Room Temperature Ionic Liquids as Lubricants for Wood-Polyethylene Composites

Abstract

Room temperature ionic liquids (RTILs) may be used as green solvents and catalysts for various chemical reactions, as anti-electrostatic agents for wood, as electrolytes for batteries, and as extraction agents for reduction of hazardous pollutants because of their unique properties such as negligible vapor pressure, high thermal stability, and high electric conductivity. In this study, we demonstrated that RTILs were excellent lubricants for making wood-plastic composites (WPCs). A lubricant is essential for making acceptable WPCs and a compatibilizer is typically added to improve their mechanical properties. However, a lubricant and a compatibilizer normally have opposite effects on the strength and stiffness of WPCs. This study revealed that RTILs had better lubrication effect than Struktol, a commonly used commercial lubricant for making WPCs. When used with MAPE, some RTILs reduced the strength-enhancing effect of MAPE (maleic anhydride-grafted polyethylene), one of the most effective compatibilizers, less than Struktol. Some RTILs were also superior to Struktol in terms of increasing or retaining the stiffness of the resulting wood-PE composites. Among five RTILs studied, RTIL F (triisobutylmethylphosphonium tosylate) was the best RTIL in terms of providing the lubrication effect and maximizing retention of the strength-enhancing effects of MAPE.