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Thermal drying makes cellulosic fibers shrink, resulting in pore collapse and degraded fiber performance. However, in this work, the pores of cellulose fibers expanded in the later stage of low-temperature thermal drying by regulating the fiber stacked structure before drying, which was called "low-temperature pore expansion effects". The results showed a high content of lignin was required because there were no low-temperature pore expansion effects during the drying process of low lignin-containing cellulosic fibers. Three-dimensional fiber stacked structure was also necessary because cellulose fiber materials with two-dimensional stacked structure, such as paper, had no pore expansion effects. The pore expansion effects first strengthened and then weakened with increasing temperature, and the optimum temperature was 60 °C. According to the results, the pore expansion effects included the pore shrinkage period and pore expansion period. Finally, a possible lignin-cellulose phase separation mechanism was proposed to explain this phenomenon. This work reveals the special ultrastructural transformation of cellulosic fibers under low-temperature drying, providing a reference for precise regulation of the properties of dried fibers. [ABSTRACT FROM AUTHOR]

Having the advantages of a higher yield, lower cost and less environmental impact, lignin-containing cellulose nanofibrils (LCNFs) obtained by mechanically fibrillating unbleached pulps have been demonstrated to be a promising alternative to high-purity nanocellulose. In this study, the structural changes after four drying methods containing freeze-drying (FD), oven-drying (OD), centrifugal followed by vacuum-drying (CVD), and evaporation followed by vacuum-drying (EVD), and efficient reuse of LCNFs were extensively explored. It was found that the structural characteristics of LCNFs after drying were maintained by freeze drying with high lignin contents where the aggregation of fibrils was alleviated by lignin. The freeze-dried LCNFs were further redispersed by homogenizer in water, which exhibited excellent dispersion characteristics. In addition, the redispersed LCNFs were further assembled into PVA films to fabricate high-strength composites. The results showed that when the addition of redispersed LCNFs was up to 16.9%, the tensile strength and elongation at break of the as-prepared composite film increased by 325.2% and 335.2%, respectively. This study demonstrated a more sustainable approach to utilize LCNFs to produce biomass-based composite films than those of CNF-based composite films. [ABSTRACT FROM AUTHOR]

The microstructure and properties of lignocellulosic fibers usually change during the drying process due to the hornification of fibers. The water retention ability of fibers is an effective way to reflect the degree of fiber hornification. In this study, the effects of lignin content on the microstructural properties of dried-redispersed LCNFs (DLCNFs) were extensively explored. The results showed that the high content of lignin could maintain the microstructural integrity of DLCNFs. The water retention value and hornification degree of high lignin content DLCNFs (22.1%, w/w) were 289.8% and 6.9%, which were much lower than those of low lignin content (6.2%, w/w) DLCNFs. This was probably because that the crosslinking between lignin and carbohydrate effectively prevented the hydrogen bonding formation in the interior-fibers and exterior-fibers, and reduced the irreversible hornicficatoin of LCNFs. This study will be beneficial for the development of the LCNF drying mechanism. [ABSTRACT FROM AUTHOR]

Lignin is a low-cost and sustainable alternative precursor for manufacturing carbon fibers (CFs). However, the properties of lignin-based CFs are inferior due to the heterogeneity and complex three-dimensional structure of lignin. In this work, a facile stepwise fractionation extraction method is devised to extract lignin. This stepwise fractionation extraction method effectively removes the small molecular branching structure of lignin, thus obtaining fractionated lignin with a high molecular weight, narrow polydispersity index, and linear structure. Based on the results of XRD and Raman spectroscopy, the high molecular weight, narrow polydispersity index, and linear structure are conducive to improving the graphitization degree of CFs. Compared with the lignin-based CFs from original lignin, the tensile strength and Young's modulus of the lignin-based CFs from the fractionated lignin increase significantly, extraordinarily approaching those of PAN-based CFs. This facile stepwise fractionation extraction method for lignin is promising for the industrial production of high performance lignin-based CFs. [ABSTRACT FROM AUTHOR]

