Lab manual

ADHERENCE

Objective : to identify and classify the adherence

Procedure :

1. Find any six species of wood in light, medium and heavy hardwood category.2. Identify the species of wood and list the characteristics of the wood such as color,

shape of pore, density range etc.3. By using the same adherence, classify the category of the adherence, (heavy, medium

or light weight density) and (specific gravity group of adherence –SG1, SG2, SG3, SG4, SG5, SG6) etc.

4. Discuss why difference species will affect the bonding strength etc. when using adhesive.

1

Six species of wood in light, medium and heavy hardwood category.

Heavy hardwood

1. Merbau (Intsia palembanica)2. Balau merah (Shorea collina)

Medium hardwood

3. Kulim (Scorodocarpus borneensis)4. Mata ulat (Kokoona coriacea)

Light hardwood

5. Jelutong ( Dyera costulata)6. Pulai ( Alstonia angustiloba)

2

Characteristics of the wood such as color, shape of pore, density range etc.

HEAVY HARDWOOD

1. Merbau (Intsia palembanica)

Color/appearance :- Has an orangish-brown color when freshly cut, which ages to a darker reddish-

brown.- Has small yellow deposit (these yellow deposits are soluble and can cause

staining)

Grain/texture :- Grain is straight to interlocked

- Texture is coarse, with a moderate natural luster

End grain/shape of pore- Diffuse-porous ; large to very large pores, very few

- Aliform shape of pore (winged or lozenge) and confluent

Density range- 515-1040 kg/m3 (32-65 lb/ka3 )

3

2. Balau merah (Shorea collina)

Color/appearance :- Heartwood is red-brown or purple-brown in color when freshly cut, weathering to

a dark brown

Grain/texture :- Grain is straight to interlocked often giving rise to stripe figure.

- Surface is rather dull without luster.

- Texture is rather coarse but even.

End grain/shape of pore- Diffuse-porous ; medium to large pores

- Have many tyloses

- Aliform shape of pore (winged or lozenge) and confluent

Density range- 800-850 kg/m3 (50-55 lb/ka3 )

4

MEDIUM HARDWOOD

3. Kulim (Scorodocarpus borneensis)

Color/appearance :- Heartwood reddish-brown to dark purplish-brown towards the centre.

Grain/texture :- Hard to cut if against the grain.

- Texture medium fine and evenly.

End grain/shape of pore- Indistinct, vessels moderately small to medium-sized, solitary but more often in

radial multiples of 2-3(-6).- tyloses mostly well-developed, occasionally with white deposits; parenchyma

moderately abundant.- apotracheal diffuse and diffuse-in-aggregates; rays very fine to moderately fine,

visible with a hand lens; ripple marks absent.

Density range- 835 kg/m3 (52 lb/ka3 )

5

4. Mata ulat (Kokoona coriacea)

Color/appearance :- Yellow brown with pinkish spot

Grain/texture :- Hard to cut if against the grain.

- Texture very fine and evenly.

End grain/shape of pore- Single pores, medium and more.

- Concentric layer of parenchyma.

Density range- 880-1040 kg/m3 (55-65 lb/ka3 )

6

LIGHT HARDWOOD

5. Jelutong ( Dyera costulata)

Color/appearance :- White color for fresh cut and turns pale yellow.

Grain/texture :- Straight grain.

- Slightly really smooth cut against the grain.

- Texture medium fine and evenly.

End grain/shape of pore- Single pores, medium size of pore with no tyloses and deposit.

Density range- 415-495 kg/m3 (26-31 lb/ka3 )

7

6. Pulai (Alstonia angustiloba)

Color/appearance :- White cream color of wood.

- Zig zag appearance along tangent surface.

Grain/texture :- Smooth solitary grain.

- Slightly really smooth cut against the grain.

- Texture medium fine to medium coarse.

End grain/shape of pore- Single pores, medium size of pore and normally have 2-9 vessels in one series.

- no tyloses and deposit

Density range- 464 kg/m3 (29 lb/ka3 )

8

PHYSICAL PROPERTIES OF WOOD THAT AFFECT ADHESIVE BONDING.

Density or Specific Gravity (SG)

Density or specific gravity is one of the most important physical properties of wood. Density is the mass or weight of wood divided by the volume of the specimen at the given moisture content. Thus unit for density are kg/m3 or lb/ka3 . In hardwood, density is depending not only on fibre wall thickness but also on amount of void space occupied by vessel and parenchyma.

The glue-bond quality required for the species listed and for other species falling within the density range given the solid wood substances of all species has about same specific gravity, but in high-density species less of the volume in capillary structure of dry wood is occupied by air. As moisture is added to the wood, the air space decreases. When wood of different species is examined with the naked eye, the ratio of wood substances to air species not readily seen.

