• 论文与研究报告 •

### 辊压预处理条件对蒙古栎干燥速率及纹孔结构的影响

1. 北华大学木质材料科学与工程省重点实验室 吉林 132013
• 收稿日期:2014-02-26 修回日期:2014-05-08 出版日期:2015-01-25 发布日期:2015-01-23
• 通讯作者: 孙耀星
• 基金资助:

国家自然科学基金项目(31470022);吉林省科技发展计划项目(20120260);吉林省教育厅"十二五"科学技术研究项目(2012-160).

### Effect of Rolling-Press Pretreatment on Drying Rate and Pit Structure of Oak(Quercus mongolica)Lumber

Dong Xiaolu, Sun Yaoxing, Du Hongshuang, Zhao Xue, Jiang Tao

1. Wood Material Science and Engineering Key Laboratory of Jilin Province, Beihua University Jilin 132013
• Received:2014-02-26 Revised:2014-05-08 Online:2015-01-25 Published:2015-01-23

[目的]针对木材干燥耗时长、效率低的问题,以改变司职水分疏导功能的木材分子关键部位的微观结构为手段,通过改善木材的渗透性和水分的流动性,建立易于水分移动的新路径,达到缩短木材干燥时间的目的.在描述蒙古栎导管分子细胞壁构造变异的形态、数量和程度以及表征处理材在常规蒸汽干燥全程和各阶段干燥速率变动的基础上,探索并建立辊压预处理工艺条件、构造特征变异与干燥速率三者的相关关系.[方法]依托木材的黏弹性和水分移动机制,以蒙古栎为试材,对其含水率47% ~55%、900 mm(长)×100 mm(宽)×30 mm(厚)的径切板和弦切板施行2个压缩方向(径向和弦向)、3种压缩率(10%,20%和30%)和3种压缩次数(1,4和9次)的辊压预处理,使用环境扫描电子显微镜(Fei Quanta 200)观察研究辊压处理材的导管分子微观构造特征变异,并在常规蒸汽干燥全程和各阶段测试和分析处理木材的干燥速率变动规律.[结果]环境扫描电镜观察表明,辊压压缩预处理使蒙古栎导管分子纹孔膜破裂和细胞壁出现裂隙,可形成水分移动的微观新路径;随着压缩率增大、压缩次数增加,纹孔膜破裂的数量和程度、细胞壁破坏的规模和尺寸增加,木材的渗透性和水分的流动性得到改善,缩短木材干燥时间.在常规蒸汽干燥的6个阶段和干燥全程,辊压预处理材的干燥速率均大于未处理材;压缩率和压缩方向相同时,干燥速率随压缩次数的增加而增大;压缩方向和压缩次数相同时,干燥速率随压缩率的增加而加快;压缩率和压缩次数相同时,径向压缩的弦切板干燥速率快于弦向压缩的径切板.[结论]以试材初含水率50%、终含水率15%计算,辊压预处理材的全程干燥时间均少于未处理材,弦向压缩径切板干燥时间缩短6.67% ~23.64%,径向压缩弦切板缩短4.55% ~13.02%.辊压预处理可在蒙古栎试材内部形成微观的水分移动新路径,改善水分的渗透性和流动性,缩短木材干燥时间.

Abstract:

[Objective]To decrease the wood drying time, the microstructure characteristics of wood was changed. The moisture permeability and flowability were improved and new paths for moisture movement were established. The relationship of the process conditions of rolling-press pretreatment, the variation of the characteristics of cell walls and the drying rate, was constructed. [Method]The present work was based on the theories of viscoelasticity and moisture movement of wood. The lumber was compressed and horizontally passed through the intervals of two vertical arrangement rollers. The diameter of the rollers was 500 mm. The rotation speed of the rollers was 30 rmin-1. Quarter-sawn and flat-sawn oak boards of 900 mm in length, 100 mm in width and 30 mm in thickness with moisture contents of 47%-55% were compressed by rollers in both radial and tangential directions, with three compression rates of 10%, 20% and 30%, and three compression times of 1, 4 and 9, respectively. The variation characteristics of the vessel element cell wall microstructure of the rolling-compressed samples and the drying rate of samples during conventional drying were studied. [Result]FE-SEM observations showed that the pit membrane of vessel elements broke and the wall of vessel elements cracked because of the pressure from rollers, which formed new paths for moisture moving. The drying period was shortened due to improvement of moisture permeability and flowability when increasing the amount and the broken degree of pit membrane, and the scale and size of cracked cell wall, with the increasing of compression rate and compression times. The results indicated that the drying rate of the treated samples was higher than that of the untreated samples in six drying stages and overall the drying process. The drying rate was increased with increasing the compression times when the compression rate and direction were the same. It was also increased with increasing the compression rate when the compression times and direction were the same. The drying rate of the quarter-sawn samples compressed in the radial direction was higher than that of the flat-sawn samples compressed in the tangential direction.[Conclusion]The drying cycles of treated samples were less than that of untreated samples when the initial and final moisture contents of the samples were 50% and 15%, respectively. The rate of shortened time of the lumber compressed by tangential direction was ranged from 6.67% to 23.64%, while that of compressed by radial direction was ranged from 4.55% to 13.02%. The results showed that the drying period of wood decreased because of the improving of moisture permeability and flowability, which were contributed by the rolling-press pretreatment.