思茅松3种密实化改性材物理性质比较

Comparison of physical properties between three types of densified Pinus kesiya var. langbianensis wood

密实化是提升低密度人工林材品质、拓展其用途的重要途径之一。以思茅松为研究对象,在考察水抽提处理对其可浸渍性影响的基础上,分析比较了糠醇化、机械压缩以及两者联合等3种密实化改性方式对其剖面密度、吸湿性、24 h吸水性和吸水厚度膨胀率的影响。结果表明:1)水抽提处理有助于提高思茅松材的可浸渍性,质量增加率可以提高11.35%,而且剖面密度分布存在显著差异;2)浸渍可均匀提高木材厚度上的密度,机械压缩促使思茅松材形成了内高外低的密度分布,联合改性材剖面密度的分布特征类似于压缩密实化材,但内外层间的过渡更为平缓;3)糠醇浸渍可以显著降低木材的吸水性和吸湿性,机械压缩对木材吸湿性的影响不明显,但其吸水率稍高,因糠醇树脂的原因,联合改性材的吸湿吸水性均显著下降;4)糠醇浸渍可以显著降低木材的吸水厚度膨胀率,对压缩密实化材具有较好的定型作用,联合改性材的24 h吸水厚度膨胀率为3.3%,接近于对照材的4.1%,而压缩材为24.7%,糠醇浸渍材只有0.4%。同时,水溶液的酸碱性对木材的吸水行为也有影响。综上,糠醇化与压缩密实化的联合改性非常有潜力用于速生低密度松木材的增值加工,而热水抽提处理可以作为提高松木糠醇浸渍的预处理手段。

Pinus kesiya var.langbianensis,commonly known as Simao pine,is a popular softwood species in Yunnan Province of Southwest China.As a fast-growth and low-density species,Simao pine wood is mainly used to manufacture plywood or low-grade timber with low added value.Densification is a well-known method to improve the properties and widen the use of low-density wood from planted forests.In order to evaluate the effects of densification on fast-grown wood,three kinds of methods including furfurylation,mechanical compression,and their combination were used to investigate the effect of water-extraction on the impregnability of the Simao pine wood.Vertical density profile(VDP),hygroscopicity,water absorption and thickness swelling rate(TSR)after water uptake of the treated wood were compared with those of the untreated wood.The 11.35%increase of weight percent gain and the VDP of the furfurylated wood showed that the impregnability increased significantly after the extraction in water at(75±2)℃for 6 h.The density increased uniformly across the thickness after furfurylation,while the mechanical compression increased the density of the outer zone more significantly.However,the VDP of the wood treated by the combined modification was similar to that of the mechanically compressed wood,although it varied less from the outer zone to the inner zone.The hygroscopicity and water absorption decreased significantly after furfurylation or combined modification,while the hygroscopicity decreased slightly and the water absorption increased considerably after mechanical compression.Furfurylation reults showed a significant effect on the set fixation of the densified wood.The TSR of the mechanically compressed wood was 24.7%compared with 4.1%of the untreated wood,while those of the furfurylated wood and the combinedly modified wood were only 0.4%and 3.3%,respectively.It is confirmed that the pH value of the aqueous solution affected the water sorption performance of the densified wood.Furfurylation combined with mechanical compression has the potential to add the value fast-grown and low-density pine wood products,while warm water extraction can be used as the pretreatment to benefit the impregnation of furfuryl alcohol in wood.