Plywood is produced by bonding together thin layers or veneers of wood with a strong adhesive. The quality of the glue adhesive is critical because the strength and integrity of the plywood relies on it.
When selecting plywood for your project, it’s important to choose one made with the adhesive that suits your application.
There are four types of glue bond used in the manufacture of plywood:
Type A (A-Bond)
This is the strongest bond and is also waterproof. It’s produced from a phenol formaldehyde resin that is set under heat and pressure, resulting in a permanent bond that can be exposed to hot, cold or wet conditions for a long time without risk of deterioration. This glue bond is used for structural, exterior and marine plywoods.
Type B (B-Bond)
Less durable than Type A, a Type B glue bond is waterproof but will deteriorate after several years when exposed continuously to weather. It is usually produced from a Melamine-Urea-Formaldehyde (MUF) resin. Plywood with a B-Bond glue is best used in situations of limited weather exposure, e.g., exterior doorskins and concrete formwork.
Type C (C-Bond)
This glue bond can only withstand occasional exposure to dampness and is, therefore, most suitable for interior applications. It should not be used for structural applications or wet/damp areas. This glue bond is usually produced from a Urea Formaldehyde (UF) resin.
Type D (D-Bond)
Similar to Type C, Type D is also made from a Urea Formaldehyde (UF) resin. D-Bond plywood is best suited for interiors where it is completely protected from wetness or dampness. It should never be used for structural applications.
There are Australian standards for glue bonds to ensure the plywood is fit for purpose. A substandard glue bond could result in a structure failure – for example, by using structural plywood that was not manufactured to the correct standard with a Type A glue bond.
To ensure that the plywood you select is manufactured correctly, it is best to buy products produced by reputable manufacturers with testing and quality control programs. Very importantly, when you see the word ‘waterproof’ in relation to plywood, keep in mind the glue is waterproof, not the wood component.
Consult with the Matilda Veneer team for assistance with selecting the right plywood for your project.