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A special issue of Forests (ISSN 1999-4907). This special issue belongs to the section "Wood Science and Forest Products".

Deadline for manuscript submissions: closed (10 May 2023) | Viewed by 25381

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Dr. Edward Roszyk

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Department of Wood Science and Thermal Techniques, Faculty of Forestry and Wood Technology, Poznan University of Life Sciences, Wojska Polskiego 28, 60-637 Poznan, Poland
Interests: wood anatomy; physical properties of wood; wood strength; wood rheology; wood modification
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Dr. Magdalena Broda

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Department of Wood Science and Thermal Techniques, Faculty of Forestry and Wood Technology, Poznań University of Life Sciences, Poznań, Poland
Interests: wood structure; wood composition; wood characterisation; wood conservation; wood preservation; waterlogged archaeological wood; structure–function relationships; wood decay; organosilicons in wood conservation; wood modification
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Special Issue Information

Dear Colleagues,

The physical properties of wood are usually defined as properties that can be determined without changing the material's size, shape, or chemical composition. Nowadays, the basic physical properties of wood are generally well understood. However, the development of more accurate and faster modern measurement methods has had a significant effect on this field. Owing to this, it is possible to continuously expand our knowledge of wood, helping us understand the materials better and thus allowing us to use it as a dedicated material for numerous new applications.

This Special Issue will present innovative methods for measuring the physical properties of wood, describing the physical properties that have so far not been well known or understood, and discuss problems and doubts relating to the physical properties of all types of wood, including industrial (sound, degraded, green, dry, and modified wood), historical (archaeological and waterlogged), and growing trees of all species. We highly encourage contributions to this Special Issue from all relevant fields in the form of both original and review articles.

Dr. Edward Roszyk
Dr. Magdalena Broda
Guest Editors

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Keywords

wood physical properties
wood density
wood colour
shrinkage
fibre saturation point
water sorption
wood drying
modified wood
wood strength
wood hardness

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Published Papers (11 papers)

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12 pages, 3054 KiB

Open AccessArticle

Swelling Behaviour of Bamboo (Phyllostachys pubescens)

by Edward Roszyk, Radosław Kropaczewski, Przemysław Mania and Magdalena Broda

Forests 2024, 15(1), 118; https://doi.org/10.3390/f15010118 - 7 Jan 2024

Cited by 2 | Viewed by 2246

Abstract

Bamboo is a plant with various applications. As a natural, renewable material that exhibits good mechanical performance, it seems to be an interesting alternative to wood, which has become a scarce and expensive commodity. However, comprehensive knowledge of its properties is necessary to maximise its potential for various industrial purposes. The swelling behaviour of bamboo is one of the features that has not yet been sufficiently investigated. Therefore, in this research, we aimed to measure and analyse the swelling pressure and kinetics of bamboo blocks. The results show that similar to wood, the swelling kinetics of bamboo depend on its density: the denser the tissue, the higher the maximum swelling value recorded. The maximum tangential swelling measured was about 5%–6%, which is lower than the value for the most commonly used wood species. Swelling pressure ranged from 1.16 MPa to 1.39 MPa, depending on the bamboo density: the denser the sample, the shorter the time required to reach maximum swelling pressure. Like in wood, the smallest linear increase in size due to swelling was observed in the longitudinal direction (0.71%). However, opposite to wood, more pronounced swelling was recorded in the radial direction (over 7%) than in the tangential direction (nearly 6%). The results show that bamboo’s swelling behaviour makes it a good material for use in variable humidity conditions, being more favourable than the unmodified wood of many species. Full article

(This article belongs to the Special Issue Physical Properties of Wood)

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13 pages, 4102 KiB

Open AccessArticle

Molecular Dynamics Simulation of the Effect of Low Temperature on the Properties of Lignocellulosic Amorphous Region

