Research

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13 pages, 3947 KiB

Open AccessFeature PaperArticle

Durability and Fire Performance of Charred Wood Siding (Shou Sugi Ban)

by Laura E. Hasburgh, Samuel L. Zelinka, Amy B. Bishell and Grant T. Kirker

Forests 2021, 12(9), 1262; https://doi.org/10.3390/f12091262 - 16 Sep 2021

Cited by 16 | Viewed by 5420

Shou sugi ban, also known as yakisugi, or just sugi ban, is an aesthetic wood surface treatment that involves charring the surface of dimensional lumber, such as exterior cladding. The goal of this research is to examine the effect of shou sugi ban [...] Read more.

Shou sugi ban, also known as yakisugi, or just sugi ban, is an aesthetic wood surface treatment that involves charring the surface of dimensional lumber, such as exterior cladding. The goal of this research is to examine the effect of shou sugi ban on the flammability and decay resistance of wood. Several species and variants of commercially available sugi ban were tested. The flammability was examined from the heat release rate curves using the oxygen consumption method and cone calorimeter. Durability was examined with a soil block assay for one white-rot fungus and one brown-rot fungus. The testing showed that the shou sugi ban process did not systematically improve the flammability or durability of the siding. Full article

(This article belongs to the Special Issue Wood Modification: Physical Properties and Biological Efficacy)

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16 pages, 60794 KiB

Open AccessArticle

Effects of Different Energy Intensities of Microwave Treatment on Heartwood and Sapwood Microstructures in Norway Spruce

by Sauradipta Ganguly, Angela Balzano, Marko Petrič, Davor Kržišnik, Sadhna Tripathi, Jure Žigon and Maks Merela

Forests 2021, 12(5), 598; https://doi.org/10.3390/f12050598 - 10 May 2021

Cited by 16 | Viewed by 2485

Abstract

Microwave modification can increase the permeability of wood by delaminating and rupturing its anatomical microstructures at their weak points. A high degree of intensity of microwave modification can cause significant structural damage to the microstructures of wood, resulting in poorer strength properties. The [...] Read more.

Microwave modification can increase the permeability of wood by delaminating and rupturing its anatomical microstructures at their weak points. A high degree of intensity of microwave modification can cause significant structural damage to the microstructures of wood, resulting in poorer strength properties. The objective of this study was to evaluate the changes in the anatomical structure of Norway spruce (Picea abies (L.) Karst.) heartwood and sapwood after microwave modification in order to develop the most effective treatment in terms of applied energy without causing significant structural damage. Analysis with light and scanning electron microscopy were performed to evaluate the effect of microwave treatment for two different energy intensities, moderate and high intensity. The results indicated structural changes in the tracheid cells. Microscopy showed varying degrees of modification within the wood microstructure, with the heartwood samples showing a greater anatomical distortion compared to their sapwood counterparts. Furthermore, the samples were subjected to pycnometric density measurements, which indicated a reduction in skeletal and absolute density after microwave modification, for both high and moderate intensity treatment on sapwood and heartwood samples. With increasing microwave energy, a gradual increase in specific pore volume and porosity percentage of the samples were also detected. Full article

(This article belongs to the Special Issue Wood Modification: Physical Properties and Biological Efficacy)

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11 pages, 2643 KiB

Open AccessArticle

Comparative Adhesive Bonding of Wood Chemically Modified with Either Acetic Anhydride or Butylene Oxide

by Charles R. Frihart, Rishawn Brandon, Rebecca E. Ibach, Christopher G. Hunt and Wolfgang Gindl-Altmutter

Forests 2021, 12(5), 546; https://doi.org/10.3390/f12050546 - 28 Apr 2021

Cited by 8 | Viewed by 1704

Abstract

Determining adhesive bond performance for chemically modified wood is important not only for its commercial utility but also for understanding wood bond durability. Bulking modifications occupy space inside the cell wall, limiting the space available for water. We used two bulking modifications on [...] Read more.

