Flexible cellulose nanofiber aerogel with enhanced porous structure and its applications in copper(II) removal.

In order to achieve an aerogel with both rigid pore structures and desired flexibility, stiff carboxyl-functionalized cellulose nanofiber (CNFs) were introduced into a flexible polyvinyl alcohol-polyethyleneimine (PVA-PEI) crosslinking network, with 4-formylphenylboronic acid (4FPBA) bridging within the PVA-PEI network to enable dynamic boroxine and imine bond formation. The strong covalent bonds and hydrogen connections between CNF and the crosslinking network enhanced the wet stability of the aerogel while also contributed to its thermal stability. Importantly, the harmonious coordination between the stiff CNF and the flexible polymer chains not only facilitated aerogel flexibility but also enhanced its increased specific surface area by improving pore structure. Moreover, the inclusion of CNF enhanced the adsorption capacity of the aerogel, rendering it effective for removing heavy metal ions. The specific surface area and adsorption capacity for copper ions of the aerogel increased significantly with a 3 wt% addition CNF suspension, reaching 19.74 m2 g-1 and 60.28 mg g-1, respectively. These values represent a remarkable increase of 590.21 % and 213.96 %, respectively, compared to the blank aerogel. The CNF-enhanced aerogel in this study, characterized by its well-defined pore structures, and desired flexibility, demonstrates versatile applicability across multiple domains, including environmental protection, thermal insulation, electrode fabrication, and beyond.

Polydopamine-Anchored Cellulose Nanofiber Flexible Aerogel with High Charge Transfer as a Substrate for Conductive Materials.

In order to obtain a flexible aerogel substrate for conductive materials used in the electrode, polydopamine-anchored cellulose nanofiber (PDA@CNF) was introduced into a polyethylene imine-poly(vinyl alcohol) (PEI-PVA) cross-linking network which used 4-formylphenylboronic acid (4FPBA) as bridge. The incorporation of rigid CNF as a structural scaffold effectively improved the pore architecture of the aerogel, potentially providing substantial advantages for the infiltration and deposition of conductive materials. Additionally, the outstanding stability and flexibility exhibited by the aerogel in aqueous solutions suggest its significant potential for applications in flexible electrodes. Furthermore, electrochemical experiments showed that the rapid pathway formed between PDA and PEI could enhance the charge-transfer rate within the aerogel substrate. It is anticipated that such an enhancement would significantly benefit the electrochemical attributes of the electrode. Inspired by mussels, our introduced PDA-anchored rigid CNF into flexible polymer networks to fabricate aerogel substrates for electrode materials. This study would contribute to the development and utilization of flexible electrodes while reducing carbon footprint in energy production and conversion processes.

A strong hydrogen bond bridging interface based on tannic acid for improving the performance of high-filled bamboo fibers/poly (butylene succinate-co-butylene adipate) (PBSA)biocomposites.

Natural plant fiber-reinforced bio-based polymer composites are widely attracting attention because of their economical, readily available, low carbon, and biodegradable, and showing promise in gradually replacing petroleum-based composites. Nevertheless, the fragile interfacial bonding between fiber and substrate hinders the progression of low-cost and abundant sustainable high-performance biocomposites. In this paper, a novel high-performance sustainable biocomposite was built by introducing a high density strong hydrogen-bonded bridging interface based on tannic acid (TA) between bamboo fibers (BFs) and PBSA. Through comprehensive analysis, this strategy endowed the biocomposites with better mechanical properties, thermal stability, dynamic thermo-mechanical properties and water resistance. The optimum performance of the composites was achieved when the TA concentration was 2 g/L. Tensile strength as well as modulus, flexural strength as well as modulus, and impact strength improved by 22 %, 10 %, 15 %, 35 %, and 25 % respectively. Additionally, the initial degradation temperature(Tonset) and maximum degradation temperature(Tmax) increased by 12.07 °C and 14.8 °C respectively. The maximum storage modulus(E'), room temperature E', and loss modulus(E")elevated by 199 %, 75 %, and 181 % respectively. Moreover, the water absorption rate decreased by 59 %. The strong hydrogen-bonded bridging interface serves as a novel model and theory for biocomposite interface engineering. At the same time, it offers a promising future for the development of high performance sustainable biocomposites with low cost and abundant biomass resources and contributes to their wide application in aerospace, automotive, biomedical and other field.

Crustacean-inspired chitin-based flexible buffer layer with a helical cross-linked network for bamboo fiber/poly(3-hydroxybutyrate) biocomposites.

