ChipBoard/Wood Veneered Chipboard/Melamine
Particleboard is cheaper, denser and more uniform than conventional wood and plywood and is substituted for them when appearance and strength are less important than cost. However, particleboard can be made more attractive by painting or the use of wood veneers that are glued 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 fiberboard and hardboard, also called high-density fiberboard, are stronger and denser than particleboard.
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 places that have high levels of moisture, with the exception of some bathrooms, kitchens and laundries, where it is commonly used as an underlayment beneath a continuous sheet of vinyl floor covering. In such an installation the edges must be properly covered upward against the wall and joints and non-covered edges must be properly sealed against moisture penetration. A higher quality material not subject to expansion is underlayment-grade plywood, which is constructed without interior voids in its layers to better resist the high local pressure from objects such as stiletto heels.
Manufacturing:
Particleboard is a form of fiberboard. Other fiberboards include medium density fiberboard (MDF) and hardboard. Particleboard is the least dense of these and, therefore, the least strong. Other forms of wood sheet products include plywood, which is constructed by gluing together thin sheets of wood (veneer).
Particleboard is manufactured by mixing wood particles or flakes together with a resin and forming the mix into a sheet. The raw material to be used for the particles is fed into a disc chipper with between four and sixteen racially arranged blades. The particles are first dried, after which any oversized or undersized particles are screened out.
Resin, in liquid form, is then sprayed through nozzles onto the particles. There are several types of resins that are commonly used. Urea formaldehyde resin is the cheapest and easiest to use. It is used for most non-water resistant boards. Melamine formaldehyde resin is significantly more expensive, as it is moisture resistant. Phenol formaldehyde is also fairly expensive. It is dark colored and highly durable. These resins are sometimes mixed with other additives before being applied to the particles, in order to make the final product waterproof, fireproof, insect proof, or to give it some other quality.
Once the resin has been mixed with the particles, the liquid mixture is made into a sheet. A weighing device notes the weight of flakes, and they are distributed into position by rotating rakes. In graded density particleboard, the flakes are spread by an air jet which throws finer particles further than coarse ones. Two such jets, reversed, allow the particles to build up from fine to coarse and back to fine.
The sheets formed are then cold-compressed to reduce their thickness and make them easier to transport. Later, they are compressed again, under pressures between two and three megapascals and temperatures between 140 °C and 220 °C. This process sets and hardens the glue. All aspects of this entire process must be carefully controlled to ensure the correct size, density and consistency of the board.
The boards are then cooled, trimmed and sanded. They can then be sold untreated, or covered in a wood veneer.