Properties of Paulownia Wood

Paulownia Wood as Presented by Dr. R. C. Tang at 1996 American Paulownia Association Auburn University.

Unique Characteristics

• Light weight: Oven-dry specific gravity: 0.17 - 0.37
• Very easy to dry and less drying defects
• Very stable in wet/humid environments after being dried(i.e. very low/slow moisture absorption)
• Highly durable/decay resistance under non-ground contact conditions
• High fire resistance: Ignition Temperature: app. 425°C (ave. softwood 257°C, ave. hardwood:233°C)
• High abrasion resistance: slow-wear against sand/soil
• Soft, but has strength
  • low compression|| to grain strength: 2,800- 3,600 psi
  • good tensile || to grain strength: 5,300 - 8,500 psi
  • Loblolly pine: 8,060 - 10,670 psi
  • Eastern W. Pine: 10,600 psi
• Excellent sound quality and absorption, less affected by change of weather
  • Excellent ,material for making high quality musical instruments
• Porosity: 75 - 885
  • Loblolly pine: 62%
  • Aspen: 73%
  • Yellow Poplar: 71%

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Density

Density of Light Weight Species

Species	Condition	Density (pcf (gr/cm3))
P. tomentosa (USA)	OD 10% MC	17.11 (0.274)
P. tomentosa (New Zealand)	OD AD	18.73 (0.300) 21.23 (0.340)
P. tomentosa (Korean)	AD	14.98 (0.2400)
P. tomentosa (China)	AD	20.41 (0.3270
P. kawakamii	OD Green	15.55 (0.249) 20.23 (0.324)
P. fortunei	AD	19.29 (0.309)
Western red cedar	12% MC	19.98 (0.320)
Balsa	9% MC	8.12 (0.130)

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Shrinkage Coefficient

Shrinkage Coefficient(%) of Light Weight Species

Species	*Specific Gravity	Radial	Tangential
Cottonwood	0.34	3.0	7.0
NW Cedar	0.31	2.2	4.9
E. W. Pine	0.35	2.1	6.1
Redwood	0.35-0.40	2.2	4.9
Paulownia	0.21-0.27	1.1-2.8	2.1-4.9

* Based on OD weight & 12% MC volume

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Absorption Properties

Absorption Properties of Paulownia Wood

Water Absorption (%)			Moisture Absorptions (%)*
1-Day	2-Day	40-Day	1-Day	2-Day	40-Day
84	108	253	12	15	19

*OD condition to conditions of 92% RH at 20°C

Species	Bound Water		Free Water
	24 hr	fsp (days)	%	days
Paulownia	17.8	25.8 (7.5)	148	48
Willow	15.2	28.5 (28)	116	53
Red Pine	12.6	24.8 (24)	189	44

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Durability

Durability of Paulownia (tomentosa)Tang 2984

Test Conditions
1. Constant 65% RH at75°f
2. Accelerated aging:	4-hr at 106 ± 2°C,Then
	4-hr water soaking, and followed by a
	16-hr under 26°F, repeated 30 days
	reconditioned to 10% MC, and then destructively
	testing in bending

 

	Strength (MOR)		Stiffness (MOE x 10 (to 6 power) psi)
	1" x 2" x 30"	1" x 1" x 16"	1' x2" x 30"	1' x 1' 16"
Test 1	5740	6260	0.758	0.641
Test 2	5420	6010	0.735	0.642

• Change of strength and stiffness due to aging was insignificant
• No visual splits, checks or severe twisting and bowing were observed after aging
• Color was slightly darkened

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Thermal Conductivity

Thermal Conductivity Coefficient of (10% MC)

	Radial	Tangential	Longitudinal
Paulownia	0.0645-0.0829	0.0584-0.0775	0.133-0.155
Sweetgum	0.136	0.121	--------------
Elm	0.143	0.143	--------------
Data sources: Hunan Agriculture College, PRC & USDA

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Fiber Properties

Paulownia Fiber Properties

Species	Length (mm)	Width (µ)	L/W Ratio
P. kawakamii (Taiwan, mature tree)	1.208	20.7	58.4
P. tomentosa USA, 6 year old tree OD condition	0.970	32.7	29.7
Data Sources: TFRI 1979, & Tang 1980 1 µ = 0.001 mm

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Bending Properties

Bending Properties of Light Species (at 12% MC)

Species	Strength:: MOR (psi)	Stiffness: MOE x 10 (6 power) psi
Cottonwood	6820	1.102
N. W. Cedar	6530	0.798
Ponderosa Pine	9430	1.291
Redwood	7830	1.102
Balsa	2800	0.550
Paulownia
tomentosa	5740	0.758
kawakamii	7020	1.200
fortunei	5700	0.867
Data Sources:	Tang, Taiwan Forest Research Institute (TFRI), Sichuan Forest Science Research Institute (SFSRI), Others: FPL-USDA/FS

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Mechanical Properties

Mechanical Properties of Paulownia Wood

	Fortunei*	Kawakamii**
Bending Modulus of Rupture MOR (10 (6 power)psi)	5760	7020
Modulus of Elasticity: MOE (10(6 power))	0.867	1200
Compression psi (||) perpendicular	2800 300	3570 440
Shear (||)	800	1150
*SFSRI, PRC **TFRI, ROC

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Relative Working Properties

Relative Working Properties

Species	Machining	Resistance to splitting in Nailing	Resistance to splitting in Screwing	Nail& Screw Holding Ability	Adhesive Bonding
S. Pines	Good	Fair - Poor	Fair		Very Good
Sweetgum	Good	Fair	Fair	Fair	Excellent
Yellow Poplar	Very Good	Excellent	Good	Fair	Excellent
Cottonwood	Good	Excellent	Excellent	Fair	Excellent
Paulownia	Very Good	Excellent	Excellent	Fair	Excellent
Data Sources:	USDA, TRFI, & Tang

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Flake board

Paulownia Flakeboard Tang 1984

Density (pcf)	MC (%)	Strength MOR (psi)	Stiffness: MOE x 10 (6 power) psi
19.5	8.3	1260	0.19
28.9	8.0	3540	0.98
P.wood (18.5)	12	5740	0.76
Sweetgum flakeboard (45)	8.7	7700	1.26

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Out Look

Outlook of Pauolwnia's Utilization

1. Fast growing species for short pulp fiber supply
2. Flakeboard, particle board, OSB, or missed with high density species for ceiling, wall & roof panel
   1. reduce weight
   2. improve dimensional stability
   3. improve insulating performance
3. Solid wood: wall panels, sidings, picture frames
4. For shipping industries: pallets, crates, boxes & fiber-glass overlaid or metal sheets overlaid container
5. Low cost and high quality activated charcoal for water pollution use
6. Sale high grade logs to Japan
7. Core material for laminated boards/panels
8. Hair tonics: hair growth and restore hair color
9. Shampoo contains ingredients of Paulownia extractives
10. Medicine?