Marine biological resources, serving as a renewable and sustainable reservoir, holds significant import for the utilization of composite material. Hence, we produced bamboo fiber/poly(3-hydroxybutyrate) (BF/PHB) biocomposites with exceptional performance and economic viability, drawing inspiration from the resilience of crustacean shells. Polyaminoethyl modified chitin (PAECT) was synthesized using the alkali freeze-thaw method and introduced into the interface between BF and PHB to improve interfacial adhesion. The resulting chitin fibers, characterized by their intertwined helical chains, constructed a flexible mesh structure on the BF surface through an electrostatic self-assembly approach. The interwoven PAECT filaments infiltrated the dual-phase structure, acting as a promoter of interfacial compatibility, while the flexible chitin network provided a greater capacity for deformation accommodation. Consequently, both impact and tensile strength of the BF/PHB composites were notably enhanced. Additionally, this flexible layer ameliorated the thermal stability and crystalline properties of the composites. This investigation aimed to leverage the distinctive helical configuration of chitin to facilitate the advancement of bio-reinforced composites.

Advanced Functionalized Materials Based on Layer-by-Layer Assembled Natural Cellulose Nanofiber for Electrodes: A Review.

The depletion of fossil fuel resources and its impact on the environment provide a compelling motivation for the development of sustainable energy sources to meet the increasing demand for energy. Accordingly, research and development of energy storage devices have emerged as a critical area of focus. The electrode materials are critical in the electrochemical performance of energy storage devices, such as energy storage capacity and cycle life. Cellulose nanofiber (CNF) represents an important substrate with potentials in the applications of green electrode materials due to their environmental sustainability and excellent compatibility. By utilizing the layer-by layer (LbL) process, well-defined nanoscale multilayer structure is prepared on a variety of substrates. In recent years, increasing attention has focused on electrode materials produced from LbL process on CNFs to yield electrodes with exceptional properties, such as high specific surface area, outstanding electrical conductivity, superior electrochemical activity, and exceptional mechanical stability. This review provides a comprehensive overview on the development of functional CNF via the LbL approach as electrode materials.

Mussel-inspired laccase-mediated polydopamine graft onto bamboo fibers and its improvement effect on poly(3-hydroxybutyrate) based biocomposite.

Bamboo fiber (BF) reinforced polyhydroxybutyrate (PHB) has become popular in developing an eco-friendly and sustainable biocomposite, while the weak interfacial compatibility between them is a major problem to overcome. This work, inspired by mussel super adhesion, creates a facile, highly efficient, and environmentally friendly solution based on in situ laccase-catalysed dopamine polymerization under a naturally acidic environment. The result indicates that a stabilized polydopamine coating is successfully grafted onto the lignin of BF, and it also enhances the thermal stability of the BF and biocomposite. Furthermore, modification of BF via laccase-catalysed polydopamine is superior to the conventional method of polydopamine under alkaline condition, and has outstanding advantages in terms of BF integrity protection. The optimal composition of biocomposite with BF treated by polydopamine under 1 U/mL concentration of laccase shows improvement in the impact strength, tensile strength, tensile modulus, bending strength, and modulus of elastic by 33.85 %, 9.27 %, 31.74 %, 11.76 %, and 12.92 %, respectively, compared to the unmodified counterpart. This work provides an insightful understanding of the mechanism and benefits of laccase-catalysed polydopamine modification of BF in a natural environment. It contributes to the efficient and environmentally friendly utilization of polydopamine for fabricating high-performance lignocellulosic fiber reinforced biocomposites.

Properties enhancement of poly(ß-hydroxybutyrate) biocomposites by incorporating surface-modified wheat straw flour: Effect of pretreatment methods.

Poly(3-hydroxybutyrate) (PHB) biocomposites filled with wheat straw flour (WSF) were enhanced through modifying WSF surface by pretreatments, i.e., alkali solution (NaOH 1-7 wt%) dipping, (3-aminopropyl)triethoxysilane solution (APTES 0.5-2 wt%) soaking, or NaOH+APTES synergistic impregnation. The WSF was characterized by microscopy, spectroscopy, diffractometry, thermogravimetry, and wetting. Through different levels of surface etching effect or grafting functional groups, all the pretreatments removed unstable, amorphous substances on WSF, obtaining higher crystallinity by 2-12 %, degradation temperature by 57-83 °C, and lower water contact angle by 7-24°. Compression-molded WSF/PHB biocomposites were examined by mechanical tests, microscopy (fracture morphology), water absorption, calorimetry, and thermogravimetry. Above pretreatments boosted mechanical-, moisture-, and heat-resistances of composites, owing to stronger interfacial interaction of PHB with surface-modified WSF, and the improved physicochemical properties of WSF itself. Alkali treatment worked better in raising mechanical, waterproof behaviors, while silane induced higher temperature for phase transition, decomposition. Enhancement achieved by alkali+silane could surpassed both single treatments. The best outcome occurred in 3 wt% NaOH + 0.5 wt% APTES, which increased strength (flexural, tensile, and impact), modulus (flexural, tensile) by 22-40 % and 14-23 %, respectively, decreased 300 h-water absorption by 18 %, and rose melting, degradation temperatures by 2 and 23 °C, respectively, showing new potential for construction-related application.

