Particle board, also spelled particleboard, originated in 1887. It is manufactured using wood chips, sawmill shavings, or sawdust (all low-cost manufacturing residues compared to veneer logs and logs for MDF) and sometimes from low quality logs.
The particles are glued together using a synthetic resin (using formaldehyde as a catalyst in the past). Waxes, dyes, and other chemicals may be added to the particles. The particles are spread on a mat and then pressed under high pressure with heat.
The final product is cut to size and is sometimes sanded to provide a uniform thickness.
The amount of adhesive and the final density (related to the pressure used) controls the board’s properties.
Because of the rough size of the particles and the many small voids, the surface is often rough and needs to be sanded to obtain the smoothest face.
In some cases, when putting the particles on a mat that will convey the loose particles into the press, the first layer will be very small particles, the core will be larger particles and the top will be small particles. This provides a final surface, top and bottom, that is solid and smooth. The change from fine to coarse to fine can be rather abrupt or graduated.
Particleboard is not as strong a similar plywood panel, but it is much lower in cost. denser and more uniform. Particleboard is an engineered product, which means the overall properties are under manufacturing control.
The particleboard surfaces, often consider not beautiful, are often painted or overlaid with wood veneer or special paper or even plastic-type materials, such as formica.
- Low cost
- Smooth faces make it easy to finish
- Low strength - cannot support heavy loads
- Conventional fasteners are not very strong
- Expands when exposed to liquid moisture and high humidity
- Edges need further treatment
Useful characteristics and processing hints
A. Strength. Particleboard panels are engineered, so properties can certainly vary. In general, particleboard used for furniture, cabinets and similar has a density between 0.6 and 0.8 which is somewhat heavier than oak. In general, MDF is stronger than particleboard and maybe stiffer. In furniture, with heavy loads, much of the particleboard will creep, which means it takes on a permanent deformation over time (or more simply, when used as a shelf, it will tend to sag if not well supported).
B. Gluing. Due to the wax and heat used in manufacturing, particleboard can be difficult to glue. Scuffing the surface or light sanding is essential if a very strong glue bond is desired. Because the board is under pressure when manufactured, the first exposure to moisture causes more swelling than expected (called springback). A good PUR adhesive is probably the best choice.
Hot melt adhesives, such as PUR, are often used for edgebanding. Some experimentation may be required to find the right adhesive and a reasonable cost.
Sanding to achieve uniform thickness before glue laminating is common.
C. Fastening with screws, nails and staples. In general, use screws with a head that can be countersunk. Screw root diameter (not counting the thread overall diameter) when used on the edge should be less than 20 percent of the panel’s thickness with a pilot hole that is 80 percent of the root diameter. Pilot holes need to be slightly deeper than the expected screw penetration.
Screws should be away from the corners; 1 inch for face screws and 3 inches for edge screws. Face screws should also be ½ inch or more from the edge. If screws are driven too much (over-torqued), the board is likely to split.
In general, nails would not be used on particleboard.
Brads and staples can be used, but the high density of the board discourages such use except when the fastener holds a cleat or similar that is being glued until the glue itself dries and can carry the load.
Many times, dowel pins are used for positioning. The dowel and hole diameter used should be no larger than 50 percent of the panel’s thickness. The hole should be about 1/64-inch more in diameter than the dowel. If the hole is too small, the dowel can push the wood, creating a bump on the surface. Note: Dowels are used more for positioning that for developing a strong joint themselves.
D. Machining. The faces can be machined fairly well, although the adhesive and density mean that sharp, durable cutters (or fresh sandpaper) must be used. Edge machining is usually not too smooth.
Machining particleboard panels requires more power than machining solid wood.
Keep all tools as sharp as possible, perhaps using carbide or other durable material. Slower feed speeds, compared to solid wood, are usually better. Special saws with many teeth are often used for particle board.
E. Warping. The uniformity of particleboard reduces the tendency to warp or shrink and swell when the moisture changes. However, springback can occur with the first exposure to moisture.
F. Finishing. The porous nature of particleboard can require fillers to be used. Sanding prior to finishing can help establish a durable binding between the wood and paint. Sometimes the added chemicals in manufacturing or even oils make the surface difficult to finish with some finishes.
Gene Wengert, “The Wood Doctor” has been training people in efficient use of wood for 35 years. He is extension specialist emeritus at the University of Wisconsin-Madison.
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