Preparation and Properties of Medium-Density Fiberboards Bonded with Vanillin Crosslinked Chitosan.

An eco-friendly medium-density fiberboard (MDF) was prepared using vanillin (V) crosslinked chitosan (CS) adhesive through a hot-pressing process. The cross-linking mechanism and the effect of different proportions of added chitosan/vanillin on the mechanical properties and dimensional stability of MDF were investigated. The results showed that vanillin and chitosan are crosslinked to form a three-dimensional network structure due to the Schiff base reaction between the aldehyde group of vanillin and the amino group of chitosan. At the same time, when the mass ratio between vanillin/chitosan was 2:1, MDF obtained the best mechanical properties, the maximum modulus of rupture (MOR) of 20.64 MPa, the mean modulus of elasticity (MOE) of 3005 MPa, the mean internal bonding (IB) of 0.86 MPa, and the mean thickness swelling (TS) of 14.7%. Therefore, the MDF bonded with V-crosslinked CS can be a promising candidate for environmentally-friendly wood-based panels.

Exploration of multifunctional wood coating based on an interpenetrating network system of rosin-CO2-based polyurethane and mussel bionic rosin-based benzoxazine.

Polyurethane (PU) prepared by blending rosin base and CO2-polyol already has good mechanical properties and hydrophobic effect and has powerful benefits in acid and alkali resistance and salt resistance. In this study, mussel bionic rosin-based benzoxazine (BZ) was synthesized using dehydroabietylamine, catechol, and paraformaldehyde. Mixing BZ into PU can endow the resulting PU/BZ with special effects such as zero curing shrinkage, excellent mechanical behavior, and flame retardancy through a 3D interpenetrating network system. From the results, the modulus of rupture (MOR) and modulus of elasticity (MOE) of PU wood coatings are 97.04 and 2601.97 MPa, respectively; in contrast, the PU/BZ wood coatings exhibited higher values of MOR and MOE of 110.87 and 2738.11 MPa. PU/BZ wood coatings show higher flexural strength and elastic modulus. They are also stronger than PU coatings in terms of acid/alkali and aging resistance. At the same time, the coating is endowed with flame retardant properties, and the LOI is 30.2 due to the presence of BZ. Thus, PU/BZ can be a versatile and practical wood coating. The interpenetrating network system of PU/BZ has an innovative impact on the preparation of wood coatings.

Efficient and Durable Flame-Retardant Coatings on Wood Fabricated by Chitosan, Graphene Oxide, and Ammonium Polyphosphate Ternary Complexes via a Layer-by-Layer Self-Assembly Approach.

An efficient and durable flame-retardant coating was constructed on wood via a layer-by-layer (LBL) self-assembly approach by using a chitosan (CS), graphene oxide (GO), and ammonium polyphosphate (APP) ternary flame-retardant system. Both scanning electron microscopy (SEM) characterization and Fourier transform infrared spectroscopy (FT-IR) analysis indicated that CS-GO and APP polyelectrolytes were successfully deposited on wood, and the deposition amount was increased with the numbers of the LBLs. Thermogravimetric analysis revealed that the CS-GO-APP coating could decrease the initial and maximum thermal decomposition temperature of the coated wood while increase the char residue significantly, which may be attributed to the earlier degradation of CS and APP and effective heat barrier of the incorporated GO, thus increasing the thermal stability of the modified wood. The limited oxygen index (LOI) and cone calorimeter analysis results of the pristine and coated wood indicated that the fire resistance was significantly improved after CS-GO-APP modification; when 15 BLs were deposited on the wood, the LOI was increased from pristine 22 to 42, while the heat release rate and total heat release decreased from pristine 105.50 kW/m2 and 62.43 MJ/m2 to 57.51 kW/m2 and 34.31 MJ/m2, respectively. What is more, the 24 h immersion experiments and abrasion tests proved the excellent durability of the deposited coating. Furthermore, the SEM images of the char residues after flaming test proved that the CS-GO-APP assembly coating could promote the char layer formation on the wood surface and block the heat and flame spread, thus protecting the wood from fire attacking.

Preparation and characterization of high-strength and water resistant lignocelluloses based composites bonded by branched polyethylenimine (PEI).

