How is chipboard made?
Chipboard, sometimes called particle board, is a board made by compressing small pieces of wood with glue.
The advantage of chipboard is that it can be made from wood pieces that would otherwise have been discarded, saving the unnecessary cutting of more trees in some wood applications not requiring a higher grade of lumber.
Chipboard is made from forest by-products. When forests are cut or thinned the resultant sawdust is collected. Small pieces of wood, left from the milling process and unsuitable for other uses, are granulated into wood chips and added to the sawdust. The mixture is formed into a slurry using urea formaldehyde and other less toxic binders according to how and where the chipboard will be used. The slurry is then subjected to high heat and pressure which eliminates the liquid and forms the wood chips into panels.
Chipboard is made in several densities depending upon how the product will be used. Chipboard's normal density is soft, making it inappropriate where strength is key. Medium density chipboard has more fibres per square inch, increasing its hardness and strength. High density chipboard is the strongest and firmest made and is therefore often used where rigidity is essential. Most chipboard is used only for interior use as it tends to soak up water and break down if it is exposed to moisture.
The lowest grade of chipboard is made mostly with sawdust or small particles that are all the same size. This method produces a soft board which bends easily and must be reinforced by regular lumber to increase its strength. Medium density chipboard contains both sawdust and coarser particles while high density chipboard contains mostly coarse chips with only a small amount of sawdust. The courser particles migrate to the interior of the panels while the sawdust floats to the top, providing a relatively smooth surface. The greater the number of large interior chips there are, the stronger the chipboard will be.
Once the basic chipboard is made, it does not provide an attractive surface for finishing. Laminate or self-sticking decorative film can be used to hide the surface irregularities of chipboard. Similarly, exposed edges of laminated chipboard can be disguised with adhesive edging strips for a dressier look. Chipboard should never be painted using water-based products. The water in the paint will be absorbed into the wood fibres and cause expansion and warping to occur. An oil-based paint will not cause the same problems but will not hide surface irregularities as well as an application of laminate.
Chipboard with a smooth veneered surface is often used for interior partitions, lining walls, work surfaces and customer assembled furniture. High density chipboard is tough enough to use for flooring. Floor joists must be close enough together to avoid bending or bowing of the chipboard. Usually boards have tongue and groove edges for firmness and ease of installation. Chipboard may also be made flame retardant and moisture resistant but not waterproof.