ABSTRACT In order to optimize the use of residues of enzymatic hydrolysis of corn stalk (REHCS) and explore the low-cost and sustainable raw material substitute for carbon fibers, three types of lignin samples were extracted from REHCS by various extraction methods, and then they were converted into carbon fibers (CFs) by electrospinning, thermostabilization, and carbonization under the same process conditions. The microstructure and mechanical properties of the three types of carbonized fibers were different. The CFs from the ethanol organosolv lignin were actually smooth and brittle carbon films. The CFs from the formic acid/acetic acid organosolv lignin had microscopic pores, causing poor mechanical properties. Comparatively, the CFs from the alkaline lignin demonstrated preferable microstructure and mechanical properties. The reasons for the differences were analyzed by characterizing the lignin samples, precursor fibers, and resultant CFs. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 45580. [ABSTRACT FROM AUTHOR]

To enhance the cellulose digestibility of energy grass hybrid Pennisetum ( P. americanum × P. purpureum , HP) with low energy-consumption and high efficiency, a novel combinatorial pretreatment of oxygen-aqueous alkaline ionic liquid (IL) 1-ethyl-3-methylimidazolium acetate ([Emim]Ac) media (OEA) was developed in this work. The combinatorial pretreatment was performed under the relatively low temperature (120 °C), short retention time (30 min), and 12 bar oxygen pressure. The combinatorial pretreatment of OEA was demonstrated effectively for pretreatment of hybrid Pennisetum , which evidenced by the removal of lignin, degradation of carbohydrate, and porosity property of the regenerated biomass. Subsequently, a higher glucose recovery (96.9%) at a low enzyme loading (20 FPU/g substrate) was obtained by the OEA pretreatment, and it was 9.1 times as much as the untreated samples. Overall, the novel OEA combinatorial pretreatment has the advantages of low thermal energy input and enzyme usage, and short retention time. [ABSTRACT FROM AUTHOR]

The industrial lignin has shown great potential to replace some of petrochemical. But the deep color of lignin limits their application in high-value field. The extraction of light-colored lignin from lignocellulose still remains challenging. Here, we reported a strategy for rapid extraction of lignin from corn stover by using a new ternary deep eutectic solvent (TDES) composed of choline chloride (ChCl), formic acid (FA) and maleic acid (MA). The color feature and structural characterization of obtained lignin was comprehensively elucidated. The results revealed that the lignin streams had light color (brightness ISO 23.44 %) with a high yield (76.3 %), purity (93.5 %), low molecular weight (Mw 1544–2040 g/mol), and low polydispersity (PDI ≤ 1.76). The introduction of MA could reduce the destruction of lignin substructure during the treatment process and avoid the deepening of lignin color. Quantitative analysis of conjugated carbonyl and quinone carbonyl and semi-quantitative analysis of lignin by 2D NMR showed that temperature had a great influence on its structure. [Display omitted] • The TDES system could extract light-colored lignin in a short time. • The brightness of TDES extracted lignin reaches up to 23.44 %. • The reason of color change of extracted lignin was analyzed. • Conjugated carbonyl and quinone carbonyl of lignin were quantitatively analyzed. • The mechanism of extraction of light-colored lignin was investigated. [ABSTRACT FROM AUTHOR]

