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Study of Timber and Wood Related Materials

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A special issue of Materials (ISSN 1996-1944). This special issue belongs to the section "Advanced Composites".

Deadline for manuscript submissions: closed (20 August 2023) | Viewed by 25242

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Prof. Dr. Hong Lei

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Chemistry and Material Engineering College, Zhejiang Agriculture and Forestry University, Hangzhou, China
Interests: wood adhesive; wood composite materials
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Being natural, renewable, and environmentally friendly, wood is a highly versatile material that has always been a common choice for many applications, including the production of tools, furniture, or art objects. Furthermore, its exceptional mechanical properties also make wood a preferable structural material for construction purposes. Some species of wood can be even stronger than steel or concrete. Although wood mechanical properties have been broadly investigated, further intensive research in this area is still in progress to provide more detailed knowledge of the relationships between wood structure, composition, and mechanical properties that would allow us to further improve the performance of wood under different environmental conditions, as well as broaden its applications.

This Special Issue aims to present updated knowledge relating to the mechanical and viscoelastic performance of wood and wood-based materials under various conditions; to report on the progress in the enhancement of wood mechanical properties by means of different treatments; to review the relationships between wood structure, chemical composition, moisture content, and its mechanical performance; and to demonstrate cutting-edge advances in the development of modern wood-based materials of enhanced mechanical properties.

The topics of interest include, but are not limited to, the following:

Relationships between wood chemical composition and its mechanical properties;
The effect of moisture on the mechanical and rheological properties of wood and wood-based materials;
The mechanical properties of weathered and decayed wood;
The effects of different treatments on the viscoelastic behavior and mechanical properties of wood and wood-based materials;
The effects of wood structure and density on its mechanical properties and viscoelastic behavior;
New methods and processes to upgrade the mechanical performance of wood;
The mechanical properties of wood-based composite materials;
New methods for the assessment of wood viscoelastic behavior and mechanical properties;
Novel wood-based materials;
Mechanical properties of waterlogged wood and archaeological wood;
Wood-based engineering materials;
New methods and technology for wood processing.

We highly encourage contributions from all relevant fields in the form of original or review articles.

Prof. Dr. Hong Lei
Guest Editor

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Keywords

wood modification
wood-based composite
wood-based engineering materials
wood processing
mechanical and rheological properties of wood
wood preservation
mechanical properties
wood structure
panel products

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Published Papers (12 papers)

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Research

16 pages, 2683 KiB

Open AccessArticle

Pyrolysis of Pine Wood in the Presence of Boron–Nitrogen Compounds

by Irina Stepina and Yulia Zheglova

Materials 2023, 16(19), 6353; https://doi.org/10.3390/ma16196353 - 22 Sep 2023

Viewed by 1038

Abstract

The actuality of this research is determined by the intensification of new ways of processing woody biomass. This requires revealing the impact of various physicochemical factors on the thermal degradation of wood biopolymers. Boron–nitrogen surface modifiers are used for wood antisepsis and we decided to check their effect on flammability. The aim of the research was to evaluate the flame retardant effect of boron–nitrogen surface modifiers of wood in an inert atmosphere (nitrogen was used). The evaluation was carried out by thermal analysis of modified and the control pine wood samples. The thermal analysis included thermogravimetry, differential scanning calorimetry and kinetic parameters of thermal degradation. It was found that the flame retardant effect of boron–nitrogen wood surface modifiers was not significantly pronounced in the nitrogen atmosphere. The mechanism of the flame retardant effect of boron–nitrogen compounds is reduced to “shielding” of the surface and increasing the proportion of carbonized residue. On the basis of correlation–regression analysis of kinetic parameters of wood thermodestruction in a nitrogen atmosphere, mathematical models of activation energy dependence on conversion were obtained and substantiated. The developed models can be further applied to calculate the predicted value of wood activation energy in the nitrogen atmosphere at any conversion value. Full article

(This article belongs to the Special Issue Study of Timber and Wood Related Materials)

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14 pages, 2548 KiB

Open AccessArticle

Mechanical Properties Variation in Wood—Plastic Composites with a Mixed Wood Fiber Size

by Hailong Xu, Yang Yang, Lifen Li, Baoyu Liu, Xiubo Fu, Xiaohui Yang and Yan Cao

