Medium-density fibreboard (MDF) is an engineered wood product formed by breaking down hardwood or softwood residuals into wood fibres, often in a defibrator, combining it with wax and a resin binder, and forming panels by applying high temperature and pressure.[1] MDF is denser than plywood. It is made up of separated fibres, but can be used as a building material similar in application to plywood. It is stronger and much more dense than normal particle board.
The name derives from the distinction in densities of fibreboard. Large-scale production of MDF began in the 1980s.
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The density is normally in the range 750–850 kg/m3, but can be as low as 600 kg/m3 or as high as 1200 kg/m3.
MDF does not contain knots or rings, making it more uniform than natural woods during cutting and in service.[2] However, MDF is not entirely isotropic, since the fibres are pressed together primarily through the sheet. Like natural wood, MDF may split when woodscrews are installed without pilot holes, and MDF may be glued, doweled or laminated, but smooth-shank nails do not hold well. Typical fasteners are T-nuts and pan-head machine screws.[3]
When MDF is cut a large quantity of dust particles are released into the air. It is important that a respirator be worn and the material be cut in a controlled and ventilated environment. It is a good practice to seal the exposed edges to limit the emissions from the binders contained in this material.
Formaldehyde resins are commonly used to bind MDF together, and testing has consistently revealed that MDF products emit urea-formaldehyde and other volatile organic compounds that pose health risks at sufficient concentrations, for at least several months after manufacture.[4][5][6] Urea-formaldehyde is always being slowly released from the surface of MDF. When painting it is good idea to coat all sides of the finished piece in order to seal in the urea-formaldehyde. Wax and oil finishes may be used as finishes but they are less effective at sealing in the urea-formaldehyde.[2]
Whether these constant emissions of formaldehyde reach harmful levels in real-world environments is not yet fully determined. The primary concern is for the industries using formaldehyde. As far back as 1987 the U.S. EPA classified it as a "probable human carcinogen" and after more studies the WHO International Agency for Research on Cancer (IARC), in 1995, also classified it as a "probable human carcinogen". Further information and evaluation of all known data led the IARC to reclassify formaldehyde as a "known human carcinogen"[7] associated with nasal sinus cancer and nasopharyngeal cancer, and possibly with leukaemia in June 2004.[8]