Bioinspired polydopamine deposition and silane grafting modification of bamboo fiber for improved interface compatibility of poly (lactic acid) composites.

The surface of bamboo fiber (BF) has poor interface compatibility with the surface of the poly (lactic acid) (PLA), which compromises composite performance. In this study, a bioinspired polydopamine (PDA) function coating was constructed on a BF surface to act as a bridge to introduce an epoxy-functionalized silane layer (KH560). The results of the test confirmed that KH560 was successfully grafted onto the surface of the BF. Therefore, the flexural, tensile, and impact strength of the modified composites increased by 37.22%, 49.64%, and 26.66%, respectively, compared with that of the untreated composites. Furthermore, the PDA-KH560-modified BF enhanced the PLA composites' thermal stability. This strategy is assumed to provide a simple and green method for improving interface adhesion strength and potentials for future manufacturing of high-performance composites.

Polydopamine-treated hierarchical cellulosic fibers as versatile reinforcement of polybutylene succinate biocomposites for electromagnetic shielding.

There is a need for scalable technologies to reduce electromagnetic pollution with materials of low density and low carbon footprint. Unfortunately, environmental adaptability, economic feasibility and lightweight are factors that are still far from optimal in most electromagnetic shielding materials. Herein, we address these challenges with polybutylene succinate (PBS) reinforced with bamboo fibers functionalized with Fe3O4 nanoparticles (Fe3O4-NPs) and polypyrrole (PPy). Such hybrid system was compatibilized via polydopamine (PDA) coupling, demonstrating magnetic, dielectric and interfacial polarization losses as well as distributed reflection, yielding a shielding effectiveness of ~36.9 dB. Simultaneously, the composite displayed gains in tensile strength and modulus (by 18 and 38%, respectively) combined with improved flexural strength and modulus (by 33% and 15%, respectively). Overall, this work demonstrates a new pathway toward low cost and lightweight bio-based materials for high-performance electromagnetic shielding.

The Long-Term Mechanical Properties of BS Perpendicular to the Grain.

As a modern bamboo composite with good mechanical properties, bamboo scrimber (BS) has achieved prominence in the sustainable architecture field. When used as a structural material, it is inevitably under continual tension perpendicular to the grain, therefore its mechanical response under long-term loading is significant for structural design. In this study, tensile tests were conducted on BS under short-term and long-term loads perpendicular to the grain. The duration of load (DOL) effect on BS perpendicular to grain and its creep effect were analyzed. Compared with BS parallel to the grain, the DOL effect on BS perpendicular to the grain was less severe, and the capacity for creep resistance was weaker. The threshold stress ratio and relative creep strain of BS perpendicular to the grain were 0.40 and 0.87, respectively. It was found that the DOL models and the viscoelastic model accurately predicted the DOL factor and creep strain. This study provides a scientific reference for the safe lifetime service of BS in practical engineering.

Gluing Techniques on Bond Performance and Mechanical Properties of Cross-Laminated Timber (CLT) Made from Larix kaempferi.

Previous studies have proved that Larix kaempferi is a good material for preparing cross-laminated timber (CLT), but under bending shear stress, CLT made by Larix kaempferi is prone to the phenomenon of bonding face cracking, which seriously affects the shear performance of CLT. To solve this problem, this paper took Larix kaempferi as raw material, conducted experiments on the surface sanding conditions, gluing pressure and adhesive types of sawing timber, and explored the influence of these three factors on the bonding quality of CLT. The microscopic characteristics of the bonding layer were further studied. The results showed that for Larix kaempferi with a density of 0.68 g/cm3 used in this experiment, a high bonding pressure is required. Among the three cold curing adhesives selected in the experiment, emulsion polymer isocyanate (EPI) adhesive needs 1.5 MPa bonding pressure to ensure the bonding quality, while for polyurethane (PUR) and phenol resorcinol formaldehyde (PRF), 1.2 MPa can meet the need of adhesive pressure. This is concerned with the permeability of different adhesives under different pressures. The microscopic results of the bonding layer show that EPI adhesives have poor permeability, so it requires high bonding pressure. The influence of sanding surface of different sand-belt on block shear strength (BSS) and wood failure percentage (WFP) is not obvious, while the durability of bonding layer is better when sanding mesh number is 100. Hence, a high pressure should be used for CLT industrial production when the laminate density is higher, especially when the adhesive has poor permeability. Reasonable sanding surface treatment can be used in laminate surface treatment to improve the durability of CLT.