Materials 2023, 16(17), 5801; https://doi.org/10.3390/ma16175801 - 24 Aug 2023

Cited by 6 | Viewed by 1560

Abstract

In this study, the influence of fiber particle size on the mechanical properties of a wood-–plastic composite (WPC) was investigated using a combination of experimental measurements and numerical modeling. Four different sizes of wood fibers (10–20 mesh, 20–40 mesh, 40–80 mesh, and 80–120 mesh) were used to reinforce high-density polyethylene (HDPE), either separately or in combination. The different sizes of fibers produced varying properties in the resulting composites. The smallest fiber size (80–120 mesh) resulted in the lowest flexural and tensile properties, but the highest impact strength (15.79 kJ/m²) compared to the other three sizes (12.18–14.29 kJ/m²). Using a blend of fiber sizes resulted in improved mechanical properties. Composites containing a mix of 20–40 mesh and 40–80 mesh fibers exhibited the best flexural (strength 74.16 MPa, modulus 5.35 GPa) and tensile performance (strength 48.27 MPa, modulus 4.30 GPa), while composites containing a mix of all four fiber sizes had the highest impact-resistant strength (16.08 kJ/m²). Several models, including the Rule of Mixtures (ROM), the Inverse Rule of Mixtures (IROM), and the Hirsch models, were used to predict the performance of WPCs. The ROM model was found to be the most accurate in describing the mechanical properties of WPCs reinforced with multi-size wood fibers, based on the sum squared error (SSE) analysis. Full article

(This article belongs to the Special Issue Study of Timber and Wood Related Materials)

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11 pages, 4271 KiB

Open AccessArticle

New Azo Derivatives of Ethanol Lignin: Synthesis, Structure, and Photosensitive Properties

by Valentina S. Borovkova, Yuriy N. Malyar, Natalia Yu. Vasilieva, Andrey M. Skripnikov, Vladislav A. Ionin, Valentin V. Sychev, Viktor A. Golubkov and Oxana P. Taran

Materials 2023, 16(4), 1525; https://doi.org/10.3390/ma16041525 - 11 Feb 2023

Cited by 5 | Viewed by 2315

Abstract

Water-soluble azo derivatives of lignin were synthesized by the azo coupling reaction using organosolv ethanol lignin and diazonium salts based on sulfanilic acid and p-nitroaniline. The structure of azo derivatives of lignin were studied by nuclear magnetic resonance, Fourier-transform infrared spectroscopy, and gel permeation chromatography. It was found that the azobenzene bonds formed in the azo coupling reaction of macromolecules impart the photosensitive properties to the synthesized polymers via cis–trans photoisomerization of the diazobenzene group. It was shown experimentally that the synthesized polymers exhibited good solubility both in the aqueous media in a wide (2–12) pH range and in DMSO and THF organic solvents, which opens up new prospects for their application. Full article

(This article belongs to the Special Issue Study of Timber and Wood Related Materials)

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9 pages, 2817 KiB

Open AccessArticle

Effect of Abrasive Grain Size on the Abrasion Volume Loss of Subfossil and Recent Oak Wood in Three Characteristic Sections

by Sara Essert, Vera Rede and Josip Barišić

Materials 2023, 16(1), 432; https://doi.org/10.3390/ma16010432 - 3 Jan 2023

Cited by 1 | Viewed by 1665

Abstract

Subfossil wood is a valuable and rare material often used for production of expensive furniture and decorative artistic items of unique beauty. Its mechanical and tribological properties are still being studied and are considered specific due to the particular conditions of its long-lasting formation in aqueous sediment sludge. Various elements that have been impregnated into the wood tissue over many years make the machining and grinding of this type of wood rather difficult compared to normal recent wood. The main objective of this study was to determine the influence of the abrasive grain size of sandpaper on the abrasion volume loss of recent and two subfossil oak samples in three characteristic sections (cross, radial, and tangential). The results showed that the average size of abrasive grains and the orientation of the wood structure have an influence on the abrasion volume loss of all three samples. The phenomenon of the critical size of abrasive grains was observed in all samples and on all sections. As the size of abrasive grains increased to the critical size, the abrasive volume loss of the sample increased simultaneously. The lowest abrasion volume loss was observed on recent oak. In all samples, the lowest volume loss was measured on the cross sections, and the tangential and radial sections had mutually equal values. It was also found that the increase in the size of abrasive grains to a critical value resulted in the increasing value of the absolute difference between the abrasion volume loss of the cross, radial, and tangential section samples, while the relative relations between the abrasive volume loss values of three different sections (C/R, C/T, R/T) within the same grit of sandpaper remained quite similar. Full article

(This article belongs to the Special Issue Study of Timber and Wood Related Materials)

