Particleboard

Particle board, also known as particleboard and chipboard, is an engineered wood product manufactured from wood chips, sawmill shavings, or even sawdust, and a synthetic resin or other suitable binder, which is pressed and extruded. Oriented strand board, also known as flakeboard, waferboard, or chipboard, is similar but uses machined wood flakes offering more strength. All of these are composite materials that belong to the spectrum of fiberboard products.

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. However, particleboard can be made more attractive by painting or the use of wood veneers onto surfaces that will be visible. 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 major disadvantage of particleboard is that it is very prone to expansion and discoloration due to moisture, 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, with the exception of some bathrooms, kitchens and laundries, where it is commonly used as an underlayment - in its moisture resistant variant - beneath a continuous sheet of vinyl flooring.

The advantages of using particleboard over veneer core plywood is it is more stable, (unless it gets wet), much cheaper to buy, and somewhat more convenient to use.

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Wikipedia