ArticlePDF Available

Physical and mechanical properties of paulownia tomentosa wood planted in hungaria

  • 1. University of Sopron, Hungary 2. Co-operational Research Centre Nonprofit Ltd, University of Sopron

Abstract and Figures

The Paulownia tree (or to its well-known name Chinese empress tree; Paulownia tomentosa) is classified among the most variable wood species of the world concerning usability. Its cultivation in Hungary in form of research plantations has just started in the last decade, first of all for the investigation of energetic properties. Due to this the information related to the physical-mechanical properties of the wood was still not determined, from which aspect this study is essential. The investigated wood with an air-dry density of 0.3 g·cm⁻³ has shown low bending (42 MPa), compressive (22 MPa), shear (7 MPa), tensile (33 MPa) and impact strength (1.6 J·cm⁻²) values, based on which its wooden material properties can be compared to poplars considering tree species in the region.
Content may be subject to copyright.
62 (2): 2017
Short note
S K, S F
U  S, I  W S
S, H
A   V
U  S, I  F  E T
S, H
(R A )
The Paulownia tree (or to its well-known name Chinese empress tree; Paulownia tomentosa) is
classified among the most variable wood species of the world concerning usability. Its cultivation
in Hungary in form of research plantations has just started in the last decade, first of all for
the investigation of energetic properties. Due to this the information related to the physical-
mechanical properties of the wood was still not determined, from which aspect this study is
essential. The investigated wood with an air-dry density of 0.3 has shown low bending
(42 MPa), compressive (22 MPa), shear (7 MPa), tensile (33 MPa) and impact strength
(1.6 values, based on which its wooden material properties can be compared to poplars
considering tree species in the region.
KEYWORDS: Paulownia tomentosa, physical properties, mechanical properties, density,
In Asia and in some European countries Paulownia species are preferred in tree cultivations
or agro-forestry plantations of industrial wood purpose, in the latter typically in combination of
industrial wood/agricultural crop plant, rarely in mixed culture of other purpose (e.g. energy).
For example in the Chinese agriculture Paulownia is cultivated as intermediate plant on almost
1.3 million hectares. The reason for this is that one manages meagre property assets in China, so
food production and industrial wood cultivation can be realized on the same ground (Vityi and
Marosvölg yi 2012).
Literature data and the results of Hungarian investigations performed present that individual
Paulownia species are basically undemanding, have a great yield and can be cultivated relative
simply. It can be well reproduced from grain, root cutting (according to some sources also from
shoot cutting), under favourable conditions it can reach a trunk diameter of 30-40 cm, the height
of 10-12 m and the wood yield of 0.2-0.6 m-3 by the age of 10 years. (Under ideal cultivation
conditions its growth can be even quicker). (Yang 2004).
Its wide utilization spectrum ranges from industrial applications (furniture and building
timber, base material for paper industry, biomass for energy purposes etc.) through apiculture and
medical industry (bark, leaf, f lower cluster) to decoration function (park tree, base material of
exquisite wood-carving). Owing to its machinable timber of decorative texture it is used in Japan
as traditional timber, where a high quality log counts as valuable base material. The less valuable
base material can be utilized on other areas such as for example chipboard (Kalaycioglu 2005),
however it is applied as heat and electric insulation material (AFBI 2008) respectively. From
the properties of a wood density is most essential concerning utilization. From this information
one can conclude on the strength properties (Kiaei 2013). Typically there is a strong correlation
between density and MOR and MOE resp (Zhang 1997). The basic density relates closely to
the quality parameters of the final usage, such as e.g. cellulose yield and strength of construction
materials (Harvald and Olesen 1987). The tree species of higher density generally have more solid
wood than the ones of lower density (Walker and Butterfield 1996).
Paulownia is mainly cultivated on areas with hotter climatic conditions of the world (mainly
on the extended plantations of China and USA), where the usage of P. elongata has spread. For
this reason there is lot of information about this tree species, while one can find much less data
related to P. tomentosa tolerating also more moderate climatic conditions. The purpose of this
research is the discovery of the properties of the wooden material cultivated in Hungary, which
is the essential condition of applicability on some utilization areas.