by Xuewei Jiang, Wei Wang, Yuanyuan Guo and Min Dai

Forests 2023, 14(6), 1208; https://doi.org/10.3390/f14061208 - 11 Jun 2023

Cited by 3 | Viewed by 1741

Abstract

In this paper, a molecular model of cellulose amorphous region-water molecule was developed using Materials Studio software by applying the molecular dynamics method. The effect of low temperature on the properties of the lignocellulosic amorphous region, the main component of wood, was investigated in an attempt to explain the macroscopic property changes from a microscopic perspective and to provide a theoretical basis for the safe use of wood and wood products in low-temperature environments and other related areas of research. Dynamic simulations were carried out at 20 °C, 0 °C, −30 °C, −70 °C, −110 °C and −150 °C for the NPT combinations to obtain the energy, volume, density, and hydrogen bonding change trends of their models, respectively. The changes in the microstructure of the water molecule–cellulose amorphous region model were analyzed, and the mechanical properties were calculated. The results showed that the interaction between the amorphous cellulose region and water molecules was enhanced as the temperature decreased, the density of the models increased, and the volume decreased. The number of total hydrogen bonds and the number of hydrogen bonds between water molecule–cellulose chains increased for each model, and the decrease in temperature made the cellulose molecular activities weaker. The values of G, E, and K increased with the decrease in temperature, and K/G decreased with the decrease in temperature. It shows that the decrease in temperature is beneficial to enhance the mechanical properties of the amorphous region of cellulose and increases the stiffness of the material. However, the toughness and plasticity decrease when the temperature is too low. Full article

(This article belongs to the Special Issue Physical Properties of Wood)

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13 pages, 3316 KiB

Open AccessArticle

Differences in Some Physical and Chemical Properties of Beechwood with False Heartwood, Mature Wood and Sapwood

by Ladislav Dzurenda, Michal Dudiak and Viera Kučerová

Forests 2023, 14(6), 1123; https://doi.org/10.3390/f14061123 - 29 May 2023

Cited by 4 | Viewed by 1986

Abstract

The article presents the differences in some physical and chemical properties of wood with false heartwood, mature wood, and sapwood of Fagus sylvatica L.: density of wood in the dry state, color in the color space CIE L*a*b* on the tangential surface and the planed surface at w = 10 ± 0.5%, as well as moisture and acidity of wet wood. As part of chemical analyses, the relative proportion of cellulose, hemicelluloses, lignin, and extractive substances in individual zones of beechwood in trunks with false heartwood was determined. From the carried out analyses, it follows that the biggest difference between the wood of false heartwood, mature wood, and sapwood is the color of the wood. The red-brown color of the wood with false heartwood in the color space CIE L*a*b* is described by the following coordinate values: L* = 64.9 ± 4.9; a* = 12.9 ± 1.4; b* = 19.6 ± 1.7. The most significant differences between the values of the color space are on the lightness coordinate, where the light ochre-white of mature wood shows a decrease of ∆L* = −14.0 compared with the color of false heartwood, and the white—pale grey color of sapwood shows a decrease of ∆L* = −17.5. The density of dry beechwood with false heartwood is higher by ∆ρ₀ = 4.7% than the density of mature wood, and the density of sapwood is ∆ρ₀ = 12.3% lower than the density of wood with false heartwood. The exact opposite applies to the acidity of wet beechwood. The results of wet wood acidity measurements also point to certain differences. While the acidity of the wet wood of false heartwood is pH = 5.32 ± 0.13, the acidity of the sapwood is 5.1% lower. The higher acidity of beech heartwood is attributed to the presence of organic acids in polyphenols during heartwood formation. From the comparison of the representation of cellulose, hemicellulose, lignin, and extractive substances, it follows that the relative content of lignin and hemicelluloses is higher in false heartwood than in mature wood and sapwood. On the contrary, the content of holocellulose and cellulose is highest in sapwood. The presented divisions in the physical and chemical properties of beechwood with false heartwood do not limit the use of beechwood in industrial applications, except for a change in color; the definition of color boundaries in the color space CIE L*a*b* creates space for sorting beechwood according to color and can be used to increase the color variety of compositions of construction-carpentry products. Full article

(This article belongs to the Special Issue Physical Properties of Wood)

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13 pages, 3086 KiB

Open AccessArticle

Wood Colour Variations of Quercus Species in Romania

by Aureliu-Florin Hălălișan, Florin Dinulică, Dan Marian Gurean, Codrin Codrean, Nikolay Neykov, Petar Antov and Nikolai Bardarov

Forests 2023, 14(2), 230; https://doi.org/10.3390/f14020230 - 26 Jan 2023

Cited by 1 | Viewed by 1883

Abstract

Wood colour metrics are increasingly being used in wood technology and ecology studies. Researchers usually determine the colours of the wood after treatment or in different habitats. There is very little research dedicated to the problem of colour variations among one specific species harvested in different forests or regions. The main purpose of the current research is to reveal and estimate the colour variability of oak species. For this study, a total of 89 samples were taken from the heartwood of seven oak species (Quercus robur L., Quercus cerris L., Quercus rubra L., Quercus pedunculiflora K. Koch., Quercus pubescens Willd., Quercus petraea (Matt.) Liebl., and Quercus palustris Muenchh.). The CIELAB system was used for the assessment of the colour differences. To determine the colour groups and variations, K-means clustering was used. The results show that colour variations do exist. According to the cluster analysis, at least five types of oak wood can be distinguished (because in some clusters, very few samples were present) in the investigated forests. The differences are mainly observed in terms of the lightness (L*) and yellowness (b*). Redness is not a feature by which oak wood differs, but the wood can be brighter or more yellow in some of the samples. The density of the Romanian oaks in the sample does not influence the colour coordinates. The only coordinate affected is a*, but with a very small probability. Full article