Kapok fibre has the advantage of low density, low porosity and low thermal conductivity, which make it an excellent substitute for fumed silica and environmentally-unfriendly synthetic polymers as core material of vacuum insulation panels (VIP). However, kapok fibre is hydrophobic, consequently, kapok fibre core materials made by conventional wet forming with weakly-bound fibres and large voids that shorten their service life. Lignin is a natural and sustainable material that has good hydrophilicity and small particle size to form nano-porous networks. Therefore, we herein present the incorporation of lignin in kapok fibre to generate a composite core material with hierarchical porous structure. Lignin functionalises the kapok fibre surface to make it hydrophilic and dispersible in water. Simultaneously, lignin enhances the mechanical properties and service life of core material by transforming its internal microstructure. The effective thermal conductivity of prepared VIP is below 6.00 mW/(m∙K), and after 28 days of accelerated ageing test without desiccant or getter, the effective thermal conductivity increases less than 5.00 mW/(m∙K). Interestingly, the addition of lignin also reduces radiative heat transfer in the VIP. So, lignin addition enables high-performance VIP to be produced. Moreover, as a natural material, kapok fibre is low-cost, environmentally-friendly, sustainable, and energy-efficient. [Display omitted] • The lignin/kapok fibres composite core materials VIP were designed and prepared. • The mechanism of lignin improving the dispersion of kapok fibre was studied. • The thermal conductivity of composite core VIP could reach below 6.00 mW/(m∙K). • The addition of lignin in the VIP prolongs the service life. [ABSTRACT FROM AUTHOR]

[Display omitted] • The waste eucalyptus slabs are treated with acidic deep eutectic solvents. • Shrinking core model is modified to include the effect of temperature. • New model fits the entire curve of delignification degree versus time. • The established model can predict experimental values well. • The model reinforces the production of lignin and cellulosic fibers. This work revealed the reaction characteristics in the delignification process of eucalyptus slabs catalyzed by acidic deep eutectic solvent (benzyltriethylammonium chloride/formic acid) from the perspective of heterogeneous reactions. The limitation of internal diffusion on delignification process cannot be ignored. Afterwards, a kinetic model based on cell wall structure was proposed to describe the relationship between the delignification degree and reaction conditions, and it also hold excellent predictive ability for lignin removal, carbohydrate retention and solid residue yield. Compared with other reported kinetic models, this novel model not only took into account all operational parameters of reaction process, but also can be applied to the entire reaction process without the need for segmentation. Besides, an essential requirement based on the developed model was a 44.40 wt% formic acid concentration and a temperature of 130 °C, when the purpose of DES treatment was pulping. Generally, this work could provide guidance on process adjustments and product quality control during the DES processing. [ABSTRACT FROM AUTHOR]

The rapid development of the industry has led to the destruction of the earth's ozone layer, resulting in an increasingly serious problem of excessive ultraviolet radiation. Exploring effective measures to address these problems has become a hot topic. Lignin shows promise in the design and preparation of anti-ultraviolet products due to its inherent properties. However, it is important to investigate way to enhance the reactivity of lignin and determine its application form in related products. In this study, phenolic reactions with tea polyphenols were conducted through acid-catalyzed conversion, utilizing organic solvent lignin as the primary material. The phenolic hydroxyl content of the original lignin increased significantly by 218.8 %, resulting in notable improvements in UV resistance and oxidation resistance for phenolic lignin. Additionally, micro-nanocapsule emulsions were formed using phenolic lignin particles as surfactants through ultrasonic cavitation with small-molecule sunscreens. A bio-based sunscreen was prepared with phenolated lignin micro-nanocapsules as the active ingredient, achieving an SPF 100.2 and demonstrating excellent stability. The sunscreen also exhibited strong antioxidant properties and impermeability, ensuring user safety. This research offers a current solution for improving the application of lignin in sunscreens while also broadening the potential uses of plant-based materials in advanced functional products. [Display omitted] • A green method for preparing phenolic lignin by tea polyphenol. • A stable Pickering emulsion was prepared by tea polyphenols phenolated lignin. • Small molecule sunscreen and phenolic lignin exhibits a synergistic effect. • Bio-based sunscreen with excellent anti-UV, antioxidant and anti-permeability [ABSTRACT FROM AUTHOR]

