Study On Decay Resistance Of Heat Treated Masson Pine Wood

Heat treatment applied to wood preservation is one of the high-technology in wood science which has been developed recently. As a result of no chemical agents, it has very good environmental performance. Therefore, it shows far-reaching influence for the application of heat treatment to protect the forest resources and improve the ecological environment.In this paper, with the peanut oil and N2 as medium respectively, the heat treatment of massoniana in different process was conducted, the process of heat treatment to wood and its mechanism of decay were studied, the following conclusions were drawn:1. The physical properties of heat treated wood were studied in this paper. In the case of constant heat treatment time, the moisture content of wood decreased with the rise of heat treatment temperature. The moisture content of the treated wood was much lower than original wood, which have inhibitory effects on propagation of epiphyte. The final water absorption rate of treated wood was lower than the original wood. At the same heat treatment time of wood, the higher the treatment temperature, the lower its water absorption rate and swelling and the better its dimensional stability; The density reduced with the rise of temperature.2. The mechanical properties of heat treated wood were studied in this paper. The compression strength parallel to grain of original wood was stronger than that of the N2 heat treated wood, which was declining as the rise of the temperature. Because of the infiltration of some oil into the wood, the compression strength parallel to grain of oil-heat treated wood was improved.3. The changes of chemical composition of heat treated wood were studied in this paper. The cellulose of the N2 heat treatment wood decreased slightly, while its hemicellulose declined sharply and the lignin increased a little. After the oil-heat treatment, the cellulose of wood reduced lightly with the greater decline of hemicellulose and appreciable climbing of lignin, of which hemicellulose in N2 heat treated wood declined the most. After the original wood was eroded by poria plaoenta, there was a sharp fall in the proportion of cellulose and hemicellulose in the original wood, which dropped comparably smaller in the N2 heat treatment and the oil-heat treatment. It showed that the heat treatment can effectively improve the decay resistant performance of wood.4. The impact of temperature, time and heating time on decay resistance was studied in this paper. There was a great relationship between the decay resistance of the wood treated by N2 and the temperature and holding time with a tiny impact of the heating rate, of which the temperature was the most important impact factor and the holding time has a certain impact on the decay resistance. As the temperature rise and the holding time increased, the decay resistance of wood enhanced. The relationship between the decay resistance of the wood treated by oil-heat treatment and the temperature and holding time was also large, of which the impact of temperature was greater than that of the holding time.5. Through the activity test of the epiphyte which has grown respectively on the original wood, N2 treated wood and oil-heat treated wood, it showed that the activity of cellulase and hemicellulase produced by epiphyte decreased at significantly. The decreasing degree of the activity of cellulase in N2 treated wood and oil-heat treated wood were both lower than hemicellulase's. The decreasing degree of both cellulase and hemicellulase in N2 treated wood were both larger than that of oil-heat treated wood.6. From the FTIR analysis, it showed that the hemicellulose in the wood which was treated by N2 at the temperature of 240℃for 5h has basically been thermal decomposed, however, the cellulose was thermal decomposed a bit with no change of the lignin. From the analysis of the oil-heat treatment at the temperature of 200℃for 4h, it could be seen that there was basically no thermal decomposition of the wood, but some peanut oil infiltrated inside it.7. From the SME scan, it showed that the basic structure of wood was not destroyed when the N2 heat treatment and oil-heat treatment were conducted at the temperature of 200℃, there are just a few local changes. After the decay by the fungal, the internal structure of the original wood has been entirely destroyed, completely rotten. Oil-heat treated wood's and the N2 treated wood's were eroded quite a lot, but their structure were significantly more intact than the original's.8. Through comprehensive survey, the optimal N2 heat treatment process for massoniana was 225℃, 4h and 15℃/min respectively. The related data was obtained from the verification test under such a process, the weight loss rate of the treated wood was 16.4%, which has already reachedⅡlevel (decay resistant); compression strength parallel to grain has decreased to 43.46MPa, which reduce by 24.73%. The best oil-heat treatment process for massoniana was 220℃and 2h. The corresponding data from the verification test under c process were as follows: the weight loss rate of the treated wood was 8.6%, which has already reachedⅠlevel (strong decay resistant); compression strength parallel to grain has decreased to 52.3MPa, which was lightly lower than that of the original wood.