Next Article in Journal
Response of Growth and Non-Structural Carbohydrates’ Allocation in Pinus yunnanensis Seedlings to Simulated Sunflecks
Previous Article in Journal
Heart Rate Monitoring for Physiological Workload in Forestry Work: A Scoping Review
 
 
Search for Articles:
Title / Keyword
Author / Affiliation / Email
Journal
Article Type
 
 
Advanced Search
 
Section
Special Issue
Volume
Issue
Number
Page
 
Journals
Forests
Volume 16
Issue 3
10.3390/f16030521
forests-logo
Submit to this Journal Review for this Journal Propose a Special Issue
► Article Menu

Article Menu

share Share announcement Help format_quote Cite question_answer Discuss in SciProfiles
first_page
settings
Order Article Reprints
Font Type:
Arial Georgia Verdana
Font Size:
Aa Aa Aa
Line Spacing:
Column Width:
Background:
Article

Effect of Superheated Steam Technology on the Deformation Recovery Performance of Teakwood Bending Components and Its Mechanism

by
Linghua Yao
1,2,
Yanxia Pan
1,
Lina Ji
1,*,
Zhangheng Wang
2 and
Junnan Liu
1
1
College of Landscape Architecture and Art, Xinyang Agriculture and Forestry University, Xinyang 464000, China
2
College of Furnishings and Art Design, Central South University of Forestry and Technology, Changsha 410004, China
*
Author to whom correspondence should be addressed.
Forests 2025, 16(3), 521; https://doi.org/10.3390/f16030521
Submission received: 23 February 2025 / Revised: 12 March 2025 / Accepted: 14 March 2025 / Published: 16 March 2025
(This article belongs to the Section Wood Science and Forest Products)
Browse Figures
Versions Notes

Abstract

To address the issue of the deformation recovery in teakwood bending components when they undergo moisture absorption, the potential for superheated steam technology to improve the dimensional stability of the material and the means of optimizing this improvement were systematically analyzed. After setting a medium temperature, treatment time, and initial moisture content, we performed a 120 h water immersion test and dynamic thermo-mechanical analysis (DMA), which revealed the multi-scale mechanism by which superheated steam technology inhibits deformation recovery. It was shown that under the optimized conditions of 130 °C, a 2 h treatment time, and a 30% initial moisture content, the deformation recovery of water-immersed teakwood bending components could be reduced to 2.02–5.13%. The water-absorption resilience was decreased by 41.05% compared with the conventional drying and shaping, which was attributed to the synergistic effect of the degradation of hemicellulose and the cross-linking of lignin, which released residual stresses efficiently. Our investigation of the chemical–mechanical coupling revealed a significant positive correlation between the water-absorption resilience and the hemicellulose content (R2 = 0.912), and the interaction of the chemical constituents resulted in a directional evolution of the energy storage modulus and loss modulus, which enhanced the stiffness of the material and effectively inhibited water-absorption resilience. This study provides a theoretical basis and process guidance for the efficient industrialization of solid wood bending components, which has important guiding value for the innovation of manufacturing technology for bending wood furniture.

1. Introduction

Teakwood components submitted to synergistic treatment with softening solution and saturated steam impregnation can obtain excellent bending properties [1,2], but even after molding, these components have a strong shape memory effect due to their high moisture content [3,4]. When wood’s cell walls are saturated with moisture and have intense internal thermal movement, and an external bending force is removed, the bending components may demonstrate rapid spring-back [5]. Solutions have been developed to address this; for instance, when the drying temperature is lower than the softening point of teakwood and the moisture content is reduced, the spacing between the internal molecules of the wood can be narrowed and friction enhanced, promoting the relaxation of the outer tensile and inner compressive stresses in the bending components and realizing drying and shaping [6]. Here, the release of internal stresses with bending effectively reduces components’ deformation recovery after moisture absorption and enhances their dimensional stability.
The traditional research mainly focuses on the regulation mechanism by which heat treatment and saturated steam produce wood deformation fixation and has systematically revealed the influence of the temperature, time, moisture content, and other process parameters on the multi-scale structure of the cell wall [7,8,9], but there are limitations to the processes proposed to date, such as their long drying times, high energy consumption, and insufficient stress release. Superheated steam is a new type of shaping technology for hygrothermal deformation fixation of bending components. This drying and shaping method uses superheated steam to remove moisture from a wood specimen, with the advantages of strong penetration, high energy utilization, and adequate stress release [10,11,12]. Superheated steam not only works by producing convective heat transfer but also thermal radiation and exothermic condensation, meaning the wood quickly undergoes drying and shaping [13]. Therefore, superheated steam is of great significance in improving the efficiency of drying teakwood bending components and shortening the production cycle.
Recently, based on the above technical advantages, scholars at home and abroad have analyzed the potential of superheated steam to significantly enhance the dimensional stability of wood, mainly via chemical composition changes, stress relaxation, and microstructural changes. Patcharawijit et al. [14] tested rubberwood, which they placed in superheated steam at 150 °C for 2 h, improving the compressive strength parallel to the grain, hardness, impact strength, and dimensional stability, as well as decreasing the hygroscopic property, though the color of the wood became yellow and dark. Gao et al. [15] revealed the deformation fixation mechanism on compressed wood by investigating the hydrophobicity of the cell walls, the reorganization of the molecular chain of microfibrils, the change in microstructure, and the relaxation of internal stresses when treated with superheated steam. Xiang et al. [16] found that after superheated steam was applied to poplar sandwich compression wood, irreversible changes occurred in the pore structure of the cell walls, and there was a molecular severing reaction of hemicellulose and lignin, which reduced the deformation recovery rate. Under steam pressure conditions, heat transfer within the wood was accelerated, and more significant changes in the cellular and chemical structures occurred, allowing permanent fixation of the compression deformation. Although this study further elucidated the effect of superheated steam on the compression fixation of sandwiching and its mechanism of action, it is worth noting that there are differences in the molding techniques used for wood bending components and compression wood. Furthermore, the study did not explore the mechanism of action of deformation fixation in depth from a mechanical point of view. Yun [17] used super-heated steam technology to study the drying and shaping of teakwood bending components and analyze the effect of steam treatment on the chemical constituents of teakwood and its color. Although the study established a correspondence between steam parameters and color characteristics, it failed to clarify the constitutive relationship between chemical composition change and deformation fixation, and it also failed to reveal the mechanism via which steam treatment produced the deformation fixation of bending components. Overall, our literature review shows that superheated steam treatment can significantly improve the dimensional stability of wood, but the research mainly focuses on straight lumber, compressed wood, and other regular forms of materials, while the optimization of the drying and shaping process and its intrinsic mechanism of action for solid wood bending and other shaped components still need to be studied in depth.
Based on the previous teakwood softening and bending process [1,17,18], superheated steam drying technology was adopted to systematically study the influence of key parameters such as a medium temperature, the initial moisture content, and the drying rate on the shaping quality of teakwood bending components; based on the drying quality, the chord length changes in teakwood bending components were tested through a 120 h water immersion test to illustrate the inhibitory effect of superheated steam drying on the deformation recovery. By combining that with the thermo-mechanical analysis (TMA) technique, the viscoelastic changes in the bending components were analyzed to reveal the intrinsic reasons for the deformation fixation of the bending components following superheated steam drying from the viewpoint of material mechanics. This study overcomes the technical problem posed by the easy deformation recovery of teakwood bending components and provides a theoretical basis and solutions for optimizing processes by developing environmentally friendly and efficient wood-drying and -shaping technology.

