Particle board, also known as particleboard, chipboard, or low-density fiberboard, is an engineered wood product manufactured from wood chips and a synthetic resin or other suitable binder, which is pressed and extruded. Particle board is often confused with oriented strand board (OSB, also known as flakeboard, or waferboard), a different type of fiberboard that uses machined wood flakes and offers more strength.
Characteristics
Particle board is cheaper, denser and more uniform than conventional wood and plywood and is substituted for them when cost is more important than strength and appearance. Particleboard can be made more appealing by painting or the use of wood veneers on visible surfaces. Though it is denser than conventional wood, it is the lightest and weakest type of fiberboard, except for insulation board. Medium-density fibreboard and hardboard, also called high-density fiberboard, are stronger and denser than particleboard. Different grades of particleboard have different densities, with higher density connoting greater strength and greater resistance to failure of screw fasteners.
A significant disadvantage of particleboard is its susceptibility to expansion and discoloration from moisture absorption, particularly when it is not covered with paint or another sealer. Therefore, it is rarely used outdoors or in places where there are high levels of moisture, except in bathrooms, kitchens and laundries, where it is commonly used as an underlayment shielded beneath a moisture resistant continuous sheet of vinyl flooring.
In dry environments, veneered particleboard is preferred over veneered plywood because of its stability, lower cost, and convenience.
History and development
The history of particleboard is unclear. The nineteenth century saw many attempts to make use of sawmill by-products, including sawdust and wood chips, by manufacturing composite boards; conceptual references to processes of manufacturing wood composites similar to particleboard date from 1887. In 1935, Farley and Loetscher Manufacturing Co. became the first plant to manufacture particleboard. A particleboard industry developed over the course of the 1940s.
In 1932, Luftwaffe pilot and inventor Max Himmelheber patented a process for making particleboard without fully impregnating wood fibers with adhesive, distinguishing it from earlier wood composites. This particleboard could be produced with waste products such as planer shavings, off-cuts or sawdust, hammer-milled into chips and bound together with a phenolic resin. Hammer-milling involves smashing material into smaller and smaller pieces until they can pass through a screen. Most early particleboard manufacturers used similar processes, though often with slightly different resins.
It was found that better strength, appearance and resin economy could be achieved by using more uniform, manufactured chips. Producers began processing solid birch, beech, alder, pine and spruce into consistent chips and flakes; these finer layers were then placed on the outside of the board, with its core composed of coarser, cheaper chips. This type of board is known as three-layer particleboard.
More recently, graded-density particleboard has also evolved. It contains particles that gradually become smaller as they get closer to the surface.
Manufacturing
Particleboard or chipboard is manufactured by mixing particles or flakes of wood or jute-stick together with a resin and forming the mixture into a sheet. The raw material is fed into a disc chipper with between four and sixteen radially arranged blades. The chips from disk chippers are more uniform in shape and size than from other types of wood chippers. The particles are then dried, and any oversize or undersized particles are screened out.
Resin is then sprayed as a fine mist onto the particles. Several types of resins are used in the procces. Amino-formaldehyde based resins are the best performing based on cost and ease of use. Urea melamine resins offer water resistance with more melamine offering higher resistance. It is typically used in external applications, with the coloured resin darkening the panel. To further enhance the panel properties, resorcinol resins can be mixed with phenolic resins, but that is more often used with marine plywood applications.
Panel production involves other chemicals including wax, dyes, wetting agents and release agents, to aid processing or make the final product resistant to water, fire or insects.