PDF《南京林业大学 本科毕业设计（论文）》

南京林业大学 本科毕业设计(论文) 题目: 杨木速生材的压缩改性研究 学院: 木材工业学院 专业: 木材科学与工程(材料工程) 学号:

0541102 学生姓名: 陈F 指导教师: 邓玉和职称: 教授二OO 九年五月二十六日 摘要 本课题对速生材杨木薄板和单板进行压缩炭化改性研究,找出最佳的压缩炭化处理工 艺;

在提高其密度、强度、硬度等物理力学性能的同时,着重研究杨木压缩后的回弹固定 问题和压缩炭化机理,以扩大低质速生材杨木的应用领域,节约珍贵的优质木材.

根据试验得出最优压缩炭化工艺为:将含水率调至 10%的杨木薄板置于温度为 100℃ 的压机内,以一恒定压力对其压缩 50min.压缩结束后,将薄板从压机上卸下,将压机升 温至 200℃,与此同时将卸下的薄板置于 103℃的烘箱中烘一个小时.然后将烘过的薄板 置于升温后的压机内,压力为 2MPa,炭化 3h 后直接卸板.经压缩炭化处理后的杨木薄板 回弹率控制在 5%以内,且板具有较好的物理力学性能. 通过研究压缩炭化木红外光谱图中主要吸收峰的变化趋势发现:一方面,高温炭化处 理使得纤维素、半纤维素和木质素发生降解,羟基的浓度减少,化学结构发生复杂的变化;

另一方面,半纤维素中的某些多糖容易裂解为糖醛和某些糖类的裂解产物,在热量的作用 下,这些物质又能发生聚合作用生成不溶于水的聚合物.由于这两个原因降低了木材的吸 湿性,减少木材的膨胀与收缩,提高了炭化木的尺寸稳定性. 通过对压缩改性杨木薄板的微观结构分析表明,木材受到 50%压缩后,细胞腔和管孔 变小,但是细胞壁并没有受到破坏,仍然保持了原有的完整性. 关键词: 杨木速生材;

回弹率;

物理力学性能;

压缩炭化机理 Abstract The compression and carbonization modification of fast-growing poplar board and veneer was studied in this research to find out the optimal treatment technology. The results showed that the physical and mechanical properties such as density, strength and hardness can be enhanced. The problem of recovery ratio fixation of compressed poplar, as well as compression and carbonization mechanism had been studied, which can enlarge the applying area and economize the high quality wood. Optimal technology could be concluded as follows. The poplar board was compressed for 50min with the temperature of 100℃ and moisture content of 10%. Then the temperature of the heat-pressing machine was raised to 200℃ after the board was moved out of it. At the same time, the board was dried in the oven for an hour. After that it was carbonized for 3h with the temperature of 200℃ and pressure of

2 MPa. After the treatment of compression and carbonization, the recovery ratio of poplar board could be controlled within 5%, and poplar board had preferable physical and mechanical properties. The chemical composition of compression and carbonization poplar board was analyzed by infrared spectroscopy. The analysis showed that high-temperature carbonization made the cellulose, hemicellulose and lignin of poplar board decomposed, the existence of OH decreased, and the chemical structure changed. On the other hand, high-temperature carbonization can also made some polysaccharide of hemicellulose divided into uronic and some polysaccharide'

s pyrolysate those can generate polymer that cannot dissolve in the water with the effects of heat. Thus, moisture absorption can be reduced and dimension stability can be improved. According to microcosmic structure analysis of the compression modificated Poplar board, when the Poplar board was compressed by 50%, the cell cavity and pipe hole got smaller, but the cell wall hadn'