Effects of posttreatment with alkaline copper quat and copper azole on the mechanical properties of wood-based composites

The static bending strengths, modulus of rupture, and modulus of elasticity of 5 commercial wood-based composites [softwood plywood (SWP), hardwood plywood (HWP), medium density fiber-board (MDF), oriented strand board (OSB), and particleboard (PB)] were measured after a postmanufacture treatment of vacuum-impregnation with alkaline copper quat (ACQ) and copper azole (CA) (target retentions: 0.65, 1.30, and 2.60 kg m^–3 for ACQ; 0.25, 0.50, and 1.0 kg m^–3 for CA). Of the composites tested, SWP exceptionally sustained no damage to its bending strengths, regardless of preservative types and retentions. Others (HWP, MDF, OSB, and PB) were necessarily affected to some degree by posttreatments. In accordance with the dimensional stability and resistance to biological attacks, of the posttreated composites, SWP seems most suitable and implemental for posttreatment when the appropriate selection of treatment concentrations and schedules is made.