Wood pores and vessel

Different wood species may influence the bondlines of adhesives. The porosity and the pore size distribution were analysed as a function of the respective position. The pores will completely bind together if the neighbouring pores during adhesion have bigger spaces or large diameter sizes of pores or vessel. The penetration of the adhesive to the adherence which have larger diameter of pores may conclude the strength of wood bonding. It is also can be explained in easy words by; before the adhesive turn to solid, it is in liquid form and travel along the pores and adhesive may penetrate easily in form of size of pores.

Less, medium or more pores with small sizes may affect the bonding strength between the adhesive with the adherence. Small sizes of pore which evenly appear in adherence may conclude the good result in bonding strength in adhesion. It can be explain when the adhesive penetrate in the pores or vessel evenly its will grip the whole surface of adherence during the process.

Grain and texture

The term of grain and texture are commonly used rather loosely in connection with wood. Grain is often used in reference to the relative sizes and distributions of cells, as is fine grain and coarse grain; this use of grain is roughly synonymous with texture. Grain is also used to indicate the orientation of the cells of axial system (fibre direction), as in “along the grain”, straight grain, spiral grain and interlocked grain.

9

The texture of wood by different direction may influence the bonding strength in adherence. Two term of direction; along the grain and against the grain. Many light hardwoods may be easily to cut by against the grain compared to the heavy or medium hardwood. The explanation maybe same as the sizes of pores but the shape of grain may conclude the dissimilar of bonding result.

10

DISCUSSION

The difference species will affect the bonding strength when using adhesive because for each type of wood has a different characteristic based on their density, texture of surface, porous and others.

For the heavy hardwood species, merbau has air dry density from 515-1040 kg/m3

(32-65 lb/ka3) meanwhile the red balau has 800-850 kg/m3 (50-55 lb/ka3 ). This is classifying as high density woods. The medium hardwood species, Kulim (Scorodocarpus borneensis) has range density from 835 kg/m3 (52 lb/ka3 ) meanwhile Mata ulat (Kokoona coriacea) has 880-1040 kg/m3 (55-65 lb/ka3 ). This is classify as moderate density woods and for the light hardwood species, Jelutong ( Dyera costulata) has range density from 415-495 kg/m3 (26-31 lb/ka3 ) and Pulai ( Alstonia angustiloba) has range from 464 kg/m3 (29 lb/ka3 ). This is classifying as low density woods.

The high density woods have thick walls and small lumen volumes, whereas low density woods have thin walls with large lumen volumes. The strength of wood is directly related to its density because thick-walled cells are capable of withstanding much greater stress than are thin-walled cells. High density woods are difficult to bond for several reasons. Because of thicker cell walls and less lumen volume, adhesives do not penetrate easily, so important mechanical interlocking of adhesives is limited to one or two cells deep. Much greater pressure is required to compress stronger, stiffer, high density wood to bring contact between wood surface and adhesive.

Texture and grain may influence the bonding strength of the adhesion. Based on the observation of the different species, the level of coarseness of wood may influence the bonding strength. On the other words, if the wood is very coarse surface it may help in the bonding strength in adhesion. The adhesive may not easily shear during gel time because of the coarseness of the wood would grip the entire surface which spread by adhesive. It is different to the smooth surface wood which is tending to shear or sliding easily during gel time.

Size of pores and vessel and number of pores appear in wood may also affect the bonding strength of the adhesion. Inference for the size of pores; the larger pores appear in wood more high strength of adhesive bind the adherence together. The liquid form of adhesive are allow travel along the pores and adhesive may penetrate easily in form of size of pores. Besides, the number pores appear in wood also affect the entire bonding strength of adhesion. Many pores appear could result high strength of wood bind process.

11

References

Lopez, D. T. 1981. Malaysian Timbers – Red Balau. Malaysian Forest Service Trade Leaflet No. 45. The Malaysian Timber Industry Board and Forest Research Institute Malaysia, Kuala Lumpur. 7 pp

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 Institute Malaysia, Kuala Lumpur. 48 pp.

Menon, P. K. B. 1997. Struktur Dan Pengecaman Kayu Kayan Malaysia. Forest Research Institute Malaysia, Kuala Lumpur. 53 pp.

Jabatan perhutanan. 1984. Peraturan Pemeringkatn Kayu Keras Gergaji Malaysia... Lembaga Perindustrian Kayu Malaysia, Kementerian Perusahaan Utama. 8 pp.

FRIM. Forest Product Technology Division. Common Commercial Timbers of Peninsular Malaysia.

12