• Lignin-polypyrrole interpenetrating networks were developed for supercapacitor (SCs). • LCNFs was used as both flexible substrates and active materials for SCs. • The capacitive strengthening mechanism of lignin was systematically investigated. • The mechanical strengthening mechanism of composite membrane was studied. Lignin-containing cellulose nanofibrils (LCNFs) are emerging and promising multifunctional nanomaterials for economical and eco-friendly flexible supercapacitors (SCs). However, the strengthening mechanism of lignin on the capacitive and mechanical performance of LCNF-based nanocomposite electrodes has not been deeply studied. Herein, a mechanically strong nanocomposite electrode with excellent capacitive performance was fabricated by decorating a sodium lignosulphonate/polypyrrole (LS/PPy) interpenetrating network onto LCNFs, the relationship between lignin content, LCNFs morphology and electrodes performance was systematically investigated. Results showed that lignin could effectively strengthen the capacitive and mechanical performance of the electrodes via providing pseudocapacitance generated by the reversible conversion of quinone/hydroquinone and controlling the fibrillation degree of LCNFs. With decreasing the lignin content, LCNFs gradually transformed from nanofibril bundles to uniform nanofibrils, forming an electrode with hierarchical porous structure, highly interconnected conductive network, high active site exposure rate and excellent capacitive and mechanical performance. However, insufficient lignin could weaken the capacitive and mechanical performance of the electrodes via reducing quinone/hydroquinone content, electrodes porosity and LCNFs strength. Therefore, electrodes with lignin content of 11.4% displayed excellent tensile strength (20.46 MPa) and areal specific capacitance (2567 mF cm−2, 1 mA cm−2). The assembled all-solid-state supercapacitor (ASSC) delivered high coulombic efficiency (∼98%) and energy density, 88.6 μWh cm−2 (499.9 μW cm−2) and 1.74 mWh cm−3 (9.8 mW cm−3) for areal and volumetric energy (power) density, respectively. This work systematically reveals the strengthening mechanism of lignin on the capacitive and mechanical performance of the electrodes and provides theoretical guidance for constructing high-performance LCNF-based nanocomposite electrodes. [ABSTRACT FROM AUTHOR]

Lignin-containing cellulose nanopapers are emerging multifunctional materials in the fields of coatings, films, and packaging. However, the forming mechanism and properties of nanopapers with various lignin content have not been thoroughly studied. In this work, a mechanically strong nanopaper was fabricated based on lignin-containing cellulose micro- and nano-hybrid fibrils (LCNFs). The influence of lignin content and fibrils morphology on the formation process of nanopapers was investigated to understand the strengthening mechanism of nanopapers. LCNFs with high lignin content provided nanopapers with intertwined micro- and nano-hybrid fibrils layers with small layer spacing, while LCNFs with low lignin content offered nanopapers interlaced nanofibrils layers with large layer spacing. Although lignin was expected to interfere with hydrogen bonds between fibrils, the uniformly distributed lignin contributed to the stress transfer between fibrils. Due to the good coordination between microfibrils, nanofibrils and lignin (as network skeleton, filler and natural binder, respectively), the well-designed LCNFs nanopapers with lignin content of 14.5 % showed excellent mechanical properties, including tensile strength (183.8 MPa), Young's modulus (5.6 GPa) and elongation (9.2 %). This work deeply reveals the relationship between lignin content, morphology and strengthening mechanism of nanopapers, and providing theoretical guidance for employing LCNFs as structural and reinforcing materials to design robust composites. • The forming mechanisms of nanopapers with different lignin content were revealed. • The strengthening mechanism of LCNFs nanopapers was systematically investigated. • Lignin can preserve the mechanical properties of nanopapers by aiding stress transfer. • The influence of different molding methods on nanopapers strength was revealed. [ABSTRACT FROM AUTHOR]

