Green, recyclable and high latent heat form-stable phase change composites supported by cellulose nanofibers for thermal energy management.

Efficiently addressing the challenge of leakage is crucial in the advancement of solid-liquid phase change thermal storage composite materials; however, numerous existing preparation methods often entail complexity and high energy consumption. Herein, a straightforward blending approach was adopted to fabricate stable phase change nanocomposites capitalizing on the interaction between TEMPO-oxidized cellulose nanofibers (TOCNF) and polyethylene glycol (PEG) molecules. By adjusting the ratio of TOCNF to PEG and the molecular weights of PEG, TOCNF/PEG phase change composites (TPCC) with customizable phase transition temperature (40.3-59.1 °C) and high phase transition latent heat (126.3-172.1 J/g) were obtained. The TPCC of high-loaded PEG (80-95 wt%) ensured a leakage rate of less than 1.7 wt% after 100 heating-cooling cycles. Moreover, TPCC exhibits excellent optical properties with a transmittance of over 90 % at room temperature and up to 96 % after heating. The thermal response analysis of TPCC demonstrates exceptional thermal-induced flexibility and good thermal stability, as well as recyclability and reshaping ability. This study may inspire others to design bio-based phase change composites with potential applications in thermal energy storage and management of smart-energy buildings, photothermal response devices, and waste heat-generating electronics.

Facile Design of Flexible, Strong, and Highly Conductive MXene-Based Composite Films for Multifunctional Applications.

Strong, conductive, and flexible materials with improving ion accessibility have attracted significant attention in electromagnetic interference (EMI) and foldable wearable electronics. However, it still remains a great challenge to realize high performance at the same time for both properties. Herein, a microscale structural design combined with nanostructures strategy to fabricate TOCNF(F)/Ti3 C2 Tx (M)@AgNW(A) composite films via a facile vacuum filtration process followed by hot pressing (TOCNF = TEMPO-oxidized cellulose nanofibrils, NW = nanowires) is described. The comparison reveals that different microscale structures can significantly influence the properties of thin films, especially their electrochemical properties. Impressively, the ultrathin MA/F/MA film with enhanced layer in the middle exhibits an excellent tensile strength of 107.9 MPa, an outstanding electrical conductivity of 8.4 × 106 S m-1 , and a high SSE/t of 26 014.52 dB cm2 g-1 . The assembled asymmetric MA/F/MA//TOCNF@CNT (carbon nanotubes) supercapacitor leads to a significantly high areal energy density of 49.08 µWh cm-2 at a power density of 777.26 µW cm-2 . This study proposes an effective strategy to circumvent the trade-off between EMI performance and electrochemical properties, providing an inspiration for the fabrication of multifunctional films for a wide variety of applications in aerospace, national defense, precision instruments, and next-generation electronics.

Effects of different types of flame-retardant treatment on the flame performance of polyurethane/wood-flour composites.

To improve the flammability of foamed polyurethane/wood-flour composites (FWPC), ammonium polyphosphate (APP) was used as a flame retardant to modified FWPC. The effects of different flame treatment processes on flame performance, smoke suppression, thermal property, and surface micrographs of flame retardant FWPC were investigated. The results showed that FWPC with the addition or impregnation process both improved the combustion behaviors. Compared with the addition process, FWPC-impregnation (FWPC-I) had a lower total heat release (THR), lower peak heat release rate (PHRR), prolonged time to ignition (TTI), more residues, and better combustion safety. FWPC-I had the highest residual carbon rate reaching 39.98%. A flame-retardant layer containing the P-O group was formed in the residual carbon of FWPC-I. Although APP had negative effects on the physical properties of FWPC, it was an effective flame-retardant ability for foamed polyurethane/wood-flour composites.

Chemical Structure and Microscopic Morphology Changes of Dyed Wood Holocellulose Exposed to UV Irradiation.