The Hungarian cultivations were established first of all for the purpose of plantation
experiences and energetic researches, for this reason older, more mature wood was not available
for investigation. The tree-trunk serving as base material for the specimen required for the
examination is situated at an altitude of 70 m; the average annual temperature ranges between
11-12°C, and the long-term total annual precipitation is approx. 608 mm. The examinations have
covered the following properties in accordance with the relevant standards:
- Annual ring structure
Based on the picture made of the disc cut from the trunk by means of the program Image Pro
Plus the annual ring width was determined along the smallest and biggest radius.
- Physical-mechanical properties
From the examined trunk the following properties were defined based on the relevant
standards: Density (DIN 68364:2003), Shrinkage and swelling (DIN 52184:1979), Compression
strength (DIN 52185:1976), Tensile strength (DIN 52188:1979), Shearing strength (DIN
52187:1979), Static bending streng th (DIN 52186:1978), Modulus of elast icity (DIN 68364:2 003).
Impact bending strength (DIN 52189:1981), Brinell hardness (MSZ EN 1534:2000).
Vol. 62 (2): 2017
The examination were performed under standard climatic conditions (T=20°C; φ=65%)
- until equilibrium moisture content - on stored specimens. The strength examinations were
carried out with universal material examining device type Instron 4208 and Charpy-impact tester
on specimen series of 25 pcs. each.
Due to the eccentric structure of the examined disc along the biggest radius the growth is
wider by approx. 30% than the value of the smallest radius. The increase cycle becomes constant
beginning from the 5th year (Fig. 1) under the growth ring width value of 1 cm. In the previous
years significantly bigger values can be found. The average growth ring width is 14.7 mm along
the biggest radius, while 8.3 mm in the direction of the smallest radius .
Fig. 1: Growth per year.
Paulownia tomentosa has an expressly light, soft wood, which is proven by the measured
density values. The air-dry density (Tab. 1.) received corresponds with the average of the values
in the literatures (Kanehira 1933, Senelwaa and Sims 1999, Flynn and Holder 2001, Kalaycioglu
2005, Akyildiz 2010). This low density does not even exceed that of the poplars for example.
Tab. 1: Values of the measured densities (kg.m-3).
Density type Average Min. Ma x. St . dev.
Air-dry (u=12%) 300.18 262.33 360.18 26.59
Oven-dry (u=0%) 275.46 240.00 328.15 23.52
Basic 264.2 224.39 309.09 23.04
In case of the Paulownia tree we have received favourable results (Tab. 2.) from aspect
of dimensional change caused by moisture. Firstly the radial and tangential values are very
favourable, which almost completely comply with the ones communicated by Meier (2015).
However related to the dimensional change of volume higher literature values by more than
20-30% can be found as well (Akyildiz 2010).
Tab. 2: Values of the measured densities.
Longitudinal Radial Tangential Volu met ric
Shrinkage 0.69 2.20 3.89 6.94
Swelling 0.68 2.17 3.73 6.28
From the low density value of the wooden material it is inferred that the different strength
values are not high as well. It is proven by the results received (Tab. 3.), which often have not
reached that of the poplars with similarly soft wooden material.
Tab. 3: Mechanical properties (parallel to the grain (MPa)).
Test type Average Min. Ma x. St .dev.
Compressive 22 .14 19.63 25.24 1.78
Tensile 33.23 21.86 52.96 8.90
Shearing 7.0 3 6.08 8.00 0.52
MOR (3 points) 41.51 28,65 48.65 4.68
MOE (3 points) 3492 2595 4142 472
Cross 26.74 20.78 31.89 3.22
Tangential 9.13 5.59 13.61 2.16
Radial 9.51 6.53 13.39 2.17
Impact bending strength
( 1.27 1.90 0 .17
The strength values of the investigated paulownia correspond in some cases, while in other
cases these deviate more or less from the ones indicated by others. The values of bending strength
as maybe the most important strength property are practically identical with the values found in
some literatures (Akyildiz 2010, Meier 2015, Shim 1948). However regarding flexibility we have
received significantly lower values than communicated by other sources (Akyildiz 2010, Meier
2015, Shim 1948).
