Wood Composites Research Articles

Color and Chemical Composition of Timber Woods (Daniellia oliveri, Isoberlinia doka, Khaya senegalensis, and Pterocarpus erinaceus) from Different Locations in Southern Mali

Wood characteristics and properties are related to various factors connected to the biochemical processes that occur in the tree during wood formation, but also, to the interactions with the environmental conditions at the tree growing location. In addition to climatic factors, several investigations drew attention to the significance of the influence of other environmental parameters at the tree growing location. In this perspective, this work aimed to characterize the variation in color and chemical composition of timber wood from different locations in southern Mali, of trees growing under the same climatic conditions. To do so, a total of 68 grounded wood samples, from 4 timber wood species (Daniellia oliveri, Isoberlinia doka, Khaya senegalensis, and Pterocarpus erinaceus), were analyzed using CIELab color space and FTIR-ATR. Overall, the results indicated that the variation in wood color and chemical properties can be related to the local environmental conditions. Pterocarpus erinaceus presented significant differences between samples from the three areas according to the highest number of variables (color parameters, molecular composition determined by FTIR-ATR spectroscopy, and FTIR-ATR ratios). Daniellia oliveri and Khaya senegalensis, however, showed significant differences between areas of provenance for a lower number of variables. Isoberlinia doka, for its part, showed no significant differences and seems to be less sensitive to environmental factors. Furthermore, the results revealed that important differences exist between wood samples from Kati and Kéniéba.

Element composition of extracts of common spruce cones

Trace elements are an integral part of any plant and animal organism.The pharmacological effect of herbal raw materials is due not only to the main active substance, but also to the chemical elements that make up herbal medicinal preparations. Previously, studies were carried out on the wood composition, as well as the polysaccharide complex from spruce cones [1], [2]. The object of this study are common spruce cones harvested on the territory of the Ilyinsky district, Perm Region. The determination of the qualitative and quantitative composition of elements in extracts of common spruce cones was carried out on the X-ray fluorescence QUANT’X spectrometer from Thermo Scientific. The results obtained by the authors demonstrate the content of microelements and ultramicroelements of a fractional extract from the raw material of the studied plant.

Influence of wood pretreatment, hardwood and softwood extractives on the compressive strength of fly ash-based geopolymer composite

This paper investigated the specific compressive strength (specific strength) of fly ash-based geopolymer composites with four hardwood extractives and two softwood extractives, as well as specific wood extractives. Additionally, the effect of the portion of pine wood (i.e., sapwood and heartwood) and wood pretreatment with NaOH were considered. Geopolymer paste (with extractives) and geopolymer wood composites (GWCs) were cured at 60 °C for 24 h. The samples were stored in a climate chamber (20 °C, 65% RH) for 7 days before finally testing under compression. From the results, the specific strengths of geopolymers with hardwood extractives were not significantly affected. However, geopolymers containing pine extractives showed the most significant reduction in specific strength. There were no significant differences in the specific strengths of geopolymers containing polyphenols and resin acid. Generally, geopolymers containing fatty acids recorded the lowest specific strengths. There was no difference between the GWCs with untreated sapwood and heartwood. However, the wood pretreatment led to a 21% and 10% increase in the specific strengths of GWCs with sapwood and heartwood, respectively. The findings of this study form the basis for improved GWCs production and a wide range of applications for green composite materials.

Comparative Study of Atmosphere Effect on Wood Torrefaction

Climate change, biomass utilization, and bioenergy recovery are among the biggest current global concerns. Wood is considered an environmentally benign material. Nevertheless, it must be processed for desired applications. Upon thermal treatment ranging from 180 °C to 280 °C, under low oxygen concentrations, wood becomes a material with improved dimensional stability, resistance to fungal attacks, grindability, hydrophobicity, and storage stability. Several strategies for wood treatment have been investigated over the course of the past decades, including the use of steam, nitrogen, smoke, vacuum, water, and hot oil. The goal of this work is to investigate the influence of pressure and atmosphere on the torrefaction of poplar. Through a systematic analysis of poplar wood samples treated under reduced pressures and different atmospheres, while keeping the same heating profile, it was possible to establish that changes observed for mass loss, color change, wood composition (via TGA/DTG analysis), functional groups (via FTIR), elemental analysis, and X-ray diffractograms relate directly to known reaction pathways occurring during torrefaction. Changes observed under reduced pressures have been associated with the relative concentration of oxygen in the reaction atmosphere and to the reduced diffusion times experienced by reactive by-products during the treatment. Conversely, extended diffusion times resulted in more significant changes for reactions carried out under N2, water vapor, and air.