Dyed wood is prone to photoaging when exposed to UV irradiation which decreases its decorative effect and service life. Holocellulose, as the main component of dyed wood, has a photodegradation behavior which is still unclear. To investigate the effect of UV irradiation on chemical structure and microscopic morphology changes of dyed wood holocellulose, Maple birch (Betulacostata Trautv) dyed wood and holocellulose were exposed to UV accelerated aging treatment; the photoresponsivity includes crystallization, chemical structure, thermal stability, and microstructure were studied. Results showed that UV radiation has no significant effect on the lattice structure of dyed wood fibers. The wood crystal zone diffraction 2θ and layer spacing was basically unchanged. With the UV radiation time extension, the relative crystallinity of dyed wood and holocellulose showed a trend of increasing first and then decreasing, but the overall change was not significant. The relative crystallinity change range of the dyed wood was not more than 3%, and the dyed holocellulose was not more than 5%. UV radiation caused the molecular chain chemical bond in the non-crystalline region of dyed holocellulose to break, the fiber underwent photooxidation degradation, and the surface photoetching feature was prominent. Wood fiber morphology was damaged and destroyed, finally leading to the degradation and corrosion of the dyed wood. Studying the photodegradation of holocellulose is helpful to understand the photochromic mechanism of dyed wood, and, further, to improve its weather resistance.

The Facile and Efficient Fabrication of Rice Husk/poly (lactic acid) Foam Composites by Coordinated the Interface Combination and Bubble Hole Structure.

The possibility of agricultural-forestry waste (rice husks) and biodegradable plastics (poly(lactic acid)) being used to produce ecologically friendly foam composite was discussed in this work. The effects of different material parameters (the dosage of PLA-g-MAH, type and content of chemical foaming agent) on the microstructure and physical properties of composite were investigated. PLA-g-MAH promoted the chemical grafting between cellulose and PLA, and made the structure denser, thus improving the interface compatibility of the two phases and resulting in good thermal stability, high tensile strength (6.99 MPa) and bending strength (28.85 MPa) of composites. Furthermore, the properties of rice husk/PLA foam composite prepared by two kinds of foaming agents (endothermic and exothermic) were characterized. The addition of fiber limited the growth of pores, which provided better dimensional stability and narrower pore size distribution, made the interface of the composite bond tightly. And the bubble can prevent crack propagation and improve the mechanical properties of the composite. The bending strength and tensile strength of composite were 37.36 MPa and 25.32 MPa, which increased by 28.35 % and 23.27 %, respectively. Therefore, the composite prepared by using agricultural-forestry wastes and poly(lactic acid) possess acceptable mechanical properties, thermal stability and water resistance, expanding the scope of application.

Ultrathin cellulose nanofiber/carbon nanotube/Ti3C2Tx film for electromagnetic interference shielding and energy storage.

Controllable fabrication of lightweight, highly conductive, and flexible films is important to simultaneously achieve excellent electromagnetic interference (EMI) shielding and high-rate energy storage. Herein, ultrathin, flexible, and conductive (up to 365,000 ± 5000 S m-1) TOCNFs/CNT/Ti3C2Tx hybrid films were fabricated by a facile vacuum-filtration. The obtained films with 60 wt% Ti3C2Tx content exhibited a high specific EMI SE of 9316.4 ± 205.32 dB cm2 g-1, which was comparable to most of the other carbon- and MXene- based materials synthesized by complex steps. Additionally, the porous structure contributed to exposing more active sites and providing efficient transport of electrolyte ions. Consequently, the hybrid films showed a high areal capacitance and high specific capacitance of 537 mF cm-2 and 279.7 F g-1 at 0.3 mA cm-2, respectively, together with impressive stability of 93.1% after 8000 cycles. This work provides an effective strategy to synthesize high-performance conductive films for applications in wearable or portable electronic devices.

Soybean Meal-Based Wood Adhesive Enhanced by Phenol Hydroxymethylated Tannin Oligomer for Exterior Use.

