Chemical changes of kenaf core binderless boards during hot pressing (I): influence of the pressing temperature condition |
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Authors: | Nobuhisa Okuda Keko Hori Masatoshi Sato |
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Institution: | (1) Department of Global Agricultural Sciences, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan |
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Abstract: | Self-bonding is the main factor of the performance expression of binderless boards, and therefore its clarification is considered
to be an important issue. For this purpose, a series of chemical analyses were conducted on kenaf core binderless boards and
their chemical changes during the hot-pressing process are discussed in this article. First of all, binderless boards were
prepared from kenaf core powder at different pressing temperatures (without steam-explosion process) and were used for chemical
analyses after they were reduced into powders and extracted with methanol. To investigate their chemical changes, lignin,
holocellulose, and neutral sugar contents were determined, Fourier transform infrared (FTIR) spectra were recorded, and the
nitrobenzene oxidation procedure was applied. As a result, it was found that parts of lignin and hemicelullose were decomposed
during the hot-pressing process; however, the contribution of the resulting fractions to selfbonding was not observed. In
addition, progress of condensation reactions in lignin and the formation of chemical bonds by low molecular weight conjugated
carbonyl compounds in methanol extractives were observed. Thermal softening of lignin is also suggested to play an important
role in the expression of board performance. |
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Keywords: | Chemical change Self-bonding mechanism Binderless board Thermal softening of lignin Condensation reaction |
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