OPTIMIZATION OF PROTECTIVE COATING COMPONENTS OF THERMOMODIFIED WOOD TO THE EXPOSURE OF WATER

Abstract. Paints and varnishes are used to a large extent to protect wood surfaces in outdoor conditions, as they are easy to maintain and reapply. Also, when developing a coating, manufacturers are guided by the need to obtain a number of properties that generally determine its ability to protect against moisture. To obtain a protective coating that meets the specified requirements, it is necessary that the components that make up the coating belong directly to the group of protective materials or form such compounds under operating conditions, be able to adhere to the surface of the product. It was found that thermal modification provides a decrease in water absorption of wood. Additional processing of the wood surface helps to reduce moisture absorption by 2 times, and for samples modified at a temperature of 220 °C – 3 times. Geometric dimensional stability is also improved by a factor of 2. The effect of heat treatment on the water absorption of wood is somewhat less – for samples modified at 190 and 220 °C for more than 10 hours. Protective substances for thermally modified wood provided similar protection of open thermally modified surfaces of wood from the effects of water. The positive effect of thermal modification on a decrease in the level of water absorption has been established. It has been proven that it is temperature that has a significant effect on such changes. Since the protective coating is also susceptible to photochemical degradation, it is very important to renew it in a timely manner in accordance with the manufacturer's instructions for the pleasant appearance of wood surfaces during external use. The optimal ratio of components in the surface layer of thermally modified wood has been determined, which ensures the fulfillment of the task, namely for a mixture of oil and wax: the density of a wood – 724 kg/m3; oils – 70.0%; wax – 17.5%. Therefore, such treatment is beneficial for the protection and aesthetic appeal of wood products.

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Thermal modification of Southern pine combined with wax emulsion preimpregnation: effect on hydrophobicity and dimensional stability

Holzforschung ◽

10.1515/hf-2014-0106 ◽

2015 ◽

Vol 69 (4) ◽

pp. 405-413 ◽

Cited By ~ 24

Author(s):

Wang Wang ◽

Yuan Zhu ◽

Jinzhen Cao ◽

Xi Guo

Keyword(s):

Water Absorption ◽

Dimensional Stability ◽

Photoelectron Spectroscopy ◽

Water Repellency ◽

Solid Content ◽

Thermal Modification ◽

Paraffin Wax ◽

Southern Pine ◽

Thermally Modified Wood ◽

Modified Wood

Abstract The aim of this study was to enhance the water repellency and dimensional stability of thermally modified wood by combining the preimpregnation of paraffin wax emulsion. To achieve this, Southern pine (SP; Pinus spp.) samples were first impregnated with paraffin wax emulsion (with 2.0% solid content) and then subjected to thermal modification (TM) in an oven at 180°C and 220°C for 4 and 8 h. The contact angle (CA), surface free energy, water absorption rate (WAR), anti-swelling efficiency (ASE), and bending properties of the control and modified samples were investigated. Moreover, the chemical and morphological alterations were analyzed by Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). Both the wax impregnation and TM decreased the surface wettability, water absorption, and tangential swelling, while the combination of wax and thermal treatment exhibited the best water repellency and dimensional stability, indicating the synergism between the two procedures. However, the wax preimpregnation did not affect the mechanical properties of thermally modified wood. The FTIR, SEM, and XPS analyses confirmed that the synergistic effect is mainly due to the redistribution of the paraffin wax during TM rather than its impact on the chemical changes caused by thermal degradation.

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Influence of Different Modifications on Bending Strength of Wood

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.800.240 ◽

2019 ◽

Vol 800 ◽

pp. 240-245

Author(s):

Andis Antons ◽

Dace Cīrule ◽

Ingeborga Andersone ◽

Anrijs Verovkins ◽

Edgars Kuka

Keyword(s):