Determining adhesive bond performance for chemically modified wood is important not only for its commercial utility but also for understanding wood bond durability. Bulking modifications occupy space inside the cell wall, limiting the space available for water. We used two bulking modifications on yellow poplar (Liriodendron tulipifera L.): acetylation (Ac), which bulks and converts a wood hydroxyl group to an ester, while butylene oxide (BO) also bulks the wood but preserves a hydroxyl group. Both result in lower water uptake; however, the loss of the hydroxyl group with Ac reduces the wood’s ability to form hydrogen and other polar bonds with the adhesives. On the other hand, the BO reaction replaces a hydroxyl group with another one along a hydrocarbon chain; thus, this product may not be harder to bond than the unmodified wood. We investigated how these chemical modifications of wood affect bond performance with four adhesives: resorcinol-formaldehyde (RF), melamine-formaldehyde (MF), emulsion polymer isocyanate (EPI), and epoxy. The ASTM D 905 bond shear strength for both dry and wet samples showed that the BO results were quite similar to the unmodified wood, but the MF and EPI performed poorly on Ac-modified wood, in contrast to the results with RF and epoxy. Full article

(This article belongs to the Special Issue Wood Modification: Physical Properties and Biological Efficacy)

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9 pages, 1821 KiB

Open AccessArticle

Effect of Thermal Modification Treatment on Some Physical and Mechanical Properties of Pinus oocarpa Wood

by Jhon F. Herrera-Builes, Víctor Sepúlveda-Villarroel, Jairo A. Osorio, Linette Salvo-Sepúlveda and Rubén A. Ananías

Forests 2021, 12(2), 249; https://doi.org/10.3390/f12020249 - 22 Feb 2021

Cited by 12 | Viewed by 2534

Abstract

This study deals with the effect of heat treatment on Pinus oocarpa specimens from forest plantations in Colombia. The effects of two heat treatments at 170 and 190 °C for 2.5 h in saturated vapor were evaluated based on the color, dimensional stability, [...] Read more.

This study deals with the effect of heat treatment on Pinus oocarpa specimens from forest plantations in Colombia. The effects of two heat treatments at 170 and 190 °C for 2.5 h in saturated vapor were evaluated based on the color, dimensional stability, air-dry and basic densities, modulus of elasticity (MOE), and modulus of rupture (MOR) in static bending of samples. The evaluations were carried out following the Colombian Technical Standards NTC 290 and 663, and the color changes resulting from heat treatments were monitored using the CIE-Lab, as well as other standards from the literature. The results show that there was 2.4% and 3.3% mass loss of wood modified at 170 and 190 °C, respectively. The air-dry and basic densities were higher in 170 °C treatment than after 190 °C treatment, and the thermal modifications applied increased the dimensional stability of the treated wood. After treatment at 170 and 190 °C, the lightness to darkness (L*) was reduced by 10% and 22%; the a* coordinate increased by 11% and 26%, causing redness in the treated wood; the b* coordinate increased by 14% and 17%; and the values of the wood color saturation (c*) increased by 14% and 18%, respectively. The general color change (ΔE*) increased gradually with the increase in the treatment temperature, resulting in a high color change to a very different color. The bending strength of thermally modified wood was improved and significantly increased to values higher than those of unmodified Pinus oocarpa wood. The high air-dry and basic densities, improved dimensional stability and resistance to bending, and attractive appearance of the treated wood indicate that thermal modification is a promising alternative for the transformation of Pinus oocarpa wood into a raw material with a high added value. Full article

(This article belongs to the Special Issue Wood Modification: Physical Properties and Biological Efficacy)

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9 pages, 3351 KiB

Open AccessArticle

Effect of Weathering on Surface Functional Groups of Charred Norway Spruce Cladding Panels

by Maija Kymäläinen, Hannu Turunen and Lauri Rautkari

Forests 2020, 11(12), 1373; https://doi.org/10.3390/f11121373 - 21 Dec 2020

Cited by 16 | Viewed by 2376

Abstract

Norway spruce cladding panels were surface charred with a prototype device utilizing a hot plate method. The panels were used to construct a test wall that was exposed to natural weathering for a period of two years. The changes in functional groups were [...] Read more.

Norway spruce cladding panels were surface charred with a prototype device utilizing a hot plate method. The panels were used to construct a test wall that was exposed to natural weathering for a period of two years. The changes in functional groups were evaluated with photoacoustic FTIR spectroscopy. The analysis revealed degradation of the thermally modified lignin component, indicating poor stability in weathering. Improvements in the prototype device process conditions, such as increased surface pressure and slower feed speed, and future research needs regarding surface charred wood are discussed. Full article

(This article belongs to the Special Issue Wood Modification: Physical Properties and Biological Efficacy)

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13 pages, 4271 KiB

Open AccessArticle

Effect of Thermal Modification on the Nano-Mechanical Properties of the Wood Cell Wall and Waterborne Polyacrylic Coating

by Yan Wu, Xinyu Wu, Feng Yang, Haiqiao Zhang, Xinhao Feng and Jilei Zhang

Forests 2020, 11(12), 1247; https://doi.org/10.3390/f11121247 - 25 Nov 2020

Cited by 15 | Viewed by 2127

Abstract

Masson pine (Pinus massoniana Lamb.) samples were heat-treated at different treatment temperatures (150, 170, and 190 °C), and the nano-mechanical properties of the wood cell wall, which was coated with a waterborne polyacrylic (WPA) lacquer product, were compared. The elastic modulus ( [...] Read more.

