WOOD RESEARCH Volume 68, Number 3, 2023
Mehmet Gunes and Mustafa Altunok

Investigation of Bending Strength of Tannin Impregnated Wooden Beams after Heat Treatment

In this study, the changes in bending strength were investigated by applying heat-treatment to laminated beams modified with acorn tannin to improve the mechanical properties of wooden load-bearing structural members. For this purpose, acorn tannin was impregnated on samples prepared from Scotch pine (Pinus sylvestris L.), oak (Quercus petraea L.), and chestnut (Castanea sativa Mill.) woods. Heat treatment was applied to the samples impregnated with acorn tannin at 150ºC for 3 hours. Untreated, heat-treated, and tannin-modified samples were conditioned until they reached constant weight at 20ºC at 65% relative humidity (RH), 40ºC at 35% RH, and 10ºC at 50% RH. Bending resistance tests were applied to the elements that are conditioned in outdoor conditions according to ISO 13061-3. The results of bilateral interaction between tree species and treatment type were compared, the highest bending strength increase was found in Scotch pine samples by 5% compared to control samples.

WOOD RESEARCH Volume 68, Number 2, 2023
VLADIMÍR IHNÁT and HENRICH LÜBKE

Water retention of beech shavings heat-treated at lower temperatures

Water retention after 2 hours and 24 hours of soaking in water was determined for beech shavings subjected to heat treatment at temperatures of 120°C, 140°C and 160°C for 2 hours, 4 hours, 6 hours and 8 hours in order to reduce the equilibrium moisture content (EMC) of the wood shavings for use in wood based composites. EMC was determined after 14 days of air conditioning at 23°C and 55% relative humidity. The measured values were compared with the sample dried at 103°C. Water retention was determined after 15 min of centrifugation at 1400 rev.min-1 for a more objective assessment of the wood’s ability to retain water in the cell lumens. The results showed that heat treatment reduces the EMC of beech shavings heat-treated at 160°C for 8 hours in the given conditions from 8.7% to 6.19%. The reduction of EMC at lower temperature was not sufficient enough, especially in the shorter treatment duration of up to 6 hours. In parallel, the reduction of water retention from 65.53% to 47.79% was caused by heat treatment for 8 hours at 160°C.

WOOD RESEARCH Volume 67, Number 6, 2022
Aokai Cheng, Dengyun Tu, Zhipeng Zhu, Qiaofang Zhou, Wei Wei, Chuanshuang Hu, and Xianghao Liu

Study on machining properties and surface coating properties of heat treated densified poplar wood

In this study, a modification combining densification and heat treatment of poplar wood (Populus tomentosa Carr.) was carried out, and the machining properties of the unmodified poplar wood (control) and the heat treated densified wood (HTD) were tested and evaluated. In addition, the water-based UV paint was covered on the control and HTD respectively, and the surface coating properties of them were evaluated. The results showed that: (1) The machining properties of poplar wood were improved after the heat treatmentdensification modification. The score of comprehensive machining properties of the HTD was 45 (excellent grade), while the score of the control was 36 (good grade). (2) The abrasion resistance, hydrophobicity and adhesion were improved after heat treatment-densification modification. Therefore, the modification combining densification and heat treatment played a significant role in enhancing the value of wood.

WOOD RESEARCH Volume 67, Number 3, 2022
Cuixiang Lu, Yuan Liu, HUICHUAN JIANG, and QUANJI LU

Impact of heat treatment on the surface color and glossiness of young eucalyptus wood

The study analyzed the impact of heat treatment conditions (temperature and duration) on the surface color and glossiness of young eucalyptus wood. The young eucalyptus wood samples were treated at different treatment temperatures (165°C, 185°C, 205°C) and duration (2 h, 3 h, 4 h). The color of the young eucalyptus wood was determined using CIE L*a*b* system and the gloss was measured with glossmeter at 20°, 60°, and 85° incident angle before and after the heat treatment. The total color difference (E* ), lightness (L*), red-green index (a*), and yellow-blue index (b*), were investigated at different treatment conditions. The values of L* and b* decrease continuously with the increasing temperature and duration. The results of analysis of variance (two-way ANOVA) indicate that the heat treatment temperature has a significant effect on the colorimetric properties of the heat-treated young eucalyptus wood. The gloss decreased after the heat treatment for both perpendicular and parallel directions. ANOVA analysis showed that the treatment temperature duration have a significant effect on the parallel glossiness of 85°(p＜0.05). These are probably due to differences in surface roughness between untreated and heat-treated wood. To achieve the desired color like teak wood, the preferred temperature is no more than 185°C.