Regarding compressive strength the average 22 MPa value can be considered as very low,
which is however connected to favourable deviation values. The average shear strength value
received can be higher by even 20% compared to some earlier researches (Shim 1948, Barton
The determination of the tensile strength values is generally performed rarely in case of
wooden material examination, contrary to e.g. bending or compressive strength. In this case the
very high deviation value was connected to relatively low (33 MPa) strength.
The determination of the impact-bending strength – which is already a dynamic strength
property - is performed also relative rarely, for this reason values in this regard were not available.
The values received are extremely low, even in case of wood species with similar low density.
The Brinell hardness values measured in the main anatomical directions of the wood have
produced similar values as the similarly soft poplars. The axial hardness is almost the triple of the
side hardness values, which are practically the same.
Vol. 62 (2): 2017
The wooden material properties of Paulownia tomentosa cultivated in Hungary do not show
any significant deviation related to the ones cultivated in other parts of the world. Due to its
low density (air-dry: 300 kg.m-3) and strength values it is not suitable for structural purposes;
however it can be a serious competition for broad-leaf tree species, f irst of all due to its growth
characteristics. Based on our investigations its properties can be compared first of all to hybrid
poplars. The density of hybrid poplars wood is between 300-400 kg.m-3. The cultivation
experiences and the current research related to the physical-mechanical properties of wooden
material can establish the more significant extension of the species in the region.
1. AFBI, 2008: Paulownia as a novel biomass crop for Northern Ireland? A review of
current knowlwedge, Occasional publication No. 7. Agri-Food and Bioscience Institute,
2. Akyildiz, M.H., Kol, S.H., 2010: Some technological properties and uses of paulownia
(Paulownia tomentosa Steud.) wood. Journal of Environmental Biology (31): 351-355.
3. Barton, I.L., Nicholas I.D., Ecroyd C.E., 2007: Paulownia. Forest Research Bulletin No.
231, 9pp. Rotorua, New Zealand, Forest Research Institute.
4. Bergmann, B.A., 1998: Propagation method influences first year field survival and growth
of Paulownia, New Forests 16(3): 251-264.
5. DIN 52188, 1979: Testing of wood - Determination of ultimate tensile stress parallel to
6. DIN 68364, 2003: Properties of wood species - Density, modulus of elasticity and strength
7. DIN 52186, 1978: Testing of wood - Bending test
8. DIN 52187, 1979: Testing of wood - Determination of ultimate shearing stress parallel to
9. DIN 52189, 1981: Testing of wood - Determination of impact bending strength
10. DIN 52185, 1976: Testing of wood - Compression test parallel to grain
11. DIN 52184, 1979: Testing of wood - Determination of swelling and shrinkage
12. Flynn, H., Holder, C., 2001: Useful wood of the world, Forest Products Society. Madison,
13. Jun-Qing, et al. 1983: Studies on the wood propertis of the genus paulownia, I. Scienta
Silvae Sinicae 19(1): 57-63.
14. Harvald, C., Olesen, P. O., 1987: The variation of the basic density within the juvenile wood
of Sitka spruce (Picea sitchensis). Scand. J. For. Res. 2: 525-53
15. Kalaycioglu, H., Deniz I., Hiziroglu, S., 2005: Some of the properties of particleboard made
from paulownia, J. Wood Sci. 51: 410-414.
16. Kanehira, R., 1933: On light-weight woods. J. Soc. For. Japan. In: Harzmann, L. J. 1988.
Kurzer Grundriß der allgemeinen Tropenholzkunde. S. Hirzel Verlag, Leipzig 255 pp.
17. Kiaei, M., 2013: Radial variation in wood static bending of naturally and plantation grown
alder stems, Cellulose Chem. Technol. 47 (5-6): 339-344.
18. Komán, Sz., 2013: Anatomical and physical characteristics inf luencing the modern
utilisation of hybrid poplars for industrial and energy purposes, Doctoral dissertation.
University of West Hungary, Sopron.
19. Meier, E., 2015: Wood. Identifying and using hundreds of woods worldwide, ISBN 978-0-
20. MSZ EN 1534, 2000: Wood and parquet f looring. Determination of resistance to
indentation (Brinell). Test method.
