Abstract:

In this paper，the chemical changes of the cunninghamia lanceolata thinning wood treated in hot air and hot vegetable oil respectively for different processing temperatures and times were analyzed by chemical component analysis and FTIR analysis. The results showed that there were different degree decreases in the content of the holocellulose of treated samples during the heat treatment compared to reference samples，as the whole the content of the degraded cellulose of treated samples was smaller，meanwhile，the content of both of benzene-alcohol and Klason lignin of treated samples were increased. The chemical compositions of treated samples vary much when processing temperature was increased and times was lengthened during the heat treatment. In addition，the effect of heat medium on the chemical changes of treated samples was obvious，and the chemical changes of the samples when the treatment of hot oil appeared to be slightly lower than that of samples when the treatment of hot air under the same condition. Analysis variance showed that chemical compositions of treated samples among different processing temperatures，processing times and different heat medium reached highly significant difference. The FTIR of specimens indicated that the hemicellulose decomposed firstly when wood samples treated at 180 ℃，and some degradation of the cellulose was occurred at temperature of 200 ℃. The degradation of polysaacharide was accelerated in atmosphere. The variations of absorption intensity both of glucosidic bonds at 3 412, 1 050, 898 cm^-1and carbonyl peak at 1 736 cm^-1 and C—H bond stretching at 2 907 cm^-1 can reflect the variations in the chemical compositions of the samples when the treatment for different processing times and temperatures，it showed a good correlation between the variations in the chemical compositions of the samples and the improved dimensional stability of heat treated wood.

Key words: thinning wood of Chinese Fir, heat treatment, chemical compositions of wood, heat medium, fourier transform infrared spectrometry （FTIR）