Plywood Facts

Gluelines

The bond types are A, B, C and D, in decreasing order of durability under conditions of full weather exposed.

Type A bond is produced from a phenol formaldehyde (PF) resin, which sets permanently under controlled heat and pressure. It forms a permanent bond that will not deteriorate under wet conditions, heat or cold. It is readily recognisable by its black colour.

Type B bond is produced from melamine fortified urea formaldehyde resin (MUF) which sets under controlled heat and pressure. Type B bond is included in the exterior plywood standard and is suitable for applications involving concrete formwork plywood is stamped with the EWPAA Approved B bond stamp.

Type C and D bond are both interior bonds and should not be recommended for any purpose where exterior use or use under wet or damp conditions are involved, or long terms load bearing conditions are Even interior use C and D type bond should not be recommended for structural applications. (Type A bonded plywood should be used for areas of doubtful moisture conditions, such as areas around sinks, vanity units and laundry tubs)

Type C and D bonds are produced from urea formaldehyde resin, (UF) which sets under controlled heat and pressure. The glueline is light coloured. The formaldehyde adhesives used in plywood manufacture are thermosetting and will not replasticise under reheating as do thermoplastic adhesives such as elastomeric wall board adhesives and PVA. Formaldehyde emission from most plywood products is at or below the stringent E1 requirement of 0.1 ppm accepted internationally. Phenolic Type A bonds have particularly ow formaldehyde emission, of between 0.00 to 0.03 ppm, corresponding to E0 (which is 0.05ppm).

Veneer Quality

There are 5 veneer qualities specified for plywood in the Australian and New Zealand Standards. The veneer qualities specified are A, S, B, C and D. The plywood face veneer quality is specified as the face veneer quality first followed by the back face veneer quality. Typical examples are: AA for marine plywood, AD for a wall cladding where only the front face of the plywood is visible, CD for structural plywood flooring and DD for structural bracing.

Structural Plywood

Structural Plywood manufactured to AS/NZS 2269 Plywood-Structural is suitable for use in all permanent structural applications. A permanent Type A phenolic resin is used to bond the individual timber veneer. The Type A bond is distinctly dark in colour and is durable and permanent under conditions of full weather exposure, long term stress, and combinations of exposure and stress. Structural plywood is manufactured from a range of softwood and hardwood timber species. These timber species may not be durable when used in weather exposed situations. In exposed applications, structural plywood must be preserved treated to ensure it last its full service life and surface finished to minimise surface checking.

Marine Plywood

Marine plywood is a purpose built structural plywood, intended for use in hulls of boats and other marine application and also in aircraft construction. It has a permanent Type A Phenolic bond and is manufactured from selected species based on density, bending strength, impact resistance and surface finishing characteristics.