High-strength and water resistant lignocelluloses based composites (LC) were fabricated using branched polyethylenimine (PEI) as the main bonding agent combined with glutaraldehyde cross-linking reaction and grinding pre-treatment. Physical and mechanical properties of different composites prepared were measured and investigated. It is evident that PEI was efficient in endowing LC with high strength and excellent water resistance. The obtained physical and mechanical properties of LC were complied with the requirement of the Chinese national standard for medium-density fiberboard (MDF). Most notably, the glutaraldehyde cross-linking and grinding pre-treatment could further improve these properties. When 5% PEI and 2.5% glutaraldehyde were incorporated, together with 2-hour grinding treatment, the LC prepared exhibited the optimum modulus of rupture (MOR) 58.1 MPa, modulus of elasticity (MOE) 5077 MPa, internal bonding strength (IB) 2.14 MPa, and thickness swell (TS) 30.2%. The excellent properties obtained could be attributed to the cross-linking effect and Schiff's base addition reaction among lignocelluloses, PEI and glutaraldehyde, which were confirmed by the Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS) analysis. The high-strength LC prepared in this study is expected to be used as load-bearing material in structural application.

Green Construction of an Oil-Water Separator at Room Temperature and Its Promotion to an Adsorption Membrane.

Underwater superoleophobic membranes as an effective means of resisting oil stains are often subjected to cumbersome modification procedures, limited stability, and difficult expansion of assembly. To develop simple, green, stable, and scalable underwater superoleophobic films, herein, cellulose-based oil-water separators with high-efficiency oil purification were constructed by using commercial carboxymethocel (CMC) as a solute and a dimethyl sulfoxide-modified ionic liquid as a solvent. Owing to the superior dissolution, regenerability, and gelation of CMC, the metal mesh and gauze can be imparted with an excellent oleophobic ability through simple dipping, spraying, and coating of the CMC solution. As a result, these modified functionalized devices exhibit a purification capacity of more than 99.5% for various oil-water mixtures. Unexpectedly, the CMC gel coating also shields the gloves from organic solvents. Significantly, when the CMC solution is applied to an adsorption membrane, it not only endows the film with excellent oil-water separation characteristics but also enhances the adsorption amount and rate of the adsorbent. Therefore, CMC-based oleophobic materials can be widely developed and applied to a variety of fields that require oleophobic properties.

Processing Lignocellulose-Based Composites into an Ultrastrong Structural Material.

Natural lignocellulose has been a significant renewable raw material attributable to its high specific mechanical performance, compared to the benefits of traditional reinforcing fibers. However, the unsatisfactory mechanical performance of lignocellulose-based materials has limited applications in many advanced engineering domains. Herein, we demonstrate that layered bulk delignified nanolignocellulose/brushite composites with a multifold increase in strength and toughness. Our procedure contains the partially removable lignin and hemicellulose from the nanolignocellulose and the precipitating process of brushite on the nanolignocellulose surface via the mechanochemical process and flow-directed assembly followed by hot-pressing, resulting in the complete toppling of cell walls and the densification of the nanolignocellulose/brushite composites with highly ordered layered structures. This composite exhibits an ultrastrong specific strength 1.8-4.4 times higher than that of modified lignocellulose-based materials, which surpasses that of most natural structural materials and some metals and alloys, opening a path for production of ultrastrong lignocellulose-based load-bearing materials in practical applications by various farming and forestry surplus operations.

Screening, Synthesis, and QSAR Research on Cinnamaldehyde-Amino Acid Schiff Base Compounds as Antibacterial Agents.

Development of new drugs is one of the solutions to fight against the existing antimicrobial resistance threat. Cinnamaldehyde-amino acid Schiff base compounds, are newly discovered compounds that exhibit good antibacterial activity against gram-positive and gram-negative bacteria. Quantitative structure⁻activity relationship (QSAR) methodology was applied to explore the correlation between antibacterial activity and compound structures. The two best QSAR models showed R² = 0.9354, F = 57.96, and s² = 0.0020 against Escherichia coli, and R² = 0.8946, F = 33.94, and s² = 0.0043 against Staphylococcus aureus. The model analysis showed that the antibacterial activity of cinnamaldehyde compounds was significantly affected by the polarity parameter/square distance and the minimum atomic state energy for an H atom. According to the best QSAR model, the screening, synthesis, and antibacterial activity of three cinnamaldehyde-amino acid Schiff compounds were reported. The experiment value of antibacterial activity demonstrated that the new compounds possessed excellent antibacterial activity that was comparable to that of ciprofloxacin.

Improved mould resistance and antibacterial activity of bamboo coated with ZnO/graphene.