21. Olson, J.R., Carpenter, S.B., 1985: Specific gravity, fibre length, and extractive content of
young paulownia, Wood and Fiber Science 17(4): 428-438.
22. Senelwa, K., Sims R.E.H., 1999: Fuel characteristics of short rotation forest biomass.
Biomass and Bioenergy 17(2): 127–140.
23. Shim, C.S., 1948: The mechanical properties of Paulownia tomentosa and Paulownia
Coreana in Korea, Report of Forest Product Lab., Dept. of Forestry, Seoul Nat’1 Univ.
Pp 1-20 .
24. Yang, X., 2004: Paulownia agroforestry systems in China, Poster. Proceedings os the
International Ecoagriculture Conference and Practitioners’ Fair. Vol. 2: Conference
abstracts. Nairobi 2004.
25. Vityi, A., Marosvölgyi, B., 2012: A fajszi kísérleti Paulownia ültetvények újabb kutatási
eredményei (Environmental resource management and protection and environmental
cooperation), Research Centre Non-profit Ltd, Sopron (in Hungaryan).
26. Walker, J.C.F., Butterfield, B.G., 1996: The variation of the basic density within
the juvenile wood of Sitka spruce (Picea sitchensis), New Zealand Journal of Forestr y
40(4): 34–40.
27. Zhang, S. Y. (1997): Wood specific gravity-mechanical property relationship at species
level, Wood Science and Technology 31(3):181-191.
S K*, S F
U  S
I  W S
B Z. S. 
H- S
Corresponding author:
A   V
U  S
I  F  E T
... Several paulownia species are extensively cultivated in China and Japan, and they have shown tremendous growth performance. With annual growth rates of up to 4 cm per annum under favorable environmental conditions (Koman et al. 2017), cultivation in these countries is successful. Most paulownia species are extremely fast growing and can be harvested in 15 years for valuable timber. ...
... The strength results of the yellow poplar and Chinese poplar wood found in this study are comparable to those reported previously (Ross 1987;Green and Evans 2003;Ming-Li et al. 2019). The strength properties of the paulownia wood in this study were comparable to the properties of the planted Paulownia tomentosa in Hungary (Koman et al. 2017). The clone Revotropix paulownia appears to be comparable to other plantation-grown paulownia species, and its strength properties demonstrate that it is suitable for furniture application. ...
Imported wood resources, especially yellow poplar and Chinese poplar, are increasingly evident in the Malaysian furniture sector due to declining supply of domestic wood materials. In order to reverse this trend, paulownia, a fast-growing forest plantation tree species, is emerging as an alternative wood material source. This study evaluated the mechanical strength, including fatigue life, machining, adhesive bond, screw withdrawal, and finishing properties of paulownia against the imported wood of yellow poplar and Chinese poplar. The results revealed that paulownia has better properties than Chinese poplar, but it is inferior to yellow poplar due to its lower density. In terms of fatigue strength, all the wood species performed comparably equal, with the allowable design stress set at 40% of the wood species’ respective ultimate bending strength. Against these findings, paulownia is a promising alternative wood resource for furniture manufacturing in Malaysia, and it could possibly replace the imported yellow poplar and Chinese poplar. Nevertheless, the successful application of paulownia for furniture manufacturing will depend on its supply volume and economics in the future.
... However, technical properties of hybrids 9501 and Shan Tong have not been investigated so far in Croatia. In addition, there are limited data on technical properties of wood of different Paulownia species (Ayhildiz and Kol, 2010; Kiaei, 2013; San et al., 2016;Komán et al., 2017). ...
... . However, these differences in mean values amounted only to about 6%. The values are similar to the fi ndings on Paulownia elongata, 240 kg/m 3(Šoškić et al., 2003); Paulownia tomentosa, 276 kg/m 3(Komán et al., 2017); Paulownia fortunei, 274 kg/m 3(Šoškić et al., 2017) and 261 kg/m 3(Kiaei, 2013).For hybrid 9501, the mean value of longitudinal shrinkage is 0.30 %, radial shrinkage 2.35 %, tangential shrinkage 4.95 % and volumetric shrinkage 7.62 % (Table 1). For hybrid Shan Tong, the mean value of longitudinal shrinkage is 0.35 %, radial shrinkage 2.47 %, tangential shrinkage 5.30 % and volumetric shrinkage 7.81 % (Table 1). ...
