Spectroscopic Analysis of the Interface for Wheat Straw Specimen Glued with PMDI

Zhi-Ming Liu, Feng-Hu Wang, Xiang-Ming Wang

Abstract


In order to obtain information about chemical characteristics on the interaction between wheat straw and PMDI, the exterior and interior surfaces of wheat straw, and the interface of wheat straw specimen glued by polymeric diphenylmethane diisocyanate (PMDI) resin were scanned by micro-Fourier Transform Infrared Spectroscopy (micro-FTIR) and Electron Spectroscopy for Chemical Analysis (ESCA), respectively. The specimens of pure cellulose and the reacted mixture of cellulose with PMDI resin were analyzed by FTIR and cross polarization/magic angle spinning carbon-13 nuclear magnetic resonance (CP/MAS C-13 NMR). Scanning by micro-FTIR showed that the major differences in functional groups between exterior and interior surfaces for the same section of wheat straw appeared in the fingerprint region (400 cm-1 to 1500 cm-1). There were a few differentiated peaks in the region of 1174~1000 cm-1 for the interior surface, whereas there was greater absorption in the exterior surface than in the interior surface, especially at 987 cm-1. Generally, there were reaction functional groups (-OH) on exterior and interior surfaces for wheat straw. ESCA scanning and curve-fitting of the C1S peaks showed that the relative content of the functional group on the exterior surface differed from that of the interior surface. Results of ESCA scanning of the interface for wheat straw specimen glued with PMDI indicated that the glued interface chemically adsorbed PMDI resin. Furthermore, the contents of functional groups of the interface specimen glued with PMDI differed from those of the specimen without PMDI. Using FTIR and CP/MAS C-13 NMR, the results imply that N=C=O functional group for PMDI could react with cellulose.

Keywords


CP/MAS C-13 NMR;ESCA (XPS);functional group;interface;micro-FTIR;PMDI resin;wheat straw

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