Pulai


INTRODUCTION

The Standard Malaysian Name for the timber of Alstonia spp. (Apocynaceae). Vernacular names applied include mergalang (Sarawak), pelai (Sarawak), pulai (Peninsular Malaysia, Sabah and Sarawak) with various epithets and sayongan (Sabah). Major species include A. angustifolia, A. angustiloba, A. macrophylla, A. pneumatophora, A. scholaris and A. spatulata. The sapwood is not differentiated from the heartwood, which is cream to light yellow in colour.

Also known as Milky Pine and White cheesewood (Australia); Pulai (Brunei); Popel khe (Cambodia); Mbulei (Fiji); Chatian and Shaitan wood (India); Kayu susu, Pulai, Pulai hitam and Rita (Indonesia); Mai Tin Pet (Laos); Lettok, Sega and Shaitan (Myanmar); Chatian (Pakistan); Kajoe soesoeh (Papua New Guinea); Batino, Cayacayao, Dita and Silhigan (Philippines); Mbulei (Samoa Islands); Ruk kattana (Sri Lanka); Kra thungfa hai, Sattaban, Teen thian, Thia, Thungfa and Tin Pet (Thailand); and Mo cua (Vietnam).


DENSITY

The timber is a Light Hardwood with a density of 210-500 kg/m3 air dry.


NATURAL DURABILITY

Based on standard graveyard test of untreated specimens of dimension 50 mm x 50 mm x 600 mm, pulai is classified as not durable. All 21 pieces of the specimens tested were destroyed within 6 months (Foxworthy & Woolley, 1930). The timber is very susceptible to both fungal and insect attacks. 


PRESERVATIVE TREATMENT

The timber is easy to treat with preservatives.


TEXTURE

Texture is moderately fine to rather coarse, with straight to shallowly interlocked grain.


STRENGTH PROPERTIES

The timber falls into Strength Group D (Engku,1988b) or SG7 (MS 544:Part 2:2001). 


Strength Properties of Pulai (A. angustiloba)

Test Condition

Modulus of Elasticity (MPa)

Modulus of Rupture (MPa)

Compression parallel to grain (MPa)

Compression perpendicular to grain (MPa)

Shear Strength (MPa)

Green

6,200

33.0

16.0

-

6.1

Air dry

7,100

43.0

25.0

-

6.3


MACHINING PROPERTIES

It is easy to saw and work and the planed surface is smooth.


Machining Properties of Pulai (A. angustiloba)

Test condition

Sawing

Planing

Boring

Turning

Re-sawing

Cross- cutting

Ease of planing

Quality of finish

Ease of boring

Quality of finish

Ease of turning

Quality of finish

Green

easy

easy

easy

smooth

easy

smooth

-

-

Air dry

easy

easy

easy

smooth

easy

smooth

easy

smooth


NAILING PROPERTY

The nailing property is rated as excellent.


AIR DRYING

The timber seasons very rapidly with very minimal degrade like cupping, bowing, twisting and end-checking. The timber is prone to powder-post beetle and sapstain fungi attacks. 13 mm thick boards take approximately 1.5 months to air dry, while 38 mm thick boards take 2.5 months.


KILN-DRYING

Kiln Schedule J is recommended. The timber dries fast but is prone to stain, mould and insect attacks. 25 mm thick boards take approximately 5 days to kiln-dry from 50 to 10% moisture content.


Kiln Schedule J

Moisture Content (%)

Temperature (Dry Bulb)

Temperature (Wet Bulb)

Relative Humidity (%) (approx.)

F

C

F

C

Green

135

57.0

123

50.5

70

50

135

57.0

119

48.0

60

40

140

60.0

118

47.5

50

30

150

65.5

121

49.0

40

20

170

76.5

127

53.0

30


SHRINKAGE

Shrinkage is rather high, especially in the radial direction, where it averages 2.3% while tangential shrinkage averages 2.8%.


DEFECTS

The timber is marred by the presence of latex traces, which can measure up to 50 mm high. These latex traces are often found in clusters. The logs are susceptible to fungal and borer attacks and are highly perishable.


USES

The timber is suitable for plywood, pattern making, fret work, carving, picture frames, toys, match boxes and splints, packing boxes and crates, pencil and tooth picks. It has also been successfully used for making wooden clogs as well as disposable chopsticks. The root-wood from A. spatulata and A. pneumatophora, which is known as basong, is very light, only 50-80 kg/m3 air dry and has been used in the manufacture of pith-helmets.


REFERENCES

  1. Engku, Abdul Rahman Chik. 1988b. Basic And Grade Stresses For Some Malaysian Timbers. Malayan Forest Service Trade Leaflet No. 38. The Malaysian Timber Industry Board And Forest Research Institute Malaysia, Kuala Lumpur. 13 pp.
  2. Foxworthy, F. W. & Woolley, H.W. 1930 . Durability of Malaysian Timbers. Mal. For. Rec. No.8.
  3. Menon, P. K. B. 1986. Uses of Some Malaysian Timbers. Revised by Lim, S. C. Timber Trade Leaflet No. 31. The Malaysian Timber Industry Board and Forest Research Insitute Malaysia, Kuala Lumpur. 48 pp.
  4. MS 544: Part 2: 2001: Code Of Practice For Structural Use Of Timber. Permissible Stress Design of Solid Timber.
  5. Sim, H. C. 1982. Malaysian Timbers - Pulai. Malaysian Forest Service Trade Leaflet No. 64. The Malaysian Timber Industry Board and Forest Research Institute Malaysia, Kuala Lumpur. 7 pp.
  6. Wong, T. M. 1982. A Dictionary of Malaysian Timbers. Revised by Lim, S. C. & Chung, R. C. K. Malayan Forest Record No. 30. Forest Research Institute Malaysia Kuala Lumpur. 201 pp.