(This article belongs to the Special Issue Physical Properties of Wood)

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13 pages, 1880 KiB

Open AccessArticle

Effects of Compression Ratio and Phenolic Resin Concentration on the Properties of Laminated Compreg Inner Oil Palm and Sesenduk Wood Composites

by Wan Nabilah Ahamad, Sabiha Salim, Seng Hua Lee, Muhammad Aizat Abdul Ghani, Rabiatol Adawiah Mohd Ali, Paridah Md Tahir, Widya Fatriasari, Petar Antov and Muhammad Adly Rahandi Lubis

Forests 2023, 14(1), 83; https://doi.org/10.3390/f14010083 - 1 Jan 2023

Cited by 4 | Viewed by 1861

Abstract

Due to its inferior properties, oil palm wood (OPW) extracted from the inner layer of the oil palm (Elaeis guineensis) trunk, referred as inner OPW in this study, is frequently regarded as a waste. Phenolic resin treatment and lamination of inner OPW with other hardwoods may be an excellent way to improve the properties of the inner OPW. In this study, inner OPW were treated with two different concentrations (15% and 20%) of low molecular weight phenol formaldehyde resin (LmwPF) and compressed at different compression ratios (10%, 20%, and 30%). The physical and mechanical properties of the modified inner OPW’s were evaluated according to British Standards (BS) 373: 1957. The results revealed that inner OPW treated with the highest compression ratio (30%) and resin concentration (20%) exhibited the highest weight percent gain, polymer retention and density. In the following phase of the research, the treated inner OPW was used as the core layer in the fabrication of a three-layer laminated compreg hybrid composites, with untreated and treated sesenduk (Endospermum diadenum) wood serving as the face and back layers. The compression ratios of 10% and 20% and resin concentrations of 10% and 20% were used in this phase of study as laminated boards made with 30% compression ratio failed. The findings showed that resin concentration had a significant impact on both the inner OPW and the laminated compreg hybrid panels. Markedly, higher resin concentrations (20%) resulted in improved physical properties, i.e., thickness swelling and water absorption, as well as enhanced mechanical properties (modulus of rupture and modulus of elasticity). Although compression ratios had no significant effect on the properties of the laminated products, those compressed at higher compression ratios (20%) performed slightly better than the panels compressed at lower compression ratios (10%). Full article

(This article belongs to the Special Issue Physical Properties of Wood)

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16 pages, 2170 KiB

Open AccessArticle

Mechanical Properties of Wood Prediction Based on the NAGGWO-BP Neural Network

by Wei Ma, Wei Wang and Ying Cao

Forests 2022, 13(11), 1870; https://doi.org/10.3390/f13111870 - 9 Nov 2022

Cited by 5 | Viewed by 1774

Abstract

The existing original BP neural network models for wood performance prediction have low fitting accuracy and imprecise prediction results. We propose a nonlinear, adaptive grouping gray wolf optimization (NAGGWO)-BP neural network model for wood performance prediction. Firstly, the original gray wolf optimization (GWO) algorithm is optimized. We propose CPM mapping (the Chebyshev mapping method combined with piecewise mapping followed by mod operation) to generate the initial populations and improve population diversity, and an ‘S’-type nonlinear control parameter is proposed to balance the exploitation and exploration capabilities of the algorithm; an adaptive grouping strategy is also proposed, based on which the wolves are divided into the predator, wanderer, and searcher groups. The improved differential evolution strategy, the stochastic opposition-based learning strategy, and the oscillation perturbation operator are used to update the positions of the wolves in the different groups to improve the convergence speed and accuracy of the GWO. Then, the BP neural network weights and thresholds are optimized using the NAGGWO algorithm. Finally, we separately predicted heat-treated wood’s five main mechanical property parameters using different models. The experimental results show that the proposed NAGGWO-BP model significantly improved the mean absolute error (MAE), the mean square error (MSE), and the mean absolute percentage error (MAPE) of the specimens, compared with the BP, GWO-BP, and TSSA-BP algorithms. Therefore, this model has strong generalization ability and good prediction accuracy and reliability, which can fully meet practical engineering needs. Full article