Bio-based adhesives have low water resistance and they are less durable than synthetic adhesives, which limits their exterior applications. In this study, a bio adhesive was developed from soybean meal and larch tannin that was designed for exterior use. Phenol hydroxymethylated tannin oligomer (PHTO) was synthesized and then mixed with soybean meal flour in order to obtain a soybean meal-based adhesive (SPA). The results showed that the moisture absorption rate, residual rate, and solid content of SPA with 10 wt % PHTO (mass ratio with respect to the entire adhesive) were improved by 22.8%, 11.6%, and 6.8%, respectively, as compared with that of pure SPA. The wet shear strength of plywood with SPA with 10 wt % PHTO (boiling in 100 °C water for 3 h) was 1.04 MPa when compared with 0 MPa of pure SPA. This met the bond strength requirement of exterior-use plywood (GB/T 9846.3-2004). This improved adhesive performance was mainly due to the formation of a crosslinked structure between the PHTO and the protein and also PHTO self-crosslinking. The formaldehyde emission of the resulting plywood was the same as that of solid wood. The PHTO-modified SPA can potentially extend the applications of SPAs from interior to exterior plywood.

Improving Mildew Resistance of Soy Meal by Nano-Ag/TiO2, Zinc Pyrithione and 4-Cumylphenol.

As a byproduct from the soybean oil industry, soy meal can be reproduced into value-added products to replace formaldehyde as a plywood adhesive. However, the use of soy meal has been limited by its poor antifungal and antiseptic properties. In this work, three kinds of material, namely nano-Ag/TiO2, zinc pyrithione, and 4-cumylphenol were applied to enhance the mildew resistance of soy meal via breakdown of the cellular structure of mildew. The fungi and mold resistance, morphology, thermal properties, and mechanism of the modified soy meal were evaluated. The success of the antifungal and antiseptic properties was confirmed by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy. The results indicated that all three kinds of material improved the fungi and mold resistance of soy meal, and sample B, which was modified with a compound of nano-Ag/TiO2 and zinc pyrithione, was the effective antifungal raw material for the soy-based adhesives. FTIR indicated that the great improvement of antifungal properties of soy meal modified with 4-cumylphenol might be caused by the reaction between COO- groups of soy protein. This research can help understand the effects of the chemical modification of nano-Ag/TiO2, zinc pyrithione, and 4-cumylphenol on soy meal, and the modified soy meal exhibits potential for utilization in the plywood adhesive industry.

Improvement of Rice Husk/HDPE Bio-Composites Interfacial properties by Silane Coupling Agent and Compatibilizer Complementary Modification.

Composites using agricultural and forestry residues as raw materials with potentially high-performance, multifunctional and biodegradable ecological advantages, are viewed as very promising for new-generation lightweight and low-cost bio-based sustainable building materials. At present, the research on wood-plastic composite materials is relatively mature. However, it is still a challenge to effectively use other biomass and improve the interface of the high-polymer compound system. Herein, we proposed a simple and effective method to enhance the interfacial adhesion properties of rice husk fibre and High Density Polyethylene (HDPE) composites by the silane coupling agent KH-550 and compatibilizer Maleic anhydride grafted polyethylene (MAPE) with complementary modification. It was found that the coupling agent KH-550 cross-linked with the hydroxyl group on the husk fibre surface and solidified with the high polymer by -NH-, -C=O- functional group generation. Compatibilizer MAPE strengthened the two phases by covalently bonding with an ester linkage and lowered the roughness of the cross-section of the composites. Meanwhile the modification enhanced the dispersibility, and mechanical properties of the husk-high polymer compound system, the bending and flexural strength were improved by 11.5% and 28.9% with KH-550, and MAPE added, respectively. The flexural strength of the composites increased by 40.7% after complementary modification. Furthermore, the complementary modification treatment reduced the hydrophilic hydroxyl groups and increased the molecular chain to improve the water-resistance, elastic modulus and toughness of the composite. This study prepared a bio-composite, which is expected to expand the use of agricultural and forestry residues as an extension of wood-plastic composites.

Preparation and Characterization of Dyed Corn Straw by Acid Red GR and Active Brilliant X-3B Dyes.