Thermal Treatment ◽

Bending Strength ◽

Treatment Method ◽

Thermal Modification ◽

Wood Products ◽

Bending Properties ◽

Wood Protection ◽

Thermally Modified Wood ◽

Mild Temperature ◽

Modified Wood

Despite intensive research in wood protection, no simple wood treatment method is available for satisfactory wood protection that could ensure appropriate strength and bio-resistance of wood products during their service life. The present study is a part of a project that is aimed to improve wood service properties by combining wood thermal treatment and impregnation with copper containing preservatives. The objective of the present study was to investigate the effect of conventional modifications (thermal modification at relatively mild temperature range (150 - 180°C) and impregnation) and double-treatments (impregnation after thermal treatment and vice versa) on the bending properties of birch (Betula spp.) and pine (Pinussylvestris L.) wood. Bending strength considerably decreased after thermal modification of wood, however MOE values generally did not significantly change. Moreover, impregnation had no effect on the bending properties for both unmodified and thermally modified wood specimens. For double-treatment in which impregnation was carried out before thermal modification no changes in bending strength were observed comparing to thermally modified wood. However, MOE values of these specimens were 10 % for birch and 19 % for pine smaller comparing to just thermally modified wood. The results of double-treatment tests imply that, regarding wood bending properties, wood impregnation after thermal modification is more appropriate.

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Corrosiveness of Thermally Modified Wood

Forests ◽

10.3390/f11010050 ◽

2019 ◽

Vol 11 (1) ◽

pp. 50 ◽

Cited By ~ 1

Author(s):

Samuel Zelinka ◽

Leandro Passarini ◽

Frederick Matt ◽

Grant Kirker

Keyword(s):

Stainless Steel ◽

Carbon Steel ◽

Water Vapor Sorption ◽

Thermal Modification ◽

Wood Products ◽

Galvanized Steel ◽

Exposure Test ◽

Corrosion Rates ◽

Thermally Modified Wood ◽

Modified Wood

Thermally modified wood is becoming commercially available in North America for use in outdoor applications. While there have been many studies on how thermal modification affects the dimensional stability, water vapor sorption, and biodeterioration of wood, little is known about whether thermally modified wood is corrosive to metal fasteners and hangers used to hold these members in place. As thermally modified wood is used in outdoor applications, it has the potential to become wet which may lead to corrosion of embedded fasteners. Here, we examine the corrosiveness of thermally modified ash and oak in an exposure test where stainless steel, hot-dip galvanized steel, and carbon steel nails are driven into wood and exposed to a nearly 100% relative humidity environment at 27 °C for one year. The corrosion rates were compared against control specimens of untreated and preservative-treated southern pine. Stainless steel fasteners did not corrode in any specimens regardless of the treatment. The thermal modification increased the corrosiveness of the ash and oak, however, an oil treatment that is commonly applied by the manufacturer to the wood after the heat treatment reduced the corrosiveness. The carbon steel fasteners exhibited higher corrosion rates in the thermally modified hardwoods than in the preservative-treated pine control. Corrosion rates of galvanized fasteners in the hardwoods were much lower than carbon steel fasteners. These data can be used to design for corrosion when building with thermally modified wood, and highlight differences between corrosion of metals embedded in wood products.

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Effects of environmental conditions on physical and mechanical properties of thermally modified wood

Canadian Journal of Forest Research ◽

10.1139/cjfr-2019-0180 ◽

2019 ◽

Vol 49 (11) ◽

pp. 1434-1440 ◽

Cited By ~ 1

Author(s):

Chenyang Cai ◽

Henrik Heräjärvi ◽

Antti Haapala

Keyword(s):

Norway Spruce ◽

Scots Pine ◽

Moisture Absorption ◽

Brinell Hardness ◽

Physical And Mechanical Properties ◽

Thermal Modification ◽

The Difference ◽

Thermally Modified Wood ◽

Modified Wood ◽

Exposure Conditions

The behaviour of industrially modified wood has not been systematically evaluated in controlled exposure conditions. The objective of this study was to assess the equilibrium moisture content (EMC), dimensions, and Brinell hardness of thermally modified wood in different conditions of temperature and relative humidity (RH). Tested materials consisted of European ash (Fraxinus excelsior L.), Norway spruce (Picea abies (L.) Karst.), and Scots pine (Pinus sylvestris L.) that were thermally modified according to ThermoWood industrial processes into the classes Thermo-S and Thermo-D. The properties were measured at the following conditions: 20 °C and 65% RH, 10 °C and 90% RH, and 30 °C and 30% RH. The results show that the reduction of EMC and the improvement in dimensional stability are dependent on the degree of thermal modification. Thermal modification was more resistant to moisture absorption at 20 °C and 65% RH than at 10 °C and 90% RH and 30 °C and 30% RH, and the more severe modification decreased the difference among different exposure conditions. The tangential–radial ratio of swelling and shrinkage was higher for thermally modified wood than for nonmodified wood. Brinell hardness of modified Scots pine and Norway spruce did not differ significantly from that of nonmodified wood in normal and dry conditions, but the more humid conditions increased the difference by 12%–17%.