(This article belongs to the Special Issue Physical Properties of Wood)

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13 pages, 1585 KiB

Open AccessArticle

Effects of Biological and Chemical Degradation on the Properties of Scots Pine—Part II: Wood-Moisture Relations and Viscoelastic Behaviour

by Magdalena Broda, Morwenna J. Spear, Simon F. Curling and Athanasios Dimitriou

Forests 2022, 13(9), 1390; https://doi.org/10.3390/f13091390 - 31 Aug 2022

Cited by 12 | Viewed by 2028

Abstract

The present research aimed to assess the moisture properties and viscoelastic behaviour of artificially degraded pine wood, intended to serve as a model material for ongoing studies on new conservation treatments for waterlogged archaeological wood. Sorption isotherms and hydroxyl accessibility were measured using a Dynamic Vapour Sorption (DVS) system, while the investigation of the selected wood rheological properties was performed using Dynamic Mechanical Analysis (DMA). Fungal decomposition of pine by Coniophora puteana decreased the maximum equilibrium moisture content (EMC) from 20.3% to 17.7% in the first and from 19.9% to 17.1% in the second DVS run compared to undegraded pine, while chemical degradation using 50% NaOH solution increased the wood EMC to 24.6% in the first and 24.2% in the second run. The number of free hydroxyls measured for the biologically degraded sample was similar to sound wood, while chemical degradation reduced their number from 11.3 mmol g⁻¹ to 7.9 mmol g⁻¹. The alterations in the wood chemical composition due to different degradation processes translated into changes in viscoelastic behaviour. For biologically degraded wood, a reduction in the loss modulus and storage modulus at the temperature of 25 °C was observed compared to undegraded pine. Surprisingly, for chemically degraded pine, the values were more similar to sound wood due to the considerable densification of the material resulting from shrinkage during drying. The loss factor values for both degraded wood types were higher than for undegraded ones, indicating an increase in damping properties compared to sound pine. Distinct changes were visible in the storage modulus and loss factor graphs for DMA of chemically and biologically degraded pine. The degradation processes used in the study produced wood types with different moisture and viscoelastic properties. However, both seem useful as model materials in the research on the new conservation agents for waterlogged archaeological wood. Full article

(This article belongs to the Special Issue Physical Properties of Wood)

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10 pages, 3341 KiB

Open AccessArticle

Shear Property and Uniform Vertical Load Capacity of Bamboo I-Beams

by Xiaomeng Yang, Cong Sun, Faren Huo, Yong Gong and Yuhui Sun

Forests 2022, 13(6), 826; https://doi.org/10.3390/f13060826 - 25 May 2022

Cited by 5 | Viewed by 2051

Abstract

Bamboo oriented strand boards (BOSB) are very suitable for application in construction structures because of their excellent mechanical properties. This research investigated the shear performance of bamboo I-beams composed of BOSB to verify the structural performance of I-beams. Short beam shear tests and uniform vertical load capacity tests were performed to investigate the effects of various factors on the properties of bamboo I-beams. The results showed that shear bearing capacity and uniform vertical load capacity of bamboo I-beams exceeded the requirements for performance-rated I-Joists in APA PRI-400-2021. The shear bearing capacity, stiffness, and failure types of bamboo I-beams were determined by the web materials, flange–web joint type, and beam depth. Increasing the bamboo I-beam depth without changing the flange dimensions had no significant effect on the shear bearing capacity and stiffness of bamboo I-beams. The shear bearing capacity and stiffness of wooden orientated strand board webbed I-beams were almost half of those of bamboo I-beams with the same depth. The shear bearing capacities of specimens calculated based on the shear bearing capacity calculation formula of I-beams recommended in the Canadian standard were reasonably close to the experimental results. The uniform vertical load capacity of bamboo I-beams gradually decreased as the depth of the bamboo I-beam increased from 300 mm to 500 mm. Full article

(This article belongs to the Special Issue Physical Properties of Wood)

