Medium-density fibreboard
From Wikipedia, the free encyclopedia
Medium-density fibreboard (MDF or MDFB) is an engineered wood product formed by breaking down softwood into wood fibres, often in a defibrator, combining it with wax and resin, and forming panels by applying high temperature and pressure. It is a building material similar in application to plywood but made up of sawdust. It is denser than normal particleboard.
Large-scale production of MDF began in the 1980s. Its name derives from the distinction in densities of fibreboard. MDF typically has a density of 600-800 kg/m³. Particle board is a low-density fibreboard and has a density of 160-450 kg/m³, while hardboard, also called high-density fibreboard, has a density of 500-1,450 kg/m³. Similar manufacturing processes are used in making all types of fibreboard.
One contentious issue is the use of formaldehyde resins and the associated health risks. Thus, other resins are being introduced.
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[edit] Manufacturing
MDF is a type of wood formed by broken down and powdered softwood, which is mixed with wax and resin. This is then formed by applying high temperatures to the MDF products to create the finish.
In Australia the main species for MDF is plantation-grown radiata pine. However a variety of other products have also been used including other woods, waste paper and fibres.
After trees have been cut, they will go though a debarking process. The bark can be sold for use in landscaping, or burned in on-site furnaces. The debarked logs are sent to the MDF plant where they go though the chipping process. A typical disk chipper contains 4-16 blades. Any resulting chips that are too large may be re-chipped; undersized chips may be used as fuel. All chips are then washed and checked for defects.
The chips are then compacted using a screwfeeder, and will be heated for 30-120 seconds to soften the wood; they are then fed into a defibrator which maintains high pressure and temperature. The pulp that exits from the defibrator is fine, fluffy, and light in weight and in colour.
From the defibrator the pulp enters a blow line where it is joined with wax (to improve moisture resistance) and resin (to stop the pulp from forming bundles). The material expands in size and is then heated by heating coils. When it comes out it may be stored in bins for an indefinite length of time.
After this drying period the board goes through a "Pendistor" process which creates 230-610 mm thick boards. Then it is cut and continues to the press. Here it is pressed for a few minutes, to make a stronger and denser board.
After pressing MDF is cooled in a star dryer, trimmed and sanded. In certain applications boards are also laminated for extra strength.
The Environmental Impact of MDF has greatly improved over the years. Today many MDF boards are made from a variety of materials. These include other woods, scrap, recycled paper, bamboo, carbon fibres and polymers, steel, glass, forest thinning and sawmill off-cuts.
[edit] Pros and Cons
Comparing MDF to Natural Woods:
Pros to MDF:
- Less expensive
- Generally easier to work with
- Is consistent in its strength, and is consistent in its size (width, length)
Cons to MDF:
- Heavier
- Must be painted; transparent finishes are not useful
- Limited water resistance
- Over time, will warp or expand if not sealed
[edit] In Media
Famously, MDF was used often on the British TV's Changing Rooms, leading to "YMDF", a YMCA parody.
[edit] See also
- Engineered wood
- Fiberboard
- Glued laminated timber
- Hardboard
- Masonite
- Oriented strand board
- Particle board
- Plywood
- Pressed wood
[edit] References
[edit] External links
- Children's furniture, on the safety issues of MDF
- Medium Density Fibreboardde:Mitteldichte Holzfaserplatte
fr:MDF it:Medium-density fibreboard he:MDF nl:Medium-Density Fiberboard pt:Medium Density Fiberboard ru:МДФ fi:MDF-levy