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Increasing the Strength of the Glue Line in the Production of Thermally Modified Wood Paneling

Coatings ◽

10.3390/coatings11020253 ◽

2021 ◽

Vol 11 (2) ◽

pp. 253

Author(s):

Ruslan Rushanovich Safin ◽

Aigul Ravilevna Shaikhutdinova ◽

Ruslan Khasanshin ◽

Shamil Mukhametzyanov ◽

Albina Safina

Keyword(s):

Wood Products ◽

Ultraviolet Rays ◽

Surface Activation ◽

Wood Block ◽

Two Stage ◽

Adhesion Properties ◽

Wood Processing ◽

Ultraviolet Treatment ◽

Thermally Modified Wood ◽

Modified Wood

This work is devoted to the study of the effect of ultraviolet rays for the surface activation of pine wood thermally modified at temperatures of 180−240 °C in order to increase the surface roughness, enhance the wettability of thermal wood and the adhesive strength of the glue in the production of wood block furniture panels. Studies were carried out to measure the contact angle of wettability of thermally modified wood samples of pine, as a result of which it was determined that the ultraviolet treatment process contributes to an increase in the adhesion properties of the surface layer of thermally modified wood by more than 13% due to the reactivity of ultraviolet rays to oxidize and degrade ligno-containing wood products. At the same time, the most active process of surface activation takes place during 60 min of ultraviolet irradiation of wood with a total irradiation of at least 125 W/cm2. It was revealed that the combined effect of two-stage wood processing, including preliminary volumetric thermal modification followed by surface ultraviolet treatment, causes an increase in the moisture resistance of glued wood products by 24%. So, if the strength of the glue seam when gluing natural wood samples after boiling decreased by 46%, then the samples that underwent two-stage processing showed a decrease only by 22%. In connection with the results obtained, an improved technology for the production of furniture boards for the manufacture of moisture-resistant wood products is proposed.

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Flammability Characteristics of Thermally Modified Meranti Wood Treated with Natural and Synthetic Fire Retardants

Polymers ◽

10.3390/polym13132160 ◽

2021 ◽

Vol 13 (13) ◽

pp. 2160

Author(s):

Milan Gaff ◽

Hana Čekovská ◽

Jiří Bouček ◽

Danica Kačíková ◽

Ivan Kubovský ◽

...

Keyword(s):

Burning Rate ◽

Flame Retardants ◽

Thermal Modification ◽

Positive Contribution ◽

Spearman Correlation ◽

Chemical Changes ◽

Combustion Properties ◽

Flammability Characteristics ◽

Thermally Modified Wood ◽

Modified Wood

This paper deals with the effect of synthetic and natural flame retardants on flammability characteristics and chemical changes in thermally treated meranti wood (Shorea spp.). The basic chemical composition (extractives, lignin, holocellulose, cellulose, and hemicelluloses) was evaluated to clarify the relationships of temperature modifications (160 °C, 180 °C, and 210 °C) and incineration for 600 s. Weight loss, burning speed, the maximum burning rate, and the time to reach the maximum burning rate were evaluated. Relationships between flammable properties and chemical changes in thermally modified wood were evaluated with the Spearman correlation. The thermal modification did not confirm a positive contribution to the flammability and combustion properties of meranti wood. The effect of the synthetic retardant on all combustion properties was significantly higher compared to that of the natural retardant.

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A review on life cycle assessments of thermally modified wood

Holzforschung ◽

10.1515/hf-2020-0102 ◽

2020 ◽

Vol 0 (0) ◽

Author(s):

Kévin Candelier ◽

Janka Dibdiakova

Keyword(s):

Life Cycle ◽

Environmental Impacts ◽

Treated Wood ◽

Single Step ◽

Thermal Modification ◽

Wood Products ◽

Wood Preservation ◽

Cumulative Energy ◽

Thermally Modified Wood ◽

Cumulative Energy Intake

AbstractThis review compiles various literature studies on the environmental impacts associated with the processes of thermal modification of wood. In wood preservation field, the wood modification by heat is considered as an ecofriendly process due to the absence of any additional chemicals. However, it is challenging to find proper scientific and industrial data that support this aspect. There are still very few complete studies on the life cycle assessment (LCA) and even less studies on the environmental impacts related to wood heat treatment processes whether on a laboratory or on an industrial scales. This comprehensive review on environmental impact assessment emphasizes environmental categories such as dwindling of natural resources, cumulative energy intake, gaseous, solid and liquid emissions occurred by the thermal-treated wood industry. All literature-based data were collected for every single step of the process of wood thermal modification like resources, treatment process, transport and distribution, uses and end of life of treated wood products.