Bamboo is susceptible to mould and attack by fungi because of its high content of starch and sugar. To make bamboo-based outdoor materials, a new type of bamboo timber with improved mould resistance and antibacterial activity, coated with reduced graphene oxide and nanocrystal ZnO (abbreviated as RGO@ZnOBT), was fabricated by a two-step dip-dry and hydrothermal process. A possible synthesis mechanism for RGO@ZnOBT was investigated by X-ray diffraction, scanning electron microscopy, transmission electron microscope, energy-dispersal X-ray analysis, X-ray photoelectron spectroscopy and Fourier-transform infrared spectroscopy. According to the China standard test method, the Aspergillus niger mould resistance of RGO@ZnOBT is grade 2, whereas the Trichoderma viride and Penicillium citrinum mould resistance of RGO@ZnOBT is grade 0, both of which are better than the grade 4 of original bamboo timber. The Escherichia coli resistance test showed that the antibacterial circle of RGO@ZnOBT is 3 mm, which is significantly higher than that of original bamboo timber (0 mm). The antibacterial activity of treated bamboo is significantly improved compared with that of untreated bamboo.

Author Correction: The properties of fibreboard based on nanolignocelluloses/CaCO3/PMMA composite synthesized through mechano-chemical method.

A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has not been fixed in the paper.

Fabrication of Superhydrophobic Mg/Al Layered Double Hydroxide (LDH) Coatings on Medium Density Fiberboards (MDFs) with Flame Retardancy.

The hydrophilicity and flammability of fiberboards have limited their real-life applications. In this study, a facile strategy for preparing the multifunctional coatings with superhydrophobicity and flame retardancy on medium density fiberboards (MDFs) has been investigated. The superhydrophobic and flame-retardant coating on the MDF surface was obtained by depositing polydimethylsiloxane (PDMS) and 1H, 1H, 2H, 2H-perfluorodecyltrichlorosilane (FDTS)-modified Mg/Al layered double hydroxide (LDH) particles step by step. The as-prepared coating exhibited superhydrophobic properties with a water contact angle (WCA) of ~155° and good self-cleaning properties. Furthermore, the limiting oxygen index (LOI) value of the superhydrophobic MDFs increased by 60.4% as compared to that of the pristine MDFs, showing improved flame retardancy. The peak heat release rate (PHRR) and total heat release (THR) of MDFs decreased after coating with PDMS@FDTS-Mg/Al LDH, suggesting that the superhydrophobic coating decreased the fire growth speed and risk of fire hazard of MDFs. This coating with multiple functions opens a new avenue for the protection and functionalization of MDFs.

Ultrafine Mn ferrite by anchoring in a cellulose framework for efficient toxic ions capture and fast water/oil separation.

The serious agglomeration phenomenon of ultrafine nanoparticles is widespread, resulting in low utilization and poor performance of adsorbents in the scavenging of toxic ions. Herein, ultrafine MnFe2O4 (8-13 nm) are uniformly anchored onto the cellulose framework by fast hydrothermal and freeze-drying processes. The as-prepared super-hydrophilic MnFe2O4/cellulose aerogel (MCA) had a three-dimensional (3D) network structure with interconnected and forked fibrils, developed porous structure and high surface area. Combined with the adsorption-aggregation effect of cellulose and high surface activity of the low agglomerated ultrafine MnFe2O4, the adsorption efficiency of MCA was strongly improved and thus achieved a higher utilization. To enable its further use in a hostile environment for the treatment of severe oil pollution, FAS-17 was used to modify the MnFe2O4/cellulose aerogel (F-MCA) for achieving full utilization of their intrinsic structural features. The lipophilic F-MCA exhibited a large bearing capacity on the water and fast adsorption performance for oils/organic solvents.

Facile Fabrication of a PDMS@Stearic Acid-Kaolin Coating on Lignocellulose Composites with Superhydrophobicity and Flame Retardancy.

The disadvantages such as swelling after absorbing water and flammability restrict the widespread applications of lignocellulose composites (LC). Herein, a facile and effective method to fabricate superhydrophobic surfaces with flame retardancy on LC has been investigated by coating polydimethylsiloxane (PDMS) and stearic acid (STA) modified kaolin (KL) particles. The as-prepared coatings on the LC exhibited a good repellency to water (a contact angle = 156°). Owing to the excellent flame retardancy of kaolin particles, the LC coated with PDMS@STA-KL displayed a good flame retardancy during limiting oxygen index and cone calorimeter tests. After the coating treatment, the limiting oxygen index value of the LC increased to 41.0. Cone calorimetry results indicated that the ignition time of the LC coated with PDMS@STA-KL increased by 40 s compared with that of uncoated LC. Moreover, the peak heat release rate (PHRR) and the total heat release (THR) of LC coated with PDMS@STA-KL reduced by 18.7% and 19.2% compared with those of uncoated LC, respectively. This LC coating with improved water repellency and flame retardancy can be considered as a potential alternative to protect the lignocellulose composite.

The properties of fibreboard based on nanolignocelluloses/CaCO3/PMMA composite synthesized through mechano-chemical method.

The purpose of this study was to develop a rapid and green method for the synthesis of lignocelluloses-based materials with superior mechanical properties. Samples were produced by hot-pressed method using different concentrations of CaCO3 and poly (methyl methacrylate) particles-filled nanolignocelluloses composites which was synthesized through mechano-chemical method. Poly (methyl methacrylate) and CaCO3 nanoparticles have been used as nanofillers. Bending strength, elasticity modulus, and dimensional stability, thermal properties of the developed lignocelluloses-based composites were determined. In view of the experimental results, it is found that the composites materials have good mechanical, dimensional stability, and thermal properties which enhanced as the filler loading increased. Thus, herein described lignocelluloses-based materials showed important characteristics to be concluded that these composites are suitable to be used for the design of flooring and construction systems.

High Mechanical Property of Laminated Electromechanical Sensors by Carbonized Nanolignocellulose/Graphene Composites.

Although widely used in nanocomposites, the effect of embedding graphene in carbonized nanolignocellulose substrates is less clear. We added graphene to a carbonized nanolignocellulose to change its mechanical and electromechanical properties. Here, the laminated carbonized nanolignocellulose/graphene composites were fabricated by carbonizing the nanolignocellulose/graphene composites prepared through mechanochemistry and flow-directed assembly process. The resulting composites exhibit excellent mechanical property with the ultimate bending strength of 25.6 ± 4.2 MPa. It is observed reversible electrical resistance change in these composites with strain, which is associated with the tunneling conduction model. This type of high-strength conductive composite has great potential applications in load-bearing electromechanical sensors.

Preparation of High Mechanical Performance Nano-Fe3O4/Wood Fiber Binderless Composite Boards for Electromagnetic Absorption via a Facile and Green Method.

Fe3O4/wood fiber composites are prepared with a green mechanical method using only distilled water as a solvent without any chemical agents, and then a binderless composite board with high mechanical properties is obtained via a hot-press for electromagnetic (EM) absorption. The fibers are connected by hydrogen bonds after being mechanically pretreated, and Fe3O4 nanoparticles (NPs) are attached to the fiber surface through physical adsorption. The composite board is bonded by an adhesive, which is provided by the reaction of fiber composition under high temperature and pressure. The Nano-Fe3O4/Fiber (NFF) binderless composite board shows remarkable microwave absorption properties and high mechanical strength. The optional reflection loss (RL) of the as-prepared binderless composite board is -31.90 dB. The bending strength of the NFF binderless composite board is 36.36 MPa with the addition of 6% nano-Fe3O4, the modulus of elasticity (MOE) is 6842.16 MPa, and the internal bond (IB) strength is 0.81 MPa. These results demonstrate that magnetic nanoparticles are deposited in binderless composite board by hot pressing, which is the easiest way to produce high mechanical strength and EM absorbers.

Mesopore-dominant nitrogen-doped carbon with a large defect degree and high conductivity via inherent hydroxyapatite-induced self-activation for lithium-ion batteries.

In this study, N-doped mesopore-dominant carbon (NMC) materials were prepared using bio-waste tortoise shells as a carbon source via a one-step self-activation process. With intrinsic hydroxyapatites (HAPs) as natural templates to fulfill the synchronous carbonization and activation of the precursor, this highly efficient and time-saving method provides N-doped carbon materials that represent a large mesopore volume proportion of 74.59%, a high conductivity of 4382 m S-1, as well as larger defects, as demonstrated by Raman and XRD studies. These features make the NMC exhibit a high reversible lithium-storage capacity of 970 mA h g-1 at 0.1 A g-1, a strong rate capability of 818 mA h g-1 at 2 A g-1, and a good capacity of 831 mA h g-1 after 500 cycles at 1 A g-1. This study provides a highly efficient and feasible method to prepare renewable biomass-derived carbons as advanced electrode materials for the application of energy storage.

