• Journal of the Korean Wood Science and Technology
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• v.47 no.5
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• pp.644-654
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• 2019

In this study, the gas permeability, sound absorption coefficient, and sound transmission loss of the Paulownia tomentosa wood were estimated using capillary flow porometry, transfer function method, and transfer matrix method, respectively. The longitudinal specific permeability constant of the Paulownia tomentosa wood with a thickness of 20 mm was 0.254 for the control sample and 0.279, 0.314, and 0.452 after being subjected to heat treatments at $100^{\circ}C$, $160^{\circ}C$, and $200^{\circ}C$, respectively. The gas permeability was observed to be slightly increased by the heat treatment. The mean sound absorption coefficients of 20-mm thick Paulownia tomentosa log cross-section for the control sample and after being subjected to heat treatments at $100^{\circ}C$, $160^{\circ}C$, and $200^{\circ}C$ were 0.101, 0.109, 0.096 and 0.106, respectively. Further, the noise reduction coefficients of 20-mm thick Paulownia tomentosa log cross-section of the control sample and after being subjected to heat treatment at temperatures of $100^{\circ}C$, $160^{\circ}C$, and $200^{\circ}C$ were 0.060, 0.067, 0.062 and 0.071, respectively. The mean of sound transmission loss of the 20-mm thick Paulownia tomentosa log cross-section was approximately 36.93 dB. Furthermore, the gas permeability and sound absorption coefficient of the heat-treated Paulownia tomentosa discs slightly increased depending on the heat treatment temperature; however, the rate of increase was insignificant.

• Journal of the Korean Wood Science and Technology
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• v.44 no.6
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• pp.890-896
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• 2016

Paulownia tomentosa is one of fast-growing wood species in Korea. In order to evaluate the solid bioenergy properties of Paulownia tree, this study examined the heating value, moisture content (MC), pH and proximate analysis of stem, branch, root, bark and leaf. The heating values of wood parts were slightly higher than those of bark and leaf, and that of branch was the highest among all the samples. The higher moisture content of bark and leaf referred to their lower heating value. Also, the pH of stem, branch and root was similar and lower than those of bark and leaf. The ash content of bark and leaf was much higher than that of wood parts, which is the one of the reasons for effect on the lower heating value and higher pH. While, the volatile matter content (VMC) of bark and leaf was lower than those of wood parts. The bark showed the highest fixed carbon content (FCC), while the FCC of stem was the lowest among all the samples. The obtained results are encouraging that the Paulownia tree could be totally utilized as alternative fuels for bioenergy production.

• Journal of the Korean Wood Science and Technology
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• v.10 no.3
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• pp.3-3
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• 1982

• Journal of the Korean Wood Science and Technology
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• v.44 no.2
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• pp.157-165
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• 2016

This study investigated several anatomical characteristics of Paulownia tomentosa roots. The root wood was separated into three parts from stem base (top, middle, and base) at different positions below ground. Qualitative anatomical data suggested that the growth rings in earlywood and latewood were structurally different. Furthermore, the root wood vessels were found having 2 to 3 radial multiples and they were appeared in the form of clusters. In addition, some sheath cells and septate axial parenchyma were observed. Regarding the quantitative anatomical characteristics, vessel and ray numbers per $mm^2$, as well as ray width and height differed significantly among the top, middle, and base rood wood parts. However, there were no significant differences in vessel diameters, cell wall thickness, and width and length of wood fibers among those parts. The crystallinity of the root top part was slightly higher than that of the middle and base parts. Furthermore, the vessel numbers, ray numbers, and ray width and height in the near pith (NP) area were higher compared to those in the near bark (NB) area. However, the fiber width and fiber length at NP were lower than those at NB. Overall, this study demonstrated some significant differences in the anatomical characteristics of the top, middle, and base parts of root wood from Paulownia tomentosa.

• Journal of the Korea Furniture Society
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• v.19 no.6
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• pp.447-451
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• 2008

This study was carried out to know the difference of vapor transmission on the thickness of Paulownia wood(Paulownia tomentosa). The behavior of moisture transmission of wood thickness direction is generally estimated by vapor permeability and vapor transmission resistance. In general, Paulownia wood is known to use of inside material for furniture making, because of the excellent ability of vapor adsorption and/or desorption. Quarter sawing Paulownia wood material is prepared and the thickness is 6.0mm, 7.0mm, 8.0mm, 9.0mm, 10.0mm, respectively. The measurement of vapor transmission were conducted by the "cup method" in accordance with JIS(Japanese Industrial Standard) Z-0208. The experiment was made in the condition of 49.8mmHg vapor pressure difference and $40^{circ}C$ at constant temperature. From the experiment results, it was considered that Paulownia wood is very stable on moisture variation and any other material conditions. In this experiment we found that the vapor permeability and vapor permeance was reduced with the increase of wood thickness to vapor direction and vapor transmission resistance and specific vapor transmission resistance was increased with the increase of wood thickness to vapor direction. Besides moisture contents of adsorption and desorption side were about 5 percent and 14 percent, respectively. Mean value was 9.5 percent and about 10 percent in dry oven method. Moisture gradient was reduced with the increase of wood thickness for a small moisture difference of adsorption and desorption side.

