Effect of immidazolium-based green solvents on the moisture absorption and thickness swelling behavior of wood flour/polyethylene composites

Abstract

The water transport kinetics and moisture-induced thickness swelling behavior of wood-plastic composites (WPCs) in the presence of two imidazolium-based ionic liquids (ILs) were studied. The wood flour chemically treated with ILs were compounded through melt mixing of high-density polyethylene and coupling agent, and finally, the test specimens were produced by compression molding. Hygroscopic rates of the composites were evaluated by immersing them in the water at room temperature and monitoring moisture sorption and thickness changes for several weeks. Besides, the water diffusion coefficients and swelling rate parameters were measured for all composites. It was found that the water absorption and thickness swelling of the WPC specimens reduced as a result of ILs treatment. The SEM analysis revealed that the presence of ILs can improve the quality of adhesion between the polymer matrix and the cellulosic materials, to decrease the gaps in the interfacial region and block the hydrophilic groups. Studying the water sorption process in the specimens showed that the process follows kinetics and mechanisms described by Fick’s law. The highest water diffusion coefficients and swelling rate parameters were found in composites with untreated wood.