Effect of Heat Treatment on Color Changes, Dimensional Stability, and Mechanical Properties of Wood

Summary In this study the effect of high temperature on mechanical properties, dimensional stability and color of spruce was investigated. Wood specimens conditioned at different relative humidities (50, 65, 80 and 95%) were subjected to heat treatment at 200°C for 2, 4, 8, 10 and 24 h and at 100, 150 and 200°C for 24 h. Color changes were measured in the Minolta Croma-Meter CR-300 color system. Bending strength and modulus of elasticity were determined according to DIN 52186. The results show that heat treatment mainly resulted in a darkening of wood tissues, improvement of the dimensional stability of wood and reduction of its mechanical properties. The darkening accelerated generally when treatment temperature exceeded approximately 200°C. Most of the darkening occurred within the first 4 h of exposure. For the specimens heated to high temperatures, the average decrease in bending strength was about 44–50%, while modulus of elasticity was reduced by only 4–9%. We found that treatment time and temperature were more important than relative humidity regarding the color responses. Strong correlations between total color difference and both modulus of elasticity and bending strength were found. Thus, the color parameters can be estimated quantitatively and used as a prediction of wood strength.

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Uphill Quenching of Aluminum Alloys

Encyclopedia of Aluminum and Its Alloys ◽

10.1201/9781351045636-140000235 ◽

2019 ◽

Author(s):

Wellington da Silva Mattos ◽

George Edward Totten ◽

Lauralice de Campos Franceschini Canale

Keyword(s):

Mechanical Properties ◽

Heat Treatment ◽

Residual Stress ◽

Aluminum Alloys ◽

Temperature Gradient ◽

Dimensional Stability ◽

Steam Chamber ◽

Conventional Heat Treatment ◽

Quenching Process ◽

Uphill Quenching

This article describes the concept of uphill quenching process applied in the heat treatment of aluminum alloys. Uphill quenching is interesting since residual stress reductions of up to 80% has been reported. In addition, substantial improvements in dimensional stability have been achieved for several types of aluminum parts. Often, uphill quenching is applied after quenching and before aging during the heat treatment of aluminum alloys. The uphill quenching process consists of the immersion of the part in a cryogenic environment, and after homogenization of the temperature, the part is transferred to the hot steam chamber to obtain a temperature gradient that will maintain the mechanical properties gained with this process. The results obtained are lower residual stress and better dimensional stability. The aim of this article is to provide a review of this process and to compare it with conventional heat treatment.

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Effect of a Combination of Moderate-Temperature Heat Treatment and Subsequent Wax Impregnation on Wood Hygroscopicity, Dimensional Stability, and Mechanical Properties

Forests ◽

10.3390/f11090920 ◽

2020 ◽

Vol 11 (9) ◽

pp. 920 ◽

Cited By ~ 3

Author(s):

Lin Yang ◽

Hong-Hai Liu

Keyword(s):

Mechanical Properties ◽

Heat Treatment ◽

Water Uptake ◽

Significant Influence ◽

Liquid Water ◽

Dimensional Stability ◽

Bending Strength ◽

Wood Properties ◽

Moderate Temperature ◽

Temperature Heat Treatment

Wood is an environmentally friendly material, but some natural properties limit its wide application. To study the effect of a combination of heat treatment (HT) and wax impregnation (WI) on wood hygroscopicity, dimensional stability, and mechanical properties, samples of Pterocarpus macrocarpus Kurz wood were subjected to HT at a moderate temperature of 120 °C and a high temperature of 180 °C, for a 4 h duration. Subsequently, half of the 120 °C HT samples were treated with WI at 90 °C. The results showed that 180 °C HT and WI decreased the capacity of adsorption and liquid water uptake and swelled the wood significantly, while WI had the biggest reduction. The effect of 120 °C HT was significant only on decreasing the capacity of adsorption and the swelling of liquid water uptake. The bending strength (MOR) of wood decreased only after 180 °C HT, and 120 °C/4h HT and WI had no significant influence on MOR. The bending stiffness (MOE) increased significantly after 180 °C HT and WI, while 120 °C/4h HT had no significant influence on MOE. Therefore, the combination of moderate-temperature HT can act synergistically in the improvement of certain aspects of wood properties such as capacity of water adsorption and liquid water uptake. WI effectively improved wood hygroscopicity, dimensional stability, and mechanical properties.

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Physical and Mechanical Properties of Five Heat-Treated Hardwood Species

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.472-475.1132 ◽

2012 ◽

Vol 472-475 ◽

pp. 1132-1134

Author(s):

Jin Sun ◽

Xiao Bo Wang ◽

Xiao Jing Wang ◽

Yan Lin ◽

Zhen Zhong Gao

Keyword(s):

Mechanical Properties ◽

Heat Treatment ◽

Dimensional Stability ◽

Negative Impact ◽

Physical And Mechanical Properties ◽

Betula Platyphylla ◽

Fraxinus Mandshurica ◽

Hardwood Species ◽

Heat Treated ◽

Betula Platyphylla Suk

Five hardwood species (Schima superba Gardn, kapur( Dryobalanops sp.), ash (Fraxinus mandshurica Rupr.), birch(Betula platyphylla Suk.), tauari (Couratari sp.)) were conducted the Heat treatment at 185°C.. The results indicated that the dimensional stability, modulus of elasticity (MOE) increased greatly while the wettability decreased after treatment. There was a negative impact of heat treatment on MORs.