2. Materials and Methods

2.1. Sample Preparation

Artificial forest teakwood (Tectona grandis L.F.) was purchased from Xishuangbanna Dai Autonomous Prefecture, Yunnan Province, with an age of 15 years and a diameter of 20 cm, and the specimens were prepared by radial bending, with a size of 500 × 40 × 20 mm3 (L × T × R). Based on the optimized process parameters determined in the previous study, the specimens were softened using the treatment temperature of 125 °C, the treatment time of 175 min, and a 15% softening (triethanolamine compounding) solution concentration and were prepared into teakwood bending components [2]. To prevent the recovery of deformation during the drying and shaping process, the components were fixed with F-type clamps (Figure 1). The components were placed in a constant-temperature and -humidity chamber (temperature 20 ± 2 °C, relative humidity 65 ± 5%) for moisture content adjustment and then dried and shaped using the preset superheated steam parameters.

2.2. Equipment

The following equipment was used for the experiment: superheated steam drying oven (Customized, Guangdong Changyu Machinery Co., Ltd., Changsha, China), water absorption rebound testing device (Customized, Jiangsu Jianhao Test Instrument Technology Co., Suzhou, China), electric blast-drying oven (DGG-9203A, Shanghai Senxin Experimental Instrument Co., Ltd., Shanghai, China), F-type fixture (SK-605, Guangzhou Xike Hardware Technology Co., Ltd., Guangzhou, China), and constant-temperature and -humidity chamber (GDJS-500B, Jiangsu Emerson Test Instrument Technology Co., Suzhou, China).

2.3. Test Methods

During the pre-treatment stage, a constant-temperature and -humidity chamber was used to ensure the specimens reach the required moisture content. The drying and shaping quality and dimensional stability of teakwood bending components under different treatment conditions were systematically evaluated when using superheated steam technology by setting four medium temperatures, of 110, 120, 130, and 140 °C.

2.3.1. Evaluation of Drying and Shaping Quality

The drying quality is an important basis for shaping teakwood bending components, mainly affected by the medium temperature, time, and drying rate, among other parameters. According to the national standard for the “Drying Quality of Sawn Timber” [19], the national industry standard for the “Sawn Timber Drying Quality of Chinese Hardwood Craft Furniture” [20], and the specific quality requirements of bending components (mainly having no cracks on the surface, no wrinkles on the inner wall, and a rounded bending shape) [21], the bending quality of the specimens was evaluated under different superheated steam conditions, mainly based on the final moisture content after drying and shaping, the difference in moisture content depending on the thickness, the cracking, and the cross-section deformation.

2.3.2. Deformation Recovery Performance Test

Superheated steam-treated and conventionally treated specimens were prepared separately, with five parallel samples in each group. The initial chord length of each specimen was tested using vernier calipers. Afterwards, the specimens were completely submerged in distilled water, and the chord lengths were measured by removing the specimens and drying the surfaces at 24 h intervals at a constant temperature (20 ± 2 °C) for 120 h (5 days).
The deformation recovery performance is quantitatively characterized by the rate of change in chord length (Y), which is calculated using Equation (1):
Y = (L1 − L0)/L0 × 100%
where L0 is the initial chord length of the bending specimen (mm); and L1 is the stabilized chord length of the bending specimen after water immersion treatment (mm).

2.3.3. Mechanical Properties of Water Absorption and Resilience Testing

A high-precision pressure-sensing system was used to monitor the water-absorption resilience behavior of teakwood bending components in real-time, to reveal the mechanical response law during the water-absorption process. The specific test method is as follows: fix the bending components on the fixture of the sensor, and then immerse it in a container of distilled water (20 ± 2 °C), making sure that the height of the liquid level exceeds the upper surface of the specimen by 20 mm. Start the mechanical data acquisition system, set the sampling frequency as 100 ms/time, and record the stress changes in the specimen in the process of water absorption. When the slope of the stress–time curve stabilizes, the test is concluded. Set 5 parallel specimens for each group of tests, and take the average value of the final results.

2.3.4. Dynamic Viscoelastic Performance Test

A dynamic thermo-mechanical analyzer (DMA 850, TA Instruments, New Castle, DE, USA) was used to characterize the dynamic viscoelastic properties of teakwood bending components before and after superheated steam treatment. According to the specimen characteristics and test requirements, a single hanging wall fixture type was selected, and the dynamic temperature scanning mode was adopted for the test, with an operating frequency of 1 Hz, a test temperature range of 30~300 °C, a temperature increase rate of 3 °C/min, and an amplitude of 20~30 μm. The response curves of the energy storage modulus (E′) and loss modulus (E″) with the change in temperature were recorded in real-time under the effect of the alternating stresses. The specimens were prepared by intercepting a radial-cut specimen at the maximum curvature of teakwood bending components with a size of 30 mm × 10 mm × 5 mm3 (L × T × R), ensuring that the grain direction of the specimen was consistent with the test direction.

2.3.5. Chemical Composition Content Testing

The relative contents of cellulose, hemicellulose and lignin in teakwood were tested and analyzed according to the Chinese national standards “Pulps-Determination of alkali resistance” [22], “Fibrous raw material-Determination of holocellulose” [23] and “Fibrous raw material-Determination of acid-insoluble lignin” [24].

3. Results and Discussion

3.1. The Effect of Superheated Steam Drying on the Quality of Teakwood Bending Components’ Shaping

3.1.1. Influence of Medium Temperature

In the experiment, the teakwood bending components were placed in the superheated steam equipment, and drying and shaping treatment was implemented. The quality of the teakwood bending components treated by superheated steam under different temperature conditions is shown in Table 1. This demonstrates that with the increase in medium temperature, the average final moisture content of teakwood bending components gradually decreased, and the core layer and the surface layer were associated with a decreasing trend in moisture content deviation. When the medium temperature reached 140 °C, the moisture content deviation with the thickness of the bending components was significantly reduced, which indicated that when treated with superheated steam at a higher temperature, the moisture contents of the inner layer and the surface layer tended to be more consistent, but multiple cracks appeared, whereas no cracking occurred at lower temperatures. Because at high temperatures, the bending components bear greater stress on the maximum bending part, especially at the beginning of superheated steam treatment, the internal and external heat and mass transfer of wood is not uniform; as a result, drying quality defects of the bending components arose due to stress concentration.
With the increase in medium temperature, the chord length shrinkage of teakwood bending components showed an increasing trend, mainly due to the drying process, along with water desorption, which caused wood cell wall shrinkage. Overall, the chord length of the specimen was shortened, and it even appeared deformed in its cross-section.