[Display omitted] • A new TDES catalysis was prepared to pretreat radiata pine. • 98.9% of sugar yield was obtained in the saccharification process. • LCNF was successfully prepared from radiata pine. • LCNF had good properties such as size, fluorescence, and thermal stability. • Effect of LCNF films with regard to barrier performance was investigated. Ternary deep eutectic solvents (TDESs) as a new class of solvents play a key role in fabrication of lignin containing cellulose nanofibrils (LCNF), however, current work requires a considerable time and thus limits industrial application of TDES. Herein, a novel strategy was proposed to produce lignin containing cellulose nanofibrils (LCNF) by TDESs based on benzyltrimethylammonium chloride (BTMAC), formic acid (FA), and maleic acid (MA). The TDESs could remove 87.80% of lignin and 89.15% of hemicellulose from Radiata Pine while most of the cellulose reserved under optimum pretreatment conditions (TDES = 100 wt%, T = 130 °C, t = 1.5 h). Benefiting from the increase in cellulase accessibility, desired sugar yield of 98.9% was obtained. Moreover, the proposed TDESs could be regarded as a green medium for the production of containing cellulose nanofibrils (LCNF) in which lignin has been esterified. The LCNF displayed a well-individualized structure with a wide size distribution (32.3–146.9 nm), which was closely associated with lignin content. 13C−1H HSQC 2D NMR test was performed to illustrate the molecular − structural features of lignin and polysaccharide in LCNF. In addition, the self-standing LCNF films exhibited excellent UV-blocking, higher thermal stability, and mechanical strength. Most importantly, LCNF films showed strong barrier property to oil and air owing to lower surface free energy and smaller pore structure. Briefly, this work highlights the pretreatment performance of TDESs for cascade utilization of lignocellulosic biomass to high-value products. [ABSTRACT FROM AUTHOR]

• Cellulose nanofibers containing various content lignin were obtained. • Lignin content of pulp had two-sides on the mechanical fibrillation and rheology. • High content lignin interfered in gel strength and yield stress of LCNF suspensions. • LCNF suspensions with residual lignin show excellent recovery capacity and strong network. This study aims to investigate the relationship between lignin content, morphology, and rheology of lignin containing cellulose nanofibers (LCNFs). The morphology and rheology of LCNFs were dominated by lignin content. Lignin content had two-sides on mechanical fibrillation. At high lignin content (23.79 %), reduced efficiency of defibrillation resulted in large LCNFs connecting with lignin patches. LCNF suspensions exhibited low viscosity, weak gel behavior due to infirm fibril network. Small yield stress of 1.14 Pa suggested that fibril network was easily disrupted. At residual lignin of 6.52 %, fibril bundles were sensitive to defibrillation, producing long and flexible LCNFs with high capacity of entanglement. The entangled fibril network had high viscosity and strong gel like behavior. Creep compliance of 0.09 Pa−1 and large yield stress of 4.25 Pa indicated excellent resistance to deformation. The desired rheology can be tailored by lignin content, providing practical guidance on novel rheology-dependent LCNF based materials. [ABSTRACT FROM AUTHOR]

• The lignin-based solid acid catalyst possessed 0.60 mmol/g of sulfonic densities and 4.62 mmol/g of total acid densities. • Five times recycling and reuse of lignin-based solid acid can be achieved. • More than 80 % yield of short rod-like cellulose nanofibers can be obtained after microfluidization. • The large crystallinity index and low aspect ratio of short rod-like cellulose nanofibers reach to 82 % and 10–28, respectively. Robust environmental regulations are driving the chemical industries to develop low-cost, eco-friendly, and efficient solid acid catalysts for catalytic transformation of cellulose into high-value products. In our work, lignin separated from enzymatic hydrolyzed residues was used as the carbon source to synthesize lignin-based solid acid (LC-SO 3 H) via facile carbonization-sulfonation process. Cellulose nanofibers (CNFs) and platform chemicals (mainly glucose and formic acid) were efficiently transformed from cellulose through LC-SO 3 H catalytic hydrolysis pretreatment combined with microfluidization. Short rod-like CNFs were obtained with large crystallinity index of 82 % and small aspect ratio of 10-28. Furthermore, LC-SO 3 H can be recycled and reused. After five successive cycles, the yield of CNFs, glucose, and formic acid reached up to 90.8 %, 3.9 %, and 2.1 %, respectively. This work provides a novel, low-cost, and environmental benign approach to prepare CNFs and platform chemicals, and it holds great potential for green and sustainable production of high value-added biomass products. [ABSTRACT FROM AUTHOR]