Masson pine (Pinus massoniana Lamb.) samples were heat-treated at different treatment temperatures (150, 170, and 190 °C), and the nano-mechanical properties of the wood cell wall, which was coated with a waterborne polyacrylic (WPA) lacquer product, were compared. The elastic modulus (E_r) and hardness (H) of wood cell wall and the coating were measured and characterized by nanoindentation, and the influencing factors of mechanical properties during thermal modification were investigated by chemical composition analysis, contact angle analysis, and colorimetric analysis. The results showed that with the increase in the heat treatment temperature, the contact angle of the water on the wood’s surface and the colorimetric difference increased, while the content of the cellulose and hemicelluloses decreased. After thermal modification of 190 °C, the E_r and H of the wood cell wall increased by 13.9% and 17.6%, respectively, and the E_r and H of the WPA coating applied to the wood decreased by 12.1% and 22.2%. The E_r and H of the interface between the coating and wood were lower than those near the coating’s surface. The E_r and H of the cell wall at the interface between the coating and wood were lower than those far away from the coating. This study was of great significance for understanding the binding mechanism between coating and wood cell walls and improving the finishing technology of the wood materials after thermal modification. Full article

(This article belongs to the Special Issue Wood Modification: Physical Properties and Biological Efficacy)

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15 pages, 3953 KiB

Open AccessArticle

Wood Properties Characterisation of Thermo-Hydro Mechanical Treated Plantation and Native Tasmanian Timber Species

by Michelle Balasso, Andreja Kutnar, Eva Prelovšek Niemelä, Marica Mikuljan, Gregory Nolan, Nathan Kotlarewski, Mark Hunt, Andrew Jacobs and Julianne O’Reilly-Wapstra

Forests 2020, 11(11), 1189; https://doi.org/10.3390/f11111189 - 10 Nov 2020

Cited by 7 | Viewed by 2536

Abstract

Thermo-hydro mechanical (THM) treatments and thermo-treatments are used to improve the properties of wood species and enhance their uses without the application of chemicals. This work investigates and compares the effects of THM treatments on three timber species from Tasmania, Australia; plantation fibre-grown [...] Read more.

Thermo-hydro mechanical (THM) treatments and thermo-treatments are used to improve the properties of wood species and enhance their uses without the application of chemicals. This work investigates and compares the effects of THM treatments on three timber species from Tasmania, Australia; plantation fibre-grown shining gum (Eucalyptus nitens H. Deane and Maiden), plantation saw-log radiata pine (Pinus radiata D. Don) and native-grown saw-log timber of the common name Tasmanian oak (which can be any of E. regnans F. Muell, E. obliqua L’Hér and E. delegatensis L’Hér). Thin lamellae were compressed by means of THM treatment from 8 mm to a target final thickness of 5 mm to investigate the suitability for using THM-treated lamellas in engineered wood products. The springback, mass loss, set-recovery after soaking, dimensional changes, mechanical properties, and Brinell hardness were used to evaluate the effects of the treatment on the properties of the species. The results show a marked increase in density for all three species, with the largest increase presented by E. nitens (+53%) and the smallest by Tasmanian oak (+41%). E. nitens displayed improvements both in stiffness and strength, while stiffness decreased in P. radiata samples and strength in Tasmanian oak samples. E. nitens also displayed the largest improvement in hardness (+94%) with respect to untreated samples. P. radiata presented the largest springback whilst having the least mass loss. E. nitens and Tasmanian oak showed similar dimensional changes, whilst P. radiata timber had the largest thickness swelling and set-recovery due to the high water absorption (99%). This study reported the effects of THM treatments in less-known and commercially important timber species, demonstrating that the wood properties of a fibre-grown timber can be improved through the treatments, potentially increasing the utilisation of E. nitens for structural and higher quality timber applications. Full article

(This article belongs to the Special Issue Wood Modification: Physical Properties and Biological Efficacy)

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12 pages, 2253 KiB

Open AccessArticle

The Effect of Acetylation on Iron Uptake and Diffusion in Water Saturated Wood Cell Walls and Implications for Decay

by Samuel L Zelinka, Carl J. Houtman, Kolby Hirth, Steven Lacher, Linda Lorenz, Emil Engelund Thybring and Christopher G. Hunt

Forests 2020, 11(10), 1121; https://doi.org/10.3390/f11101121 - 21 Oct 2020

Cited by 7 | Viewed by 2232

Abstract

Acetylation is widely used as a wood modification process that protects wood from fungal decay. The mechanisms by which acetylation protects wood are not fully understood. With these experiments, we expand upon the literature and test whether previously observed differences in iron uptake [...] Read more.