3.1.2. Influence of Initial Moisture Content

Superheated steam treatment has the advantages of a large exothermic coefficient, high heat transfer efficiency, strong permeability, etc., but under a high moisture content, the bending components will rapidly lose moisture after the high-humidity heat-shaping treatment. This causes drying quality defects, meaning components do not meet the subsequent requirements of furniture processing. Therefore, the initial moisture content is an important process parameter determining the quality of dried and shaped teakwood bending components.
Under the superheated steam temperature of 130 °C, the effect of the initial moisture content on the drying and shaping quality of teakwood bending components is shown in Table 2. This demonstrates that the drying quality can be effectively improved with a reduction in the initial moisture content, with reduced the degree of wood cracking and deformation. After the softening bending treatment, the components had high moisture content, so when they were directly put into the superheated steam equipment for drying and shaping, the bending components’ surface cracks, end cracks, and other problems easily occurred, although the time can be achieved in the softening, bending drying, and shaping of wood in the integration of the process. Through humidification, the moisture content of the bending components was 30%, and then they were dried and shaped using 130 °C superheated steam, during which no surface cracks, end cracks, or other visible drying quality defects formed, and chord length shrinkage was stabilized at about 1.25%.
From the above test results, it can be seen that when the moisture content of the bending components is higher than 30%, surface cracking will appear in the drying process. This is because, under high-temperature conditions, the moisture inside the bending components moves too fast and places pressure on the cells that is greater than their ultimate mechanical strength, thus forming a defect impairing the drying quality [25,26]. When the moisture content was at 30% or below, there was no cracking, which was attributed to the fact that the moisture content of teakwood was close to the fiber saturation point, and the deviation of the moisture content between the surface layer and the core layer in terms of thickness was small, which reduced the possibility of drying quality defects of the teakwood bending components [27,28]. Therefore, when superheated steam drying is used for teakwood bending components, the initial moisture content should be controlled at 30% or less to ensure the drying quality of the specimens.

3.1.3. Influence of Heating Rate

The effect of different heating rates on the drying quality of teakwood bending components is shown in Table 3. Under the medium temperature of 130 °C, initial moisture content of 30%, and heating rate of 20–60 °C/h, the drying and shaping quality index is relatively stable. However, when the heating rate reaches 90 °C/h, the surface and end face of teakwood bending components begin cracking, which is due to the heating rate being too fast; furthermore, the specimen surface-layer and inner-layer moisture content deviation is large, so the stretching outer easily cracks. Therefore, in the process of drying and shaping, the heating rate should be appropriately reduced to limit the internal capillary tension of the wood, to avoid the double effect of tensile stress and bending stress during drying [29,30], which raises the drying and shaping quality of the teakwood bending components.
The test results show the superior superheated steam drying and shaping process parameters for teakwood bending components through drying pre-treatment: the moisture content of the specimen is adjusted to 30%, the medium temperature is 130 °C, the heating rate is 60 °C/h, and the holding time is 120 min. This process can reduce drying defects, such as surface cracks, internal cracks, and end cracks, and its quality indexes can reach the requirements of the national secondary standards [19], thus meeting the processing and manufacturing criteria for bentwood furniture, interior decoration, and other products after processing.

3.2. Effect of Superheated Steam Drying on the Deformation Recovery Properties of Teakwood Bending Components

3.2.1. Influence of Medium Temperature

The bending components dried and shaped at different medium temperatures were left for 12 h, and then the fixture was removed to obtain a chord length of about 400 mm. The specimens were immersed in water, and the change in chord length was recorded according to the time; the results are shown in Table 4. It can be seen that when teakwood is shaped under conventional drying conditions and then completely immersed in water, the value of the change in chord length is the largest, while the value of the change is significantly smaller when using superheated steam. At the same time, with the increase in medium temperature, the chord length change value shows a gradual decrease. Therefore, the temperature of superheated steam can effectively inhibit the deformation recovery of teakwood bending components and improve their dimensional stability.
The water-absorption chord length recovery of teakwood bending components under different medium temperature conditions is shown in Figure 2. After 120 h of soaking, the chord length recovery rate of conventional drying and shaping varied from 11.90% to 24.86%. This rate was the greatest after 48 h of water soaking and stable after 72 h. Meanwhile, the chord length recovery rate of teakwood bending components under superheated steam drying conditions showed a gradual decrease with the increase in medium temperature. When the medium temperatures were 110, 120, 130, and 140 °C, this rate varied in the ranges of 6.60–15.33%, 4.00–10.24%, 2.02–5.13%, and 1.61–4.30%, respectively, with a decreasing trend. It can be seen that the higher the drying and shaping temperature of teakwood bending components, the lower the water-immersed deformation recovery rate and the better the dimensional stability. However, too high a medium temperature will cause cracking and other quality defects in the bending components, so 130 °C is taken as the ideal temperature.
Figure 3 shows the correlation analysis of the chord length recovery rate of teakwood bending components with the content of chemical constituents. As can be seen, the correlation coefficients R2 between the deformation recovery rate of the specimen and the hemicellulose and cellulose in the chemical constituents of teakwood were 0.974 and 0.738, respectively, which were positively correlated, while the correlation coefficient R2 with lignin was 0.883, which was negatively correlated. It can be seen that superheated steam treatment reduced the hemicellulose content in teakwood bending components, and the degradation of polysaccharides increased the lignin relative content, which in turn affected its deformation recovery rate [31]. Therefore, from the point of view of wood chemical constituents, superheated steam treatment effectively reduced deformation recovery, mainly due to the degradation of hemicellulose and the increase in the relative lignin content.