Full-text available
There is a growing trend in the world of planting fast growing species (rotations 5 to 10 years). Their primary purpose is the production of wood fibers and biomass, but they certainly represent the potential in making solid wood products as well. One of the fast-growing species is Paulownia sp., a species of extremely fast growing wood. Plantation breeding of Paulownia sp. in Croatia is increasing, although there is a little knowledge about the technical properties of Paulownia wood and its end use is questionable. This paper presents preliminary results of some physical properties of juvenile wood of two Paulownia hybrids planted in the area near the town of Glina in the Republic of Croatia. One hybrid is 9501 ((Paulownia fortunei × Paulownia elongata) × (Paulownia fortunei × Paulownia tomentosa)) and the other hybrid is Shan Tong (Paulownia fortunei × Paulownia tomentosa). The aim of this study was to investigate physical properties of juvenile wood of two Paulownia hybrids from one site in Croatia, to determine differences in physical properties of wood between two hybrids and to evaluate the correlation between density and shrinkages of each hybrid. Significant differences in oven dry density, basic density and density at maximum MC, between the two hybrids were determined. There is no statistically significant difference in longitudinal, radial, tangential and volumetric shrinkages between the two hybrids.
... Occasionally, as indicated by certain authors [92], a density of above 400 kg m −3 has been measured (Shan Tong, Bulgaria). Paulownia wood static bending strength ranges from 23.98 to 43.56 MPa, depending on the species, while the modulus of elasticity ranges from 2651 to 4917 MPa [44,89,93,94], or even up to 5900 MPa for P. tomentosa [87]. In both standing-tree and log tests performed using non-destructive methods, a higher modulus of elasticity has been reported for trees with larger diameters [95]. ...
Full-text available
This review aimed to determine the current state of research on the growth conditions and use pertaining to paulownia wood, mainly in European countries where paulownia has been introduced only relatively recently. Several studies carried out on Paulownia hybrids have shown significant differences in the growth dynamics of individual clones in their response to local environmental and climatic conditions. For example, dry biomass production yields in the second year of cultivation range from 1.5 t ha−1 to as much as 14 t ha−1. This diversity has manifested itself not only in growth characteristics but also in the properties of the wood and the possibilities for its use. Despite having clear similarities to the genus Paulownia, the cultivation of species and hybrids under different conditions has produced varying results. The best growing conditions for this wood (that make economic sense) are in the Middle East and Southern Europe. These regions have accumulated the most experience because of the earlier establishment of the crop. Today, paulownia cultivation is dominated by hybrids with selected traits that are propagated mainly in vitro. The most commonly planted hybrids include the clones in vitro 112, Cotevisa 2 and Shan Tong. The growth results and production capacity in central European countries are lower compared to Southern Europe. Experiments on paulownia cultivation are still relatively young, mainly consisting of replicating the cultivation of hybrids developed in Asia or Southern Europe. However, agronomic procedures are being developed and reactions to local climatic conditions are being studied. It is likely that, in the next few years, the profitability of growing paulownia in these regions will become apparent.
... In comparing the bulk density with paulovnia species to other countries, the bulk density of Paulownia elongata from Hungary was 0.3 g . cm -3 (Koman et al. 2017), Turkey specie was 0.326 g . cm -3 (Kaygin et al. 2009), that of the Malaysian specie was 0.325 g . ...
Full-text available
The article deals with the effects of bulk density on thermal conductivity in specimens of 15Korean woods (Zelkova serrata, Pinus densiflora, Cornus controversa, Betula schmidtii, Betula platyphylla var. japonica, Ginkgo biloba L.,Cedrela sinensis A. Juss., Fraxinus mandshurica, Ulmus davidiana var. japonica, Prunus sargentii Rehder, Paulownia tomentosa (Thunb.) Steud., Larix kaempferi (Lamb.) Carrière, Robinia pseudoacacia, Kalopanax septemlobus and Tilia amurensis).The results of this study were compared with previous studies performed on wood specimens fromChina, India, and Turkey. Consistent with these previous studies, bulk density and thermal conductivity were positively correlated in Korean woods, and a simple regression model with a very high correlation of R2(94%) was obtained. Interestingly, we observed some variation between our simple regression models and those generated by previous researchers who had examined non-Korean woods.
