Medium-density fibreboard properties

Medium-density fiberboard (MDF) is an engineered wood product made by breaking down hardwood or softwood residues into wood fibers, usually in a fiber mill, mixing them with wax and resin binders, which are then The pressure forms it into panels.MDF is generally denser than plywood.It consists of separated fibers, but can be used as a building material similar to plywood.It is stronger and denser than particle board.The name comes from the difference in the density of the fiberboard. Mass production of MDF began in the 1980s.

Physical properties

Over time, the term "MDF" has become a generic name for any dry-laid fibreboard.MDF is usually composed of 82% wood fiber, 9% urea-formaldehyde resin glue, 8% water and 1% paraffin.Densities typically range from 500 to 1,000 kg/m3 (31 to 62 lb/ft3).The density range and classification as light, standard or high density board is a misnomer and confusing.When evaluating the density of a board, it is important that its density is related to the density of the fibers used to make the board.Thick MDF boards with a density of 700-720 kg/m3 (44-45 lb/ft3) would be considered high density in the case of softwood fiberboards, while boards of the same density made of hardwood fibers would not .The development of different types of MDF is driven by different needs for specific applications.

Types

The different kinds of MDF (sometimes color-coded) are:

• Ultralight Medium Density Fiberboard (ULDF)

• Moisture barriers are usually green

• Flame retardant MDF is usually red or blue

Although all types of fiberboard use a similar manufacturing process, MDF has a typical density of 600–800 kg/m3 or 0.022–0.029 lb/in3, compared to particleboard (500–800 kg/m3) and HDF (600–1,450 kg/m3).

Manufacturing

In Australia and New Zealand, the main species used for MDF is plantation-grown radiata pine, but a variety of other products are also used, including other wood, waste paper and fibers.Where moisture resistance is required, a percentage of eucalyptus species can be used to take advantage of the oil content characteristic of this type of tree.

Chip production

Trees are stripped after being felled.The bark can be sold for landscaping or used as biomass fuel for on-site furnaces.The debarked logs are sent to the MDF mill where they are chipped.A typical disc chipper contains 4 to 16 blades. Any chips that are too large may be re-chipped; undersized chips can be used as fuel.The chip is then cleaned and inspected for defects. Chips can be stored in large quantities as manufacturing reserves.

Fiber production

Compared to other fiberboards such as Masonite, MDF is characterized by the next part of the process and how the fibers are handled as individual but complete fibers and containers, manufactured by a dry process.The wood chips are then crushed into small pieces using a screw feeder, heated for 30-120 seconds to soften the lignin in the wood, and then fed into a shredder.A typical defibrillator consists of two counter-rotating disks with grooves on their surfaces.Chips are fed into the center and sent out between the discs by centrifugal force.The reduction in groove size gradually separates the fibers with the help of softened lignin between the fibers.The pulp goes from the refiner to the blowing line, which is a unique part of the MDF process.This is an expanded circular duct with an initial diameter of 40 mm which increases to 1500 mm.Injected in the first stage, the wax coats the fibers and is evenly distributed by the turbulent movement of the fibers.Urea-formaldehyde resin is then injected as the main binder.The wax improves moisture resistance and the resin initially helps reduce clumping.The material dries quickly in the final heated expansion chamber of the nozzle and expands into fine, fluffy and lightweight fibers.Even at high pressure (100 bar, 10 MPa, 1,500 psi), glue and other components (hardeners, dyes, urea, etc.) Connect to heating chamber.The fiber can be used immediately or stored.