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15 pages, 3658 KiB

Open AccessArticle

Effects of Low-Energy-Density Microwave Treatment on Graphene/Polyvinyl Alcohol-Modified Poplar Veneer

by Shuangshuang Wu and Wei Xu

Forests 2022, 13(2), 210; https://doi.org/10.3390/f13020210 - 31 Jan 2022

Cited by 5 | Viewed by 2344

Abstract

The combination of natural wood and graphene can provide a new type of material with excellent mechanical properties and thermal conductivity. However, it is difficult for graphene to uniformly penetrate the wood due to the anisotropy of natural wood and the agglomeration of graphene. In this work, poplar veneer was treated with low-energy-density microwave to expand the entry pathways for the graphene steering liquid. The porosity, weight percent gain, and chromatic aberration were used to examine the impact of the microwave time and power. We tested the mechanical properties, thermal conductivity of the graphene/polyvinyl alcohol-modified poplar veneer to evaluate its properties. At the same time, SEM, XRD, and FT-IR were used to characterize its physical and chemical structure. The results showed that low-energy-density microwave treatment increased the weight percentage gain (WPG) and porosity without affecting the mechanical properties of the poplar veneer. The graphene-modified poplar veneer with the optimal overall performance was obtained by microwave treatment at 100% microwave power for 50 s. Indeed, the micro-characterization also revealed that the microwave treatment mostly attacked the wood rays but had little effect on the materialized structure. Therefore, low-energy-density microwave treatment could be an energy-saving and efficient way to improve graphene-impregnated veneers. Full article

(This article belongs to the Special Issue Physical Properties of Wood)

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23 pages, 6881 KiB

Open AccessArticle

Hydraulic Function Analysis of Conifer Xylem Based on a Model Incorporating Tracheids, Bordered Pits, and Cross-Field Pits

by Wen Qu, Chunmei Yang, Jiawei Zhang, Yan Ma, Xinchi Tian, Shuai Zhao and Wenji Yu

Forests 2022, 13(2), 171; https://doi.org/10.3390/f13020171 - 22 Jan 2022

Cited by 3 | Viewed by 3694

Abstract

Wood has a highly complex and anisotropic structure. Its xylem characteristics are key in determining the hydraulic properties of plants to transport water efficiently and safely, as well as the permeability in the process of wood impregnation modification. Previous studies on the relationship between the xylem structure and hydraulic conductivity of conifer have mainly focused on tracheids and bordered pits, with only a few focusing on the conduction model of cross-field pits which connect tracheids and rays. This study takes the xylem structure of conifer as an example, drawing an analogy between water flow under tension and electric current, and extends the model to the tissue scale, including cross-field pits by establishing isometric scaling. The structure parameters were collected by scanning electron microscopy and transmission electron microscopy. The improved model can quantify the important hydraulic functional characteristics of xylem only by measuring the more easily obtained tracheid section size. Then, this model was applied to quantify the relationship between the xylem anatomical structure and hydraulic properties in the pine (Pinus sylvestris L. var. mongholica Litv.) and the spruce (Picea koraiensis Nakai), and also to evaluate the effects of the number and size of cross-field pits on xylem conduction. The results showed that the growth ring conduction value of the pine was more than twice that of the spruce for the two tree species with similar growth widths in this study. The tracheid wall resistance of the pine reflected the result of the interaction of the size and number of cross-field pits, in comparison, the wall resistance of the spruce was more sensitive to the number of cross-field pits. Finally, the calculation output of the new model was cross-validated with the literature, which verified the accuracy and effectiveness of the model. This study provides an effective and complete solution for xylem conductivity measurement and the study of wood ecophysiological diversity and processing. Full article

(This article belongs to the Special Issue Physical Properties of Wood)

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7 pages, 1153 KiB

Open AccessTechnical Note

Flammability and Acetic Acid Emissions from Acetylated Wood under Well-Ventilated Burning Conditions

by Laura E. Hasburgh and Samuel L. Zelinka

Forests 2023, 14(6), 1186; https://doi.org/10.3390/f14061186 - 8 Jun 2023

Viewed by 1409

Abstract

Acetylation is a type of commercial wood modification used to enhance the durability of wood. Despite its adoption, especially in outdoor environments, there are mixed data on how acetylation affects the combustion of wood. This paper evaluates the differences in acetylated and untreated wood using a cone calorimeter in combination with Fourier Transform Infrared Spectroscopy (FTIR) to look for acetic acid vapors in the combustion gases. Two thicknesses of acetylated pine boards were tested and compared against an untreated board from the same genus. No differences were observed between the peak heat release between the acetylated and untreated boards. Likewise, there were no trends in the time to ignition between the acetylated wood and the control group. Differences were observed however in the chemical composition of the combustion products. An increase in acetic acid in the products of combustion was observed for the acetylated samples that corresponded with the peak heat release of the sample. Full article

(This article belongs to the Special Issue Physical Properties of Wood)

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