Particleboard (‘Chipboard’)
Composition
Wood chips comprise the bulk of particleboard and are prepared in a mechanical chipper generally from coniferous softwoods principally spruce, though pine and fir and hardwoods, such as birch, are sometimes used. Particleboards may also incorporate a large proportion from recycled sources (up to 95% plus but generally around 40%). These chips are generally bound together with synthetic resin systems such as urea- formaldehyde (UF) or melamine urea-formaldehyde (MUF), though phenol- formaldehyde (PF) and polymeric methylene di-isocyanate (PMDI) are used by a few manufacturers.
The binding system employed depends on the end use intended and the grade of the product. The most common resin employed is urea-formaldehyde, but this is only suitable for use in dry conditions: the other three resin systems confer a measure of moisture resistance to the composite.
Typical constituents of a particleboard are of the order (by mass) of 83-88% wood chips, 6-8% formaldehyde based resin or 2-3% PMDI, 5-7% water, and 1-2% paraffin wax solids.
Manufacturing process
Raw material in the form of either virgin wood or reclaimed wood is chipped, dried and graded into different sizes. Resin is added to the chips and a mat is formed, this would normally have fine chips on the surfaces with coarse chips in the centre. This mat will then be hot pressed either with what is known as a multi-daylight or daylight press which are batch presses or a continuous press. The heat involved and the time in the hot press will cure the resins so that they bind the chips together forming a board with the desired properties (e.g. strength, density etc…). All of the manufacturing processes are usually controlled by complex computer systems that enable the operators to reproduce the same quality with consistency and accuracy on a 24 hour basis. Once the boards are conditioned and cut to size, they will be tested to prove compliance with the relevant specification and claims.
Applications
The special properties of particleboard have several advantages in a wide range of construction and furniture applications. Thus, its good mechanical performance which is the same along and across the panel, and its availability in large sizes renders it appropriate for use as floor decking, either on timber joists, or as a floating floor system. Different grades of the product are available for different environmental conditions and different levels of loading, ranging from domestic to industrial usage including both platform and raised access floors. The higher grades also find widespread use in industrial storage systems. Guidance on the use of load-bearing grades of particleboard in floors, walls and roofs is given in DD CEN/TS 12872.
Large quantities of particleboard are also used in the manufacture of kitchen units and worktops, and in dining-room and bedroom units; these generally have a veneered or laminated finish.
Particleboard is commonly used in furniture and worktops (Grades P1, P2, P3) and structural flooring (Grades P4, P5, P6 & P7).
