林业工程学报2018，Vol.3Issue(4)：30-34,5.DOI:10.13360/j.issn.2096-1359.2018.04.005
预冻及压缩预处理对尾巨桉干燥特性的影响
Effect of freezing and compressing pre-treatment on collapse of Eucalyptus urophylla × E. grandis during drying
摘要
Abstract
Being widely planted in China, eucalyptus is one of the faster growing type with good mechanical and physi-cal properties, which are suitable for fabricating high value wood products, e.g.,furniture, door, and flooring. How-ever, as well known, the eucalyptus is difficult to be dried due to its native characteristics. Collapse is a very severe defect during drying, which would result in the degradation of wood products. The collapse is caused by the ununiform shrinkage during wood drying, especially occurred above the fiber saturated point (FSP). Resulted from the free water migration in the poor permeability lumens, the factors affecting the extent of collapse could be the permeability of wood species, drying rate, drying temperature, wood structures and extractive content in the wood. In order to im-prove the product quality and utilization ratio, it is important to control and reduce the collapses during drying. Cur-rently, several control methods including pre-treatment, low temperature kiln drying, continuous and intermittent dr-ying, etc. were carried out to change cell structures, reduce extractives, improve the permeability of wood for the pur-pose of reducing, or preventing collapse. In this study, Eucalyptus urophylla × E. grandis wood samples were pre-treated by freezing, compress or freezing-compress, and then the treated and un-treated samples were dried at a con-ventional kiln drying condition. The effects of pre-treatment on drying rate, residual stress and total shrinkage during the conventional kiln drying were examined. Results indicated that the drying rates of the samples pre-treated by freez-ing, compress and freezing-compress increased by 11.1%, 17.7%, 15.6% above FSP and 5.3%, 10.7%, 19.6% be-low FSP, respectively, compared with the drying rates of the un-treated samples. The results showed that the best pre-treatment method is the freezing-compress and the total drying rate was improved by 20%. The pre-treatment modified the micro-structure of cell walls, created new moisture migration channels and resulted in not only even moisture dis-tribution in wood cross sections, but also released of the drying stress during the drying process. Therefore, the residu-al deformation of the treated samples was reduced. It was concluded that the pre-treatment can reduce wood collapse in some degrees, and the total shrinkage of freezing-compress samples was reduced by 15.8%, which significantly re- duced the collapse during drying.关键词
尾巨桉/预冻处理/压缩处理/干燥特性/皱缩Key words
Eucalyptus urophylla × E. grandis/freeze treatment/compress treatment/drying characteristics/collapse分类
农业科技引用本文复制引用
杨琳,毛恒之,刘洪海,吴智慧..预冻及压缩预处理对尾巨桉干燥特性的影响[J].林业工程学报,2018,3(4):30-34,5.基金项目
国家自然科学基金青年项目( 31500479) （ 31500479）
国家自然科学基金面上项目( 31570558) （ 31570558）
南京林业大学高层次人才科研启动基金(GXL010) （GXL010）
江苏省"青蓝工程"资助项目 （）
南京林业大学大学生实践创新训练计划项目(2017NFUSPITP336). （2017NFUSPITP336）
