consider the subject of hybridization with metal and metal oxide nanoparticles, as well as uses as precursor of carbon materials and the assembly with other biobased nanoparticles, for instance to form nanohybrids. We provide cues to understand the fundamental aspects related to lignins, their self-assembly and supramolecular organization, all of which are critical in nanocomposites and nanohybrids. We highlight the possibilities of lignin in the fields of flame retardancy, food packaging, plant protection, electroactive materials, energy storage and health sciences. The most recent outcomes are evaluated given the importance of lignin extraction, within established and emerging biorefineries. We consider the benefit of lignin compared to synthetic counterparts. Bridging the gap between fundamental and application-driven research, this account offers critical insights as far as the potential of lignin as one of the frontrunners in the uptake of bioeconomy concepts and its application in value-added products.

Antioxidant and UV-Blocking Properties of a Carboxymethyl Cellulose-Lignin Composite Film Produced from Oil Palm Empty Fruit Bunch

Oil palm empty fruit bunch (EFB) pulp with the highest cellulose content of 83.42% was obtained from an optimized process of acid pretreatment (0.5% v/v H2SO4), alkaline extraction (15% w/w NaOH), and hydrogen peroxide bleaching (10% w/v H2O2), respectively. The EFB cellulose was carboxymethylated, and the obtained carboxymethyl cellulose (CMC) was readily water-soluble (81.32%). The EFB CMC was blended with glycerol and cast into a composite film. Lignin that precipitated from the EFB black liquor was also incorporated into the film at different concentrations, and its effect on the UV-blocking properties of the film was determined. Interestingly, the EFB CMC film without lignin addition completely blocked UV-B transmittance. The incorporation of lignin at all concentrations significantly enhanced the UV-A blocking and other physical properties of the film, including the surface roughness, thickness, and thermal stability, although the tensile strength and water vapor permeability were not significantly affected. Complete UV-A and UV-B blocking were observed when lignin was added at 0.2% (w/v), and the film also exhibited the highest antioxidant activity against 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radicals with an half-maximal inhibitory concentration (IC50) value of 3.87 mg mL-1.

Research and application progress of lignin-based composite membrane

In view of the serious environmental pollution, which is the greatest problem the world is facing, and the continuous consumption of raw materials, it is imminent to search for green and sustainable resources. Lignin is an organic polymer that exists widely in nature, and if it can be transformed from traditional low-value waste product with low range of applications to functional materials with high application prospects, it can be of great significance to alleviate environmental pollution and shortage of fossil resources. One of the functional applications of lignin involves its use to fabricate composite with other polymeric materials, which can then be used to prepare membrane materials. This review summarizes the recent research and application progress of combining lignin with polypropylene, polyvinyl alcohol, starch, cellulose, chitosan, and other polymeric materials to prepare composite membranes; and summarizes the future development direction of lignin-based composite membranes. We hope this review may provide a new perspective to the understanding of lignin-based composite membranes and a useful reference for future research.

Application of Polyvinyl Acetate/Lignin Copolymer as Bio-Based Coating Material and Its Effects on Paper Properties

In this work, lignin-vinyl acetate copolymers containing different fractions of lignin were synthesized by the copolymerization technique. The synthesized copolymer was successfully applied to coat the paper for enhancing its properties and performance. The effects of the lignin-vinyl acetate copolymer on the physicochemical, air permeability and mechanical properties of paper were investigated. The mechanical strength, hydrophilic, and air permeability properties of coated paper were improved with the increasing content of the lignin. Lignin-vinyl acetate copolymer containing 15% lignin coated paper exhibited a 1.86 times increase in the tensile index, 45 times increase in the water contact angle, and a 41.1% reduction in the air permeability compared with uncoated paper. Scanning electron microscopy was applied to study the morphology of the coated and uncoated paper. The results showed that paper surface porosity structure was decreased, while the surface smoothness was enhanced considerably with increasing lignin fraction in the copolymer. Therefore, the successful fabrication of such an enchanting coated paper may afford new potential and great applications in the packaging paper.