Acetylation is widely used as a wood modification process that protects wood from fungal decay. The mechanisms by which acetylation protects wood are not fully understood. With these experiments, we expand upon the literature and test whether previously observed differences in iron uptake by wood were a result of decreased iron binding capacity or slower diffusion. We measured the concentration of iron in 2 mm thick wood sections at 0, 10, and 20% acetylation as a function of time after exposure to iron solutions. The iron was introduced either strongly chelated with oxalate or weakly chelated with acetate. The concentrations of iron and oxalate in solution were chosen to be similar to those found during brown rot decay, while the concentration of iron and acetate matched previous work. The iron content of oxalate-exposed wood increased only slightly and was complete within an hour, suggesting little absorption and fast diffusion, or only slight surface adsorption. The increase in iron concentration from acetate solutions with time was consistent with Fickian diffusion, with a diffusion coefficient on the order of 10⁻¹⁶ m² s⁻¹. The rather slow diffusion rate was likely due to significant binding of iron within the wood cell wall. The diffusion coefficient did not depend on the acetylation level; however, the capacity for iron absorption from acetate solution was greatly reduced in the acetylated wood, likely due to the loss of OH groups. We explored several hypotheses that might explain why the diffusion rate appears to be independent of the acetylation level and found none of them convincing. Implications for brown rot decay mechanisms and future research are discussed. Full article

(This article belongs to the Special Issue Wood Modification: Physical Properties and Biological Efficacy)

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11 pages, 3638 KiB

Open AccessArticle

Effect of Supercritical CO₂ Drying on Moisture Transfer and Wood Property of Eucalyptus urophydis

by Lin Yang and Honghai Liu

Forests 2020, 11(10), 1115; https://doi.org/10.3390/f11101115 - 20 Oct 2020

Cited by 12 | Viewed by 2549

Abstract

Wood dried using supercritical CO₂ has unique properties because water is removed directly from the cell lumens through the cycling between supercritical and gas phases. Eucalyptus urophydis green wood was dried by supercritical CO₂ at 50 °C and pressure of 10, [...] Read more.

Wood dried using supercritical CO₂ has unique properties because water is removed directly from the cell lumens through the cycling between supercritical and gas phases. Eucalyptus urophydis green wood was dried by supercritical CO₂ at 50 °C and pressure of 10, 20, and 30 MPa; the effect of supercritical CO₂ drying on moisture content distribution and transfer, as well as the permeability and extractive content of the wood, was investigated. The results showed that the supercritical CO₂ drying rate was high, showing the highest drying rate at 20 MPa and the lowest at 10 MPa. Drying rate increased with pressure below 20 MPa in this study; drying rate represented no positive relation to pressure over 20 Mpa. Moisture content distribution was more uneven in the low-pressure drying conditions and in the middle transverse section of the specimens. The moisture content gradient in tangential was greater than that in longitudinal, especially for the drying of 10 MPa, indicating that water was removed mainly in the former direction of wood. More extractives were removed from wood at higher pressure during supercritical CO₂ drying. Bordered pits were broken up more at higher pressure conditions. The decreased extract yields and increased amount of opened bordered pits increased the permeability of the wood after supercritical CO₂ drying. Full article

(This article belongs to the Special Issue Wood Modification: Physical Properties and Biological Efficacy)

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12 pages, 2694 KiB

Open AccessArticle

Preparation of Wood-Based Panel Composites with Poplar Veneer as the Surface Layer Modified by In-Situ Polymerization of Active Monomers

by Xiaoyan Yu, Dandan Xu, Yan Sun, Yuran Geng, Jilong Fan, Xiaohan Dai, Zaixin He, Xiaoying Dong, Yufeng Dong and Yongfeng Li

Forests 2020, 11(8), 893; https://doi.org/10.3390/f11080893 - 18 Aug 2020

Cited by 17 | Viewed by 2747

Abstract

Wood-based panels covered by melamine-impregnated paper are widely used in floors and furniture, due to its good surface texture, hardness, wear resistance, and waterproof function. However, there are still some problems, such as formaldehyde release from the impregnated resin, non-wood touch, and complex [...] Read more.