WOOD RESEARCH Volume 61, Number 3, 2016
Osman Percin, Huseyin Peker, and Abdi Atilgan

The effect of heat treatment on the some physical and mechanical properties of beech (Fagus orientalis Lipsky) wood

This study describes the effect of heat treatment on the some of the physical and mechanical properties of beech (Fagus orientalis Lipsky) wood at different temperatures and times. Samples of beech wood were heat-treated at 150, 175, and 200°C for 1, 3 and 5 h. The mechanical properties of the heat-treated and untreated samples were determined by bending tests, modulus of elasticity in bending, compression strength parallel to grain, and Brinell hardness. Physical properties were determined by weight loss, density, and volumetric swelling tests. The results showed that the heat treatment increased the weight loss, density loss and dimensional stabilization. In addition, an increase was observed for compression strength parallel to grain (except for at 200°C for 5 h), while a small increase was determined in the bending strength, modulus of elasticity in bending, hardness values of heat-treated wood samples at 150°C for 1 and 3 h. However, the heat treatment at higher temperature and duration clearly decreased bending strength, modulus of elasticity in bending,and hardness.

WOOD RESEARCH Volume 61, Number 2, 2016
Hong Yun, Kaifu Li, Dengyun Tu, and Chuanshuang Hu

Effect of heat treatment on bamboo fiber morphology crystallinity and mechanical properties

This study aimed to investigate the fiber morphology, crystalline structure and mechanical properties of heat-treated bamboo. Moso bamboo was treated by superheated steam at 120, 140, 160, and 180ºC. Fiber morphology and crystalline structure of heat-treated Moso bamboo were researched by transmission electron microscope and X-ray diffraction. The mechanical properties of heat-treated bamboo were tested in the paper. The result showed that the relative crystallinity and length-width ratio of heat-treated bamboo were increased with increased temperature. The elastic modulus of bamboo was increased as the temperature rose from 120 to 140ºC. and then decreased with higher temperature, which was associated with the increase of the crystallinity.

WOOD RESEARCH Volume 62, Number 6, 2017
Mustafa Kucuktuvek, Ergun Baysal, Turkay Turkoglu, Huseyin Peker, Ahmet Gunduz, and Hilmi Toker

Surface characteristics of scots pine wood heated at high temperatures after weathering

This study was conducted to investigate some surface properties of wood specimens of heat treated Scots pine (Pinus sylvestris L.) after weathering such as surface hardness, surface roughness, gloss, and color changes. Heat treatment of Scots pine wood was carried out by hot air in an oven for 1, 2, and 3 hours at 210, 220, and 230°C. The results showed that generally surface hardness losses of heat treated Scots pine wood were lower than that of un-heated Scots pine wood after weathering. Heat treated Scots pine wood gave smooth surface after weathering. Except for heat treatment at 230°C for 1 and 2 hours, heat treatment resulted in better glossiness compared to un-heated Scots pine wood after weathering. According to the test results, while heat treated Scots pine wood become lighter after weathering, un-heated wood become darken after weathering. In general, heat treated wood surface to become reddish and yellowish after weathering.

WOOD RESEARCH Volume 62, Number 6, 2017
Turkay Turkoglu, Yahya Kabasakal, Ergun Baysal, Ahmet Gunduz, Mustafa Kucuktuvek, Dursun Kemal Bayraktar, Hilmi Toker, and Huseyin Peker

Surface characteristics of heated and varnished Oriental beech after accelerated weathering

This study was performed to investigate some surface characteristics such as surface hardness, surface roughness, and color changes of heated and varnished Oriental beech (Fagus orientalis Lipsky) after accelerated weathering. Heat treatment of Oriental beech wood was carried out by hot air in an oven for 0.5, 1, and 1.5 h at 210, 220, and 230°C. After heat treatment, Oriental beech wood specimens were varnished using a polyurethane varnish. The results showed that accelerated weathering generally caused increase of surface hardness of Oriental beech. Surface roughness and total color changes of heated and varnished Oriental beech were lower than only varnished (control) Oriental beech after accelerated weathering. Heated and varnished Oriental beech wood gave better surface characteristics than only varnished oriental beech after accelerated weathering.

