All-wood biocomposites by partial dissolution of wood flour in 1-butyl-3-methylimidazolium chloride

After cedar-derived wood flour (WF) and bark flour (BF) were mixed with 1-butyl-3-methylimidazolium chloride (BMIC) at 100 degrees C, the obtained compounds with BMIC content 40 wt % were compression-molded at 210 degrees C to give WF/BMIC and BF/BMIC composites, respectively. The BMIC contained in the composites was twice extracted with ethanol at 60 degrees C to afford WF/BMIC-E and BF/BMIC-E biocomposites, which were subsequently annealed at 200 degrees C for 24 h to produce WF/BMIC-A and BF/BMIC-A biocomposites. The Fourier transform infrared spectroscopic analysis revealed that WF has a higher content of cellulose and a lower content of lignin than BF does, and that the BMIC content diminished by the extraction process. The scanning electron microscopy analysis showed that woody particles joined together by the compression molding of WF/BMIC and BF/BMIC compounds, and that the extraction of BMIC roughened the surface and the annealing again smoothed the surface due to the fusion of the residual BMIC and woody particles. The XRD measurements indicated that the annealing enhanced the crystallinity of cellulose component. The tensile properties and 5% weight loss temperature of the biocomposites were considerably improved by the extraction of BMIC and further by the annealing. (c) 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013