Rubberwood


INTRODUCTION

The Standard Malaysian Name for the timber of Hevea brasiliensis (Euphorbiaceae). Vernacular names applied include kayu getah (Peninsular Malaysia and Sabah), rubberwood (Peninsular Malaysia, Sabah and Sarawak) and para rubber (Peninsular Malaysia, Sabah and Sarawak). The sapwood is not differentiated from the heartwood, which is pale cream in colour, often with a pink tinge.

Also known as Rubberwood (Brunei); Kausuu (Cambodia); Rubberwood (India); Kayu getah, Kayu karet and Pokok getah para (Indonesia); Jaang (Laos); Kyetpaung (Myanmar); Katoh and Yang phara (Thailand); and Cao su (Vietnam).


DENSITY

It is a Light Hardwood with a density of 560-640 kg/m3 air dry. The timber is moderately hard and light to moderately heavy.


NATURAL DURABILITY

Rubberwood in its natural form is classified as non-durable. It is very susceptible to attack by fungi and insects. Biodeterioration starts almost immediately after the tree is felled. Blue stain fungi penetrate the ends of logs within a week of felling and the infection is found to be more severe during the raining season (Hong et al, 1980). Ambrosia beetles attack the logs and Browne (1961) has recorded 16 species of ambrosia beetles attacking rubber logs. Timber from rubber logs, before or after seasoning, is attacked by 7 powder-post beetles and one scolytid (Norhara, 1981). This attack is considered more severe as it renders the timber non useable.


PRESERVATIVE TREATMENT

Rubberwood is very amenable to preservatives. Normal treatment for boards involves mere dipping into tanks containing a preservative solution. Treatment, however, must be carried out almost immediately after the boards emerge from the saw. The resistance against biodeterioration could be enhanced by subsequent kiln-drying of the boards. Pressure impregnation with copper-chrome-arsenic compounds is seldom used to treat rubberwood because of the undesirable greenish yellow colour produced by these preservatives.


TEXTURE

Texture is moderately coarse but even, with straight to shallowly interlocked grain.


STRENGTH PROPERTIES

The timber falls into Strength Group C (Burgess, 1958) or SG5 (MS 544:Part 2:2001). 


Strength Properties of Rubberwood

 Test Condition

Modulus of Elasticity(MPa)

Bending(MPa)

Compression parallel to grain (MPa)

Compression perpendicular to grain (MPa)

Shear Strength (MPa)

Green

8,800

58.0

26.0

3.65

9.0

Air dry

9,240

66.0

32.0

4.70

11.0


MACHINING PROPERTIES

It is moderately easy to slightly difficult to resaw and easy to cross cut although latex may tend to clog up the saw teeth. The timber planes easily and the finish is smooth.


Machining Properties of Rubberwood

Test condition

Sawing

Planing

Boring

Turning

Resawing

Cross Cutting

Ease of planing

Quality of finish

Ease of boring

Quality of finish

Ease of turning

Quality of finish

Green

slightly difficult

easy

easy

smooth

easy

rough

-

-

Air dry

moderately easy

easy

easy

smooth

easy

rough

easy

rough


NAILING PROPERTY

The nailing property is rated as good.


AIR DRYING

The timber seasons fairly rapidly with bowing and springing as the main defects. 13 mm thick boards take 2.5 months to air dry while 38 mm thick boards take 3.5 months.


KILN-DRYING

Kiln Schedule D is recommended. 25 mm thick boards can be dried in approximately 6 days. Main defects are bowing, springing and end-splitting.


Kiln Schedule D

 Moisture Content (%)

Temperature (Dry Bulb)

Temperature (Wet Bulb)

Relative Humidity (%) (approx.)

F

C

F

C

Green

105

40.5

101

38.0

85

60

105

40.5

99

37.0

80

40

105

40.5

96

35.5

70

35

110

43.5

97

36.0

60

30

115

46.0

97

36.0

50

25

125

51.5

101

38.0

40

20

140

60.0

105

40.5

30

15

150

65.5

112

44.5

30


SHRINKAGE

Shrinkage is rather low. Radial shrinkage averages 0.8% while tangential shrinkage averages 1.9%.


DEFECTS

The logs are generally free from defects.


USES

The timber is used extensively for the manufacture of furniture. Other major uses include flooring, interior finishing, panelling, mouldings, plywood, charcoal manufacture, wooden pallets (expendable type), staircase (tread, baluster, steps and railing), ornamental items, door components, joinery, cabinet making, tool handles (non impact), ladies shoe soles, picture frames, toy, fruit bowl, chopping block and bentwood. It has also been used as core material for blockboard and has been chipped for pulp and paper manufacturing. Rubberwood is used as the main source of fibre material for the production of medium density fibreboard (MDF) in the country. A possible end-use for this timber is the manufacture of rayon.


REFERENCES

  1. Anonymous. 1982. Malaysian Timbers - Rubberwood. Malaysian Forest Service Trade Leaflet No. 58. The Malaysian Timber Industry Board and Forest Research Institute Malaysia, Kuala Lumpur. 7 pp.
  2. Browne, F. G. 1961. The Biology of Malayan Scolytidae and Platypodidae. Malayan Forest Record No. 22. Forest Department, Kuala Lumpur. 
  3. Burgess, H. J. 1958. Strength Grouping of Malaysian Timbers. Malayan Forest Service Trade Leaflet No.25. The Malaysian Timber Industry Board and Forest Research Institute Malaysia, Kuala Lumpur. 15 pp.
  4. Hong, L. T., Tam, M. K., K. Daljeet Singh & Arshad Omar. 1980. The Effectiveness of Preservatives in the Control of Sap-stain in Rubberwood (Hevea brasiliensis) Logs. Mal. For . Vol. 43, pp. 522-527.
  5. 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.
  6. MS 544:Part 2:2001. Code of Practice for the Structural Use of Timber: Permissible Stress Design of Solid Timber.
  7. Norhara bt Hussein. 1981. A Preliminary Assessment of the Relative Susceptibility of Rubberwood to Beetle Infestations. Mal. For. Vol. 44, pp. 482-487.
  8. 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.