Chemical reactivity of heat-treated wood Nguila Inari, G; Petrissans, M; Gerardin, P
Wood science and technology,
02/2007, Letnik:
41, Številka:
2
Journal Article
Recenzirano
Chemical reactivity of heat-treated wood was compared with that of untreated wood. For this purpose, heat-treated pine or beech sawdust was reacted with different carboxylic acid anhydrides in ...pyridine or with phenyl isocyanate in dimethyl formamide. Compared to controls, weight gains obtained with heat-treated sawdust are smaller showing a lower chemical reactivity. FTIR analyses of lignin and holocellulose fractions, isolated after acidic hydrolysis of polysaccharides or delignification with sodium chlorite, indicate that both components are involved in the reactions. Compared to lignin, holocellulose exhibits important infrared absorptions of about 1,730 cm-¹, characteristic of ester or urethane linkages formed. Lower reactivity of heat-treated sawdust is explained by the decrease in free reactive hydroxyl groups in holocellulose due to the thermal degradation of hemicelluloses, considered more reactive than cellulose.
Chemical composition of Norway spruce and pine, two softwood species, has been investigated by X-ray Photoelectron Spectroscopy (XPS). Contrary to results previously obtained with beech wood, which ...allow to obtain information on bulk chemical composition from surface composition analysis, XPS analysis appears to be unsuitable for the characterisation of Norway spruce and pine wood chemical composition. Indeed, chemical compositions calculated from XPS data differ strongly from those obtained from microanalyses which are in good agreement with theoretical composition described in the literature. XPS analysis of both the softwood surfaces indicated high carbon contents explained by migration of lipophilic extractives to the surface under the influence of the vacuum necessary for XPS analysis. Nonvolatile extractives contained in wood were extracted and deposited on glass plates and analysed. Survey and detailed C1s spectra indicated similar signals to those recorded on wood surfaces. This phenomenon was not observed when samples had been previously extracted before analysis. These results strongly evidenced that extractives present in both species are able to migrate through resin canals from the bulk of the sample to the surface when put into ultra high vacuum. XPS presents, therefore, some limits in the case of the analysis of softwood species containing extractives able to migrate to the surface during analysis. This behaviour, difficult to control, could lead to erroneous interpretations due to extractives enrichment of the surface under the effect of vacuum.
Chemical reactivity of heat-treated wood Pétrissans, Mathieu; Nguila Inari, G.; Gérardin, Philippe
Wood science and technology,
2007, Letnik:
41, Številka:
2
Journal Article
Recenzirano
Chemical reactivity of heat-treated wood was compared with that of untreated wood. For this purpose, heat-treated pine or beech sawdust was reacted with different carboxylic acid anhydrides in ...pyridine or with phenyl isocyanate in dimethyl formamide. Compared to controls, weight gains obtained with heat-treated sawdust are smaller showing a lower chemical reactivity. FTIR analyses of lignin and holocellulose fractions, isolated after acidic hydrolysis of polysaccharides or delignification with sodium chlorite, indicate that both components are involved in the reactions. Compared to lignin, holocellulose exhibits important infrared absorptions of about 1,730 cm–1, characteristic of ester or urethane linkages formed. Lower reactivity of heattreated sawdust is explained by the decrease in free reactive hydroxyl groups in holocellulose due to the thermal degradation of hemicelluloses, considered more reactive than cellulose.
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