Plywood

Plywood Composition

Plywood is composed of three parts:

• Core (or heartwood): consists of many thin wood veneers, approximately 1mm thick.

• Surface layer: is a layer of natural wood.

• Glue: commonly used adhesives for plywood include Urea Formaldehyde (UF) and Phenol Formaldehyde (PF).

Raw materials for plywood production often include wood types such as pine, birch, poplar, rubberwood, eucalyptus, etc.

Physical Properties and General Characteristics

The average density of plywood is 600 – 700 kg/m3.

Common plywood sizes: 1220 x 2440 mm; 1160 x 2440 mm; 1000 x 2000 mm.

Common plywood thicknesses: 3, 4, 5, 6, 8, 10, 12, 15, 18, 20, 25 (mm).

The layers of a plywood sheet are always odd in number (3, 5, 7, 9…) so that the sheet has a core layer in the middle, creating the same grain direction in the two outer layers. These layers restrain each other, preventing warping or cracking. As a result, the thin layers on either side of the core layer are held firmly by the core layer and cannot freely expand or contract. Because of this arrangement of wood layers, plywood does not warp or shrink under normal conditions.