Civil Engineering Reference
In-Depth Information
3.
It is heated and ground between two coarse steel rollers.
4.
The mass of fibres is mixed with water to a thin pulp and made into sheets on a mov-
ing band.
5.
The sheets are put through a press heated to 200°C at a certain pressure, depend-
ing upon the degree of hardness required. The natural glue liquor is extruded and
binds the board.
6.
The sheets are cut to standard sizes.
7.
The boards are hardened by warm air, at about 165°C, for two to seven hours.
8.
They are then conditioned in warm humid air to give them a moisture content of 5-8
per cent.
Production of chipboard
Chipboard can be made from many types of timber. There is no need for the timber to have
its own active glue, as the process includes gluing. Urea formaldehyde glue is used for both
economic and technical reasons, but melamine, phenol formaldehyde/resorcinol and
Figure 15.25: Production of hard and semi-hard wood fibreboards.