Corn straw is a kind of biomass material with huge reserves, which can be used in plate processing, handicraft manufacturing, indoor decoration, and other fields. To investigate the dyeing mechanism of corn straw with different dyes, corn straw was pretreated and dyed with Acid Red GR and Brilliant Red X-3B. The dyeing properties and light resistance of the two dyes were analyzed by dyeing rate, photochromaticity, FTIR, SEM, and water-washing firmness. The results showed that the structure and stability of the dyes were the main factors which influenced fading. A bleaching pretreatment could remove the waxiness of the corn straw epidermis and increase the porosity on the surface of the straw, which accelerated the photochromic coloring of the corn straw skin. The corn straw dyed with both dyes had good light resistance, but the straw dyed with Reactive Brilliant Red X-3B had higher dyeing rate, brighter color, and higher photochromaticity than the straw dyed with Acid Red GR. FTIR and water-washing firmness showed that Acid Red GR mainly bound to lignin, while Reactive Brilliant Red X-3B mainly bound to cellulose, hemicellulose, and lignin in corn straw through covalent bonds, which increased the coloring rate.

Preparation and Characterization of Epoxy Resin Cross-Linked with High Wood Pyrolysis Bio-Oil Substitution by Acetone Pretreatment.

The use of cost effective solvents may be necessary to store wood pyrolysis bio-oil in order to stabilize and control its viscosity, but this part of the production system has not been explored. Conversely, any rise in viscosity during storage, that would occur without a solvent, will add variance to the production system and render it cost ineffective. The purpose of this study was to modify bio-oil with a common solvent and then react the bio-oil with an epoxy for bonding of wood without any loss in properties. The acetone pretreatment of the bio-oil/epoxy mixture was found to improve the cross-linking potential and substitution rate based on its mechanical, chemical, and thermal properties. Specifically, the bio-oil was blended with epoxy resin at weight ratios ranging from 2:1 to 1:5 and were then cured. A higher bio-oil substitution rate was found to lower the shear bond strength of the bio-oil/epoxy resins. However, when an acetone pretreatment was used, it was possible to replace the bio-oil by as much as 50% while satisfying usage requirements. Extraction of the bio-oil/epoxy mixture with four different solvents demonstrated an improvement in cross-linking after acetone pretreatment. ATR-FTIR analysis confirmed that the polymer achieved a higher cross-linked structure. DSC and TGA curves showed improved thermal stability with the addition of the acetone pretreatment. UV-Vis characterization showed that some functional groups of the bio-oil to epoxy system were unreacted. Finally, when the resin mixture was utilized to bond wood, the acetone pretreatment coupled with precise tuning of the bio-oil:epoxy ratio was an effective method to control cross-linking while ensuring acceptable bond strength.

[Changes in chemistry component structure and microstructure characterization of acetylated wood before and after UV radiation].

The poplar powder was acetylated with different duration as sample, processed ray radiation by using ultraviolet test box, contrasting the influences to lightfastness of wood with different acetylation degree, analyzing changing rules of characteristic peaks' intensity which belonged to the chemistry components of samples based on FTIR spectra, and the relationship between duration of acetylation and changes of chemistry components was established, The results showed that: Before UV radiation, the characteristic peaks' intensity of acetylated poplar powder at 1 739 cm(-1) which belonged to C = O in saturated esters compounds and 1 385 cm(-1) which belonged to C-H in acetate were higher than untreated ones', the poplar powder with 40 min's acetylation has the highest characteristic peaks' intensity, highest weight gain rate, remarkable acetylation effect; After UV radiation, characteristic peaks' intensity of Benzene at 1 504 cm(-1) which belonged to lignin of poplar powder was obviously higher than untreated ones', and characteristic peaks' intensity of poplar powder with 40 min's acetylation was the highest, this showed that acetylation could effectively reduce the light degradation of wood chemistry components, in order to improve the lightfastness, especially the poplar powder with 40 min's acetylation; SEM photos showed that, the fibrous surface of acetylated poplar powder was more smooth and had more narrow particle size than untreated ones', so acetylation can effectively improve the stability of wood.