Irrigation with primary wastewater alters wood anatomy and composition in willow Salix miyabeana SX67.

Traditional treatment of wastewaters is a burden for local governments. Using short rotation coppice willow (SRCW) as vegetal filter has several environmental and economic benefits. Here, we investigated the effect of primary wastewater irrigation on wood structure and composition of the willow cultivar Salix miyabeana 'SX67' following two years of growth. Compared to unirrigated plants (UI), stem sections of plants irrigated with primary wastewater (WWD) showed an unexpected decrease of hydraulic conductance (KS) associated with a decrease in vessel density but not vessel diameter. The majority (86%) of vessels had diameters range groups [20-30[, [30-40[and [40-50[µm and contributed to > 75% of theoretical KS, while the group class [50-60[µm (less than 10% of vessels) still accounted for > 20% of total KS regardless irrigation treatments. WWD significantly alters the chemical composition of wood with an increase of glucan content by 9 to 16.4% and a decrease of extractives by 35.3 to 36.4% when compared to UI or to plants irrigated with potable water (PW). The fertigation did also increase the proportion of the tension wood which highly correlated with glucan content. In the context of energetic transition and mitigation of climate change, such results are of high interest since WWD effectively permit the phytofiltration of large amounts of organic contaminated effluents without impairing SRCW physiology.

Glucuronic acid: not just another brick in the cell wall.

This article is a Commentary on Debra‐Maceluch et al. (2023), 238: 297–312.

Changes in chemical composition, crystallinity, and microstructure of wood fiber mat-reinforced composite caused by white-rot fungus Trametes versicolor and brown-rot fungus Gloeophyllum trabeum

ABSTRACT Wood fiber mat-reinforced composite (WFMRC) is a novel type of engineering wood-based polymer composite for decorative and building applications. Fungal decay strongly influences the service life of wood composites in outdoor environments. In this study, fungal durability tests were conducted to investigate how white- and brown-rot fungi (Trametes versicolor and Gloeophyllum trabeum, respectively) affect the chemical composition, crystallinity, and morphology of WFMRCs made from two different wood species (poplar and larch). The poplar WFMRC lost more mass (18.3% and 18.4% by T. versicolor and G. trabeum, respectively) than the decayed larch WFMRC (11.4% and 18.4% by T. versicolor and G. trabeum, respectively) after 12 weeks of fungal exposure. Chemical analysis and Fourier-transform infrared spectroscopy measurement revealed the degradation of holocellulose of the WFMRCs after fungal decay. X-ray diffraction analyses demonstrated that fungal decay increased the crystallinity of the poplar WFMRC but decreased the crystallinity of the larch WFMRC. Bore hole formation on the walls of wood cells, cell wall thinning, and collapsed cells were found in decayed samples, particularly in the poplar WFMRC. Although the WFMRCs could be classified as resistant to fungal decay, an appropriate protective measure should be considered to improve the outdoor durability of the WFMRC.

Bamboo–Alginate Composite as a Sustainable Structural Material

In the current context of environmental concern and energy crisis, wood-based composites are attracting attention as sustainable materials; however, their mechanical properties require improvement. Herein, we report a novel method for the preparation of bamboo composites with excellent mechanical properties and formability. After delignification of bamboo, an alginate solution was filled into the voids of delignified bamboo (DB) under reduced pressure to obtain alginate-impregnated DB (ADB). Then, the alginate was subjected successively to ionic and chemical cross-linking by adding CaCl2 and glutaraldehyde, respectively. The mechanical strength of the resulting dually cross-linked ADB (DCB) was improved by removing unfilled voids via a hot-press forming process. The tensile and flexural strengths of the hot-pressed DCB (HP-DCB) showed the highest values ever reported for wood composites, i.e., 1.12 GPa and 678 MPa, respectively, which can be attributed to the strong adhesion and effective load transfer stemming from the dual cross-linking of alginate between the bamboo fibers. In particular, the presence of flexible and adhesive alginate enabled the reshaping of HP-DCB into desired shapes through rehydration and molding, demonstrating its potential for various applications requiring ecofriendly, high-strength, and lightweight materials.

Form-Stable Phase Change Material with Wood-Based Materials as Support

Building shape-stable phase change materials (PCMs) are crucial for their practical applications. Particularly, it is vital to utilize renewable/recyclable biomass media as the support material of form-stable PCMs. In this review article, we summarized the recent developments for building form-stable PCMs consisting of wood as a supporting material, either carbonized wood or wood composites. Moreover, the electrothermal conversion and photothermal conversion of form-stable PCMs based on carbonized wood are also demonstrated. In addition, the current technical problems and future research developments of wood-based PCMs are discussed, especially the leakage problem of PCMs during the phase change transition process. All of this information will be helpful for the in-depth understanding and development of new PCMs suitable for wide application perspectives.