Reinforcement of Polylactic Acid for Fused Deposition Modeling Process with Nano Particles Treated Bamboo Powder.

The focus of this report was to understand the tensile properties and dynamic mechanical properties of bamboo powder (BP) reinforced polylactic acid (PLA) composite filaments which were treated with nano calcium carbonate (CaCO3), cellulose nanofibers (CNF), and micro-crystalline cellulose (MCC) using impregnation modification technology. The storage modulus (E') of nano CaCO3-BP/PLA, MCC-BP/PLA, and CNF-BP/PLA composite filaments increased compared with BP/PLA composite filaments before the glass transition temperature Tg. When the temperature was above Tg, the reinforcement effect of nano CaCO3, MCC, and CNF gradually became less apparent. The loss modulus (E'') and loss factor (tan δmax) of the nano CaCO3-BP/PLA, MCC-BP/PLA, and CNF-BP/PLA composite filaments was higher than that of BP/PLA composite filaments produced by the "one-step" method. The tensile strength (TS) results showed a similar trend. Compared with the control samples, the TS of nano CaCO3-BP/PLA, MCC-BP/PLA, and CNF-BP/PLA composite filaments produced by the "one-step" method (and the "two-step" method) increased by 40.33% (and 10.10%), 32.35% (and -8.61%), and 12.32% (and -12.85%), respectively. The TS of nano CaCO3-BP/PLA, MCC-BP/PLA, and CNF-BP/PLA composite filaments produced by the "one-step" method was slightly higher than those produced by the "two-step" method. The elongation at break (EAB) of BP/PLA composite filaments was higher than that of BP/PLA samples treated with nano CaCO3, MCC, or CNF. The PLA and modified BP were readily accessible through a simple mixing process. The rheological investigation of such mixtures showed that nano CaCO3, CNF, and MCC have different effects on the processability and rheological properties of composites.

Physicochemical properties of biochar derived from anaerobically digested dairy manure.

Biochar was produced from anaerobically digested dairy manure under different processing temperatures (300, 600 and 1000 °C). The process could transform the biomass waste to high-value-added biochar products in high efficiency as well as reduce the manure biological pollution to the environment. By the results of thermogravimetric analysis (TGA) two kinetic models (FWO and Starink) were used to evaluate the activation energy. The biochar was studied for its surface area and pore size, chemical functionality, and crystalline structure by BET analysis, Fourier transform infrared (FTIR) spectroscopy, and X-ray diffraction (XRD). More porous and channel structures were observed under higher temperature and inert gas atmosphere, as characterized by scanning electron microscopy (SEM). The biochar with tunable physicochemical properties that was produced under different temperatures may be used for soil amendment or other fields.

The Effect of Alkali Treatment on Properties of Dopamine Modification of Bamboo Fiber/Polylactic Acid Composites.

In this study, a synergistic treatment including dopamine (DA) modification and alkali pretreatment on bamboo fiber (BF) was used as reinforcement in a polylactic acid (PLA) matrix to improve the mechanical and thermal properties of BF/PLA composites. The effects of the sodium hydroxide loading rate on the performance of mussel-inspired dopamine-modified bamboo fiber and the BF/PLA composites were evaluated using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), mechanical testing (examining flexural, tensile, and impact properties), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). Analysis of the composites suggested that the optimal condition was treatment with a 4 wt % solution of NaOH and a 1 wt % concentration of dopamine. Compared with the untreated bamboo fiber/polylactic acid composites, the synergistic treatment improved the thermal properties and mechanical properties; flexural, tensile, and impact strengths increased by 16.1%, 34.4%, and 3.7%, respectively. It was further verified that appropriate alkali treatment was a promising approach in promoting the effect of dopamine-modified coating while maintaining the crystal structure of the cellulose.

Mussel-Inspired Polydopamine as a Green, Efficient, and Stable Platform to Functionalize Bamboo Fiber with Amino-Terminated Alkyl for High Performance Poly(butylene succinate) Composites.