WOOD RESEARCH Volume 62, Number 5, 2017
Osman Emre Özkan, Ali Temiz, and Hasan Vurdu

Effects of heat treatment on Turkish fir wood properties

In this study, Turkish fir wood (Abies nordmanniana subsp. bornmulleriana) was subjected to two heat treatment process with varying temperatures (150, 180 and 200°C) and durations (2, 4 and 6 h). Some properties of the heat treated Turkish fir wood; mass change, water absorption, volumetric swelling, bending strength, modulus of elasticity (MOE), compression strength parallel to grain, color change and surface roughness have been tested and evaluated by statistical analysis. Consequently, volumetric swelling and water absorption values of the heat treated wood samples reducing. Bending strength, modulus of elasticity and compression strength parallel to grain values were decreased by heat treatment at high temperatures. Additionally, color change and surface roughness values of heat treated wood decreased with weathering compared to those of control samples.

WOOD RESEARCH Volume 62, Number 3, 2017
Bruno Esteves, Fábio Ribeiro, Luísa Cruz-Lopes, José Ferreira, Idalina Domingos, Marta Duarte, Sónia Duarte, and Lina Nunes

Densification and heat treatment of maritime pine wood

Pine (Pinus pinaster Ait.) wood samples were subjected to a combined treatment by densification and heat treatment. Samples were densified before and after heat treatment. The heat treatment was made inside an oven at 190ºC during 2 to 6 h and wood densification was made in a hot press at around 48 bar pressure and temperatures between 160ºC and 200ºC for 30 min. Compression-set, compression-set recovery after three cycles of water soaking followed by oven drying, density, hardness, bending strength and stiffness and durability against subterranean termites were determined after the treatment. Results show that densification increases density, hardness, bending strength, stiffness and durability against termites. Heat treatment applied after the densification is more effective in reducing compression-set recovery than if applied before.

WOOD RESEARCH Volume 63, Number 5, 2018
Saban Kart, Ergun Baysal, Turkay Turkoglu, Mustafa Kucuktuvek, Huseyin Peker, Caglar Altay, Ahmet Gunduz, and Hilmi Toker

The effect of natural weathering on change in the color of heat treated and varnished scots pine and oriental beech woods

This study was designed to investigate color changes of heat treated and varnished Scots pine (Pinus sylvestris L.) and Oriental beech (Fagus orientalis L.) after 3 months of weathering. Heat treatment of Oriental beech and Scots pine wood was carried out by hot air in an oven for 1, 2, and 3 hours at 205, 215, and 225°C. After heat treatment, wood specimens were varnished using a polyurethane varnish (PV) and cellulosic varnish (CV). The results of study showed that heat treatment generally caused decrease of lightness of both wood specimens before weathering. In general, while heated and PV coated Scots pine and Oriental beech wood surfaces turned to reddish and yellowish, heated and CV coated Scots pine and Oriental beech wood surfaces turned to reddish and bluish after weathering. The total color changes of heated and varnished both wood specimens were lower than only varnished both wood specimens after weathering.

WOOD RESEARCH Volume 63, Number 5, 2018
Mitani Andromachi and Rammou Ekaterini

Cadhesive bond performance of heat- treated fir wood (Abies borrissiregis)

The thermal treatment of wood leads to chemical, structural and natural changes in the wood components which can significantly affect the adhesive bond performance of the wood in various ways depending on the type of adhesive that is used. In the present research, fir wood (Abies borrissiregis) was undergone thermal treatment at 180°C, and 200°C for 3, 5 and 7 hours. Two different types of adhesives were used for the adhesive bond: polyurethane (PUR) and polyvinyl acetate PVAc. During all the wood treatment conditions, higher endurance in the bonding shear strength was noticed for the non-modified samples and the shearing strength by compression load was decreased while the thermal treatment was becoming more intense. Generally, while the PVAc bond shows better performance during the adhesion and higher modulus of rupture in comparison with the polyurethane PU after the thermal treatment of the wood.

