尾巨桉自由干缩率及纤维饱和点的测定

摘要

The samples of Eucalyptus urophylla ×E.grandis wood with 1-,2-,3-mm thickness were dried under six levels of relative humidity(RH),and the size in tangential and radial and weight of every samples were measured during drying process at interval of time,the shrinkage properties,total shrinkage and fiber saturated point(FSP)were studied.The re-sults indicated that the thin samples also collapsed at high moisture content(MC), including samples of 1 mm.The shrinkage curves of various thickness performed similarly under same RH, collapse or recovery occurred under high RH conditions.Shrinkage properties were affected by RH,under the conditions of high or low RH,collapse occurred and fol-lowed by recovery,the extent of collapse or recovery are great under high RH.No collapse recovery occurred under medium RH.Final collapse of 1-mm samples was smallest when RH was 33%or more.Through the analysis of regression equa-tions,the effect of sample thickness on the determination of total shrinkage was no significant,while its effects were signifi-cant on the determination of FSP.The 3-mm sample was increased by 15%compared with that of 1-mm samples.Non-free shrinkage occurred during the drying process, and tiny collapses resulted in the difference of total shrinkage and FSP of samples.%在6种湿度条件下检测了1、2、3 mm厚(纤维方向)尾巨桉(Eucalyptus urophylla×E.grandis)试件的弦、径向尺寸及含水率,研究了试件的干缩特性、全干缩率及纤维饱和点.结果表明:包括1 mm厚的试件在高含水率范围内也产生了皱缩.相同湿度条件下不同厚度试件的干缩曲线类似,在高含水率范围内试件出现不同程度的皱缩或回复.湿度对试件干缩特性有影响.高湿度条件下,试件均先皱缩再回复,且皱缩与回复均较大;中等湿度条件下试件的皱缩没有产生回复;湿度≥33%时,1 mm厚的试件残余皱缩程度最小.回归方程分析得出,试件厚度对全干缩率测量影响不显著,而对纤维饱和点的测量影响明显,3 mm厚的试件纤维饱和点测量值比1 mm厚的试件增加了约15%.干缩过程试件产生的微小皱缩并非自由干缩,因此全干缩率和FSP略有不同.