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17 pages, 4877 KiB

Open AccessArticle

Fully Bio-Based Adhesive from Tannin and Sucrose for Plywood Manufacturing with High Performances

by Guoming Xiao, Jiankun Liang, De Li, Yuan Tu, Bengang Zhang, Feiyan Gong, Wen Gu, Min Tang, Xinyue Ding, Zhigang Wu and Hong Lei

Materials 2022, 15(24), 8725; https://doi.org/10.3390/ma15248725 - 7 Dec 2022

Cited by 15 | Viewed by 2325

Abstract

Fully bio-based adhesives are beneficial to reduce the dependence of the wood adhesive industry on synthetic resins based on petrochemical resources and enhance the market competitiveness of adhesives. A fully bio-based wood adhesive composed of tannin and sucrose was developed and successfully used in the preparation of plywood. Effects of the preparation technology on the bonding strength and water resistance of plywood were investigated, and the properties of the adhesive were analyzed by Fourier transform infrared spectroscopy (FT-IR), thermogravimetry (TG) and X-ray diffraction (XRD) in this study. The results showed that: (1) Compared with other biomass adhesives, tannin–sucrose adhesive had the characteristics of high-solid content and low viscosity, which had the potential to prepare particleboard and fiberboard. (2) A proper mass ratio of tannin to sucrose was key to obtaining a tannin–sucrose adhesive with better properties. (3) The optimum preparation process of tannin–sucrose adhesive for plywood was as follows: hot-pressing temperature of 210 °C, hot-pressing time of 1.2 min/mm, m(tannin):m(sucrose) of 60:40 and adhesive loading of 160 g/m². Under these conditions, the water-resistant bonding strength of the plywood was 0.89 MPa, which met the strength requirements of the Type II standard of plywood in GB/T 17657-2013. (4) The hot-pressing temperature played a decisive role in the tannin–sucrose adhesive, and the good performance of the plywood was maintained when the temperature was 210 °C or above. Thus, the prepared tannin–sucrose adhesive had high-bonding strength, good water resistance and thermal stability. Full article

(This article belongs to the Special Issue Study of Timber and Wood Related Materials)

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16 pages, 1987 KiB

Open AccessArticle

Effect of Mat Moisture Content, Adhesive Amount and Press Time on the Performance of Particleboards Bonded with Fructose-Based Adhesives

by Catherine Rosenfeld, Pia Solt-Rindler, Wilfried Sailer-Kronlachner, Thomas Kuncinger, Johannes Konnerth, Andreas Geyer and Hendrikus W. G. van Herwijnen

Materials 2022, 15(23), 8701; https://doi.org/10.3390/ma15238701 - 6 Dec 2022

Viewed by 1963

Abstract

The study evaluates the performance of laboratory, single-layered particleboards made out of fructose-hydroxymethylfurfural-bishexamethylenetriamine (SusB) adhesive as a sustainable alternative. Several production parameters such as mat moisture content (MMC), adhesive amount and press time were varied and their effect on the bonding efficiency investigated. The internal bond strength (IB) and thickness swelling after 24 h of water immersion (TS) were taken as evaluation criteria for the bonding efficiency. pMDI-bonded particleboards were produced as fossil-based, formaldehyde-free reference. Particleboard testing was complemented by tensile shear strength measurements and thermal analysis. It was found that the MMC has the highest impact on the internal bond strength of SusB-bonded particleboards. In the presence of water, the reaction enthalpy of the main curing reaction (occurring at 117.7 °C) drops from 371.9 J/mol to 270.5 J/mol, leading to side reactions. By reducing the MMC from 8.7%, the IB increases to 0.61 N/mm², thus surpassing P2 requirements of the European standard EN312. At a press factor of 10 s/mm, SusB-bonded particleboards have a similar IB strength as pMDI-bonded ones, with 0.59 ± 0.12 N/mm² compared to 0.59 ± 0.09 N/mm². Further research on the improvement of the dimensional stabilization of SusB-bonded PBs is needed, as the TS ranges from 30–40%. Full article

(This article belongs to the Special Issue Study of Timber and Wood Related Materials)

