热处理辐射松吸湿解吸等温线的测定与分析

为了筛选出适合新西兰辐射松的等温吸湿解吸模型,以新西兰辐射松板材为研究对象,经热处理温度为160,170,180,190,200和210℃,处理时间为2.0 h的热处理后,通过动态水分吸附仪研究热处理材的平衡含水率与热处理温度的关系,同时选用PEK模型及6种吸湿解吸等温线模型对平衡含水率数据进行非线性拟合并对其拟合效果进行评价,以确定最佳拟合模型及其参数。结果表明:在相同湿度条件下,热处理材平衡含水率最高为15.102%,低于对照材16.323%,相同处理温度的木材在相同湿度下,吸湿平衡含水率小于解吸平衡含水率; 不同处理温度的木材吸湿解吸平衡含水率随热处理温度的升高而逐渐降低。PEK模型可以预测木材在吸湿和解吸过程中的含水率,其拟合度R2在0.99以上。在6种吸湿解吸等温线模型中,GAB模型为最优拟合模型,可以预测不同环境湿度下木材的平衡含水率,其拟合度R2在0.99以上。
As an effective modification method for wood, heat treatment improves the dimensional stability of timber by lowering its hygroscopicity. The purpose of this study was to analyzed the effect of heat treatment temperature on the equilibrium moisture content(EMC)of heat-treated wood by using the dynamic vapor sorption(DVS)apparatus, and the EMCs obtained from DVS measurements were fitted by the parallel exponential kinetics(PEK)model, BET(Brunauer-Emmett-Teller), GAB(Guggenheim-Anderson-deBoer), Halsey, Henderson, Oswin, and Smith sorption isotherms models, so as to determine the best fitting model and its parameters. Radiata pine(Pinus radiata D.Don)timber was used as a tested material and heat-treated with steam at 160℃, 170℃, 180℃, 190℃, 200℃ and 210℃, respectively, for 2.0 h. The EMC of heat-treated wood was studied by using the dynamic vapor sorption(DVS)apparatus. Then the EMC was analyzed by parallel exponential kinetics(PEK)model and six typical sorption isotherm models. The resulte showed that the relative humidity(RH), the adsorption and desorption EMCs of the heat-treated wood(15.102%)were lower than those of the control sample(16.323%). At the same RH and heat treatment temperature, the EMC was lower in adsorption than that in desorption process, and the moisture content in both adsorption and desorption processes increased with the increase of heat treatment temperature and relative humidity. Under 25℃ and 70% RH, the EMC of treated wood that underwent adsorption were 6.302%-10.188%, while that of the control sample was 11.433%. The EMC of wood decreased by about 44.88% after the heat treatment. The treated wood that underwent desorption attained the EMC between 8.068% and 12.800%, while the control sample was 13.772%. The EMC of heat-treated wood decreased by 41.42% compared with that of the control sample. The results of the PEK model showed an excellent fit to the sorption-desorption curve of the heat-treated wood(R2>0.99). Among the 6 typical sorption isotherm models, the GAB model showed a good fit to the experimental EMC of wood(R2 > 0.99). The heat treatment with steam improved the dimensional stability of Radiata pine. The increase