• Journal of the Korean Wood Science and Technology
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• v.40 no.4
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• pp.229-236
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• 2012

This study was conducted to investigate the effect of gamma radiation on cell wall degradation, cellulose crystallinity, and flexural strength of Pinus densiflrora, Zelkova serrenata, and Paulownia tomentosa. By the gamma radiation at the dose up to 100 kGy, the cell wall degradation was not detected with scanning electron microscope (SEM) observation from all samples, and the flexural strength was not significantly changed. Cellulose crystallinity was neither changed by the gamma radiation. This high stability of wood against gamma radiation means that the radiation technology can be used for eradicating fungal and insect infestation of wood without the changes in wood properties.

• Journal of the Korean Wood Science and Technology
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• v.16 no.3
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• pp.48-64
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• 1988

This study was carried out to investigate the free vibrational properties of traditional and replaceable species for sounding board, using piezoelectrical accelerometer and signal analyzer. In the study, the frequency equations of free-free beam carrying a concentrated mass in the transverse vibration and of free-mass beam in the longitudinal vibration were used. The results obtained were as follows. 1. Average values of dynamic modulus of rigidity of Korean commercial species measured were as follows. Paulownia tomatosa (Thunb.) Steudel: $5.590\times10^9\;dyne/cm^2$ Tilia amurensis Rupr.: $5.414\times10^9\;dyne/cm^2$ Macckia amurensis Rupr.: $10.044\times10^9\;dyne/cm^2$ Fraxinus mandshurica Rupr.: $8.876\times10^9\;dyne/cm^2$ Ulmus davidiana var.japonica Nakai: $8.677\times10^9\;dyne/cm^2$ Pinus rigida Miller: $6.33\times10^9\;dyne/cm^2$ Fraxinus rhynchophylla Hance: $4.666\times10^9\;dyne/cm^2$ 2. The ratio of dynamic transverse Young's modulus to dynamic modulus of rigidity, $E_T/G_{LT}$, was 24.922 for Fraxinus rhynchophylla Hance, which was the highest, 7.317 for Paulownia tomentosa (Thunb.) Steudel, which was the lowest among Korean commercial species measured. 3. The value of longitudinal dynamic Young's modulus was about 3.7% and 19.8%, respectively, higher than those of transverse dynamic and static Young's modulus. The value of transverse dynamic Young's modulus was about 15.5% higher than that of static Young's modulus. 4. Predicted value of MOR in terms of correlation coefficient by transverse dynamic Young's modulus was slightly higher than that of static Young's modulus, but no significance was found out. 5. Transverse dynamic Youne's modulus was $(2.002\pm0.288)\times10^{11}\;dyne/cm^2$ for Fraxinus mandshurlca Rupr., which was the highest, $(0.601\pm0.100)\times10^{11}\;dyne/cm^2$ for Paulownia tomentosa (Thunb.) Steudel, which was the lowest among Korean commercial species measured. The sound velocity of sitka spruce was 5,685 m/sec, which was the highest. 6. Internal friction of Paulownia tomentosa (Thunb.) Steudel was shown the lowest value among Korean commercial species, $(8.795\pm1.795)\times10^{-3}$, but was higher than that of sitka spruce, $(7.331\pm0.991)\times10^{-3}$. Internal friction was shown negative correlation with density and dynamic Young's modulus, respectively. 7. K value was affected largely by internal friction and was the highest, $2.225\times10^8$ for Paulownia tomentosa (Thunb.) Steudel and was the lowest, $0.550\times10^8$ for Fraxinus rhynchophylla Hance. K value of Paulownia tomentosa (Thunb.) Steudel was higher than that of sitka spruce and K values of melapi and cottonwood, which have been considered to be replaceable species with sitka spruce in the piano industry, were lower than those of Paulownia tomentosa (Thunb.) Steudel and mill amurensis Rupr.