Eco-Friendly Wood Composites: Design, Characterization and Applications

The ongoing transition from a linear to a circular, low-carbon bioeconomy is crucial for reducing the consumption of global natural resources, minimizing waste generation, reducing carbon emissions, and creating more sustainable growth and jobs, the prerequisites necessary to achieve climate neutrality targets and stop biodiversity loss [...].

Comparative wood anatomy, composition and saccharification yields of wastewater irrigated willow cultivars at three plantations in Canada and Northern Ireland

Conventional wastewater treatment strategies can have high financial costs which often leads to discharge of undertreated wastewater into the ecosystem. In parallel, the cultivation of willows for bioenergy can be limited due to their high water demand. Despite the potential for treatment using willow plantations, the effect of wastewater irrigation on biomass development and biofuel potential has yet to be investigated across different cultivars and sites. Here, the effect of secondary treated wastewater irrigation on wood anatomy, biomass composition and enzymatic saccharification were investigated in one poplar and thirteen willow cultivars planted at one of three sites in either Canada or Northern Ireland. There was significant anatomical and compositional variation between cultivars at all three sites, but wastewater irrigation had little impact on biomass development. Vessel and fibre cell frequencies ranged between cultivars from 129 to 178 and 4322–7058 per mm2, with average transverse areas of 838–1278 and 120–190 μm2, respectively. Glucan and lignin content varied from 42.3 to 50.7% dry matter (DM) and 27.3–32.4% DM, respectively, whereas glucose release varied from 50 to 160 mg g−1 of glucan or 30–90 mg g−1 of DM. Glucan content and fibre cell frequency had significant positive correlations with glucose release yields, whereas average fibre cell area had an inverse correlation. These findings suggest both cell wall structure and tissue morphology could be important factors when considering biomass recalcitrance to deconstruction. Maintenance of biomass quality during irrigation provides evidence that integration of dedicated bioenergy production with environmental wastewater treatment using willow phytofiltration has potential as a promising clean biotechnology.

Effective and environmentally safe self-antimildew strategy to simultaneously improve the mildew and water resistances of soybean flour-based adhesives

Wide applications of soybean-based adhesives in the production of wood composites are significantly restricted by mildew attacks. Increasing mildew resistance without increasing costs and causing environmental risks and/or loss of bonding properties remains challenging. This study proposes a self-antimildew strategy that involves the easy conversion of mildewing primary amines of soybean proteins of soybean flour (SF) into mildew-tolerant secondary amine linkages based on the structural design and synthesis of polyamidoamine–epichlorohydrin (PAE) resins. This effectively and environmentally safely improves the mildew resistance of SF-based adhesives without using additional mildew preventives and simultaneously enhances the bonding properties. NMR and FTIR results confirmed that the azetidine content of the PAE resin increased by 123.1% as the epichlorohydrin ratio increased from 0.75 to 1.2. The SF-based adhesive fabricated from the optimal PAE resin improved the mildew resistance by ≥ 367% and water resistance by 61.3% owing to the effective conversion of primary amines into secondary amine linkages via sufficient protein-PAE cross-linking. Furthermore, the addition of 0.45 wt% of environmentally safe and low-cost sodium formate into self-antimildew SF-based adhesives could maintain the desired mildew resistance and reduce the dosage of expensive PAE resin by 33% without compromising the bonding properties. This novel antimildew strategy allows cost-effective and environmentally safe improvements in both antimildew and mechanical performances, thereby allowing cleaner production of protein-based adhesives and composites.

Preservatives penetration and retention in post-treated cross-laminated timber panels with different layup and thickness

Cross-laminated timber (CLT), a prefabricated multilayer engineered wood product, is a promising construction material for mid-and-high rise buildings due to its good mechanical properties, renewability, and low-carbon footprint. However, the vulnerability of CLT to biodeterioration limits its broad applications. Preservative treatment is an effective method of increasing the service life of structural wood products, while the treatment of CLT has not been widely studied. Herein, we fabricated 3- and 5-ply CLT panels and treated them with Cu-based preservatives. The effects of panel layup (lengthwise and crosswise) and thickness (3-and 5-layer) on the impregnation quality (i.e., Cu penetration and retention) are investigated using a color-based indicator approach and X-ray fluorescence spectroscopy . Generally, the Cu penetration ratio was mostly above 90%, especially for the top layers (1st layer in 3-ply and 1st and 2nd layers in 5-ply) of the treated CLT panels. Similarly, higher Cu retention values were observed in the 1st layer of the 3- and 5-layer CLT panels. Further, there was a similarity in the Cu penetration of the 2nd layer in 3- and 5-ply CLT, indicating the preservative diffusion across adjacent layers is negligible in the preservative treatment of lumber-based wood composites. Overall, copper-azole type C (CA-C) exhibited better treatability than micronized copper azole (MCA) for CLT panels, resulting in higher Cu penetration and retention across the panels. Also, we found the lengthwise orientation preferable in fabricating preservative-treated CLT, this is due to the complete panel protection of the 1st and 2nd layers at all panel locations. Thus, our results show the feasibility of successfully treating CLT, especially when CA-C preservative and lengthwise orientation are utilized in fabricating the panels.