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13 pages, 4536 KiB

Open AccessArticle

Decay Resistance of Surface Carbonized Wood

by Maija Kymäläinen, Tiina Belt, Hanna Seppäläinen and Lauri Rautkari

Materials 2022, 15(23), 8410; https://doi.org/10.3390/ma15238410 - 25 Nov 2022

Cited by 4 | Viewed by 1945

Abstract

Surface carbonization, or charring, of wood is a one-sided modification method primarily intended for protection of exterior cladding boards. The heavily degraded surface acts as a barrier layer shielding the interior from environmental stresses, and as such acts as an organic coating. To test the durability of surfaces created in this manner, unmodified, contact charred, and flame charred spruce and birch samples were exposed to the brown rot fungus Coniophora puteana and white rot fungus Trametes versicolor for a period of nine weeks. All sides of the samples except the modified surfaces were sealed to investigate the protective effect of the surface. Mass losses were greatest for unmodified references (up to 60% and 56% for birch and spruce, respectively) and smallest for contact charred samples (up to 23% and 32%). The wood below the modified surfaces showed chemical changes typical of brown rot and simultaneous white rot. The measured glucosamine content revealed fungal biomass in both the modified surface as well as the layers beneath. According to the recorded values, the fungal biomass increased below the surface and was higher for flame charred samples in comparison to contact charred ones. This is likely due to the more intact, plasticized surface and the thicker thermally modified transition zone that restricts fungal growth more effectively in contact charred samples in comparison to the porous, cracked flame charred samples. Scanning electron microscope images verified the results by revealing fungal hyphae in all inspected wood types and species. Full article

(This article belongs to the Special Issue Study of Timber and Wood Related Materials)

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10 pages, 2413 KiB

Open AccessArticle

Evaluation of the Shear Performance of Douglas-Fir Wood at Elevated Temperatures

by Lingfeng Zhang, Qianyi Li, Weiqing Liu, Qian He, Yan Liu and Kai Guo

Materials 2022, 15(23), 8386; https://doi.org/10.3390/ma15238386 - 25 Nov 2022

Cited by 1 | Viewed by 1660

Abstract

Shear fracture frequently occurs in timber beams and panels subjected to transverse loads. At elevated temperatures, wood will undergo complex physical and chemical processes which significantly affect the shear properties. In this paper, the v-notched Douglas-fir specimens with three different shear planes: (a) Radial-Tangential (RT); (b) Radial-Longitudinal (RL), and (c) Longitudinal-Radial (LR), were fabricated and tested under the elevated temperatures from 20 °C to 180 °C. The digital image correlation (DIC) technique was used to measure the shear strain. It was found that the shear plane had a significant effect on the failure modes, shear strength, and shear modulus. The shear strength and shear modulus generally decreased with the increase of temperature. However, the shear strength was significantly improved when the hardening of the dry lignin occurred between 100 °C and 140 °C. Moreover, the design curve for the shear strength in Eurocode 5 is conservative for all the specimens with different shear planes. Full article

(This article belongs to the Special Issue Study of Timber and Wood Related Materials)

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12 pages, 2563 KiB

Open AccessArticle

Change in Selected Mechanical Properties of Beech Wood at the Contact Drying

by Ivan Klement, Peter Vilkovský and Tatiana Vilkovská

Materials 2022, 15(21), 7433; https://doi.org/10.3390/ma15217433 - 23 Oct 2022

Cited by 3 | Viewed by 1766

Abstract

The mechanical properties of wood have remarkable influence on its use in buildings. The improvement of the mechanical properties enables the reduction in the cross-sections of structural elements, particularly the increase in their load. The paper deals with the change in the mechanical properties of beech wood through the process of contact drying. Plate pressures of 1.0, 1.4, and 1.6 MPa at a temperature of 160 °C were used. It was found that contact drying increased the bending strength by more than 30% compared to convection drying. The value of Brinell’s hardness measured on the surface of the samples increased by 80 to 98% after contact drying, and the measured values of impact toughness were higher, about 31.1% compared to the samples dried by the convection drying method. As a result of contact drying, the density in the absolutely dry state increased for radial samples by 102.3 kg·m⁻³ and for tangential samples by 83.1 kg·m⁻³. The pressure of the plates also had an effect on the change in density. Full article

(This article belongs to the Special Issue Study of Timber and Wood Related Materials)

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18 pages, 7952 KiB

Open AccessArticle

Surface Characteristics of Thermally Modified Bamboo Fibers and Its Utilization Potential for Bamboo Plastic Composites