WOOD RESEARCH Volume 66, Number 4, 2021
Sahin Akyurek, Murat Akman, and Murat Ozalp

Effects of heat treatment on some chemical compound and mechanical properties of black pine wood

In this study, effects of heat treatment on bending strength, compression strength, chemical compound and solubility of Black pine wood (Pinus nigra J.F. var. seneriana) was examined. For this purpose, Black pine wood samples were kept in temperature of 250°C for 2 hours. Test results of heat-treated Black pine wood and control samples indicated that mechanical characteristics including compression strength and bending strength were affected negatively with heat treatment. Bending strength of heat treated and non-treated test samples were 129 and 76 N.mm-2, respectively. Compression strength of heat treated and non-treated test samples were 53 and 43 N.mm-2, resp. In addition, level of extractives, cellulose and hemicellulose decreased while lignin content increased with percentage of 40%. Significant decreases occurred in all chemical solubility values.

WOOD RESEARCH Volume 65, Number 6, 2020
Lin Yang, Tianqi Han, and Yudong Fu

Effect of heat treatment and wax impregnation on dimensional stability of Pterocarpus macrocarpus wood

In order to improve dimensional stability and control deformation, heat treatment (HT) and wax impregnation (WI) were conducted to large size boards (LB) of Pterocarpus macrocarpus and the tangential swelling were compared in various relative humidity (RH) conditions. The results show that the tangential swelling and shrinking of control group and treated group performed differently corresponded to various relative humidity (RH). Comparing with control group, the swelling ratio of HT combined WI group was much less, and followed by 180°C-3h HT group. The maximum swelling ratio decreased by 31% and 29% in humidity chamber and indoor conditions respectively. The swelling ratio was affected by size of samples, LB showed smaller welling ratio than small sample. Wax filled in cell cavities and presented uneven distributions after impregnation. The rate of wood hygroscopicity was reduced after HT combined WI treatment which was an effective method on improvement of wood dimensional stability.

WOOD RESEARCH Volume 64, Number 4, 2019
Kang-Jae Kim, Ji-Ae Ryu, and Tae-Jin Eom

Characteristics of the heat treated wood packaging materials according to international standards for phytosanitary measures and verifiability of heat treatment

We aimed to develop a control method to assess compliance with International Standards for Phytosanitary Measures No.15 (ISPM 15) heat treatment wood packaging materials by physicochemical properties and chemo-metrical approach. Larix leptolepis (Siebold & Zucc.) (Gordon larch), Pseudotsuga menziesii (Douglas fir) and Picea jezoensis (spruce) as wood samples were used in this study. The ISPM 15 processing of wood did not alter the physico-chemical characteristics. By the ISPM 15 processing of wood, the core moisture content of timber was approximately 6%, regardless of the wood species, whereas that before heat treatment was 10-12%. Among the different parameters of wood, the moisture content can be classified by the PCA according to the ISPM 15 processing, which can be easily changed by mild heat treatment. Furthermore, the changes in chemical properties occurring after the ISPM 15 processing were clearly distinguished by using the ATR-PCA system.

WOOD RESEARCH Volume 65, Number 4, 2020
HUICHUAN JIANG, QUANJI LU, GUANJUN LI, MIN LI, and JIANING LI

Effect of heat treatment on the surface color of rubber wood (Hevea brasiliensis)

In this study the effect heat treatment process parameters (temperature, duration and heating rate) on the surface color of rubber wood was evaluated. The color of the rubber wood was determined using CIE L*a*b* system before and after the heat treatment. The colorimetric properties, including total color difference (ΔE*), lightness index (L*), red-green index (a*), and yellow-blue index (b*), were investigated at different treatment conditions. The results of analysis of variance (ANOVA) indicate that the heat treatment temperature has a significant effect on the colorimetric properties of the heat-treated rubber wood, duration and heating rate has no effect. Within the experimental range, as the heat treatment temperature and duration increasing, the color of the rubber wood gradually deepens. In order to achieve a surface color like the teak wood, the optimum process conditions are heat treatment temperature 190°C, duration 4 h, heating rate 10°C.h-1.

