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Rubberwood: Sustainable and Versatile Wood

 

Introduction
Rubberwood, known locally as Kayu Getah, is derived from Hevea brasiliensis. It is a pale cream wood with a pink tinge and is widely used across Malaysia and Southeast Asia. Despite being non-durable in its natural state, rubberwood is a sustainable and cost-effective material for various applications, especially in furniture manufacturing.

Key Characteristics

• Density: A Light Hardwood with a density ranging from 560-640 kg/m³ (air dry), making it moderately hard and suitable for light to medium construction uses.

• Durability: Naturally non-durable, rubberwood is highly susceptible to fungi and insect attacks. However, it can be easily treated with preservatives to extend its lifespan.

• Strength: Classified under Strength Group C or SG5, it provides adequate strength for furniture and interior uses.

• Machining: Rubberwood is easy to plane and provides a smooth finish, though resawing can be slightly challenging due to latex residue.

Applications

Rubberwood is highly versatile and is widely used in:

• Furniture Manufacturing: Ideal for producing a variety of furniture pieces due to its workability and affordability.

• Flooring & Interior Finishing: Suitable for flooring, mouldings, panelling, and other interior applications.

• Plywood & MDF: A key source for Medium Density Fibreboard (MDF) production and plywood.

• Ornamental Items & Tool Handles: Used for crafting decorative items, picture frames, and non-impact tool handles.

Handling and Drying

• Air Drying: Rubberwood seasons quickly, with minimal defects such as bowing and springing.

• Kiln-Drying: The recommended Kiln Schedule D ensures efficient drying with reduced warping and splitting. It takes approximately 6 days for 25 mm thick boards to kiln-dry.

Conclusion
Rubberwood is an excellent choice for sustainable wood solutions. Its adaptability, ease of treatment, and wide range of uses make it a valuable resource in furniture, interior applications, and more.

 

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.