Effects of Lysine on the Interfacial Bonding of Epoxy Resin Cross-Linked Soy-Based Wood Adhesive.

Soy protein isolate (SPI) is an attractive natural material for preparing wood adhesives that has found broad application. However, poor mechanical properties and unfavorable water resistance of wood composites with SPI adhesive bonds limit its more extensive utilization. The combination of lysine (Lys) with a small molecular structure as a curing agent for modified soy-based wood adhesive allows Lys to penetrate wood pores easily and can result in better mechanical strength of soy protein-based composites, leading to the formation of strong chemical bonds between the amino acid and wood interface. Scanning electron microscopy (SEM) results showed that the degree of penetration of the S/G/L-9% adhesive into the wood was significantly increased, the voids, such as ducts of wood at the bonding interface, were filled, and the interfacial bonding ability of the plywood was enhanced. Compared with the pure SPI adhesive, the corresponding wood breakage rate was boosted to 84%. The wet shear strength of the modified SPI adhesive was 0.64 MPa. When Lys and glycerol epoxy resin (GER) were added, the wet shear strength of plywood prepared by the S/G/L-9% adhesive reached 1.22 MPa, which increased by 29.8% compared with only GER (0.94 MPa). Furthermore, the resultant SPI adhesive displayed excellent thermostability. Water resistance of S/G/L-9% adhesive was further enhanced with respect to pure SPI and S/GER adhesives through curing with 9% Lys. In addition, this work provides a new and feasible strategy for the development and application of manufacturing low-cost, and renewable biobased adhesives with excellent mechanical properties, a promising alternative to traditional formaldehyde-free adhesives in the wood industry.

Surface modification of wood and its effect on the interfacial bonding properties of cement-based wood composites

Surface modification of wood and its effect on the interfacial bonding properties of cement-based wood composites

Developing on the well performance and eco-friendly sucrose-based wood adhesive

The development of eco-friendly wood adhesives has attracted tremendous attention due to the aggravation of the oil resource crisis and the enhancement of environmental protection awareness. In this study, sucrose as a biomass material that was treated with an oxidizing agent to form bio-aldehydes, which were then reacted with hexanediamine via a Schiff base to prepare wood adhesives(OSUH). Several oxidants were tried in this work such as sodium permanganate(KMnO4), hydrogen peroxide(H2O2), sodium periodate(NaIO4), ammonium persulfate((NH4)2S2O8) and ammonium nitrate(NH4NO3). Among these, the (NH4)2S2O8, relatively low-cost, presented the best treatment effect. Hence, we further investigated the effects of the oxidation time of (NH4)2S2O8, the amount of (NH4)2S2O8 added and the pressing temperature on the bonding properties of the plywood bonded with this sucrose-based adhesive. The results show that the OSUH adhesive displayed the optimal bonding performance when the oxidation time, the addition of (NH4)2S2O8, and hot-pressing temperature were 45 min, 13 %, and 160 ℃, respectively. In this condition, the dry strength, 24 h cold water and 3 h hot water(63 ℃) soaking wet strength of the plywood are 1.52 MPa, 0.93 MPa, and 0.98 MPa, respectively, which indeed higher than the requirements of the GB/T 9846–2015 standard(≥0.7 MPa). The reaction mechanism between oxidized sucrose and hexanediamine was studied by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. The experimental results showed that the CN chemical bonds were observed in the cured adhesives, which confirms that the reaction of oxidized sucrose with hexanediamine obtained a resin with three-dimensional network structure by means of a Schiff base reaction, thus ensuring favourable bonding performance.Therefore, this work provides a new approach to prepare a high-performance, water-resistant and eco-friendly sucrose wood adhesive that have the potential to be used in wood composites.

Synthesis of Cu-Doped TiO2 on Wood Substrate with Highly Efficient Photocatalytic Performance and Outstanding Recyclability for Formaldehyde Degradation.

Photocatalytic oxidation is considered one of the most effective ways to remove formaldehyde from indoor air. However, the use of powder photocatalysts is limited by their low adsorption capacity and strong aggregation tendency. Hence, there is a need for a composite material with good cycling stability and high degradation efficiency. In the present study, a unique wood-based composite is produced by arranging Cu-TiO2 nanoparticles on porous structured wood. The porous structure of wood can adsorb formaldehyde, and the abundant functional groups on the surface can act as a reaction platform for anchoring the Cu-TiO2 nanoparticles. Cu doping facilitates electron interaction between TiO2 and Cu, promotes the transfer of charge carriers, lowers the electron-hole recombination rate, and improves the photocatalytic degradation efficiency of formaldehyde. The photocatalytic efficiency of the wood-based composites was highest (85.59%) when the n(Cu)/n(Ti) ratio was 7%. After nine cycles, the wood composites still had a high degradation rate, indicating good recyclability. Overall, this wood composite is an eco-friendly and promising material for indoor air filtration.

A facile method for cross-linking of methacrylated wood fibers for engineered wood composites

Chemical modifications are widely used to enhance the properties of wood composites and create a strong bonding mechanism for enhancing the dimensional stability, water resistance as well as decreasing carcinogenic formaldehyde emission. Esterification is the most-known modification way to enhance the durability of wood composites, but it does not improve mechanical performance. In this work, we demonstrated a two-step, easy and quick wood surface modification strategy based on microwave heating and UV crosslinking. Firstly, the fiber surface was reacted with methacrylic anhydride, then using methacrylated groups on wood, the fibers are covalently linked. As a proof-of-concept the fibers cross-linked within five minutes under UV radiation using benzophenone solution. Then, the effect of crosslinked wood fiber on the properties of mechanical and swelling of fiberboard were studied. Using SEM, FTIR-ATR, and swelling tests, we investigated the wood-based products' reaction mechanism, morphology, and internal bonding strength. The chemical cross-linking gives stronger bonding, compared to hydrogen bonding, between fibers even in wet conditions, resulting in a cross-linked foam-like structure. Also, wood panels were fabricated, compared to unmodified fibers, the internal bond strength and dimensional stability of fiberboards increased slightly. Overall, these results show that chemical cross-linking of wood fibers can be a fast and promising way to produce multi-functional wood composites.

The Impact of Wood Fibers in Composite Panels Made from Recycled Fiberglass Wind Turbine Blades

The utilization of wind power has increased almost exponentially during the last decade, leading to the growth in both the number and size of wind turbines. Modern turbine blades are typically made of fiberglass sandwiched around a balsa wood (BW) core. With an increase in the use of wind energy a collateral issue of what to do with the large and voluminous wind turbine blades (WTB) that reached end-of-life has arisen. Through previous research, we developed a recycling process that will keep these turbine blades out of the landfill by considering recycled wind turbine blades as a feedstock for second generation composite panels. The objective of this research is to further the research by understanding the effect that different compositions of wood and fiberglass have on the properties of these panels. Through testing, it was found that the addition of balsa wood increases the modulus of rupture (MOR) and the modulus of elasticity (MOE). The internal bonding (IB) strength values are well above that of typical particle board. All panels tested were visibly more resistant to water sorption than typical particle board. The thermal conductivity for all samples was within the typical range for particleboard. Fire test result indicates that the addition of balsa wood increases the heat and visible smoke release rate of composites.

Bioadhesive Design Toward Renewable Composites: Adhesive Distribution and Molecular Adhesion

Improvements in renewable compositions of adhesives are key for advancing the existing wood industry and developing biocomposites. Building upon prior studies on fundamental interactions between model compounds of fiber and bioadhesives, more complex bioadhesives are investigated. Cold denaturation of soy protein isolate (SPI) in dilute sodium hydroxide provide sufficient physical strength for wood composites. Due to swelling, 5% epoxy resin is added to the SPI adhesive resulting in improved physical strength and water resistance. The SPI and epoxy are evenly distributed on the fiber surface, while additional SPI fills the gaps between fibers based on fluorescence microscopy and X‐ray photoelectron spectroscopy. Molecular dynamics (MD) simulations show that the physical strength of the composites increases with the content of SPI, with the number of hydrogen bonds (H‐bonds) as primary driver; in MD simulations, the composite strength is highest at 3% epoxy, though higher epoxy doses results in more H‐bonds. In ReaxFF MD simulations, other contributions (e.g., van der Waals energy) show no correlation. The developed bioadhesive and the interaction mechanism demonstrate here emphasize the weak physical interactions in these materials, though covalent bonds and other larger scale phenomena are important as well for macro performances of the bioadhesives.