Medium-density fibreboard (MDF) is an engineered wood product made 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. MDF is generally 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 denser than particle board.
In Australia and New Zealand, the main species of tree used for MDF is plantation-grown radiata pine; but a variety of other products have also been used, including other woods, waste paper and fibres.
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, are heated/steamed for 30–120 seconds to soften the wood, then joined with liquefied wax and fed into a defibrator. The defibrator maintains a high pressure and temperature while grinding the wood chips into a pulp.
From the defibrator, the pulp enters a blow line, where it is joined with resin, often urea-formaldehyde. The wax improves moisture resistance and the resin initially helps reduce clumping, but ultimately is the primary binding agent. The material dries quickly when it enters an expansion chamber and expands into a fine, fluffy and lightweight fibre that is stored until needed at the forming line.
The atmosphere created by machining or sanding MDF board contains a mixture of softwood dust and hardwood dust (if it is present). In addition, there will also be free formaldehyde, dust particles onto which formaldehyde is adsorbed and potentially, the resin binder itself and its derivatives. However, the levels of free formaldehyde in boards made within Australia at levels of formaldehyde class E1 are thought to be insignificant. This is because at these levels the resin is fully reacted (polymerised).
When MDF is cut, a large quantity of dust particles are released into the air. It is important that a respirator is worn and that the material is 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 together the fibres in MDF, and testing has consistently revealed that MDF products emit free formaldehyde and other volatile organic compounds that pose health risks at concentrations considered unsafe, for at least several months after manufacture. Urea-formaldehyde is always being slowly released from the edges and surface of MDF. When painting, it is a good idea to coat all sides of the finished piece in order to seal in the free formaldehyde. Wax and oil finishes may be used as finishes but they are less effective at sealing in the free formaldehyde
If dust is swallowed, give water to drink. Seek medical attention if any abdominal discomfort.
Irrigate eyes thoroughly with plenty of water for at least 15 minutes. If symptoms persist seek medical attention.
Wash thoroughly with mild soap and water. Remove clothing if contaminated with dust.
Leave the dusty area.
Provide eye-wash facilities.
Notes to doctor: