Particle board

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Particleboard with veneer

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. Particleboard is a composite material.[1]

Characteristics[edit]

The cross section of a particle board

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 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. It does, however, have some advantages when it comes to constructing the cabinet box and shelves. For example, it is well suited for attaching cabinet door hinges to the sides of frameless cabinets. Plywood has the potential to feather off in sheaves when extreme weight is placed on the hinges. In contrast, particle board holds the screws in place under similar weight.[2]

History and development[edit]

Modern plywood, as an alternative to natural wood, was re-invented in the 19th century ( given that it was well known by the ancient Egyptians, severeal thousand years before ) but by the end of the 1940s a shortage of lumber made it difficult to manufacture plywood affordably. Particleboard was intended to be a replacement. Its inventor was Max Himmelheber of Germany.[citation needed] The first commercial piece was produced during World War II at a factory in Bremen, Germany.[clarification needed] For its production, waste material was used - such as planer shavings, offcuts 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 other 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[edit]

Particleboard or chipboard is manufactured by mixing wood particles or flakes together with a resin and forming the mixture into a sheet. The raw material to be used for the particles 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 chipper). The particles are then dried, after which any oversized or undersized particles are screened out.

Resin is then sprayed through nozzles onto the particles. There are several types of resins that are commonly used. Amino-formaldehyde based resins are the best performing when considering cost and ease of use. Urea Melamine resins are used to offer water resistance with increased melamine offering enhanced resistance. is typically used where the panel is used in external applications due to the increased water resistance offered by phenolic resins and also the colour of the resin resulting in a darker panel. Melamine Urea phenolic formaldehyde resins exist as a compromise. To enhance the panel properties even further the use of resorcinol resins typically mixed with phenolic resins are used, but this is usually used with plywood for marine applications and a rare occasion in panel production.

Panel production involves various other chemicals—including wax, dyes, wetting agents, release agents—to make the final product water resistant, 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 that 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 2 and 3 megapascals (290 and 440 psi) and temperatures between 140 and 220 °C (284 and 428 °F). 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 as raw board or surface improved through the addition of a wood veneer or laminate surface.

Furniture design[edit]

Particle board has had an enormous influence on furniture design. In the early 1950s, particle board kitchens started to come into use in furniture construction but, in many cases, it remained more expensive than solid wood. A particle board kitchen was only available to the very wealthy.[citation needed] Once the technology was more developed, particle board became cheaper.

Large companies such as IKEA and Fantastic Furniture base their strategies around providing furniture at a low price; for example, IKEA’s stated mission is to “create well-designed home furniture at prices so low that as many people as possible will be able to afford it”.[citation needed] They do this by using the least expensive materials possible, as do most other major furniture providers. In almost all cases, this means particle board or MDF or similar. However, manufacturers, in order to maintain a reputation for quality at low cost, may use higher grades of particle board, e.g., higher density particle board, thicker particle board, or particle board using higher-quality resins. One may note the amount of sag in a shelf of a given width in order to differentiate the difference.

In general the much lower cost of sheet goods (particle board, medium density fiberboard, and other engineered wood products) has helped to displace solid wood from many cabinetry applications.

Safety[edit]

Safety concerns are two part, one being fine dust released when particleboard is machined (e.g., sawing or routing), and occupational exposure limits exist in many countries recognizing the hazard of wood dusts.[3] The other concern is with the release of formaldehyde. In 1984 concerns about the initial indoor level of formaldehyde led the United States Department of Housing and Urban Development to set standards for construction of manufactured homes. This however was not solely because of the large amounts of pressed wood products that manufactured homes contain but also because of other building materials such as Urea-formaldehyde foam insulation.[4] Formaldehyde is classified by the WHO as a known human carcinogen.[5]

Comparison of solid wood to particleboard[edit]

Particleboard’s selling points compared to solid timber are its low cost, its availability in large flat sheets, and its ability to be decorated with all kinds of overlays.

Solid wood has structural advantages over particleboard. It is stronger, particularly in tension (as required for horizontal spans), allowing it to support greater weights. Unless adequately braced or built with thick material, particleboard shelves will visibly sag over time (or snap near the fasteners).

Screw fasteners should be installed with caution, taking into account the specific mechanical properties of particleboard. Otherwise, these will not provide the correct holding power, over time. There is a tendency, for improperly installed screws to strip the material into which they are inserted. For example, over-torquing a screw will, over time, lead to premature failure of the material. The tolerance to over-torquing is less for particleboard as compared to ply- or solid wood. Portions of the particleboard may "blow out" when subjected to excessive tension stress. In part, this arises from the lack of elasticity in particleboard resins as compared to the long strands and compressible voids contained in solid wood, a feature that, while preserved in the manufacture of plywood, is compromised in particleboard.

The strength of particleboard, in the context of application and cost, can offer advantages over solid wood when the cost is virtually the sole consideration. In cabinet carcass construction, relatively thick particleboard is used (typically ¾"), particularly in the sidewalls to support compressive loads of countertops and appliances, where its lower cost and adequate strength make it a frequent choice.

Solid wood is much more durable than particleboard: for example, damage to solid wood can be repaired by removing and replacing damaged material, then refinishing using known wood treatments, that can be matched. Since particleboard is typically faced with by a non-wood veneer, it is practically impossible to match the original finish. In addition, damage to particleboard is typified by structural failure and exposure of sizable jagged faults. Damage to particleboard is therefore normally impossible to repair effectively, that is without too obvious traces, usually requiring replacement of the whole damaged part(s).

The reduced durability of particleboard furniture is a consequence of reduced strength in tension. This drawback contributes to damage when furniture is carelessly handled, or dragged. Whenever possible therefore, the furniture should be disassembled into smaller components, easily handled by one person, to eliminate the possibility of damage in transit.

Furniture makers often cover particleboard with real or imitation veneers, in an effort to simulate the look of solid wood.

See also[edit]

References[edit]

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