Lignocellulose-Chitosan-Multiwalled Carbon Nanotube Composites with Improved Mechanical Strength, Dimensional Stability and Fire Retardancy.

A novel composite composed of lignocellulose (LC), glutaraldehyde crosslinked chitosan (GC) and multiwalled carbon nanotube (MWCNT) was fabricated by the hot-pressing process. The effect of the additional GC and MWCNT on the mechanical strength, dimensional stability and fire retardancy of lignocellulose composites was investigated. The results showed that LC/GC/MWCNT composite exhibited the maximum modulus of rupture (MOR) of 35.3 MPa, modulus of elasticity (MOE) of 2789.1 MPa and internal bonding (IB) strength of 1.2 MPa. Meanwhile, the LC/GC/MWCNT composite displayed improved dimensional stability with a thickness swelling (TS) value of 22.4%. Besides, the LC/GC/MWCNT composite exhibited improved fire retardancy with a limiting oxygen index of 29.0%. The peak heat release rate, the total heat release, the total smoke production and the maximum smoke production ratio of LC/GC/MWCNT composite decreased by 15.9%, 10.7%, 45.5% and 20.7% compared with those of LC composite, respectively. Therefore, the LC/GC/MWCNT composite may be a promising candidate for green wood based composites.

Fabrication of a Nano-ZnO/Polyethylene/Wood-Fiber Composite with Enhanced Microwave Absorption and Photocatalytic Activity via a Facile Hot-Press Method.

A polyethylene/wood-fiber composite loaded with nano-ZnO was prepared by a facile hot-press method and was used for the photocatalytic degradation of organic compounds as well as for microwave absorption. ZnO nanoparticles with an average size of 29 nm and polyethylene (PE) powders were dispersed on the wood fibers' surface through a viscous cationic polyacrylamide (CPAM) solution. The reflection loss (RL) value of the resulting composite was -21 dB, with a thickness of 3.5 mm in the frequency of 17.17 GHz. The PE/ZnO/wood-fiber (PZW) composite exhibited superior photocatalytic activity (84% methyl orange degradation within 300 min) under UV light irradiation. ZnO nanoparticels (NPs) increased the storage modulus of the PZW composite, and the damping factor was transferred to the higher temperature region. The PZW composite exhibited the maximum flexural strength of 58 MPa and a modulus of elasticity (MOE) of 9625 MPa. Meanwhile, it also displayed dimensional stability (thickness swelling value of 9%).

Design of cinnamaldehyde amino acid Schiff base compounds based on the quantitative structure-activity relationship.

Cinnamaldehyde amino acid Schiff base (CAAS) is a new class of safe, bioactive compounds which could be developed as potential antifungal agents for fungal infections. To design new cinnamaldehyde amino acid Schiff base compounds with high bioactivity, the quantitative structure-activity relationships (QSARs) for CAAS compounds against Aspergillus niger (A. niger) and Penicillium citrinum (P. citrinum) were analysed. The QSAR models (R2 = 0.9346 for A. niger, R2 = 0.9590 for P. citrinum,) were constructed and validated. The models indicated that the molecular polarity and the Max atomic orbital electronic population had a significant effect on antifungal activity. Based on the best QSAR models, two new compounds were designed and synthesized. Antifungal activity tests proved that both of them have great bioactivity against the selected fungi.

Utilizing cellulose sheets as structure promoter constructing different micro-nano titanate nanotubes networks for green water purification.

In this work, we provide a novel strategy of constructing different micro-nano structure (arrayed, multilevel, flower-like) titanate nanotubes (TNTs) networks with cellulose sheets as structure promoter. Through cellulose self-locking and inter-locking, several micro-nano TNTs networks with higher specific surface area are obtained and applied to toxic heavy metal Pb2+ cations removal. It not only makes abundant toxic Pb2+ ions exchange with the inter-layer Na+ ions of TNTs, but also allows many Pb2+ ions to be deposited onto the TNTs surface. As expected, heavy metal Pb2+ removal performance of the as-prepared TNTs networks miraculously reaches 5.24mmolg-1. Moreover, the prepared titanate network is also exhibited a good co-removal capacity of multi-component ions (Pb2+, Sr2+ and Cs+) and superior acid/alkali adaptability. Therefore, the as-fabricated TNTs network with cellulose sheets as structure promoter could be regarded as a promising water purifier.