3.2.2. Influence of Treatment Time

The influence of the treatment time with superheated steam on the deformation recovery of teakwood bending components was analyzed with the temperature when drying and shaping teakwood bending components at 130 °C, an initial moisture content of 30%, and a temperature increase rate of 60 °C/h. After the water immersion test, the results for the chord length change are shown in Table 5. The maximum change in chord length of teakwood bending components after drying and shaping is 12.6 mm under superheated steam treatment for 1 h. With the extension of the treatment time, the maximum change in chord length reaches 8.1 mm and 7.9 mm, respectively, which shows that the drying and shaping treatment time has a certain influence on the deformation recovery. From the experimental data, we found that the degree of elastic recovery of teakwood bending components maintains certain dimensional stability with the extension of the drying and shaping time.
The influences of different treatment times on the water absorption chord length recovery of teakwood bending components are shown in Figure 4. After 1 h of drying treatment, the chord length recovery rate of the bending components varied from 3.58 to 9.40%; after 120 h of immersion, and the chord length recovery rate was larger than those after 24 h and 48 h of water immersion, and we found that the chord length recovery rate was more stable after 72 h. The trend of its change was close to that of the effect of drying temperatures on the rate of change in the absorbed water chord length. When the drying times were 2 h and 3 h, the chord length recovery rate varied in the ranges of 2.02–5.13% and 1.98–5.10%, respectively, and the degrees of change in deformation recovery between the two were similar. This is because teakwood bending components undergo slow drying and shaping, the center part contains a small amount of moisture, and the influence of the time of exposure to superheated steam on the chemical constituents of teakwood is small. Therefore, when considering the cost, efficiency, and dimensional stability of drying and shaping, 2 h was taken as the optimal treatment time with superheated steam.
According to the above test results, the moisture content of the teakwood remains at a high level after the soft bending process. Therefore, in the drying and shaping process, it is necessary to uniformly discharge the moisture in the interior and surface of the bending components through the steam medium, thus reducing the distance between the molecules and effectively relieving the stress generated in the bending process. At the same time, at a certain temperature, the wood matrix molecules will cause cross-linking reactions, promoting the bending components’ more stable hygrothermal deformation fixation [32,33,34]. It is worth noting that, in the drying and shaping process, a superheated steam temperature increase can accelerate the discharge of internal moisture in teakwood, but it will also correspondingly increase the internal drying stress, coupled with the tensile and compressive stresses generated, and these factors may lead to deformation, cracking, and other problems in the bending part of the specimen. Therefore, a reasonable setting for the treatment temperature and time is conducive to eliminating the internal stresses generated in the drying process as well as the rate of return of deformation under hot and humid conditions, thus enhancing the quality of shaping.

3.2.3. Influence of Initial Moisture Content

The influence of the initial moisture content on the deformation recovery of teakwood bending components was analyzed by setting the drying and shaping temperature to 130 °C, a temperature increase rate of 30 °C/h, and a treatment time of 2 h. After the water immersion test, the values of chord length change and deformation recovery of teakwood bending components were recorded, as shown in Table 6 and Figure 5. When the initial moisture content was 40%, the change in chord length of the bending components after water immersion was 23.2 mm, which was the largest change value, while when the initial moisture content was 50%, the change in chord length was 19.7 mm, which was the smallest change value. This is mainly because when the initial moisture content is high, superheated steam drying and shaping will cause dry quality damage to the fibers, limiting the elastic recovery of the bending components [17]. In Figure 5, when the initial moisture content is 20–50%, the chord length recovery rate fluctuates at 2.26–5.45%, 2.02–5.13%, 2.30–5.74% and 2.50–4.86%, respectively; these values are relatively close to each other, which suggests that the initial moisture content does not have a significant effect on the deformation recovery of the specimen, but too high a moisture content often introduces quality defects to teakwood bending components during the drying and shaping process.

3.3. Effect of Superheated Steam Drying on the Resilient Mechanical Properties of Teakwood Bending Components

3.3.1. Water-Absorption Resilience Analysis

The water-absorption resilience of teakwood bending components shaped under different drying conditions is shown in Figure 6. Under superheated steam treatment, this showed a gradual increase with the prolongation of the treatment time, and then tended to stabilize; in contrast, under conventional drying and shaping conditions, it firstly increased sharply and then tended to stabilize. This is mainly because the chemical constituents do not change during conventional drying and shaping. During the bending process, the elastic strain energy of the wood is stored in the cellulose macromolecules. When the bending components are water-immersed, the elastic strain energy stored in the cellulose molecules will be released rapidly [35,36], which triggers an increase in resilience and a deterioration in the dimensional stability.
The slopes of the curves in Figure 6a show that the initial resilience rates of the superheated steam-treated teakwood bending components were significantly lower than those of the conventional drying and shaping. The water-absorption resilience of the conventionally dried specimens plateaued after about 12 h, while that of the superheated steam-dried specimens leveled off after 24 h. This is mainly related to the hydrophilic properties of the samples before and after the superheated steam drying treatment. During the process of superheated steam treatment, hemicellulose in teakwood bending components was degraded to a certain extent, the hydrophilic groups on the branched chains were relatively reduced, and the number of effective adsorption sites on the cell wall lessened [37,38], which decreased the hydrophilicity and therefore significantly reduced the water uptake rate and resilience in the bending components.
As shown in Figure 6b, the maximum water-absorption resilience of teakwood bending components under conventional drying conditions was about 176.45 N. A significant decrease was observed with superheated steam-drying treatments at 110, 120, 130, and 140 °C, which produced results of 110.35, 106.71, 104.01, and 93.24 N, respectively. Compared to conventional drying and shaping, these marked decreases by 37.46%, 39.52%, 41.05%, and 47.16%, respectively. This is mainly attributed to the degradation of the chemical constituents of the specimens under high-temperature and high-humidity conditions during the superheated steam treatment process, so that the residual stresses inside the bending components are released. As a result, in the water immersion test, the water-absorption resilience of these specimens decreased significantly compared with that of a conventionally dried specimen. The decrease in resilience of teakwood bending components was greatest at 140 °C, which may be related to dry quality defects.
The results of the correlation analysis of the water-absorption resilience of teakwood bending components with the content of wood chemical constituents and the rate of deformation recovery are shown in Figure 7. It can be seen that the resilience is mainly linearly correlated with hemicellulose, with a correlation coefficient R2 of 0.912. Figure 7b presents the correlation between the resilience and the deformation recovery rate, and the positive correlation between the resilience and the water-absorption recovery rate, with a degree of fitting 0.995, which suggests a direct correlation between the water-absorption resilience of bending components and changes in hemicellulose, consistent with the results in Figure 3. Analysis of the experimental data shows that the deformation recovery of teakwood after drying and shaping is mainly related to the change in chemical constituents, which is mechanically attributed to the residual stresses stored in the interior of the wood during the bending process, causing the change in the water-absorption resilience. Therefore, the drying and shaping of teakwood bending components by superheated steam treatment change the chemical constituents of the wood under high hygrothermal conditions, to release internal residual stress, reduce the water-absorption resilience and the rate of deformation recovery, and improve the stability of the teakwood bending components fixed by hygrothermal deformation.

