Physical and mechanical characteristics of poor-quality wood after heat treatment (original) (raw)
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Effects of heat treatment on some characteristics of Scots pine (Pinus sylvestris L.) wood
BioResources, 2019
Heat treatment of wood materials is generally performed to improve the physical, mechanical, chemical, surface, thermal, and crystallinity characteristics. In this way, the usage areas of wood material in different purposes can be expanded by means of heat treatment. The goal of this study was to determine the physical, mechanical, chemical, crystallinity, and surface properties of heat-treated Scots pine (Pinus sylvestris L.) wood. The test samples were heat-treated at 120 °C, 150 °C, 180 °C, and 210 °C for 4 and 6 h in a laboratory-scale oven. The shrinking and swelling chracteristics of wood was decreased as a function of heat treatment processes. Bending strength, compression strength, and modulus of elasticity decreased. In addition, lignin ratios and crystallinity index increased as temperature and duration of the treatment were increased. Consequently, heat-treated wood materials can be used in various areas by developing some of their properties.
Elastic and Strength Properties of Heat-Treated Beech and Birch Wood
Forests
This paper deals with the impact of heat treatment on the elastic and strength properties of two diffuse porous hardwoods, namely Fagus sylvatica and Betula pendula. Two degrees of the heat treatment were used at temperatures of 165 • C and 210 • C. The dynamic and static elasticity modulus, bending strength, impact toughness, hardness, and density were tested. It is already known that an increase in treatment temperature decreases the mechanical properties and, on the other hand, leads to a better shape and dimensional stability. Higher temperatures of the heat treatment correlated with lower elastic and strength properties. In the case of higher temperature treatments, the decline of tested properties was noticeable as a result of serious changes in the chemical composition of wood. It was confirmed that at higher temperature stages of treatment, there was a more pronounced decrease in beech properties compared to those of the birch, which was the most evident in their bending strength and hardness. Our research confirmed that there is no reason to consider birch wood to be of a lesser quality, although it is regarded by foresters as an inferior tree species. After the heat treatment, the wood properties are almost the same as in the case of beech wood.
Physical and Mechanical Properties of Heat Treated Daniella oliveri (Africa Balsam Tree) Wood
Current Journal of Applied Science and Technology, 2019
Aims: This work investigated the effect of thermal modification on some of the physical properties and mechanical properties of Daniella oliveri wood. Study Design: The study design used for this experiment was 3 x4 Factorial experiment in Completely Randomized Design. Place and Duration of Study: The study was conducted at the Federal University of Technology, Akure wood laboratory and the study lasted for 6 months. Methodology: Wood samples were thermally treated at the temperature of 120, 140, 160 and 180°C, for different durations of 1, 1.5 and 2 hours in a muffle furnace. The planks were air-dried to reduce the moisture content and then machined into the required dimensions in the direction parallel to grain with a circular saw. Thirty-nine defect-free samples of dimensions 20 mm × 20 mm × 60 mm were prepared for dimensional stability and compression test, static bending tests and the hardness tests to make a total of 117 samples. Original Research Article Iyiola et al.; CJAST, 35(2): 1-9, 2019; Article no.CJAST.48727 2 Results: The result showed that the average weight loss of the treated wood samples varied from 3.79% at 120°C for 1 hour to 7.51% at 180°C for 2 hours. The treatment led to reduction in density from 528 to 459 kg/m 3 at 180°C for 2 hours. The heat treatment also led to reduction in water absorption and volumetric swelling of the treated samples. The mean value for Modulus of elasticity (MOE) ranges from 2.17x10 3 N/mm 2 to 2.96 x 10 3 N/mm 2 for the treated samples while the untreated was 2.22x10 3 N/mm 2. Heat treatment brought about improvement in the maximum compressive strength and the Janka hardness parallel to the grain of wood samples. The value of compressive strength increased from 26.58 N/mm 2 to 41.71 N/mm 2 and hardness from 69.24 N to 75.5 N. It can therefore be concluded that thermal modification greatly enhanced the dimensional stability and mechanical properties of wood samples.
BioResources
Effects of heat treatment parameters on the physical properties, mechanical properties, and crystallinity index of Scots pine and beech wood were investigated. Scots pine (Pinus sylvestris L.) and beech (Fagus orientalis Lipsky) sapwood samples were prepared in 2 cm × 2 cm × 36 cm dimensions by considering the physical and mechanical tests. The samples were heat-treated for 2 h and 4 h at 150 °C, 180 °C, and 210 °C in an atmospheric environment. The shrinking and swelling percentages of all samples were calculated. The compressive strength, bending strength, modulus of elasticity (MOE), and hardness tests were carried out. X-ray diffraction (XRD) was performed to calculate the crystallinity index values. As a result of the study, it was determined that heat treatment generally had a positive effect on the physical properties of Scots pine and beech samples. It was observed that the bending strength of the wood samples decreased up to 180 °C as the temperature increased and then incr...
Mechanical and chemical behavior of spruce wood modified by heat
Building and environment, 2006
In this study the effects of heat treatment on compression strength (CS) of spruce wood (Picea orientalis) were examined and changes in the chemical structure of the treated wood were determined by analyzing contents of cellulose, hemicellulose and lignin.