Consolidation of cellulose nanofibrils with lignosulphonate bio-waste into excellent flame retardant and UV blocking membranes

The use of biomass to produce value-adding materials is a core objective of the circular economy, which has attracted great research interest in recent decades. In this context, we present here a simple dispersion-casting process for consolidation of cellulose nanofibrils (CNF), lignosulphonate (LS)-rich bio-waste and CaCl₂ in composite membranes. The addition of CaCl₂ to CNF and LS dispersions reduces the ζ potential, due to an electrostatic screening, which promotes the aggregation of CNF, increases its moisture content and promotes LS deposition on CNFs already in the dispersion phase. Addition of both the LS and CaCl₂ to CNF dispersion has an adverse effect on the mechanical properties of the final membranes. The effectiveness of the new composite membranes has been described in terms of their passive (charring) flame retardancy and 100 % UVA/UVB shielding capacity, both identified for membranes with the highest LS content, as well as high electronic resistance.

Design strategies, properties and applications of cellulose nanomaterials-enhanced products with residual, technical or nanoscale lignin-A review

With the increasing demand for greener alternatives to fossil-derived products, research on cellulose nanomaterials (CNMs) has rapidly expanded. The combination of nanoscale properties and sustainable attributes makes CNMs an asset in the quest for a sustainable society. However, challenges such as the hydrophilic nature of CNMs, their low compatibility with non-polar matrices and modest thermal stability, slow the development of end-uses. Combination of CNMs with amphiphilic lignin can improve the thermal stability, enhance the compatibility with non-polar matrices and, additionally, endow CNMs with new functionalities e.g., UV shielding or antioxidative properties. This article comprehensively reviews the different design strategies and their influence on properties and applications of CNMs containing lignin in various forms; either as residual lignin, added technical lignin, or nanoscale particles. The review focuses especially on the synergy created between CNMs and lignin, paving the way for new production routes and use of CNM/lignin materials in high-performance applications.

Natural lignocellulosic nanofibril film with excellent ultraviolet blocking performance and robust environment resistance

Due to the current state of ozone layer depletion and potential risk of skin cancer, researches on sustainable cellulose-based films with ultraviolet (UV) blocking capabilities has attracted widespread attention. However, pure cellulose-based film required UV absorbent to be incorporated because of its poor UV blocking ability. In this work, natural lignocellulosic nanofibril (LCNF) film was fabricated by vacuum filtration and pressing process without any complex chemical modification or adding UV absorbers. The residual lignin retained in LCNF was found to act as natural macro-molecular UV absorber. LCNF film with lignin content of 4.89-15.68% exhibited excellent thermal stability, and their UVA and UVB blocking were in the range of 81.4-99.5% and 96.7-100%, respectively. Moreover, LCNF film exhibited stable UV shielding performance under high temperature, UV irradiation, acidic or alkaline conditions, providing LCNF film with a long-term use capacity. Overall, LCNF film is more environmentally friendly and harmless, which shows high potentials in anti-counterfeiting materials, UV protection, and windshields for vehicles.

Towards lignin derived thermoplastic polymers

Lignin is the second most abundant biobased material found on earth. It is produced mainly as a byproduct of pulp and paper industry and biorefineries. Despite its abundance, lignin valorization is not achieved on a large scale. Recently, there has been a growing demand for using the renewable and biodegradable raw materials in the commodity polymers. Potential use of lignin as a component in thermoplastic polymers is a promising approach for its value-added utilization. Given the vast applications of thermoplastic materials, there is lack of comprehensive review on lignin based thermoplastic polymers in literature. This review focuses on the utilization of lignin as functional and structural component of the thermoplastic polymers which requires structural modifications of lignin pertaining to the polymeric system. First, various lignin modifications were discussed in view of controlling the homogeneity, reactivity, processability and compatibility of lignin for successful thermoplastic copolymer synthesis and blend processing. Then, various copolymerization methodologies of lignin applicable for thermoplastic monomers are reviewed. Lastly, the lignin based thermoplastic blends are discussed which covers the lignin blends with various thermoplastic polymers and the chemical modifications required to improve its compatibility in polymer matrix. Some of the promising potential applications and future perspectives to achieve the goal of lignin-based commercial thermoplastics polymers are addressed.