by Fu Hu, Lifen Li, Zhigang Wu, Liping Yu, Baoyu Liu, Yan Cao and Hailong Xu

Materials 2022, 15(13), 4481; https://doi.org/10.3390/ma15134481 - 25 Jun 2022

Cited by 11 | Viewed by 2686

Abstract

Bamboo fibers are considered as a more attractive option for the reinforcement of wood plastic composites as compared to wood fiber due to its fast growth rate and good toughness. Heat treatment is an environment-friendly method of improving the integrated performance of bamboo materials. This paper highlights the heat treatment of bamboo fiber for suitable properties as reinforcements in bamboo plastic composites. The effects of vacuum heat treatment on the surface characteristics of bamboo fibers and the properties of bamboo plastic composites were analyzed by studying the chemical composition, surface elements and polarity of bamboo fiber before and after treatment, and the physical and mechanical properties of bamboo plastic composite. The results showed that after vacuum heat treatment, the bamboo fibers became darker and experienced a transition from green to red. Moreover, FTIR, XPS and contact angle analysis indicated that the hemicellulose content, the oxygen/carbon ratio and the polar component of the bamboo fiber had a decreasing trend as the treatment temperature increased. In addition, the 24 h water absorption and the 24 h thickness expansion rate of the water absorption showed a trend of first decreasing and then increasing as the treatment temperature increased, while the bending performance of bamboo plastic composite showed a trend of increasing first and then decreasing as a result of increased treatment temperature. Therefore, a combined process of vacuum heat treatment and the addition of MAPE could improve the physical and mechanical properties of bamboo plastic composites to a certain extent. Full article

(This article belongs to the Special Issue Study of Timber and Wood Related Materials)

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15 pages, 2997 KiB

Open AccessArticle

Effects of Biological and Chemical Degradation on the Properties of Scots Pine Wood—Part I: Chemical Composition and Microstructure of the Cell Wall

by Magdalena Broda, Carmen-Mihaela Popescu, Simon F. Curling, Daniel Ilie Timpu and Graham A. Ormondroyd

Materials 2022, 15(7), 2348; https://doi.org/10.3390/ma15072348 - 22 Mar 2022

Cited by 15 | Viewed by 2975

Abstract

Research on new conservation treatment for archaeological wood requires large amounts of wooden material. For this purpose, artificial wood degradation (biological—using brown-rot fungus Coniophora puteana, and chemical—using NaOH solution) under laboratory conditions was conducted to obtain an abundance of similar samples that mimic naturally degraded wood and can serve for comparative studies. However, knowledge about its properties is necessary to use this material for further study. In this study, the chemical composition and microstructure of degraded cell walls were investigated using FT-IR, XRD, helium pycnometry and nitrogen absorption methods. The results show that biological degradation caused the loss of hemicelluloses and celluloses, including the reduction in cellulose crystallinity, and led to lignin modification, while chemical degradation mainly depleted the amount of hemicelluloses and lignin, but also affected crystalline cellulose. These changes affected the cell wall microstructure, increasing both surface area and total pore volume. However, the chemical degradation produced a greater number of mesopores of smaller size compared to fungal decomposition. Both degradation processes weakened the cell wall’s mechanical strength, resulting in high shrinkage of degraded wood during air-drying. The results of the study suggest that degraded wood obtained under laboratory conditions can be a useful material for studies on new consolidants for archaeological wood. Full article

(This article belongs to the Special Issue Study of Timber and Wood Related Materials)

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15 pages, 3721 KiB

Open AccessArticle

A New Wood Adhesive Based on Recycling Camellia oleifera Cake-Protein: Preparation and Properties

by Xue Deng, Zhigang Wu, Bengang Zhang, Hong Lei, Jiankun Liang, Lifen Li, Yuan Tu, De Li and Guoming Xiao

Materials 2022, 15(5), 1659; https://doi.org/10.3390/ma15051659 - 23 Feb 2022

Cited by 8 | Viewed by 1704

Abstract

In order to improve the initial viscosity and stability of Camellia oleifera cake-protein adhesive, Camellia oleifera cake-protein was blended with defatted soybean protein (DSP), soybean protein isolate (SPI), and casein, followed by adhesive preparation through degradation and crosslinking methods. The performance of Camellia oleifera cake-protein adhesive was investigated by Fourier transform infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC), scanning electron microscopic (SEM), and thermogravimetric (TG) and X-ray diffraction (XRD). The results showed that DSP, SPI, and casein likely promoted the effective degradation of Camellia oleifera cake-protein, and, thus, more active groups were formed in the system, accompanied by more reactivity sites. The prepared adhesive had a lower curing temperature, and higher initial viscosity and stability, but the storage time was shortened. Moreover, DSP, SPI, and casein, themselves, were degraded into peptide chains with lower molecular weights; thus, improving the overall flexibility of the adhesive, facilitating a better elastic contact and regular array between crosslinking products, and further strengthening the crosslinked structure and density of the products. After curing, a compact and coherent reticular structure was formed in the adhesive layer, with both bonding strength and water resistance being significantly improved. According to the results obtained, the next step will be to study the DSP-modified Camellia oleifera cake-protein adhesive in depth. Full article

(This article belongs to the Special Issue Study of Timber and Wood Related Materials)

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