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The application of light weight particleboard in furniture industry becomes more inevitable because of the requirement to facilitate transportation and assembly by the customer. Herein, a novel method for the fabrication of foaming particleboard was proposed, which is achieved by adding azodicarbonamide (AC) foaming agent into the formulation that consist of oven-dry poplar ( Populus alba ) particles (with the moisture content about 4%) and phenol formaldehyde resin (PF resin) (solid content of 48%). In this study, the effects of AC foaming agent and adhesive contents incorporation and its content on mechanical, physical and chemical properties of particleboards were investigated. The results showed that the addition of AC foaming agent played a critical role in properties of particleboard and the optimal particleboard performance was achieved at the particleboard density of 0.6 g/cm 3 , the PF resin amount of 12%, and the AC foaming agent amount of 1%. Furthermore, the pores appeared on the particle surface were the products of the radical pyrolysis of the foaming agent, which has been proved by the FTIR results and the pores also affect the properties of the particleboards.

Highlights The advantages of biomass materials for electromagnetic interference (EMI) shielding are analyzed, the mechanism of EMI shielding is summarized, and the factors affecting EMI shielding are analyzed systematically. Various biomass materials (wood, bamboo, lignin, cellulose) were modified to obtain unique structures and improve EMI shielding performance. The problems encountered in the application of biomass materials for EMI shielding are summarized, and the potential development and application in the future are prospected. Research efforts on electromagnetic interference (EMI) shielding materials have begun to converge on green and sustainable biomass materials. These materials offer numerous advantages such as being lightweight, porous, and hierarchical. Due to their porous nature, interfacial compatibility, and electrical conductivity, biomass materials hold significant potential as EMI shielding materials. Despite concerted efforts on the EMI shielding of biomass materials have been reported, this research area is still relatively new compared to traditional EMI shielding materials. In particular, a more comprehensive study and summary of the factors influencing biomass EMI shielding materials including the pore structure adjustment, preparation process, and micro-control would be valuable. The preparation methods and characteristics of wood, bamboo, cellulose and lignin in EMI shielding field are critically discussed in this paper, and similar biomass EMI materials are summarized and analyzed. The composite methods and fillers of various biomass materials were reviewed. this paper also highlights the mechanism of EMI shielding as well as existing prospects and challenges for development trends in this field.

Wood polymer composites (WPCs) with core–shell structure reinforced with barite (BA)-filled high-density polyethylene (HDPE) shell layer were successfully fabricated, and their thermal expansion and mechanical properties were thoroughly analyzed. The incorporation of BA improved the flexural properties and reduced the impact strength and linear coefficients of thermal expansion (LCTEs) of the resulting composites, in comparison with unmodified HDPE. The use of relatively rigid pure HDPE with high LCTE values reduced the overall thermal stability and modulus of the WPCs. Both flexural properties and thermal expansion were significantly enhanced for BA-filled HDPE shells compared to the unmodified material. Thus, the novel core–shell layer showed a well-balanced performance. The employment of BA HDPE or unmodified HDPE layers as the shell for the WPC core significantly enhanced the impact strength of the co-extruded WPCs. The tensile modulus for BA-filled composite was predicted by the PPA-based model.

Studies on the influence of drying processes on cellulose nanofiber (CNF) aerogel performance has always been a great challenge. In this study, CNF aerogels were prepared via two different drying techniques. The CNF solution was prepared via existing chemical methods, and the resultant aerogel was fabricated through supercritical CO2 drying and liquid nitrogen freeze-drying techniques. The microstructure, shrinkage, specific surface area, pore volume, density, compression strength, and isothermal desorption curves of CNF aerogel were characterized. The aerogel obtained from the liquid nitrogen freeze-drying method showed a relatively higher shrinkage, higher compression strength, lower specific surface area, higher pore volume, and higher density. The N2 adsorption capacity and pore diameter of the aerogel obtained via the liquid nitrogen freeze-drying method were lower than the aerogel that underwent supercritical CO2 drying. However, the structures of CNF aerogels obtained from these two drying methods were extremely similar.

Talc is a popular filler for the fabrication of plastic composites. The presence of talc helps improve mechanical, thermal, and flame resistance properties of the composite. In this work, we report the influence of a talc-filled plastic shell layer on thermal stability and fire flammability of the core-shell structured wood high-density polyethylene (HDPE) composites manufactured through coextrusion. The result showed that morphological analysis of the char layer after combustion confirmed the formation of a continuous surface char layer with talc addition in the composites, helping block fire penetration and enhance overall fire resistance of the composites. The shell thickness averaged at 1.0±0.2 mm, which represents a fair thick shell over a 10 mm thick WPC core layer. The surface of regular wood-filled HDPE showed large cracks, allowing more rapid fire penetration and reducing its fire resistance. At 800°C, average residual weight for all composite was 21.5±13.8%, most of which was attributed to the inorganic nonvolatile talc components. With the increase of talc level, THR values of coextruded WPC decreased from 302.47 MJ/m2 (5 wt% of talc) to 262.96 kW/m2 (50 wt% of talc). When talc content in the shell layer was less than 25 wt%, the flame resistance properties were slightly enhanced compared with the composites containing unmodified HDPE shells. When talc content in the shell exceeded 25 wt%, the composite’s total heat release and its rate substantially decreased.

