MDF belongs to the hardboard family of products which are made from wood fibers glued under heat and pressure. Medium Density Fiberboard typically has densities between 33 and 50 pounds per cubic feet while High Density Fiberboard (HDF) ranges between 50 and 80 pounds per cubic feet.

Medium Density Fibreboard (MDF) is an engineered wood-based sheet material made by bonding together wood fibres with a synthetic resin adhesive.  MDF is extremely versatile and can be machined and finished to a high standard.  As a result, MDF has replaced solid timber as a low-cost alternative in a wide range of applications across industry. 

The majority of MDF is mainly composed of softwood, although some brands may contain a higher percentage of temperate hardwood if this is locally available to the manufacturer.  High levels of hardwood can be found in MDF board from outside the UK and Ireland.

The most common binder for boards intended for dry environments is urea-formaldehyde.  Other binders may be used depending on the grade of board and its intended end-use.  For example, melamine urea-formaldehyde, phenolic resins and polymeric diphenylmethane diisocyanate (PMDI) are generally used in boards that require an improved moisture resistance.  PMDI binder is not formaldehyde-based and consequently does not emit any formaldehyde.  The exact constituents of an MDF board will vary from product to product.

Q: What properties does MDF exhibit?

A: MDF has many qualities that make it an ideal replacement for plywood or particle board. It is dense, flat, stiff, has no knots and is easily machined. Its fine particles provide dimensional stability without a predominant “grain” (as is the case with lumber). Unlike most plywoods, MDF contains no voids, and will deliver sharp edges with no tearout.

Below are some metrics for MDF and other types of wood. Ex: Weight of MDF board. As you can see, MDF is very dense and heavy, but is not as stiff as other types of wood which is why bracing is suggested.

Wood Modulus of Elasticity
(in million pounds per square inch)
density
(in pounds per cubic feet)
weight of 4×8 sheet
1/2″ thick (in pounds)
MDF 0.53 48 75-85
Oak 1.55 38 60-70
Pine 1.3 29 45-50
Plywood 1.2 33 45-55

The modulus of elasticity (MOE), also called Young’s modulus, is the ratio of stress to strain, where stress is the force per unit area placed on the item and strain is the deformation caused by the stress. The MOE is therefore a measure of stiffness.

Q: What does MDF look like?

A: Here is an image of a birch veneered MDF board on top and for contrast an image of veneered particle board below. Notice the much larger and obvious particles.

 
Q: Are there any drawbacks to using MDF?

A: While MDF has been in use for almost 30 years, it is only now becoming available to the general public. Finding MDF may end up being the single toughest part of using it. As its density implies, MDF is very heavy and thus potentially difficult to handle.

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