... Kaźmierski [2009] [Zhu i in. 1986;Akyildiz, Sahin Kol 2010;Kiaei 2013;Koman, Feher 2017]. ...
Full-text available
Lachowicz H., Giedrowicz A. 2020. Charakterystyka jakości technicznej drewna paulowni COTE−2. Sylwan 164 (5): 414−423. DOI: Seedlings of Paulownia (Paulownia sp.) has increasingly appeared in the merchant offers in Poland. However, the knowledge of the technical characteristics of its wood is still insufficient because comprehensive studies of wood properties for this species have not been performed. The main aim of this study was to determine the selected physical and mechanical properties of Paulownia COTE−2 wood. The wood comes from the plantation of Paulownia COTE−2 located in Granada region in Spain. The investigation were carried on 162 samples, according to Polish standards. We analysed the following physical properties: air−dry density, oven−dry density, basic density, proportion of wood substance, wood porosity, total shrinkage of wood in longitudinal, tangential and radial anatomical directions, volumetric shrinkage, coefficients of each of mentioned shrinkage, the anisotropy index of shrinkage and mechanical properties: compression strength, static bending, modulus of elasticity in static bending, including the coefficients of the mechanical properties mentioned before. The results show that Paulownia wood is very light, with the density of 270 kg/m 3 and low shrinking (volumetric shrinkage equaled to 7%). The mechanical properties of Paulownia wood are closely related to its density. Static bending equaled to 38 MPa and compression strength parallel to grain amounted to 24 MPa. KEY WORDS mechanical and physical properties, Paulownia COTE−2, wood of fast growing trees
... Several studies present results related to the mechanical characterization of wood species and their variability, such as: Aquino et al. (2018), Couto et al. (2018), Gherardi Hein et al. (2012), Koman et al. (2017). Besides these, we can highlight the studies of and Silva et al. (2018) that evaluated the variability of physical and mechanical properties of wood as a function of the geographical origin, as well as the studies of Lima Junior et al. (2018) and Zeidler et al. (2014), which investigated the variability of the mechanical properties of wood extracted from different positions in a tree. ...
Wood has several advantages as structural material. For this use to be applied in a safe way, it is necessary to know the statistical behavior of the mechanical properties. Some works and normative codes, such as the “Brazilian timber standard” (as well as its review project), accepts a normal distribution model for determining the characteristic value of compressive strength parallel to wood fiber, with the adoption of a coefficient of variation for this property equal to 18 %. This work evaluates the distribution model of compressive strength parallel to the fibers, as well as the coefficient of variation of this property. Tests and statistical treatment were performed in compression parallel to the fibers for 7 species of hardwood commonly found in Brazil. It was observed that the compressive strength of wood actually follows a normal distribution, and the adoption of an average coefficient of variation equal to 18 % is acceptable and in favor of safety.
... Exact knowledge of the physical-mechanical properties of the wood has not yet been determined, for which this study is important. The values of Paulownia tomentosa are also shown in the examined characteristics, which are originated from a previous study ( Komán et al. 2017). Clone density for Paulownia species is typically extremely low. ...
... Exact knowledge of the physical-mechanical properties of the wood has not yet been determined, for which this study is important. The values of Paulownia tomentosa are also shown in the examined characteristics, which are originated from a previous study ( Komán et al. 2017). Clone density for Paulownia species is typically extremely low. ...
... Exact knowledge of the physical-mechanical properties of the wood has not yet been determined, for which this study is important. The values of Paulownia tomentosa are also shown in the examined characteristics, which are originated from a previous study ( Komán et al. 2017). Clone density for Paulownia species is typically extremely low. ...