UV-protection from chitosan derivatized lignin multilayer thin film

Lignin is one of the most abundant renewable materials on the earth. Despite possessing useful antioxidant and UV absorbing properties, its effective utilization in technology has been hampered by its relative insolubility and difficulty to process. In this work, a simple chemical derivatization process is utilized which yields water-soluble lignin possessing anionic carboxylate groups. These carboxylate groups give lignin polyanionic behavior and enable its utilization in the growth of a functional film via layer-by-layer (LbL) assembly with biologically sourced chitosan. The growth mechanism of this film is hypothesized to be a result of both hydrogen bonding and ionic interactions. The film demonstrates excellent UV-absorptive capability. A 100 nm thick chitosan/lignin coating was applied to a poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) film and shown to reduce its degradation sixfold over the course of a 1 hour exposure to harsh UV light. This is the first demonstration of lignin being utilized in a fully biologically derived LbL film. Utilization of lignin in LbL assembly is an important step in the development of renewable nanotechnology.

An environmentally benign derivatization process enables the use of lignin in an entirely biosourced functional thin film.

Lignin as a UV Light Blocker-A Review

Lignin is the by-product of pulp and paper industries and bio-refining operations. It is available as the leading natural phenolic biopolymer in the market. It has chromophore functional groups and can absorb a broad spectrum of UV light in range of 250–400 nm. Using lignin as a natural ingredient in sunscreen cream, transparent film, paints, varnishes and microorganism protection has been actively investigated. Both in non-modified and modified forms, lignin provides enhancing UV protection of commercial products with less than a 10% blend with other material. In mixtures with other synthetic UV blockers, lignin indicated synergic effects and increased final UV blocking potential in compare with using only synthetic UV blocker or lignin. However, using lignin as a UV blocker is also challenging due to its complex structure, polydispersity in molecular weight, brownish color and some impurities that require more research in order to make it an ideal bio-based UV blocker.

In a nutshell: prospects and challenges on coatings for edible kernels

Edible kernels have been popular food items since ancient times. Although in-shell nuts are naturally protected and relatively shelf stable, convenience demands require their commercialization in shelled form. However, whereas shelled kernels are more convenient, they are more exposed to oxygen, and thus more susceptible to oxidative rancidity and loss of crunchiness, which negatively affect the product acceptability. In this review, we discuss the role of edible coatings in extending stability of edible kernels, which is an opportunity to be better explored by the industry. The discussion also includes the role of antioxidants in the context of active coatings. Finally, future prospects and research challenges are addressed. © 2019 Society of Chemical Industry.

Corn stover valorization by one-step formic acid fractionation and formylation for 5-hydroxymethylfurfural and high guaiacyl lignin production

One-step fractionation with concentrated formic acid at elevated temperatures with short retention time was investigated for corn stover valorization. Crude pulp (CP) with high purity of cellulose and FA-lignin (FAL) with high guaiacyl content were fractionated through one-step mild pretreatment. Formylation reaction on both CP and FAL fractions occurred during the pretreatment and improved the hydrophobicity and thermal stability of CPs and FALs. The presence of formyl group on CPs significantly inhibited the enzymatic hydrolysis efficiency for sugar production, however, the formylated cellulose showed super high reactivity and selectivity for HMF production through catalysis by maleic acid and aluminum chloride in acetonitrile-water co-solvent system. In addition, the fractionated FAL fraction exhibited a loose structure which is prominent for its further catalytic conversion into chemicals and energy.

Cellulose hydrolysis using ionic liquids and inorganic acids under dilute conditions: morphological comparison of nanocellulose

The preparation of cellulose nanocrystals (CNCs) from cellulose extracted from cotton gin motes (CGM) using an ionic liquid (1-butyl-3-methylimidazolium chloride, [BMIm]Cl) under dilute conditions is reported. The concurrent process involves minimal swelling of cellulose with an ionic liquid and hydrolysis of the cellulose initiated by the addition of either phosphoric (H₃PO₄), hydrochloric (HCl), or sulfuric (H₂SO₄) acid. The obtained nanocrystals had similar physical properties (e.g. crystallinity) to the counterparts prepared under conventional conditions and exhibited superior thermal properties for sulfate CNCs. Additionally, the obtained CNCs had low surface functionalization, yet were colloidally stable for >90 days, which is a desirable trait for post-functionalization of CNCs. This process represents a general strategy utilizing dilute ionic liquids in the preparation of nanocellulose under mildly acidic conditions.

Cellulose nanocrystals prepared with 1-butyl-3-methylimidazolium chloride ([BMIm]Cl) and HCl, H₂SO₄, or H₃PO₄ in a one-pot process under dilute conditions are investigated for changes in CNC dimensions, crystallinity, and thermal stability.

