生材单板挤压脱水的研究

A study on Squeezing Water out of Greenwood Veneer

经分析计算，基本密度为０．３６ｇ／ｃｍ￣３的木材，在１２０％的含水率状态下木材中细胞壁物质、水和空气三者的体积比约为１：１：１，因此当该木材体积压榨率达到６６％时，木材中的水分（自由水）几乎将被全部挤出。据此，使用表面有沟槽的几种不同模板对速生树种Ｉ－６９杨和火炬松的生材单板进行了不同压榨车的挤水试验，结果表明：Ｉ－６９杨２．０２ｍｍ生材单板用７０％的压榨率挤压后，含水率显著降低，组内试件间的合水率差异显著缩小；火炬松２．３８ｍｍ和３．３３ｍｍ生材单板，压榨率６０％比４０％的挤水量大、挤后与挤前组内含水率极差比值小，因而达到了降低并均匀生材单板含水车的目的。另外，模板不同也显出不同的挤水效果。

On the basis of theoretical calculation,the volumetric ratio of wood substances towater and air for the wood in basic density 0.36g/cm￣3 at 120% moisture content is about 1 :1:1.Therefore,the free water in wood will all be squeezed out as the volumetric squeezingratio of the wood reached 66%. Based upon this consideration,squeezing tests were made forgreenwood veneer of fast grown loblolly pine(pinus taeda)and poplar I-69(Populus del-toides Bartr cv.' Lux ' I-69/55)in various squeezing ratios by using various types specialgrooved plates. The moisture content of 2.02mm thick greenwood veneer of poplar I-69 wasdecreased remarkably after squeezing in 70%squeezing ratio and the distribution of moisturecontent of the veneer got more uniform. The differences among moisture contents of the sam-ples taken from different parts of the veneer from the same bolt got smaller remarkably alsoafter squeezing.More water were squeezed out of 2.38mm and 3.33mm thick greenwood ve- neers of loblolly pine in 60%squeezing ratio than in 40%squeezing ratio,and greater uni-form distribution of moisture content of the veneers were obtained in the former case. It wasevident that squeezing with grooved plates could effectively make the moisture content ofgreenwood veneer lower and more uniform distribution. It was also found that squeezing withvarious type of grooved plates showed different results.