碱液处理对改善竹束液体渗透性能的研究

竹材液体渗透性是影响竹材改性处理效果的重要因素。采用碱液处理(80℃,质量分数1%～4%,处理时间1～4 h)竹束,分析工艺参数对竹束质量损失率、染液质量增加率的影响,解析处理前后竹材微观构造、孔隙结构参数的变化情况,揭示碱液处理改善竹材液体渗透性的机理。结果显示,碱液质量分数及处理时间对竹束质量损失率影响显著。碱液质量分数2%、处理时间1 h条件下,可以在保证竹束液体渗透性改善效果和处理效率的同时,使竹束质量损失率较小。扫描电镜观察发现,碱液处理后竹束导管等细胞产生明显皱缩,导管壁上规则的网状孔隙结构产生破坏,竹材部分闭塞孔隙结构重新打开,竹纤维产生剥离现象。压汞测试分析发现,碱液处理后竹材显微构造变化会导致竹束内部孔体积增大;细胞壁内部孔径40 nm左右的孔隙增多,孔径增大。竹束纤维细胞剥离可增加液体渗透通道,缩短液体渗透路径,降低液体渗透压,提升液体渗透效率。孔体积的增大导致流体在竹束内部的渗透量增大,孔径增大导致流体在竹束内部渗透的效率提高。竹束细胞壁内部小尺寸孔隙的增加,使流体有更多的渗透路径向细胞壁内部渗透,易于实现深度均匀渗透。

Improvement of liquid permeability of bamboo bundle through alkali treatment

Liquid permeability is one of the most important factors affecting the efficiency of the property modification of bamboo. This study investigated the effect of process parameters on mass loss ratio and dye solution uptake percentage for alkali-treated bamboo bundles (80℃, the mass ratio of alkali solution of 1%-4%, treatment time duration of 1-4 h). The microstructure examination and pore structure characterization were carried out by the scanned electron microscope (SEM) and mercury intrusion porosimetry (MIP) methods, respectively, and the mechanism of liquid permeability improvement of alkali-treated bamboo was revealed. As the results shown, the mass ratio of alkali solution and treatment time duration had significant effect on the mass loss ratio and dye solution uptake percentage of alkali-treated bamboo bundle. In order to maintain the modified liquid permeability while shorten the processing time duration without compromising mass loss ratio, it was found that the optimum mass ratio of alkali solution was 2% and the treatment time duration was 1 h. The SEM examination results showed that vessels and other cells were obviously shrank after the treatment. The original net structure in the cell walls of vessels was destroyed and aspirated pores reopened while bamboo fiber cells were stripped after the alkali treatment. The MIP test results showed that the cumulative pore volume increased as the changes of microstructure of bamboo after the treatment. Meanwhile, the number of pores with diameters around 40 nm was increased compared with control samples. Accompanied by the microstructure and pore structure changes, the liquid permeability of bamboo bundles enhanced. The stripped bamboo fibers created new paths for liquid flow, and shortened the permeating route length. Finally, the treatment resulted in the lower liquid permeation pressure and improved the permeation efficiency. The increased pore volume made the increase in liquid uptake in bamboo bundle. The enlarged pore diameter facilitated the liquid flow in bamboo bundles. The larger number of pores in cell walls meant more paths for liquid flow, which made the liquid penetration deeper and more homogeneous in the bamboo bundle.