Production of Particleboards from Steam-pretreated Rice Straw and Castor Oil-based Polyurethane Resin

Abstract

The high extractives content in rice straw inhibits the reactivity of castor oil-based polyurethane (CPUR) resin and hinders its bonding. This study employed steam treatment to pretreat rice straw to decrease the extractives content before using it for particleboard production. The effects of steam pressure and time on the chemical composition of the rice straw were investigated. Variable parameters tested were steam pretreatment time (5, 10 min) and steam temperature (110, 120, 130, and 140 °C). In addition, the mechanical properties and water resistance of particleboard manufactured from rice straw bonded with CPUR resin were evaluated. A three-phase hot press schedule at 110 °C was adopted. Other production parameters, such as resin content (20 wt%), hot press time (5 mm/s), and board density (800 kg/m³) were held constant. The resulting particleboards were tested for their mechanical properties in terms of modulus of rupture (MOR), modulus of elasticity (MOE), and internal bond (IB). Further, the physical properties including water absorption (WA) and thickness swelling (TS) were analyzed. The results showed that steam pretreatment significantly decreased the hemicellulose and extractives contents of the rice straws. Furthermore, steam pretreatment improved the mechanical properties and water resistance of the rice straw particleboards.