A new and eco-friendly mussel-inspired surface modification pathway for bamboo fiber (BF) is presented in this study. The self-assembly polydopamine (PDA) coating can firmly adhere on BF surface, which also serves as a bridge to graft octadecylamine (ODA) for hydrophobic surface preparation. The as-formed PDA/ODA hybrid layer could supply abundant hydrophobic long-chain alkyls groups and generated a marked increase in BF surface roughness and a marked decrease in surface free energy. These changes provided advantages to improve fiber⁻matrix interfacial adhesion and wettability. Consequently, high performance was achieved by incorporating the hybrid modified BF into the polybutylene succinate (PBS) matrix. The resultant composite exhibited excellent mechanical properties, particularly tensile strength, which markedly increased by 77.2%. Meanwhile, considerable high water resistance with an absorption rate as low as 5.63% was also achieved. The gratifying macro-performance was primarily attributed to the excellent interfacial adhesion attained by hydrogen bonding and physical intertwining between the PDA/ODA coating on the BF and the PBS matrix, which was further determined by fracture morphology observations and dynamic mechanical analysis. Owing to the superior adhesive capacity of PDA, this mussel-inspired surface modification method may result in wide-ranging applications in polymer composites and be adapted to all natural fibers.

Interfacial Properties of Bamboo Fiber-Reinforced High-Density Polyethylene Composites by Different Methods for Adding Nano Calcium Carbonate.

The focus of this study was to observe the effect of nano calcium carbonate (CaCO3) modification methods on bamboo fiber (BF) used in BF-reinforced high-density polyethylene (HDPE) composites manufactured by extrusion molding. Two methods were used to introduce the nano CaCO3 into the BF for modification; the first was blending modification (BM) and the second was impregnation modification (IM). In order to determine the effects of the modification methods, the water absorption, surface free energy and interfacial properties of the unmodified composites were compared to those of the composites made from the two modification methods. The results revealed that the percentage increase in the weight of the composite treated by nano CaCO3 decreased and that of the IMBF/HDPE composite was the lowest over the seven months of time. The results obtained by the acid-base model according to the Lewis and Owens-Wendt- Rabel-Kaelble (OWRK) equations indicated that the surface energy of the composites was between 40 and 50 mJ/m². When compared to the control sample, the maximum storage modulus (E'max) of the BMBF/HDPE and IMBF/HDPE composites increased 1.43- and 1.53-fold, respectively. The values of the phase-to-phase interaction parameter B and the k value of the modified composites were higher than those of the unmodified composites, while the apparent activation energy Ea and interface parameter A were lower in the modified composites. It can be concluded that nano CaCO3 had an effect on the interfacial properties of BF-reinforced HDPE composites, and the interface bonding between IMBF and HDPE was greatest among the composites.

An Investigation on Formaldehyde Emission Characteristics of Wood Building Materials in Chinese Standard Tests: Product Emission Levels, Measurement Uncertainties, and Data Correlations between Various Tests.

As a large producer and consumer of wood building materials, China suffers product formaldehyde emissions (PFE) but lacks systematic investigations and basic data on Chinese standard emission tests (CST), so this paper presented a first effort on this issue. The PFE of fiberboards, particleboards, blockboards, floorings, and parquets manufactured in Beijing region were characterized by the perforator extraction method (PE), 9-11 L and 40 L desiccator methods (D9, D40), and environmental chamber method (EC) of the Chinese national standard GB 18580; based on statistics of PFE data, measurement uncertainties in CST were evaluated by the Monte Carlo method; moreover, PFE data correlations between tests were established. Results showed: (1) Different tests may give slightly different evaluations on product quality. In PE and D9 tests, blockboards and parquets reached E1 grade for PFE, which can be directly used in indoor environment; but in D40 and EC tests, floorings and parquets achieved E1. (2) In multiple tests, PFE data characterized by PE, D9, and D40 complied with Gaussian distributions, while those characterized by EC followed log-normal distributions. Uncertainties in CST were overall low, with uncertainties for 20 material-method combinations all below 7.5%, and the average uncertainty for each method under 3.5%, thus being acceptable in engineering application. A more complicated material structure and a larger test scale caused higher uncertainties. (3) Conventional linear models applied to correlating PFE values between PE, D9, and EC, with R2 all over 0.840, while novel logarithmic (exponential) models can work better for correlations involving D40, with R2 all beyond 0.901. This research preliminarily demonstrated the effectiveness of CST, where results for D40 presented greater similarities to EC-the currently most reliable test for PFE, thus highlighting the potential of Chinese D40 as a more practical approach in production control and risk assessment.