Medium-density fibreboard

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Medium-density fiberboard (MDF or MDFB) is an engineered wood product formed by breaking down softwood into wood fibers, often in a defibrator, combining it with wax and a resin binder, and forming panels by applying high temperature and pressure.^[1] It is a building material similar in application to plywood but made up of separated fibers, not wood veneers. It is denser than normal particle board.

Large-scale production of MDF began in the 1980s.^{[citation needed]} Its name derives from the distinction in densities of fiberboard. MDF typically has a density of 600-800 kg/m³, in contrast to particle board (160-450 kg/m³) and to high-density fiberboard (600-1450 kg/m³). Similar manufacturing processes are used in making all types of fiberboard.

MDF is also known as Customwood or Craftwood.^{[citation needed]}

MDF has been controversial in regard to its use of formaldehyde resins and the associated health risks. Thus, other resins are being considered and used instead of formaldehyde.^{[citation needed]}

MDF is often used in school projects because of its flexibility.

When MDF is cut, a large quantity of dust particles are released into the air. It is important that dust masks are worn and it is cut in a controlled and ventilated environment.

Contents 1 Manufacturing 2 Comparison to natural woods 3 Different kinds of MDF 4 Notes 5 References 6 External links

[edit] Manufacturing

In Australia the main species of tree used for MDF is plantation-grown radiata pine. However a variety of other products have also been used including other woods, waste paper, sea cucumbers and fibers.

The trees are debarked after being cut. 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 through 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. The chips are then washed and checked for defects.

The chips are then compacted using a screw feeder, 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.^{[citation needed]} Today many MDF boards are made from a variety of materials. These include other woods, scrap, recycled paper, bamboo, carbon fibers and polymers, steel, glass, forest thinning and sawmill off-cuts.

[edit] Comparison to natural woods

Benefits of MDF:

• Some varieties are less expensive than many natural woods
• Isotropic (no grain), so no tendency to split
• Consistent in strength and size
• Flexible. Can be used for curved walls or surfaces.
• Shapes well.

Drawbacks of MDF:

• Heavier than plywood or chipboard (the resins are heavy)
• Swells and breaks when waterlogged
• May warp or expand if not sealed
• Contains urea-formaldehyde which may cause eye and lung irritation when cutting and sanding
• Dulls blades more quickly than many woods
• Though it doesn't have a grain in the plane of the board, it does have one into the board. Screwing into the edge of a board will generally cause it to split in a fashion similar to delaminating.
• Subject to significant shrinkage in low humidity environments.

[edit] Different kinds of MDF

There are different kinds of MDF, which are sometimes labeled by colour:

• Moisture-resistant is typically green^{[citation needed]}
• Fire-retardant MDF is typically red^{[citation needed]}

Lighter densities of fiberboard are commonly marketed as ultralight or LDF boards.

[edit] Notes

[edit] References

• Lignocellulosic Composites
• Spence, William P. (2005). The Home Carpenters & Woodworker's Repair Manual. New York: Sterling. ISBN 1402710550

[edit] External links

• A video podcast from podcastschool.net
• The Production Process of Humewood MDF (Humewood is a product of Hume Fiberboards Sdn Bhd, a Malaysian fiberboard manufacturer)
• Wood Dust - dangers of exposure to wood dust, including MDF dust (from the Worker's Health Centre)
• Medium Density Fiberboard - from Investment New Zealand, a division of New Zealand's economic development agency.
• The Medium Density Fiberboard Home Page (although not updated or maintained, still a valuable reference)