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Colour stability of surface finishes on thermally modified beech wood

Annals of WULS, Forestry and Wood Technology ◽

10.5604/01.3001.0015.2391 ◽

2021 ◽

Vol 114 ◽

pp. 116-124

Author(s):

Gabriela Slabejová ◽

MÁRIA ŠMIDRIAKOVÁ

Keyword(s):

Surface Finish ◽

Beech Wood ◽

Surface Finishing ◽

Colour Stability ◽

Colour Difference ◽

Surface Finishes ◽

Before And After ◽

Thermally Modified Wood ◽

Wood Surfaces ◽

Modified Wood

Colour stability of surface finishes on thermally modified beech wood. The paper deals with the influence of the type of transparent surface finish on the change of colour of the surfaces of native beech wood and thermally modified wood. At the same time, the colour stability of three surface finishes on the surfaces of native and thermally modified beech wood was monitored. Beech wood was thermally modified at temperature of 125 °C for 6 hours. The thermal treatment was performed in a pressure autoclave APDZ 240, by the company Sundermann s.r.o in Banská Štiavnica. Three various types of surface finishes (synthetic, wax-oil, water-based) were applied onto the wood surfaces. The colour of the surfaces of native wood and thermally modified wood was measured in the system CIELab before and after surface finishing; the coordinates L*, a*, b*, C*ab and h*ab were measured. From the coordinates measured before and after surface finishing, the differences were calculated and then the colour difference ∆E* was calculated. Subsequently, the test specimens with the surface finishes were exposed to natural sunlight, behind glass in the interior for 60 days. The surface colour was measured at specified time of the exposure (10, 20, 30, 60 days). The results showed that the colour of the wood surfaces changed after application of the individual surface finishes; and the colour difference reached a change visible with a medium quality filter up to a high colour difference. The wax-oil surface finish caused a high colour difference on native wood and on thermally modified wood as well. On native beech wood, the lowest colour difference after exposure to sunlight was noticeable on the synthetic surface finish. On the surface of wood thermally modified, after exposure to sunlight, the lowest colour difference was noticeable on the surface with no surface finish.

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Hygroscopic properties of thermally modified false Iroko [Antiaris toxicara (Lesch)]

Journal of Agriculture Forestry and the Social Sciences ◽

10.4314/joafss.v18i1.7 ◽

2021 ◽

Vol 18 (1) ◽

pp. 51-57

Author(s):

F.A. Faruwa ◽

K. Duru

Keyword(s):

Weight Loss ◽

Dimensional Stability ◽

Thermal Process ◽

Colour Change ◽

Wood Properties ◽

Thermal Modification ◽

Hygroscopic Properties ◽

Different Temperatures ◽

Thermally Modified Wood ◽

Modified Wood

The study investigated the use of thermal modification to improve the hygroscopic properties of False Iroko [Antiaris toxicaria (Lesch)]. Samples of Antiaris toxicara Lesch wood were subjected to thermal modification in a furnace at temperatures of 160, 180 and 200°C for 30 and 60 minutes. Results showed that wood properties were improved with exposure to different temperatures. Subsequent to the thermal process, a colour change from pale yellow to darkish brown was observed progressively with increase in temperature, accompanied by a weight loss in the range of 12.08% to 23.67%. The outcome of these treatments resulted in a decrease in volumetric swelling and increase in dimensional stability of modified wood; this can be attributed to observed decrease in moisture intake. The thermal modification of Antiaris toxicara Lesch wood affected the dimensional stability properties. Thus, due to significant changes via modification carried out on the selected species which is classified as lesser utilized wood species, lesser utilized wood,Antiaristoxicara Lesch wood is recommended for use due to its efficient dimensional stability after modification . keywords:, Thermally modified wood ;False Iroko

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