Modification of Wood-Based Material by Ultrasound

Wood-based materials such as particle board or fiber board are widely used as structural members in buildings and furniture. To recycle these materials after use, steaming at temperatures over 100 °C or chemical treatments with esterification or etherification is sometimes performed. However, little is known about technologies using relatively low temperatures and no chemical additives. Sonication is one such technology that can be used to break down materials with high-amplitude cavitation bubbles. These bubbles emit shock waves and liquid jets close to materials, which produce physical effects leading to the effective deformation of materials. In this study, sonication at around 20 kHz was applied to wood-based samples. Sonicated samples exhibited an 8.81% higher expansion ratio and 0.890 MPa lower maximum compressive stress than samples treated by hot-water dipping in a similar temperature range. Sonication is an effective method for softening wood-based materials that could be a useful technique for advanced recycling.