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Dimensional stability, fungal resistance and mechanical properties of radiata pine after combined thermo-mechanical compression and oil heat-treatment

Holzforschung ◽

10.1515/hf-2015-0174 ◽

2016 ◽

Vol 70 (8) ◽

pp. 793-800 ◽

Cited By ~ 16

Author(s):

Manoj Kumar Dubey ◽

Shusheng Pang ◽

Shakti Chauhan ◽

John Walker

Keyword(s):

Mechanical Properties ◽

Heat Treatment ◽

Dimensional Stability ◽

Linseed Oil ◽

Treated Wood ◽

Untreated Wood ◽

Radiata Pine ◽

Fungal Resistance ◽

Compression Set ◽

Decay Test

Abstract The dimensional stability and mechanical properties of radiata pine (Pinus radiata) has been investigated after thermo-mechanically compression (TMC) followed by oil heat-treatment (OHT). Wood specimens were first compressed in the radial direction then heat-treated in a linseed oil bath at 160–210°C. Spring-back percentage, water repellence efficiencies, and compression set recovery percentage were determined as indicators of dimensional stability. The resistance of treated wood against a brown rot fungi was assessed based on an accelerated laboratory fungal decay test. Strength, stiffness and hardness were determined as a function of different treatment parameters. After TMC, high compression set (39%) was achieved without any surface checks and cracks. Specimens undergoing TMC followed by OHT showed relatively less swelling and low compression set recovery under high moisture conditions. The fungal resistance of wood after TMC+OHT slightly increased compared to untreated wood and TMC wood. The mechanical properties of TMC+OHT wood were inferior to those of TMC wood.

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Chemical, physico-mechanical properties and biological durability of rubberwood particleboards after post heat-treatment in palm oil

Holzforschung ◽

10.1515/hf-2017-0086 ◽

2018 ◽

Vol 72 (2) ◽

pp. 159-167 ◽

Cited By ~ 6

Author(s):

Seng Hua Lee ◽

Zaidon Ashaari ◽

Wei Chen Lum ◽

Aik Fei Ang ◽

Juliana Abdul Halip ◽

...

Keyword(s):

Mechanical Properties ◽

Heat Treatment ◽

Palm Oil ◽

Dimensional Stability ◽

Urea Formaldehyde ◽

Chemical Properties ◽

Water Repellency ◽

Post Heat Treatment ◽

Termite Resistance ◽

Biological Durability

AbstractThe chemical properties, dimensional stability, mechanical strength and termite resistance of urea formaldehyde (UF) bond rubberwood (RW) particleboard (PB) were assessed after a two-step oil heat treatment (OHT). The PB was immersed in palm oil before heating to 180, 200, and 220°C in a laboratory oven for 2 h. Anti-swelling efficiency (ASE) and water repellency efficiency (WRE) as well as bending (MOE, MOR) and internal bonding strength (IB) were determined. Resistance against a subterranean termite,Coptotermes curvignathusHolmgren, was tested. The degradation of hemicelluloses and cellulose, that are mainly responsible for wood wetting processes, was confirmed by Fourier transform infrared (FTIR) spectra. Formation of an elevated cross-linking density in lignin also contributed to the dimensional stability, where 93.6% ASE and 46.3% WRE were achieved in the samples treated at 220°C. Mechanical properties of treated samples were inferior to the control samples due to hemicelluloses degradation and breakage of the UF bonding network. A significant improvement in termite resistance has been found in the treated samples.

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Selected Physical and Mechanical Properties of Microwave Heat Treated Rubberwood (Hevea brasiliensis)

Applied Sciences ◽

10.3390/app10186273 ◽

2020 ◽

Vol 10 (18) ◽

pp. 6273

Author(s):

Aujchariya Chotikhun ◽

Jitralada Kittijaruwattana ◽

Emilia-Adela Salca ◽

Salim Hiziroglu

Keyword(s):

Mechanical Properties ◽

Heat Treatment ◽

Electron Microscope ◽

Dimensional Stability ◽

Hevea Brasiliensis ◽

Physical And Mechanical Properties ◽

Modulus Of Rupture ◽

Heat Treated ◽

Temperature Levels ◽

Microwave Heat

The objectives of this study were to evaluate some of physical and mechanical properties of rubberwood (Hevea brasiliensis) as function of microwave heat treatment process. The specimens were heat treated at three temperature levels of 150 °C, 180 °C, and 220 °C for 20 min in a small microwave oven connected to a computer. Bending characteristics, namely modulus of elasticity (MOE), modulus of rupture (MOR) as well as hardness of the samples were tested. Dimensional stability in the form of swelling and water absorption of the specimens were also determined. Based on the findings in this work it appears that microwave can be used successfully for heat treatment of rubberwood. Overall mechanical properties of the samples were adversely influenced by the treatment. MOE, MOR and hardness values of the samples treated at a temperature of 220 °C had 2.37, 3.69, and 2.12 times reduced than those of control samples, respectively. Dimensional stability of the heat treated samples as a result of 2-h and 24-h water soaking improved. Micrographs take from scanning electron microscope (SEM) and transmission electron microscope (TEM) revealed that certain amount of damage took place in the cellwall of the treated specimens. Overall discoloration on the samples due to microwave heat treatment was found insignificant.

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