PREPARATION OF BINDERLESS BOARDS FROM STEAM EXPLODED PULPS OF OIL PALM (ELAEIS-GUINEENSIS JAXQ.) FRONDS AND STRUCTURAL CHARACTERISTICS OF LIGNIN AND WALL POLYSACCHARIDES IN STEAM EXPLODED PULPS TO BE DISCUSSEDFOR SELF-BINDINGS

Oil palm (Elaeis guineensis Jacq.) is one of the most abundant, unutil ised waste biomass from plantation in South-East Asia. The binderless boards were prepared from steam-exploded pulps of oil palm fronds and characterised for the mechanical strengths and chemical natures to dis cuss mechanism of self-binding. The mechanical strength of these board s satisfied the requirements of the relevant standard specifications ( JIS: Japanese Industrial Standards) for the boards. To make clear the mechanism of the self-bonding of these binderless boards, oil palm fro nds themselves, their steam exploded pulps, boards and lignins isolate d by Bjorkman's procedure from extract-free oil palm fronds and steam exploded pulps, were analysed by chemical and spectrometrical methods and pyrolysis-gaschromatography/mass spectrometry. Lignin of oil palm frond was characterised by the presence of significant amounts of este rified p-hydroxybenzoic acid together with small amounts of etherified p-hydroxybenzoic acid. Vanillic and syringic acids were esterified or etherified to lignin. Some extents of these ester bonds and beta-O-4 interunit linkages of lignin were cleaved during steam explosion, in a ddition to great condensation of guaiacyl nuclei, as revealed by H-1- and C-13-NMR spectra of isolated lignins from the steam exploded pulps , of which yields were quite high, suggesting that lignin has been rel eased from other wall polymers. Wall polysaccharides of oil palm frond are composed of cellulose and significantly high concentration of ara binoxylan, which produced great abundance of 5-hydroxymethyl-furfural and furfural during steam explosion, respectively, and even hot pressi ng at 125 degrees C to prepare binderless boards. It is suggested that released lignin and furfural derivatives generated during steam explo sion contribute to self-binding of the steam exploded pulps. However, severe conditions of steam explosion caused great damages in lignin ma cromolecules, and gave poor quality of binderless boards.