Lignin Particles for Multifunctional Membranes, Antioxidative Microfiltration, Patterning, and 3D Structuring

We introduce a new type of particle-based membrane based on the combination of lignin particles (LPs) and cellulose nanofibrils (CNF), the latter of which are introduced in small volume fractions to act as networking and adhesive agents. The synergies that are inherent to lignin and cellulose in plants are re-engineered to render materials with low surface energy (contact angle measurements) and can be rendered water-resistant with the aid of wet-strength agents (WSAs). Importantly, they are most suitable for antioxidative separation (ABTS^•+ radical inhibition): membranes with uniform porous structures (air permeability and capillary flow porosimetry) allow effluent oxidation at 95 mL/cm², demonstrating, for the first time, the use of unmodified lignin particles in flexible membranes for active microfiltration. Moreover, the membranes are found to be nonfouling (protein adhesion and activity rate). The inherent properties of lignin, including UV radiation blocking capacity (UV transmittance analysis) and reduced surface energy, are further exploited in the development of tailorable and self-standing architectures that are almost entirely comprised of nonbonding LP (solids content as high as 92 w/w%). Despite such composition, the materials develop high toughness (oscillatory dynamic mechanical analysis), owing to the addition of minor amounts of CNF. Multifunctional materials based on thin films (casting), 3D structures (molding), and patterned geometries (extrusion deposition) are developed as a demonstration of the potential use of lignin particles as precursors of new material generation. Remarkably, our observations hold for spherical LPs since a much poorer performance was observed after using amorphous powder, indicating the role of size and shape in related applications.

High-Strength, Low-Permeable, and Light-Protective Nanocomposite Films Based on a Hybrid Nanopigment and Biodegradable PLA for Food Packaging Applications

Herein, a multifunctional filler, a dye (organic)-clay (inorganic) hybrid nanopigment (DCNP), was embedded into polylactic acid (PLA) to fabricate a colored biodegradable/biocompatible film, which is explored as a high thermomechanical resistant as well as a superior light and mass transport barrier for food packaging applications. In this respect, the DCNP was synthesized through a wet chemical process with a reaction yield of 76% and incorporated into a PLA matrix at various concentrations using a solution casting method. The morphological characterizations revealed partially intercalated/exfoliated structure for PLA-DCNP films. The samples filled with DCNP showed up to 20% and 12 °C improvements in storage modulus (E') and glass transition temperature (T g), respectively, compared to those with neat PLA. Incorporation of a small amount of DCNP into the PLA matrix significantly declined the water vapor and gas permeability of PLA by 36 and 54%, respectively. The optical property investigations indicated remarkable color characteristics and light protection performance of the samples containing DCNP. The results also showed better performance of the PLA-DCNP film compared to that of the PLA-Cloisite 20A sample at an identical filler loading. In conclusion, the desirable properties of the resulting films highlighted the potential application of such nanocomposite films as a promising option for food packaging materials.

Tailored cellulose nanocrystals as a functional ultraviolet absorbing nanofiller of epoxy polymers

Epoxy is an extensively used polymer in several applications such as coatings, adhesives, structural composites etc. However, it is a poor ultraviolet (UV) absorber and suffers from UV-degradation, which usually leads to discoloration and loss of structural integrity. In this study, cellulose nanocrystals (CNCs) conjugated with a UV absorbing molecule were investigated as a functional nanomaterial to enhance the UV absorption of epoxy polymers. The grafting of a UV absorbing molecule, para-aminobenzoic acid (PABA), on the surface of CNCs was confirmed using FTIR, proton NMR, and via elemental analysis. The modified CNCs were then incorporated into an epoxy polymer and their efficacy in mitigating the photo-degradation of epoxy was evaluated. For this, a neat epoxy control, native CNCs and modified CNC based nanocomposite specimens were subjected to controlled UV irradiation and the resulting structure-property changes were assessed. Results of UV absorption and discoloration showed that the neat epoxy was impacted the most as a result of the UV irradiation. While the incorporation of native CNCs displayed some UV absorption and reduction in the UV mediated discoloration of the epoxy polymer, the most pronounced effect was obtained in PABA decorated CNC based epoxy nanocomposites. The use of such tailored CNCs has great potential to mitigate UV induced degradation of a range of polymers that are used especially in outdoor applications where direct exposure to UV is significant.