Investigation of the Structural Characteristics of Corn Stalk during Hot-Pressing
2016
Xi Le | Junjian An | Guangyan Zhang | Lei Wang | Jianyun Fan | Peng Wang | Yimin Xie
Corn stalk is one of the most abundant agricultural residues in China. In this experiment, corn stalks were hot-pressed to prepare formalin-free particleboard. Milled wood lignin (MWL) samples were isolated from original and hot-pressed corn stalks. To illuminate the self-bonding mechanism of binderless particleboard, the structural characteristics of original corn stalk, hot-pressed corn stalk, and MWL samples were thoroughly investigated by Fourier transform infrared spectroscopy (FT-IR), solid-state cross-polarization magic angle spinning carbon-13 nuclear magnetic resonance spectroscopy (CP-MAS 13C-NMR), X-ray diffraction (XRD), carbon-13 nuclear magnetic resonance spectroscopy (13C-NMR) and gel permeation chromatography(GPC). The degradation of hemicellulose and a portion of amorphous cellulose occurred during hot-pressing. Hot-pressing increased the crystallinity and crystallite size of cellulose in treated corn stalk. The analysis of MWL showed that hot-pressing resulted in corn stalk lignin depolymerization through cleavage of a substantial portion of the β-O-4 linkages in lignin, as well as the decrease of molecular weight of lignin in corn stalk. In addition, acid-catalyzed condensation occurred between lignin and xylose when liberated from hemicellulose. These results demonstrated that condensation between lignin and xylose may contribute to the self-bonding mechanism and improve board properties.
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