Timber based products

TIMBER BASED PRODUCTS

The demand for good varieties of timber like teak, deodar, sal, sissoo, etc., is so high that Indian forests are unable to meet it. Timber-based products make lesser known species to meet the demand equally well. The common industrial-based timber products are briefed below:

 

1.  VENEERS

Veneers are thin sheets of superior quality woods of 0.4-6 mm thickness. Teak, rosewood and sissoo yield good veneers. These good quality woods are cut into logs of 1.5-2.5 m length and steamed. They are then cut into thin sheets by rotary saw or by slicing manually.

 

2. PLYWOOD

Plywood is made by gluing thin layers of wood or veneers. The number of veneers is always odd. The directions of veneers in successive layers are kept at right angles to each other in order to achieve good strength in all directions. The outside layers are called faces, while the central portion is called the core and others are called cross-bands. In order to have a good appearance and to maintain economy, one face of the veneer is of very good quality while the bulk is of ordinary quality.

Plywoods are of the following types:

• Ordinary grade, used as a packing material.

• Exterior grade, made of good quality wood and bonded with waterproof glue.

• Marine grade, in which the core and exterior are of superior quality.

The thicknesses of plywood boards are as given below:

(i) 3 ply – 3,4,5,6 mm

(ii) 5 ply – 5,6,8,9 mm

 (iii) 7 ply - 9,12,15,16 mm

(iv) 9 ply – 12,15,16,19 mm

(v) 11 ply - 19,22,25 mm

(vi) More than 11 ply - as per order

 

3.  PARTICLE BOARD

Particle board is made from chips of wood, rice husk or bagasse obtained after crushing sugarcane. Using automatic driers, the moisture content of these wood wastes is reduced to 15% and they are sprayed with gluing material like formaldehyde. This adhesive-coated material is spread in three layers along with a resin mix.

The middle layer usually consists of coarser particles. The outer layer consists of finer particles and higher resin content. The mat is then pressed in the presence of heat. Hydraulic presses are used for this process. Particle boards of various sizes are manufactured where the thickness is the range of 6 to 40 mm.

 

4.  FIBRE BOARDS

For making fibre boards, wooden chips and vegetable fibres are placed in boiling water till wood fibres separate. These fibres are blended with resin and steam under pressure. Steam pressure is raised for a few seconds and then released. These wood fibres are allowed to flow out and are cleaned. The fibres are then spread in the form of sheets. They are machine pressed under controlled heat and pressure.

 

5.  HARDBOARD

Hardboard is made from wood and wood waste, which is pulped and mixed with water-repellent agents like paraffin wax and resins like phenol formaldehyde. The fibres so formed are wet felted or dry felted. In wet felting, a mat is formed from a low consistency felt and initially cold pressed, and then hot pressed. In case of dry felting, relatively dry fibres are pressed by air or mechanical means. Hardboards are of three types, viz., medium, standard and tempered.

 

6. BLOCK BOARD

Block boards are known as batten boards and also as solid core plywood. The core consists of strips of wood of width 25-80 mm glued to form a slab. Veneers are glued on either side, and these may be in single or multiple layers. The thickness of a veneer is 0.5-1.5 mm. The veneers shall be of ornamental quality, either on one or both sides. The total thickness of these boards is 18 mm and above. Grade I quality block boards are used for building the bodies of buses and railway coaches. Grade II quality boards are used for making partitions and furniture.

 

7.  GLULAM

de Glued laminated timber is called glulam. It is a type of structural timber product made up of several layers of timber bonded together with adhesive. It is made of solid wood without the use of veneers. The timber sections are joined with the help of glue. It is used for making long-span beams and trusses for long-span column free roofs. The above timber-based products offer the following advantages:

1. Many secondary species of timber and all kinds of wood waste can be utilized.

2. The products are adequately strong in all directions and their shrinkage is less due to cross-grained production.

3. They can be made functionally superior by giving plastic coating.

4. They have better insulation properties.

5. Their aesthetic appeal can be enhanced.