3.3.2. Dynamic Viscoelastic Analysis

  • Storage modulus
In dynamic viscoelastic analysis, the storage modulus E′ reflects the ability of a material to store energy under alternating stress for one cycle, which is an indicator of the resilience of wood after deformation. The storage modulus is in accordance with Hooke’s law: the higher the storage modulus, the more rigid the specimen and the less likely the material will be to deform under the same conditions [39,40].
Figure 8 shows a comparison of the storage moduli of teakwood bending components before and after treatment. The values for all groups of specimens show a decreasing trend with increasing temperature in the range of 30–300 °C. This is because at lower temperatures, the molecular energy in the wood cell walls is low, the polymer is in the glassy state, and the molecular chains and their segments are in a relatively static state, thus showing a higher storage modulus. However, when the temperature increases, the thermal energy of the molecules in the wood cell walls increases, which leads to the gradual movement of small-scale units such as chain segments, branched chains, or side groups in the macromolecular structure, resulting in a gradual decrease in the storage modulus [35].
Compared with conventional drying and shaping, the storage modulus of the superheated steam-treated bending components was significantly increased, i.e., the rigidity of the bending components was enhanced. On the one hand, this is due to the degradation of hemicellulose in the process of superheated steam treatment, resulting in a reduction in hydrophilic groups within teakwood and a weakening of water-absorbent properties, which in turn caused a reduction in toughness [41], and at the same time, the degradation of hemicellulose will cause cellulose microfibrils to polymerize, which further enhances the rigidity of the specimen; on the other hand, the superheated steam will also cause some cross-linking reaction of lignin to occur, resulting in the formation of a more stable network structure [42,43]. Superheated steaming of a specimen can induce the main chemical constituents of teakwood to interact, which increases the internal storage modulus and enhances rigidity.
The storage modulus curves of the specimens have two major relaxation peaks, ɑ and β, located near 80 °C and 220 °C, respectively. When compared with conventionally dried wood, the positions of the ɑ and β peaks of the superheated steam-treated specimens were shifted to the left and the peaks increased, which was attributed to the degradation of unstable chemical constituents in teakwood bending components after steam treatment, which caused a decrease in hygroscopicity and an increase in thermal stability. The steam treatment of the specimens resulted in a tighter arrangement of teakwood cellulose microfibrils and an increase in crystallinity [44], which also contributed to an increase in the storage modulus.
2.
Loss Modulus
In dynamic viscoelastic analysis, the loss modulus E″ reflects the ability of material to dissipate energy in one cycle of change, used to characterize the heat consumption of a material undergoing deformation. It is one of the most important parameters of viscoelastic material properties: the larger the value of the loss modulus, the larger the damping loss factor of the material [45]. Figure 9 shows the loss moduli of teakwood bending components before and after treatment. The loss modulus of bending components treated with superheated steam is increased compared to that with the conventional drying method, which indicates an increase in the internal energy loss of the treated wood. This is due to the interaction of the chemical constituents of teakwood after exposure to superheated steam, which increases the relative crystallinity and polymerization of cellulose, and an increase in the friction between the molecular chains, which leads to a corresponding increase in the heat loss modulus of the specimens [46,47,48].
Two major relaxation peaks, ɑ and β, appeared in each group of specimens in the 30–300 °C test range, located near 220 °C and 100 °C, respectively. The major relaxation peak ɑ represents the glass transition temperature (Tg) of the specimens, the feature attributed to the wide range of pyrolytic reactions occurring in the wood’s major constituents and the dramatic increase in the thermal mobility of the internal polymers [49,50]. Below the glass transition temperature, the movement of wood polymers lags behind the alternating stress, the movement of fiber molecular chains is restricted, internal friction increases, and the loss modulus is higher; when above the glass transition temperature, the movement of wood polymer molecules tends to be synchronized with the alternating stress, which decreases viscosity and gradually decreases the loss modulus of the wood.
Compared to conventional drying, the main relaxation peaks ɑ of teakwood bending components treated with superheated steam showed a different degree of forward shift and an increase in the peak values. These effects were mainly due to the cross-linking reaction that occurs within wood, which increases the peak value of mechanical loss [51,52]. The displacement and change in the peak value of the secondary relaxation peak β may be related to the mechanical relaxation induced by hemicellulose. From the above analysis, it is clear that superheated steam treatment changes the chemical constituents and structure of teakwood, increasing the loss modulus compared to conventionally dried timber, which improves the reduction in water-absorption resilience and increases the dimensional stability of the bending components.

4. Conclusions

In this study, teakwood bending components were shaped using superheated steam, and we analyzed the mechanical properties of deformation recovery and resilience before and after this treatment via immersion experiments, which revealed that superheated steam drying and shaping can fix deformation. The results showed that under the optimal conditions of a medium temperature of 130 °C, treatment time of 2 h, and initial moisture content of 30%, the deformation recovery rate of water immersion could be reduced to 2.02–5.13%, mainly due to the synergistic effect of hemicellulose degradation and lignin cross-linking, which effectively released the residual stresses of teakwood bending components, and at the same time, reduced the deformation resilience by 41.05% compared with that of the conventional drying method. Dynamic viscoelastic analysis revealed that the interaction of chemical constituents led to the directional evolution of the storage modulus and loss modulus, which enhanced the rigidity of the material and reduced the water-absorption deformation recovery rate and resilience. However, this study faced some limitations in the construction of the process optimization model and in-depth analysis of the chemical structure. Subsequent research should further focus on the multi-physical-field coupling mechanism of superheated steam technology, deeply analyze the synergistic regulation law of wood deformation shaping technology, and seek to find breakthrough applications in high-end fields such as high-precision wood-shaped components and precision instruments through the development of gradient pressure regulation and an intelligent drying system.

Author Contributions

Conceptualization, L.Y.; methodology, L.Y. and L.J.; software, Z.W.; validation, J.L.; formal analysis, L.J.; investigation, Y.P.; resources, Y.P.; data curation, L.Y.; writing—original draft preparation, L.Y. and L.J.; writing—review and editing, L.Y. and J.L.; visualization, L.Y.; supervision, L.J.; project administration, L.Y.; funding acquisition, L.J. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded by the China National Key Research and Development Program (NO, 2017YFD0601104) and the Youth Fund Program of Xinyang Agriculture and Forestry University (NO, QN2021053).

Data Availability Statement

The datasets generated or analyzed during the current study are available from the corresponding author on reasonable request.

Conflicts of Interest

The authors declare no conflicts of interest.

