Preservative treatment of wood-based composites with 3-iodo-2-propynyl butylcarbamate using supercritical carbon dioxide impregnation

Abstract

Five structural-use wood-based composites [medium density fiberboard (MDF), hardwood plywood, softwood plywood, particleboard, oriented strand board (OSB)] were treated with 3-iodo-2-propynyl butylcarbamate (IPBC) using supercritical carbon dioxide (SC-CO₂) as a carrier solvent. Treatment was conducted at 35°C/7.85 MPa (80 kgf/cm²), 35°C/9.81 MPa (100 kgf/cm²), 35°C/11.77 MPa (120 kgf/cm²), 45°C/7.85 MPa, 45°C/9.81 MPa, 45°C/11.77 MPa, 55°C/7.85 MPa, 55°C/9.81 MPa, and 55°C/11.77 MPa. A decay test was carried out in the laboratory according to the modified Japanese standard method in which untreated and treated specimens were exposed for 12 weeks to a monoculture of the white-rot fungus Trametes versicolor (L.: Fr.) Pilat or the brown-rot fungus Fomitopsis palustris (Berk. et Curt.) Gilbn. and Ryv. IPBC/SC-CO₂ treatment protected the treated materials from decay by the two fungi, although the relative efficiency against decay varied with the treatment conditions and the type of wood-based composite. Better performance for MDF, hardwood plywood, and particleboard was generally obtained at high temperatures and pressures, whereas softwood plywood and OSB were most protected at low temperatures under any of the pressure levels tested.