These boards are made of particles of wood embedded in synthetic resins, which are then pressed under heat. They are made by extrusion pressing or by pressing between parallel plates. In the extrusion pressing process, the particles are oriented in the direction perpendicular to the plane of the board, whereas in the other case the particles are oriented parallel to the plane of the board.
Particle board is heavier than solid wood. Further, it provides broad and stable panels of reasonable strength. They can be sawn just like regular wood. Particle boards are preferred for furniture works than for construction works.
Hard Board
Hard Board is made as per the Indian Standard (IS: 1658–1966). It is made out of wood pulp that is compressed to make sheets usually of 3-mm thickness. Its top surface is smooth and hard and the rear side is rough with patterns or cross lines.
As per the CPWD specification, they are classified as given in Table 10.2.
Table 10.2 CPWD specification of hard board
For door shutters only tempered hard board should be used.
Fibre Board
The technique adopted for the manufacture of fibre board is the combination of the process used is making particle board and hard board. In this case, wood chips are steamed to separate the fibres from each other. These fibres are blended with resin and wax. These are turned into sheets by pressing under controlled heat and pressure. The boards are available in thicknesses of 25–32 mm and as sheets of 2.44 m × 1.22 m size. They are suitable for flush doors, cabinets, etc.
Block Board
Block board is also known as batten-board or solid-core board. Batten board consists of a core solid block of thin wood sawn from natural wood. The central block is then glued between two or more outer veneers on either side (Fig. 10.11). Thicknesses are from about 19 mm upwards. They are suitable for door panels, partitions, table tops, etc.
Figure 10.11 Typical batten board and lamin board
Lamin board is similar to that of batten board with the difference being the core is made up of multiply veneers. The thickness of veneers is about 6 mm, and the total thickness of the board is about 50 mm.
Another type of block board called the metal-faced plywood is the one where the core is sandwiched between thin sheets of aluminium, steel, copper, etc. This is a rigid type of plywood (Fig. 10.12).
Figure 10.12 Metal-faced block board
Decorative Laminates
Laminates are the products made by bonding together two or more layers of materials. High-pressure decorative laminates are pasted on plywood sheets, which are used for large areas like cabinets, wide door shutters, tables, etc.
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