SiO2溶胶在欧洲赤松和火炬松边材中的渗透性

Penetration of SiO_2 sols in sapwood of Scots pine and loblolly pine

为了考察微纳米液体改性剂在木材中的渗透规律,采用2种粒径(30和150 nm)和3种浓度(质量分数5%,15%、30%)的SiO2溶胶真空30 min-常压浸渍24 h欧洲赤松和火炬松边材,比较其24 h内吸液率的经时变化规律和24 h增重率,通过质量法分析30nm、15%的硅溶胶处理材轴向SiO2的浓度梯度,并采用扫描电镜-X射线能谱仪分析各轴向深度木材细胞壁中硅元素的分布。结果表明:1)粒径小的硅溶胶在浸渍初期更易于在木材中渗透,随着浸渍时间的延长,粒径的影响变小,甚至可能出现相反的趋势;浓度对吸液率影响显著,一般浓度越高,吸液率越小。浓度高的改性剂处理木材时,粒径的影响更为显著。2)树种对硅溶胶的渗透性影响显著。硅溶胶在欧洲赤松边材的吸液率通常高于火炬松边材,但由于硅溶胶颗粒和水分在欧洲赤松中渗透不同步,硅溶胶在端头部分的大量沉积,导致欧洲赤松中SiO2在轴向分布浓度梯度远高于火炬松。3)硅元素进入各个轴向深度的木材细胞壁,硅元素的浓度分布规律与质量法结果一致。

In order to investigate the penetration of micro or nano emulsion modifiers in wood,SiO 2sols with two different particle sizes（ 30 and 150 nm） and three concentrations（ 5%,15% and 30%） were used to impregnate sapwood of Scots pine（ Pinus sylvestris） and loblolly pine（ Pinus taeda） under vacuum for30 min followed by atmospheric pressure for 24 h. Then the time-dependent liquid absorption curves during 24 h and the weight percent gain at 24 h were tested. In addition, the longitudinal SiO 2concentration gradients of wood samples treated by 30 nm,15% silicasols were obtained by mass method,and their longitudinal silicon distribution in wood cell wall was analyzed by using scanning electronic microscope coupled with energy dispersed X-ray analyzer（ SEM-EDXA）. The research results indicated that： 1） smaller particle sized silica sols are easier to penetrate in wood during the initial impregnation.With the impregnation proceeding,the influence of particle size weakened,and a reverse trend could even be observed. The concentration of silica sols also showed an obvious impact on liquid adsorption.Lower concentration usually resulted in higher liquid adsorption. The effect of particle size on liquid absorption was more obvious for wood treated with modifiers at high concentrations. 2） Wood species greatly affected the penetration of SiO 2sols. The liquid adsorption of sols in Scots pine sapwood was generally higher than that in loblolly pine. However,numerous SiO 2particles deposited at the opening end of Scots pine samples,resulting in non-simultaneous penetration of silica sol particles and water in Scots pines. As a result,the longitudinal SiO 2concentration gradient in Scots pines was much greater than that in loblolly pines. 3） SEM-EDXA analysis showed that the silicon could enter the wood cell walls in each axial depth profile. The scanned silicon concentration distribution was consistent with the results obtained by mass methods. These results are of great importance on improving the penetration of micro or nano emulsion modifiers in wood.