BioResources, 2015
This paper investigates the effect of heat treatment temperature on the stiffness and strength properties of Douglas fir (Pseudotsuga menziesii Franco) and common alder (Alnus glutinosa Gaertn.) woods. Two temperatures of heat treatment were used: 165 and 210 °C. The effects of dynamic elasticity modulus, static elasticity modulus, impact toughness, bending strength, and density were evaluated. It is already understood that the mechanical properties, primarily the bending strength, decreases with increasing temperature. In contrast to the favorable stability in shape and dimension that was achieved, the changes in the woods' properties with temperature were mostly negative. Higher heat treatment temperatures corresponded with lower stiffness and strength properties. For higher temperature treatments, above 200 °C, deterioration of the tested properties was noticable as a result of the significant changes in the wood chemical structure. Even the positive effect of the equilibrium moisture decrease was not able to counterbalance the unfavorable changes. Moreover, it was observed that as the hemicellulose content is higher in alder wood, density, static bending strength, and toughness all decreased steadily at high temperatures, compared to Douglas fir wood.
Mechanical behaviour of Québec wood species heat-treated using ThermoWood process
Holz als Roh- und Werkstoff, 2007
Finnish wood heat treatment technology, Ther-moWood, was recently introduced to Québec, Canada by Ohlin Thermo Tech. Subsequently, a large number of initial trials were conducted on five commercially important Québec wood species, spruce (Picea spp.), pine (Pinus spp.), fir (Abies spp.), aspen (Populus spp.), and birch (Betula spp.). These species were thermally-modified in different batches at temperatures of 200 • C or higher. The static bending and hardness of the thermally-modified wood were examined. Decreases of 0% to 49% were observed in modulus of rupture of heat-treated spruce, pine, fir, and aspen depending on species and treatment schedules used; modulus of rupture of birch increased slightly after the heat treatment. The decrease in modulus of elasticity of heat-treated spruce and pine ranged from 4% to 28%; but the modulus of elasticity of heat-treated fir, aspen, and birch increased except one trial for fir. Hardness of the heat-treated wood increased or decreased depending on the species, test directions (radial, tangential, and longitudinal), and treatment schedules.
Mechanical characterization of heat-treated ash wood in relation with structural timber standards
Heat treatment is an attractive method to enhance wood durability, and valorize local hardwood species with natural low durability. Yet no standard allows the certification of such products. This study first aims to observe the influence of heat treatment on the different mechanical properties. The standard mechanical tests; bending, tension parallel and perpendicular to grain, compression parallel and perpendicular to grain and shear, have been performed on native and heat-treated woods samples. The measurements are then compared to values of EN 338 standard. Results reveal that shear strength is the property most affected by heat treatment and that the modulus of elasticity perpendicular to grain is increased. The values given by EN 338 standard are generally safe with the exception of shear strength which is underestimated by current relationships. It is suggested that new relationships have to be provided for heat-treated wood, taking into account the loss of shear resistance.
Forestist, 2018
Impact of heat treatment (ThermoWood) on the macro structure and physical properties of Scots pine sapwood and heartwood were studied by visual examinations, using the following relevant standard test methods: ASTM D2244 and TS 2472, respectively. In the study, two processes-Thermo-S (190 ̊ C) and Thermo-D (212 ̊ C)-were employed for heat treatment. To compare the effect of different types of heat treatment, kiln dried wood samples were used for reference. Macroscopic investigation showed that superficial cracks occurred in all samples, and as the temperature increased, the severity and number of cracks increased. In the Thermo-D process, internal cracks and cupping were seen only in heartwood samples. Physical examination showed that as the temperature increased, color of the samples darkened, the density of the samples decreased, dimensional stability was enhanced. The Anti Swelling-Efficiency (ASE) in the Thermo-S and Thermo-D processes evaluated in sapwood samples was 17.04% and 24.77%, respectively; however, values in the heartwood samples were 11.97% and 30.45%, respectively. The highest reduction ratio of air dried density was 14.04% in the Thermo-D process applied to the heartwood samples. Thus, it can be concluded that this reduction due to the increased temperature is related to the formation of internal cracks.
Microstructural and physical aspects of heat treated wood. Part 1. Softwoods
Heat treatment of wood is an effective method to improve the dimensional stability and durability against biodegradation. Optimisation of a two-stage heat treatment process at relatively mild conditions (<200°C) and its effect on the anatomical structure of softwoods were investigated by means of a light and scanning electron microscopic analysis. Heat treatment did have an effect on the anatomical structure of wood, although this depends on the wood species considered and on the process method and conditions used. Softwood species with narrow annual rings and/or an abrupt transition from earlywood into latewood were sensitive to tangential cracks in the latewood section. Radial cracks occurred mainly in impermeable wood species such as Norway spruce, caused by large stresses in the wood structure during treatment. Sapwood of treated pine species revealed some damage to parenchyma cells in the rays and epithelial cells around resin canals, whereas this phenomenon has not been noticed in the heartwood section. Treated radiata pine resulted in a very open and permeable wood structure limiting the applications of this species. Broken cell walls perpendicular to the fibre direction resulting in transverse ruptures have been noticed in treated softwood species. This contributes to abrupt fractures of treated wood as observed in bending tests which can lead to considerably different failure behavior after impact or mechanical stress. In some treated softwood species maceration (small cracks between tracheids) was noticed after heat treatment. Heat treatment did not cause damage to the ray parenchyma pit membranes, bordered pits and large window pit membranes; the margo fibrils appeared without damage. Compared to the other softwood timbers tested European grown Douglas fir was the timber that stands heat treatment the best.