Full-text available
A study of selected features of Shan Tong variety of plantation paulownia and its wood properties. The study was conducted on three-year-old and representative paulownia tree of the Shan Tong variety, from a plantation in the Kujawsko-Pomorskie Voivodeship, Poland. The three-year-old paulownia tree was 4.2 m high and its diameter at butt level was of 11 cm. The tree provided material for the study from its three-year-old shoot, which was divided into three parts: leaves, branches and the main trunk. According to calculations, this typical paulownia tree (a three-year-old shoot) from a plantation accumulated 4.664 kg of carbon in the part above the ground level, which corresponds to the absorption of 17.101 kg of CO2 from the atmosphere. Taking into account the underground part of this plant, it can be estimated that it absorbed over 30 kg of CO2 (on average, ca. 10 kg CO2 per year). The density of paulownia wood in absolute dry state was ca. 250 kg/m3. The width of annual growth rings was ca. 1.5 cm. This kind of wood is highly porous, with porosity of about 85% (good thermal insulation), and at the same time it has favourable resistance properties characterized by the modulus of elasticity of 4.05 GPa.
Full-text available
The objective of this study was to determine some of the properties of experimental particleboard panels made from low-quality paulownia (Paulownia tomentosa). Chemical properties including holocellulose, cellulose, lignin contents, water solubility, and pH level of the wood were also analyzed. Three-layer experimental panels were manufactured with two density levels using urea–formaldehyde as a binder. Modulus of elasticity (MOE), modulus of rupture (MOR), internal bond strength (IB), screw-holding strength, thickness swelling, and surface roughness of the specimens were evaluated. Panels with densities of 0.65 g/cm3 and manufactured using a 7-min press time resulted in higher mechanical properties than those of made with densities of 0.55 g/cm3 and press times of 5 min. Based on the initial findings of this study, it appears that higher values of solubility and lignin content of the raw material contributed to better physical and mechanical properties of the experimental panels. All types of strength characteristics of the samples manufactured from underutilized low-quality paulownia wood met the minimum strength requirements of the European Standards for general uses.
Full-text available
Field trials at three locations were used to evaluate survival and early growth of Paulownia elongata, P. fortunei, and P. ''Henan 1'' plants produced from seeds, shoot cuttings, and micropropagated shoots. One year after field establishment, trees produced by either vegetative propagation method survived with higher frequency and were taller and of greater diameter breast height than trees grown from seed. The influence of propagation method was more pronounced in P. elongata and P. fortunei than in P. ''Henan 1''. Survival frequency was similar for each species/hybrid, but both species were taller than P. ''Henan 1'' across propagation method and site. Field site had a pronounced influence on tree survival and height. Species/hybrid differences were not detected at the site that promoted the greatest tree growth, but P. elongata outperformed P. fortunei and P. ''Henan 1'' at the two sub-optimal sites. Clones within species/hybrid produced through micropropagation differed in survival frequency, height, and diameter breast height. Under the conditions used for this study, Paulownia field survival and early growth in central North Carolina was improved by using P. elongata or P. fortunei produced by rooting shoot cuttings or micropropagated shoots. Significant variation among clones within these species demonstrated the potential benefit of identifying superior clones to improve first year field survival and growth.
Full-text available
The aim of this study is to determine some physical and mechanical properties of Paulownia tomentosa wood grown in Turkey. The samples trees harvested from Kargi in Corum. Physical properties including air-dry density oven-dry density basic density swelling, shrinkage and oven-dry and air-dry thermal conductivity coefficients; mechanical properties including bending strength, modulus of elasticity in bending, compression strength parallel to grain, hardness, bonding strength were analyzed. Paulownia tomentosa wood's air dry and oven dry densities were determined as 0.317 and 0.294 g cm(-3); basic density was determined as 0.272 g cm(-3); volumetric shrinkage and swelling were determined as 7.78 and 8.41%; tangential, radial and longitudinal air-dry thermal conductivity coefficients were determined as 0.089, 0.090 and 0.133 kcal/mh degrees C, respectively. Fiber saturation point (FSP) was found 28.79%; bending strength, Modulus of elasticity in bending, compression strength parallel to grain and Brinell hardness values (parallel and perpendicular to grain) were determined as 43.56 N mm(-2), 4281.32 N mm(-2), 25.55 N mm(-2), 2.01 kgf mm(-2) and 0.88 kgf mm(-2), respectively. Consequently paulownia wood can be widely used for various purposes such as house construction, furniture making, pulp and paper and handicrafts.
This study was carried out to determine radial variation of wood density, modulus of elasticity (MOE), modulus of rupture (MOR) and stress at elastic limit in plantation and natural alder forests in the north of Iran. Testing samples were taken at breast height of the stem and in three radial positions (10, 50 and 90% of radius) from natural and plantation forests to determine wood mechanical strength properties, according to the ASTM standard. The analysis of variance indicated that planting conditions (natural and plantation forests), radial position and their interaction had no significant effects on the modulus of elasticity (MOE), modulus of rupture (MOR) and stress at elastic limit in alder wood, while only radial position had a significant effect on wood density. Wood density was increased along radial direction from the pith to the periphery for both planting conditions. Overall, the mechanical strength properties in the plantation forest were slightly higher compared to the natural forest. The relationship between wood density and mechanical properties were analyzed by linear regression. A positive relationship was found between wood density and mechanical properties for both planting conditions. This relationship was stronger in plantation grown, compared to naturally grown trees.
The variation in the basic‐density level of 45 stems of Sitka spruce from two Danish sites has been examined. It is shown that the basic‐density level, i.e. the basic density as a function of ring width, within the juvenile wood decreases with (1) increasing distance from the pith and (2) increasing height in the stem (same ring number from pith provided). Furthermore, the basic‐density level seems to decrease with increasing stand quality, which may affect the pattern of variation in basic‐density level if the stand quality class varies with age. The basic density of the juvenile wood is markedly higher in Sitka spruce than in Norway spruce, whereby the risk of stem cracks probably is reduced.
Based on the data set of specimen tests on 16 timber species belonging to four distinct wood categories, the specific gravity-mechanical property relationship at species level was examined, and differences in the relationship between species from distinct wood categories were discussed. The linear equation (S =a +bG) was compared with the curvilinear one (S = G) in terms of the goodness at predicting mechanical properties through specific gravity at species level. The specific gravity-mechanical property relationship, to a differing extent, varies with mechanical properties and wood categories. Among three mechanical properties studied, MOR is most closely and almost linearly related to specific gravity, followed by Cmax, whereas MOE is poorly and least linearly related to specific gravity. In general, the relationship between MOE and specific gravity in a species from the ring-porous category is stronger than in a species from the diffuse-porous category. It appears that Cmax in a species from the second softwood category and the ring-porous category is more closely related to specific gravity than in a species from the first softwood category and the diffuse-porous category, respectively. In addition, MOE in a softwood species is generally less related to specific gravity as compared to a hardwood species. Yet, Cmax in a softwood species appears more closely related to specific gravity. Overall, the curvilinear equation is better than the linear one at predicting mechanical properties (especially MOE) in a species.
Fuel characteristics of biomass from 12 tree species grown under a short rotation forestry regime were analysed. E. globulus, E. nitens and A. dealbata had the biggest trees while A. glutinosa, P. tomentosa and S. matsudana×alba 1002 had the smallest trees when the trees were harvested at the age of 3, 4 and 5 years. Higher heating value (HHV) ranged from 19.6–20.5 MJ/kg for wood, 17.4–20.6 MJ/kg for bark, and 19.5–24.1 MJ/kg for leaves, with the highest values for wood and bark being obtained from Pinus radiata. Wood basic density ranged from 250–500 kg/m3; ash content, 0.7–1.4%; volatile matter content, 91.5–95.1%; fixed carbon content, 4.2–7.3%; and extractives content, 3.3–11.9%. Wood properties were significantly different from those of bark, and also different from those of leaves. Except basic density and the proportion of bark on the stem, properties of wood did not vary with either cutting age or stocking density. Wood from coppice crops did not differ from that of single stem, first harvest crops.Differences in tree size for species planted at similar plant populations determine species yields. Variations in properties between species and between tree parts have implications for feedstock handling, transport, drying, storage, and on the design of conversion systems.
Paulownia as a novel biomass crop for Northern Ireland? A review of current knowlwedge
AFBI, 2008: Paulownia as a novel biomass crop for Northern Ireland? A review of current knowlwedge, Occasional publication No. 7. Agri-Food and Bioscience Institute, Hillsborough.