【作者】 魏萍；

【导师】 陈瑞英；

【作者基本信息】 福建农林大学 ， 木材科学与技术， 2003， 硕士

【摘要】 通过对杉木速生材压缩密化过程的压缩成型条件、水分和物理力学性能等指标进行分析，并观察木材微观结构的变化，得出以下结果： (1)利用杉木速生材生产压缩木是可行的。通过压缩密化实验，可得最佳的工艺条件是：压缩率为50-60％、压后的厚度为13mm、压前含水率为50％、压缩时间在30min左右、热压温度为180～200℃之间。 (2)从纵向、径向和弦向的水分分布曲线可以看出，压缩木各方向的水分分布不均匀，所以容易翘曲变形。随着压前含水率的增加，压缩木的水分分布越不均匀，特别是大尺寸的压缩木水分分布更不均匀。同时利用多元回归分析建立数学模型，回归方程拟合优度均在92％以上。为了降低压后含水率，使水分分布均匀，可以采取两个办法：一是使初始含水率尽可能低，二是热压时间尽可能长。 (3)水分对压缩木的物理力学性质具有一定的影响。当压前含水率在50％左右时，压缩木的硬度、抗弯弹性模量和抗弯强度最大，回复率最小。冲击韧性随着压前含水率的增加而呈下降趋势。压前含水率在饱水状态下耐磨性最大。密度随着压前含水率的增加而升高，重量损失率随着压前含水率的上升而减少。压缩木的物理力学性能比天然材有明显的提高。 (4)从微观结构可知，杉木速生材压缩木的细胞只是被挤压，细胞腔变小而细胞壁未受到破坏。木材在压缩密化过程中，主要是木材细胞壁主成分上的羟基数量减少、结晶度增加、交联作用以及热降解等反应使木材变定得到固定。同时，压缩木也存在弛豫现象，木材在压缩密化过程应采取分段加压，压缩密化后的木材应堆垛放置一段时间，可以降低压缩木的回弹。更多还原

【Abstract】 Through analyzing the fast-growing china fir’s compression shaping condition , water, physical and mechanical properties during compression process, and observing the change of the micro structure ,we can draw the following results:(1) Utilize the fast-growing china fir produce compressed wood feasible. Its best process parameters are: compression ratio is 50~60%,thickness after compressed is 13mm,moisture content before compressed is 50%, hot compress time is about 30min, hot compress temperature is between 180℃ and 200℃.(2) Through lengthways , radial, tangential water distribution curve of compressed wood, water distributions are uneven and easy to warp and distort.The higher the moisture content of compressed wood is, the greater the compressed wood restore; the more crooked the water distribution curve is, the easier warping is out of shape. With moisture content before compressed being high, water distribution curve change very heavy, especially the big size compressed wood. In order to reduce moisture content, make the water distributed steadily, we can adopt two methods: first, make the wood before compressed as possible as low; second, hot compress time tries it’s best to be long.(3) Moisture content before compressed has influence on compressed wood’s physical and mechanical properties. When moisture content before compressed is about 50%, compressed wood’s hardness , bending elastic modulus , bending strength is best, toughness show a tendency to drop with moisture content increase, wearability is the best when wood compressed under the full water stated. WL decreases with moisture content rising definitely before compressed. Compressed wood’s physical and mechanical properties of have obvious improvement to natural material.(4) Through observing micro structure, we can find the fast-growing china fir’s cell is compressed just, cell cavity is smaller and cell wall has not been destroyed. In the course of compressed, compressed wood fixation is mainly because hydraxyl amount decrease, crystallization and hot decomposition and crosslink reaction in cell wall’s composition. Besides, because of relaxation, wood must be compressed by stage and compressed wood must put for some time, it can reduce compressed wood rebound.更多还原