References

  1. Yao, L.; Ji, L.; Sun, D.; Wang, Z.; Ge, H.; Xu, M.; Yu, M. Preparation of Teakwood Bending Components with Excellent Softening Properties by Vacuum Impregnation with Triethanolamine Compounding Solution. Forests 2023, 14, 1773. [Google Scholar] [CrossRef]
  2. Yao, L.; Ji, L.; Wang, Z.; Liu, J. Bending Performance of Plantation Teakwood and Its Mechanism Based on Radial and Tangential Directions. Forests 2024, 15, 2203. [Google Scholar] [CrossRef]
  3. Shao, Y.; Yu, J.; Liu, H.; An, Y.; Li, L.; Chen, Z.; Wang, X.; Zhang, X. Wood as a Hydrothermally Stimulated Shape-Memory Material: Mechanisms of Shape-Memory Effect and Molecular Assembly Structure Networks. Holzforschung 2023, 77, 426–436. [Google Scholar] [CrossRef]
  4. Zhang, C.; Chen, M.; Keten, S.; Derome, D.; Carmeliet, J. Towards Unraveling the Moisture-Induced Shape Memory Effect of Wood: The Role of Interface Mechanics Revealed by Upscaling Atomistic to Composite Modeling. NPG Asia Mater. 2021, 13, 74. [Google Scholar] [CrossRef]
  5. Shao, Y.; Wang, X. A Review of Shape Memory Effect and Mechanism of Wood. Mater. Rep. 2021, 35, 7190–7198. [Google Scholar] [CrossRef]
  6. Zhao, Y.; Feng, S.; Huang, R. A Review of Researches on Wood Bending Techniques. World For. Res. 2010, 23, 40–44. [Google Scholar]
  7. Hill, C.; Altgen, M.; Rautkari, L. Thermal Modification of Wood—A Review: Chemical Changes and Hygroscopicity. J. Mater. Sci. 2021, 56, 6581–6614. [Google Scholar] [CrossRef]
  8. Xiao, S.; Chen, C.; Xia, Q.; Liu, Y.; Yao, Y.; Chen, Q.; Hartsfield, M.; Brozena, A.; Tu, K.; Eichhorn, S.J.; et al. Lightweight, Strong, Moldable Wood via Cell Wall Engineering as a Sustainable Structural Material. Science 2021, 374, 465–471. [Google Scholar] [CrossRef]
  9. Chen, S.; Obataya, E.; Matsuo-Ueda, M. Shape Fixation of Compressed Wood by Steaming: A Mechanism of Shape Fixation by Rearrangement of Crystalline Cellulose. Wood Sci. Technol. 2018, 52, 1229–1241. [Google Scholar] [CrossRef]
  10. Sobulska, M.; Wawrzyniak, P.; Woo, M.W. Superheated Steam Spray Drying as an Energy-Saving Drying Technique: A Review. Energies 2022, 15, 8546. [Google Scholar] [CrossRef]
  11. Zhang, H.; Yu, F.; Yi, J.; Xu, X.; Ma, Y. Superheated Steam Technology: Recent Developments and Applications in Food Industries. Compr. Rev. Food Sci. Food Saf. 2024, 23, 1–25. [Google Scholar] [CrossRef] [PubMed]
  12. Li, Y.; Li, X.; Quan, P.; Cheng, X.; He, X.; Mou, Q. Investigation of Drying Characteristics in Superheated Steam Drying of UF-Impregnated Chinese Fir. Eur. J. Wood Wood Prod. 2018, 76, 583–589. [Google Scholar] [CrossRef]
  13. Xiang, E. Study on the Permanent Fixation Mechanism of Wood Compressive Deformation Based on Superheated Steam Pressure. Ph.D. Thesis, Chinese Academy of Forestry, Beijing, China, 2022. [Google Scholar]
  14. Patcharawijit, A.; Yamsaengsung, R.; Choodum, N. Superheated Steam Treatment of Rubberwood to Enhance Its Mechanical, Physiochemical, and Biological Properties. Wood Mater. Sci. Eng. 2020, 15, 261–268. [Google Scholar] [CrossRef]
  15. Gao, Z.; Huang, R. Effects of Pressurized Superheated Steam Treatment on Dimensional Stability and Its Mechanisms in Surface-Compressed Wood. Forests 2022, 13, 1230. [Google Scholar] [CrossRef]
  16. Xiang, E.; Feng, S.; Yang, S.; Huang, R. Sandwich Compression of Wood: Effect of Superheated Steam Treatment on Sandwich Compression Fixation and Its Mechanisms. Wood Sci. Technol. 2020, 54, 1529–1549. [Google Scholar] [CrossRef]
  17. Yun, S. The Bending Process Technology Research of Tectona Grandis L.F. Master’s Thesis, Central South University of Forestry and Technology, Changsha, China, 2019. [Google Scholar]
  18. Huang, D.; Shen, H.; Zhang, J.; Zhuo, X.; Dong, L. Effects of Hydrothermal–Microwave Treatment on Bending Properties of Teak in Plantation. Front. Mater. 2024, 11, 1–16. [Google Scholar] [CrossRef]
  19. GB/T 6491-2012; National Standard of the People’s Republic of China. Quality of Sawn Timber Drying. General Administration of Quality Supervision, Inspection and Quarantine of the People’s Republic of China, Standardization Administration of the People’s Republic of China: Beijing, China, 2012.
  20. T/ZSRFA 8-2020; Sawn Timber Drying Quality of Chinese Hardwood Craft Furniture. Zhongshan Mahogany Furniture Industry Association: Zhongshan, China, 2020.
  21. Geng, Y. Synergistic Softening Process of Ammonium Salt/Steam in Solid Wood Furniture Bending Components. Master’s Thesis, Central South University of Forestry and Technology, Changsha, China, 2019. [Google Scholar]
  22. GB/T 744-2004; Pulps-Determination of Alkali Resistance. General Administration of Quality Supervision, Inspection and Quarantine of the People’s Republic of China, Standardization Administration of the People’s Republic of China: Beijing, China, 2004.
  23. GB/T 2677.10-1995; Fibrous Raw Material-Determination of Holocellulose. The State Bureau of Technical Supervision of the People’s Republic of China: Beijing, China, 1995.
  24. GB/T 2677.8-1994; Fibrous Raw Material-Determination of Acid-Insoluble Lignin. The State Bureau of Technical Supervision of the People’s Republic of China: Beijing, China, 1994.
  25. Wang, X. Wood Collapse; China Forestry Press: Beijing, China, 2003; pp. 18–26. [Google Scholar]
  26. Yin, Q.; Liu, H.H. Drying Stress and Strain of Wood: A Review. Appl. Sci. 2021, 11, 5023. [Google Scholar] [CrossRef]
  27. Gao, Y.; Fu, Z.; Fu, F.; Zhou, Y.; Gao, X.; Zhou, F. The Formation Mechanism of Microcracks and Fracture Morphology of Wood during Drying. Dry. Technol. 2023, 41, 1268–1277. [Google Scholar] [CrossRef]
  28. Zhou, F.; Fu, Z.; Zhou, Y.; Zhao, J.; Gao, X.; Jiang, J. Moisture Transfer and Stress Development during High-Temperature Drying of Chinese Fir. Dry. Technol. 2020, 38, 545–554. [Google Scholar] [CrossRef]
  29. Ma, T.; Morita, G.; Inagaki, T.; Tsuchikawa, S. Moisture Transport Dynamics in Wood during Drying Studied by Long-Wave near-Infrared Hyperspectral Imaging. Cellulose 2022, 29, 133–145. [Google Scholar] [CrossRef]
  30. Elustondo, D.; Matan, N.; Langrish, T.; Pang, S. Advances in Wood Drying Research and Development. Dry. Technol. 2023, 41, 890–914. [Google Scholar] [CrossRef]
  31. Gao, Z.; Huang, R.; Chang, J.; Li, R.; Wu, Y. Effects of Pressurized Superheated-Steam Heat Treatment on Set Recovery and Mechanical Properties of Surface-Compressed Wood. BioResources 2019, 14, 1718–1730. [Google Scholar] [CrossRef]
  32. Huang, R. Advances in Wood Plastic Deformation Fixation by Hygro-Thermal Treatments and the Fixation Mechanisms. Sci. Silvae Sin. 2022, 58, 206–216. [Google Scholar] [CrossRef]
  33. Jiang, Z.; Yamamoto, H.; Matsuo-Ueda, M.; Yoshida, M.; Dohi, M.; Tanaka, K.; Konishi, H. Effect of High Temperature Drying with Load on Reduction of Residual Stress and Correction of Warp of Japanese Cedar Lumber. Dry. Technol. 2023, 41, 3–16. [Google Scholar] [CrossRef]
  34. Wang, D.; Fu, F.; Lin, L. Molecular-Level Characterization of Changes in the Mechanical Properties of Wood in Response to Thermal Treatment. Cellulose 2022, 29, 3131–3142. [Google Scholar] [CrossRef]
  35. Wang, J.; Chai, Y.; Liu, J.; Zhu, J.Y. The Viscoelastic and Hygroscopicity Behavior of Delignified and Densified Poplar Wood. Forests 2023, 14, 1721. [Google Scholar] [CrossRef]
  36. Shao, Y. Study on shape memory effect and mechanism of radial compression of wood. Ph.D. Thesis, Inner Mongolia Agricultural University, Hohhot, China, 2022. [Google Scholar]
  37. Awais, M.; Altgen, M.; Belt, T.; Teräväinen, V.; Mäkelä, M.; Altgen, D.; Nopens, M.; Rautkari, L. Wood-Water Relations Affected by Anhydride and Formaldehyde Modification of Wood. ACS Omega 2022, 7, 42199–42207. [Google Scholar] [CrossRef]
  38. Gašparík, M.; Gaff, M.; Kačík, F.; Sikora, A. Color and Chemical Changes in Teak (Tectona grandis L. f.) and Meranti (Shorea spp.) Wood after Thermal Treatment. BioResources 2019, 14, 2667–2683. [Google Scholar] [CrossRef]
  39. An, S.; Ma, X.; Zhu, L. Preparation and Characterization of the P34HB Composite Reinforced by Wood Flour. Sci. Silvae Sin. 2019, 55, 125–133. [Google Scholar] [CrossRef]
  40. Zheng, S.; Tang, W.; Tong, J.; Cao, K.; Yu, H.; Xie, L. Innovative Treatment of Ancient Architectural Wood Using Polyvinyl Alcohol and Methyltrimethoxysilane for Improved Waterproofing, Dimensional Stability, and Self-Cleaning Properties. Forests 2024, 15, 978. [Google Scholar] [CrossRef]