• Journal of the Korean Wood Science and Technology
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• v.14 no.4
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• pp.40-46
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• 1986

Change of color of woods is a trouble frequently found in decorative wood products. In this paper, studies were carried out on discoloation sensitivities of wood specimens to iron (0.1%, $FeCl_3{\cdot}6H_2O$), alkali (pH12.0, NaOH), acid (pH 1.0 $C_2H_2O_4$) and exposing to sunlight (40 hrs.). Four soft-woods and eleven hard-woods grown in Korea were used in this test. The results obtained were as follows: 1. In iron stain, strong discolored wood species were Larix leptolepis, Quercus mongolica. Zelkova serrata and Prunus yedoensis, and light discolored were Paulownia lomentosa and Pinus rigida. 2. In alkali stain. light discolored wood species were Abies holophylla, Kalopanax pictum, Populus ${\times}$ albaglandulosa, Acer mono, Pinus rigida, Pinus densiflora, Quercus mongolica, Betula platyphylla var. japonica, Prunus yedoensis, Zelkova serrata, Populus euramericana, Pinus koraiensis and Paulownia tomentosa, but there was no wood species of strong discolored compared with the color difference values of other reports. 3. In acid stain, light discolored wood species were Pinus rigida, Paulownia tomentosa. Pinus koraiensis, Quercus mongolica, Kalopanax piclum and Acer mone, but there was no strong discolored species compared with the color difference values of other reports. 4. In exposing to sunlight, strong discolored species were Larix leptolepis, Acer mono, Paulownia tomentosa, Populus euramericana, Pinus densijlora, Robinia pseudoacacia, Abies holophylla, Populus ${\times}$ albaglandulosa, Zelkova serrata, Prunus yedoensis and Pinus rigida, and light discolored was Alnus japonica. In general, it was shown that Korean wood species were susceptible to change of color by exposing to sunlight and iron stain compared with by alkali stain and acid stain.

• Journal of the Korean Wood Science and Technology
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• v.25 no.2
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• pp.61-66
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• 1997

Paulownia wood has been used as sound board for Korean traditional musical instruments such as Keomungo(Korean lute), Kayagum(twelve-stringed Korean harp) and Changgu(hour-glass shaped drum), etc. The acoustic properties of wood affected not only by dimensions but also by density and stiffness of wood. Due to inhomogeneity and hygroscopicity of wood. the acoustic properties of wood are inconsistent. To clarify the effect of moisture content and air dry density on acoustic properties, longitudinal vibration experiment was accomplished in 3 moisture content levels of 9.6, 11.1 and 12.5% and in 3 air dry density levels of 0.22, 0.25 and 0.28g/$cm^3$. The results were as follows: As the moisture content increased, the fundamental frequency. specific dynamic Young's modulus and sound velocity decreased, but the internal friction increased so that loss of energy increased. The values in damping of sound radiation were rapidly decreased at 12.5%. It meant that the damping of internal friction was larger than damping of sound radiation at high moisture content. As the air dry density increased, the fundamental frequency, specific dynamic Young's modulus and sound velocity increased, but the internal friction and damping of sound radiation decreased so that loss of energy decreased. And acoustic converting efficiency was hardly influenced by increasing air drying density.

• Journal of the Korean Wood Science and Technology
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• v.45 no.2
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• pp.213-222
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• 2017

Heat treatment of wood is an attractive alternative environmentally-friendly treatment to add value of less valuable woods by improving color, dimensional stability, and natural durability. To improve the color properties of Korean white pine (Pinus koraiensis) and royal paulownia (Pauwlonia tomentosa), we treated the woods at $160^{\circ}C$, $180^{\circ}C$, $200^{\circ}C$, and $220^{\circ}C$ for 2 hours. Color change after heat treatment was evaluated using the CIE-Lab color system and survey was conducted to determine the consumer preferences towards color of heat-treated wood. Lightness ($L^*$) decreased with increasing temperature and the higher degree of change was obtained in royal paulownia. The red/green chromaticity ($a^*$) in both wood decreased after heat treatment at $160^{\circ}C$, and constantly increased after heat treatment at $180^{\circ}C$ to $220^{\circ}C$. Yellow/blue chromaticity ($b^*$) in Korean white pine tended to increase after heat treatment at $160^{\circ}C$, then decreased gradually afterwards. In royal paulownia, $b^*$ values linearly increased with increasing temperature. Overall color change (${\Delta}E^*$) increased with increasing temperature with higher degree obtained in royal paulownia. Samples with the clamps in both wood species showed lower degree of the change in $L^*$, $a^*$, b and ${\Delta}E^*$. The results of the consumer preferences test showed that the darker colors of heat-treated woods were more preferred by consumers compared to the lighter colors of untreated woods. Consequently, heat treatment could enhance the color properties of Korean white pine and royal paulownia woods for value added products.