Biochar is a byproduct generated from the hydrothermal liquefaction of biomass, such as corn stover, in an anaerobic environment. This work aims to convert biochar into a value-added product of carbon nanofibrous felt. First, the biochar-containing precursor membrane was prepared from simultaneous electrospinning and electrospraying. After thermal stabilization in air and carbonization in argon, the obtained precursor membrane was converted into a mechanically flexible and robust carbon nanofibrous felt. Electrochemical results revealed that the biochar-derived carbon nanofibrous felt might be a good candidate as a supercapacitor electrode with a good rate capability and high kinetic performance.

Reinforcing effect of hybrid filler including wheat straw (WS) and inorganic filler (heavy calcium carbonate, silicon dioxide, and fly ash) in recycled polypropylene (R-PP) has been investigated. The effects of individual filler (WS) and combined fillers (WS and inorganic filler) on morphological, mechanical, and thermal expansion and water absorption properties of hybrid composites were investigated. The flexural modulus and flexural strength were both reduced when reinforced with three kinds of inorganic fillers, respectively, which was possibly due to the poor interphase adhesion as observed in SEM. The high surface energy of heavy calcium carbonate due to its high acidic character provides an opportunity of better PP-heavy calcium carbonate interfacial interactions compared to PP-straw, PP-fly ash, and PP-SiO2 interface. The water absorption at saturation increased markedly by introduction of WS in it. The hybrid composites from WS and inorganic fillers showed better water absorption compared to those WS/PP composites. The thermal expansion of composites decreased with the increase of WS loading. Heavy calcium and SiO2 can obviously reduce the LCTE value of composite. At the 25% inorganic filler content, composites had the smallest LCTE values.

Thermogravimetric analysis (TGA) was used for the observation of the pyrolysis kinetics characteristics of high density polyethylene (HDPE)-based composites enhanced by a variety of basalt fibers (BFs) and wood flour (WF). The improved Coats-Redfern (C-R), Flynn-Wall-Ozawa (F-W-O), Friedman, and Kissinger methods were utilized to ascertain the specific apparent activation energy (Ea) of each component and composite material. The results indicate that BFs do not decompose under 800 °C, while the pyrolysis of WF and waste HDPE showed two significant weight loss zones (250–380 °C and 430–530 °C), relative to cellulose/hemicellulose and HDPE thermal degradation, respectively. The average Ea of WF/BF/HDPE composites over the entire pyrolysis process obtained by the modified C-R method fluctuated in a range of 145–204 kJ/mol and increased with the BF content, which was higher than that of WPC (115–171 kJ/mol). The value of Ea computed by the F-W-O method was significantly lower than that computed with the improved C-R method, which could validate the reliability of two methods by comparing with the literature. The Friedman and Kissinger methods were not applicable to this composite material reinforced by mixed fillers, so the obtained Ea values were quite different from the previous two methods. The changes in Ea showed that the addition of BFs could improve the average Ea and further enhance the thermal stability and flame resistance of the composites.

Basalt fiber can be used as a reinforcing phase to improve the mechanical properties of wood thermoplastic composites. The purpose of this study was to use differential scanning calorimetry to study the effect of the addition of basalt fiber and wood flour on the non-isothermal crystallization kinetics of high-density polyethylene (HDPE)-based composites. The Avrami method and Avrami–Ozawa method were adopted to describe the non-isothermal crystallization process, and Gaussian model was used to calculate the surface activation energy. This study showed that the addition of basalt fiber and wood flour significantly changed the crystallinity of wood flour/high-density polyethylene (HDPE)/basalt fiber three-phase composites. The apparent activation energy of the three-phase composites was calculated using Gaussian multi-peak simulations, and the trend of the conversion rate was modeled. In addition, basalt fiber and wood flour, as nucleating agents, had the ability to accelerate the crystallization of wood flour/high-density polyethylene (HDPE)/basalt fiber three-phase composites without changing the crystallization mechanism of these composite materials.

The effect of individual and combined particleboard dust (PB dust) and basalt fibers (BFs) on mechanical and thermal expansion performance of the filled virgin and recycled high density polyethylene (HDPE) composites was studied. It was shown that the use of PB dust had a positive effect on improving mechanical properties and on reducing linear coefficient of thermal expansion (LCTE) values of filled composites, because the adhesive of the particle board held the wheat straw fibers into bundles, which made PB dust have a certain aspect ratio and high strength. Compared with the commonly used commercial WPC products, the flexural strength of PB dust/VHDPE, PB dust/RHDPE, and PB dust/VHDPE/RHDEPE at 40 wt% loading level increased by 79.9%, 41.5%, and 53.9%, respectively. When 40 wt% PB dust was added, the crystallization degree of the composites based on three matrixes decreased to 72.5%, 45.7%, and 64.1%, respectively. The use of PB dust can help lower the composite costs and increase its recyclability. Mechanical properties and LCTE values of composites with combined BF and PB dust fillers varied with PB dust and BF ratio at a given total filler loading level. As the BF portion of the PB dust/BF fillers increased, the LCTE values decreased markedly, which was suggested to be able to achieve a desirable dimensional stability for composites. The process provides a useful route to further recycling of agricultural wastes.