  41. Xiang, E.; Jin, X.; Li, J.; Huang, R. The Hygroscopic Behavior of Surface Compressed Wood in Response to Superheated Steam Treatment at Varying Steam Pressures. Ind. Crops Prod. 2024, 216, 118740. [Google Scholar] [CrossRef]
  42. Cheng, Y.; Jiang, T.; Zhai, S.; Ding, T. Performance of Heat-Treated Sitka Spruce Wood for Soundboards. Chin. J. Wood Sci. Technol. 2022, 36, 57–62. [Google Scholar] [CrossRef]
  43. Park, Y.; Jang, S.K.; Park, J.H.; Yang, S.Y.; Chung, H.; Han, Y.; Chang, Y.S.; Choi, I.G.; Yeo, H. Changes of Major Chemical Components in Larch Wood through Combined Treatment of Drying and Heat Treatment Using Superheated Steam. J. Wood Sci. 2017, 63, 635–643. [Google Scholar] [CrossRef]
  44. Wu, S. Effects of Thermal Treatment on Characterizations and Properties of Cork from Quercus variabilis. Master’s Thesis, Northwest A&F University, Yangling, China, 2019. [Google Scholar]
  45. Cai, S.; Huang, Y.; Li, Z.; Li, Y. Effect of Wood Chemical Composition on Longitudinal Viscoelastic Properties of Cell Walls. For. Eng. 2022, 38, 54–62. [Google Scholar] [CrossRef]
  46. Zhu, Y.; Zhang, Y.; Pan, B. The Viscoelasticity and Deformation Mechanism of Taxodium Hybrid ‘Zhongshanshan’ Wood by Dynamic Mechanical Analysis. BioResources 2021, 16, 6933–6942. [Google Scholar] [CrossRef]
  47. Wang, D.; Xiang, E.; Fu, F.; Lin, L. The Differences of Viscoelastic Properties between the Secondary Wall S2 Layer and Compound Middle Lamella of Thermally Treated Wood. Wood Sci. Technol. 2022, 56, 1509–1525. [Google Scholar] [CrossRef]
  48. Kutnar, A.; O’Dell, J.; Hunt, C.; Frihart, C.; Kamke, F.; Schwarzkopf, M. Viscoelastic Properties of Thermo-Hydro-Mechanically Treated Beech (Fagus sylvatica L.) Determined Using Dynamic Mechanical Analysis. Eur. J. Wood Wood Prod. 2021, 79, 263–271. [Google Scholar] [CrossRef]
  49. Li, L. Study on Preparation and Recovery Mechanism of Thermally Compressed Scots pine (Pinus sylvestris L.). Ph.D. Thesis, Inner Mongolia Agricultural University, Hohhot, China, 2018. [Google Scholar]
  50. Sharma, H.; Dolui, S.; Saksham; Saini, D.; Bedi, R.; Kaith, B.S. Mercerized Flax-g-Poly(Polyvinyl Alcohol + Acrylic Acid) Reinforced Polyester Resin Derived from Waste Plastic Bottles: Dynamic Mechanical Analysis and Chemical-Thermal Resistance. Iran. Polym. J. 2024, 34, 39–53. [Google Scholar] [CrossRef]
  51. Wang, J.; Ye, C.; Zhang, Z.; Hu, J.; Yang, R.; Guo, F.; Yu, Y. Impact of Heat Treatment on Wood Toughness: A Review of Research Progress. World For. Res. 2023, 36, 51–57. [Google Scholar] [CrossRef]
  52. Lemaire-Paul, M.; Foruzanmehr, M.R. The Study of Physico-Mechanical Properties of SiO2-Impregnated Wood under Dry and Saturated Conditions. Wood Sci. Technol. 2023, 57, 1039–1059. [Google Scholar] [CrossRef]
Forests 16 00521 g001
Figure 1. Sample drawing of fixture fixing for teakwood bending components.
Figure 1. Sample drawing of fixture fixing for teakwood bending components.
Forests 16 00521 g001
Forests 16 00521 g002
Figure 2. Effect of different medium temperatures on the chord length recovery rate of teakwood bending components.
Figure 2. Effect of different medium temperatures on the chord length recovery rate of teakwood bending components.
Forests 16 00521 g002
Forests 16 00521 g003
Figure 3. Correlation analysis between the deformation recovery rate and chemical constituents of teakwood bending components.
Figure 3. Correlation analysis between the deformation recovery rate and chemical constituents of teakwood bending components.
Forests 16 00521 g003
Forests 16 00521 g004
Figure 4. Effect of different treatment times on the chord length recovery rate of teakwood bending components.
Figure 4. Effect of different treatment times on the chord length recovery rate of teakwood bending components.
Forests 16 00521 g004
Forests 16 00521 g005
Figure 5. Effect of different initial moisture contents on the chord length recovery rate of teakwood bending components.
Figure 5. Effect of different initial moisture contents on the chord length recovery rate of teakwood bending components.
Forests 16 00521 g005
Forests 16 00521 g006
Figure 6. Absorption resilience of teakwood bending components: (a) resilience curve, (b) maximum resilience.
Figure 6. Absorption resilience of teakwood bending components: (a) resilience curve, (b) maximum resilience.
Forests 16 00521 g006
Forests 16 00521 g007
Figure 7. Correlation analysis of water absorption resilience of teakwood bending components: (a) chemical constituent content, (b) deformation recovery rate.
Figure 7. Correlation analysis of water absorption resilience of teakwood bending components: (a) chemical constituent content, (b) deformation recovery rate.
Forests 16 00521 g007
Forests 16 00521 g008
Figure 8. Storage modulus E′ before and after specimen treatment.
Figure 8. Storage modulus E′ before and after specimen treatment.
Forests 16 00521 g008
Forests 16 00521 g009
Figure 9. Loss modulus E′ before and after specimen treatment.
Figure 9. Loss modulus E′ before and after specimen treatment.
Forests 16 00521 g009
Table 1. Drying quality of teakwood bending components under different medium-temperature conditions.
Table 1. Drying quality of teakwood bending components under different medium-temperature conditions.
Drying Temperature/°CInitial Moisture Content/%Average Final Moisture Content/%Deviation of Moisture Content with Thickness/%Epithelial Crack/StripInner Crack
/Strip		End Crack
/Strip		Chord Length Shrinkage
/%
110309.232.270001.24
120309.021.980001.51
130308.751.650001.68
140308.361.452011.79
Table 2. Drying quality of teakwood bending components under different initial moisture content conditions.
Table 2. Drying quality of teakwood bending components under different initial moisture content conditions.
Drying Temperature/°CInitial Moisture Content/%Average Final Moisture Content/%Deviation of Moisture Content with Thickness/%Epithelial Crack/StripInner Crack
/Strip		End Crack
/Strip		Chord Length Shrinkage/%
130509.252.793012.00
130409.122.241011.75
130308.751.650001.25
130208.161.200001.25
Table 3. Drying quality of teakwood bending components under different heating rate conditions.
Table 3. Drying quality of teakwood bending components under different heating rate conditions.
Drying Temperature/°CInitial Moisture Content/%Heating Rate/°C/hAverage
Final
Moisture
Content/%		Deviation of Moisture Content with Thickness/%Epithelial Crack/StripInner Crack
/Strip		End Crack
/Strip		Chord Length Shrinkage/%
13050208.751.650001.25
13040308.321.430001.21
13030607.801.220001.16
13020907.061.042011.16
Table 4. Results of different medium temperatures’ variation in water-absorption chord lengths of teakwood bending components (mm).
Table 4. Results of different medium temperatures’ variation in water-absorption chord lengths of teakwood bending components (mm).
TimePre-Immersion24 h48 h72 h96 h120 h
Temperature
Conventional drying405.0453.2500.2502.4504.6505.7
110 °C401.8428.3452.8457.6462.5463.4
120 °C400.2416.2430.3436.3440.3441.2
130 °C401.5409.6414.7420.6421.8422.1
140 °C402.1408.7414.3419.0419.1419.4
Table 5. Results of treatment times’ change in water absorption chord length of teakwood bending components (mm).
Table 5. Results of treatment times’ change in water absorption chord length of teakwood bending components (mm).
TimePre-Immersion24 h48 h72 h96 h120 h
Condition
Superheated steam: 1 h402.3414.9426.8437.3439.6440.1
Superheated steam: 2 h401.5409.6414.7420.6421.8422.1
Superheated steam: 3 h399.8407.7412.5418.7419.9420.1
Table 6. Results of the effect of different initial moisture contents on the variation in water absorption chord length of teakwood bending components (mm).
Table 6. Results of the effect of different initial moisture contents on the variation in water absorption chord length of teakwood bending components (mm).
TimePre-Immersion24 h48 h72 h96 h120 h
Initial Moisture Content
50%407.5417.7420.8425.7426.2427.2
40%404.1413.4418.1423.8425.6427.3
30%401.5409.6414.7420.6421.8422.1
20%403.3412.4416.1423.9424.9425.3
Disclaimer/Publisher’s Note: The statements, opinions and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions or products referred to in the content.

Share and Cite

MDPI and ACS Style

Yao, L.; Pan, Y.; Ji, L.; Wang, Z.; Liu, J. Effect of Superheated Steam Technology on the Deformation Recovery Performance of Teakwood Bending Components and Its Mechanism. Forests 2025, 16, 521. https://doi.org/10.3390/f16030521

AMA Style

Yao L, Pan Y, Ji L, Wang Z, Liu J. Effect of Superheated Steam Technology on the Deformation Recovery Performance of Teakwood Bending Components and Its Mechanism. Forests. 2025; 16(3):521. https://doi.org/10.3390/f16030521

Chicago/Turabian Style

Yao, Linghua, Yanxia Pan, Lina Ji, Zhangheng Wang, and Junnan Liu. 2025. "Effect of Superheated Steam Technology on the Deformation Recovery Performance of Teakwood Bending Components and Its Mechanism" Forests 16, no. 3: 521. https://doi.org/10.3390/f16030521

APA Style

Yao, L., Pan, Y., Ji, L., Wang, Z., & Liu, J. (2025). Effect of Superheated Steam Technology on the Deformation Recovery Performance of Teakwood Bending Components and Its Mechanism. Forests, 16(3), 521. https://doi.org/10.3390/f16030521

Note that from the first issue of 2016, this journal uses article numbers instead of page numbers. See further details here.

Article Metrics

Back to TopTop