Study On Impregnation Enhancement-Heat Treatment Process Of Eucalyptus Pellita Lumber

Eucalyptus, which covers more than 2 million hectares planted area, is one of important species of fast-growing plantations in China. In this study,Eucalyptus pellita was chose as the main study object. Through resin impregnation and heat treatment, dimensional stability of Eucalyptus pellita was improved and the loss of mechanical strength was reduced. Thus, this study favors the extended application of eucalyptus pellita, which has great significance to ease the contradiction between supply and demand of wood.Taking melamine, methanol, formaldehyde,urea as main raw materials, and adding some additives and catalyst, after long time section synthesis process at low temperature, MMFU resin was synthesized, which was water-soluble, colorless, transparent resin. And then under the conditions, that vacuum time was 60min, pressure was 1.1 MPa and holding time was one hour, MMFU resin was impregnated into Eucalyptus wood. After that, the wood was treated at different temperatures (160℃,180℃,200℃,220℃,240℃) for 2h,4h,6h,8h and10h respectively. Through the comparison of the physical and mechanical properties of heat-treated wood and resin impregnation heat-treated wood, the enhancement effect of resin impregnation was analyzed. And taking Contact Angle Apparatus, Fourier Transform Infrared Spectroscope and Integrated Thermal Analyzer, surface properties and weight loss of treated properties were also analyzed. The study indicated that:⑴By adjusting parameters in the formula and the mole ratio of main components, the optimal parameters and formula were obtained. MMFU resin was colorless transparent liquid, which had good performance, low formaldehyde release and long storage period, Using vacuum pressure impregnating process to treat Eucalyptus Pellita wood, the effects of vacuum degree,pressure value and concentration of resin on weight gain percentage were fixed. Therefore, selecting the best parameters and the concentration of MMFU resin, the reasonable weight gain percentage was 15.6%.⑵Heat treatment can improve the dimentional stability of eucalyptus pellita wood. For example, the untreated wood's radial, tangential and volume shrinkage from wet to air dry is 4.3%, 6.3% and 10.9% respectively, and those of treated wood at 240℃for 10 hours is 3.1%, 3.5%, and 6.7% respectively. Resin impregnation-heat treatment can further improve its dimension stability. The radial, tangential and volume shrinkage of resin impregnation heat treated wood under 240℃for 10 hours from wet to air dry is 2.7%, 3.3% and 6.1% respectively. ⑶Heat treatment can decrease the mechanical strength of eucalyptus pellita wood. For example, the untreated wood's MOE and bending strength is 16 820 MPa, 155.4MP respectively. And those of heat treated wood at 200℃for 4h is 15 680 MPa, 139.4 MPa. Resin impregnation heat treatment can prevent the loss of mechanical strengt.The MOE and bending strength of resin impregnation heat treated wood at 200℃for 4 hours is 17 160 MPa, 155.5 MPa respectively.⑷Heat treatment can reduce the surface wettability of EucalyptusPellita wood. With the increasing of heat treatment temperature and the extension of time, the surface free energy of eucalyptus pellita wood declined, and the surface wettability reduced. Resin impregnation can improve the surface wettability to some extent. FTIR analysis shows that heat treatment reduces polargroup carboxyl. With the increasing of heat treatment temperature and the extension of time, the more obviously carboxyl peak declines. Thermogravimetric analysis indicates that heat treatment lead to lumber weight dropped. With the increasing of temperature and the extension of time, the weight-loss increases, and resin impregnation can prevent the weight-loss during heat treatment.