WOOD RESEARCH Volume 65, Number 2, 2020
Hamid Reza Taghiyari, Ayoub Esmailpour, Stergios Adamopoulos, Kurosh Zereshki, and Reza Hosseinpourpia

Shear strength of heat-treated solid wood bonded with polyvinyl-acetate reinforced by nanowollastonite

This study investigated the shear strength of heat-treated solid wood of three species (beech, poplar, and fir) bonded with polyvinyl-acetate (PVA) adhesive reinforced by nanowollastonite (NW). Wood specimens were heat-treated at 165°C and 185°C, and then bonded using PVA reinforced by 5% and 10% of NW. Shear strength tests parallel to the grain of bonded specimens were performed according to ASTM D143-14 (2014). The results demonstrated that the shear strength was significantly dependent upon the density of the specimens. Heat treatment decreased the shear strength of the bonded specimens considerably. This was attributed to several factors, such as a reduction in polar groups in the cell wall, increased stiffness of the cell wall after heat treatment, and a reduction in the wettability of treated wood. However, NW acted as a reinforcement agent or extender in the complex, and eventually improved the shear bond strength. Moreover, the density functional theory (DFT) proved the bond formation between calcium atoms in the NW and hydroxyl groups of cell wall polymers. The overall results indicated the potential of NW to improve the bonding strength of heat-treated wood.

WOOD RESEARCH Volume 64, Number 1, 2019
Xiangyu Zhao, Dengyun Tu, Chuanfu Chen, and Qiangfang Zhou

Prediction of the mechanical properties of thermally-modified rubber wood on the basic of its surface characteristic

The goal of this research was to investigate the effect of thermal treatment on mechanical properties and surface characteristic of rubberwood (Hevea brasiliensis) and find the mathematical model to predict the mechanical properties used by its surface characteristic. Rubberwood specimens were treated by steaming at five different temperature levels of 170, 185, 200, 215, and 230°C for two different durations of 1.5 and 3 h. Based on the results, the values of bending strength, modulus of elasticity, compression strength and impact bending decreased, and the glossiness and chromatic aberration (∆E) increased with increasing temperature and enlarging duration further. This study revealed that chromaticity parameters b*, ∆E and the gloss of perpendicular to grain (GZT) could evaluate the mechanical properties of thermally-modified wood to achieve the mechanical properties detection without destruction.

WOOD RESEARCH Volume 64, Number 1, 2019
Liu Ming-Li, Li Chun-Feng, and Liu Yan-Long

Physical and mechanical properties of modified poplar wood by heat treatment and impregnation of sodium silicate solution

The objective of this study was to improve physical and mechanical properties of fast-growing Chinese white poplar wood (Populus tomentosa Carrière). To this purpose, the heat treatment and impregnation by sodium silicate solution were investigated. In experiments, four processes under four different conditions were applied on poplar wood samples: temperature treatment (T), solution treatment (J), first solution and then temperature treatment (J-T) and first temperature and then solution treatment (T-J). The results showed that all measured mechanical properties were improved under conditions of J process. The hardness, impact toughness, bending strength and modulus of elasticity were improved by 8.4%, 29.2%, 12.0% and 16.1%, respectively. Additionally, tested wood samples exhibited significant increasing of values some mechanical properties such as hardness (70.1%) and modulus of elasticity (80.4%) in comparison with values for untreated samples if treatment was conducted under J-T process conditions. Treated wood by this technology could be utilized as solid wood composite or material for flooring substrate.

WOOD RESEARCH Volume 66, Number 3, 2021
Roman Dudík, Vlastimil Borůvka, Marcel Riedl, and Tomáš Holeček

Data mining and its impact on marketing communication – case: heat-treated birch wood

The article presents the results of a marketing survey in the area of customer preferences in the case of different degrees of heat-treated solid wood and birch veneer. Part of the marketing survey was a questionnaire survey, where the respondents, as potential customers, expressed their preferences for individual samples which, at first glance, differed in colour due to the different degrees of heat treatment. The result of the research is a clear preference for the heat-treated samples compared to the reference sample without heat treatment. A more detailed secondary analysis of the data from the questionnaire survey was performed with regard to the gender, age and education of the respondents. Here, too, it is possible to conclude a clear preference for heat-treated samples for these groups of respondents. The article also analyses the possibilities of the marketing strategy with a focus on marketing communication, especially in relation to wood processors and producers.