What is medium density fibreboard?

Answer 1

Basically sawdust and resin compressed under very high pressure. It's typically used for counter tops, furniture, speaker boxes and many other indoor applications.

Yse, basically you are right.

Medium Density Fibreboard (MDF) is a reconstituted wood panel product. It is a dry-processed fibreboard manufactured from wood fibres, as opposed to veneers or particles, and is denser than plywood and particleboard. MDF has an even density throughout and is smooth on both sides.

MDF is reconstituted into wood sheets in a variety of widths and lengths. Bonding is achieved by the addition of synthetic resin adhesives, which are cured under heat and pressure. Paraffin wax is added to assist with water repellency, while other chemicals can be added during manufacturing for more specific protection.

MDF is primarily used for internal use applications, in part due to its poor moisture resistance. It is available in raw form with a fine sanded surface or with decorative overlay such as wood veneer, melamine paper or vinyl.