Wood-based panels covered by melamine-impregnated paper are widely used in floors and furniture, due to its good surface texture, hardness, wear resistance, and waterproof function. However, there are still some problems, such as formaldehyde release from the impregnated resin, non-wood touch, and complex preparation processes. Therefore, this study designed glycidyl methacrylate (GMA) and ethyleneglycol dimethacrylate (EGDMA), combined with maleic anhydride (MAN) as a reactive catalyst, to build an active monomers system. It was first impregnated into poplar veneers, and then in-situ polymerized within the veneer using a hot pressing process, which realized the gluing of the veneer onto the wood-based panel substrate, synchronously. Such treatment aims to obtain wood-based panel composites decorated by the modified veneer, with real solid wood touch feeling, satisfied surface properties, and environment friendly glue bonding. The results indicated that the optimized reaction ratio of the active monomers (GMA:EGDMA) was 2:1 (molar ratio), and the maleic anhydride addition accounted for 6 wt.% of the total monomers. Under the optimized hot pressing condition, the modified veneer closely bonded to the wood-based panel substrate without obvious interfacial gaps. The hardness, abrasion resistance, modulus of rupture, and water resistance of the composites were significantly improved. Such results indicate that the treatment realized the perfect merging of solid wood touch feeling, environment friendly feature, and excellent properties of the composite. It was highly expected to replace the traditional melamine-impregnated paper to decorate wood-based panels, and could be potentially applied as surface decorating materials in wide areas of desktop, floor, cupboard, wardrobe, and so on. Full article

(This article belongs to the Special Issue Wood Modification: Physical Properties and Biological Efficacy)

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Review

Jump to: Research

18 pages, 2550 KiB

Open AccessReview

Wood Modification as a Tool to Understand Moisture in Wood

by Emil Engelund Thybring and Maria Fredriksson

Forests 2021, 12(3), 372; https://doi.org/10.3390/f12030372 - 20 Mar 2021

Cited by 47 | Viewed by 8240

Abstract

Moisture plays a central role in the performance of wood products because it affects important material properties such as the resistance to decomposition, the mechanical properties, and the dimensions. To improve wood performance, a wide range of wood modification techniques that alter the [...] Read more.

Moisture plays a central role in the performance of wood products because it affects important material properties such as the resistance to decomposition, the mechanical properties, and the dimensions. To improve wood performance, a wide range of wood modification techniques that alter the wood chemistry in various ways have been described in the literature. Typically, these modifications aim to improve resistance to decomposition, dimensional stability, or, to introduce novel functionalities in the wood. However, wood modification techniques can also be an important tool to improve our understanding of the interactions between wood and moisture. In this review, we describe current knowledge gaps in our understanding of moisture in wood and how modification has been and could be used to clarify some of these gaps. This review shows that introducing specific chemical changes, and even controlling the distribution of these, in combination with the variety of experimental methods available for characterization of moisture in wood, could give novel insights into the interaction between moisture and wood. Such insights could further contribute to applications in several related fields of research such as how to enhance the resistance to decomposition, how to improve the performance of moisture-induced wooden actuators, or how to improve the utilization of wood biomass with challenging swelling anisotropy. Full article

(This article belongs to the Special Issue Wood Modification: Physical Properties and Biological Efficacy)

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23 pages, 6139 KiB

Open AccessReview

USDA Forest Service Forest Products Laboratory: Acetylation of Wood 1945–1966

by Rebecca E. Ibach and Roger M. Rowell

Forests 2021, 12(3), 260; https://doi.org/10.3390/f12030260 - 24 Feb 2021

Cited by 3 | Viewed by 1807

Abstract

The first research on acetylation of wood started in 1928, and the first research done on acetylation of wood at the USDA Forest Service Forest Products Laboratory (FPL) started in 1945. This is a review of the research done between 1945 and 1966 [...] Read more.

The first research on acetylation of wood started in 1928, and the first research done on acetylation of wood at the USDA Forest Service Forest Products Laboratory (FPL) started in 1945. This is a review of the research done between 1945 and 1966 at the FPL. This research was the first to show that acetylated wood was both decay-resistant and dimensionally stable. It was the pioneering research that ultimately led to the commercial production of acetylated wood. Full article

(This article belongs to the Special Issue Wood Modification: Physical Properties and Biological Efficacy)

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