阔叶材CLT的研究进展

交叉层积材(Cross-Laminated Timber,CLT)作为一种新型的工程木制品,于20世纪90年代初在欧洲开发。CLT是由相邻层锯材垂直正交组坯形成的多层结构型工程木质复合材料。CLT材料具有施工速度快、施工方便、抗震性能好、固碳性能好、生态环保等优点。传统的CLT几乎完全由针叶材制成,包括樟子松、挪威云杉、白杉、欧洲落叶松和花旗松等。随着一些地区森林的构成发生变化,以及希望低价值阔叶材实现高附加值的应用,人们正越来越关注使用阔叶材来制造CLT。本文通过回顾阔叶材CLT的相关文献,探讨了制造阔叶材CLT的技术可行性,以期对我国阔叶材CLT的研究和应用提供一些借鉴和参考。     

常见四种阔叶材纤维形态和化学成分的研究

对我国常见四种速生阔叶材的纤维形态和化学成分进行了测定及分析,旨在为其用于制浆造纸提供必要的基础数据。研究结果表明,尾巨桉和杨木纤维质量较好,均为优质的制浆造纸原料,桑树枝和光叶楮杆芯纤维质量较差。     

无损检测阔叶材纤维长度的近红外光谱法

比较了近红外光谱分析技术测量木材纤维长度与传统的测量方法的优缺点并详细介绍了应用近红外光谱分析技术测量木材纤维长度,其中包括木材样品选择及制备、近红外光谱采集及纤维长度真值测量、多变量数据分析与模型建立的实验方法与操作步骤.实验表明近红外光谱分析技术可以快速准确地预测阔叶材纤维长度.     

基于VB的中国主要阔叶材信息化研究

采用Access数据管理和Visual Basic开发技术,对中国主要阁叶材的树种名称、主要产地、用途、构造与识别、物理性质、加工性质、木材宏观微观图像等多方面数据进行了信息整理和程序设计,实现了中国主要阔叶材按木材名称、木材特征和木材用途等多方向、多关键字的计算机查询检索.     

阔叶材原料特性与制浆之间关系的探讨

选择８种有代表性的阔叶材种进行制浆和强度试验。对试验结果进行回归分析，建立制浆得率和化学组成、裂断长和纤维形态有关因子的回归模型。分析结果表明建立预测回归模型是可行的。     

混合阔叶材高得率浆配抄文化用纸白度稳定性的研究

在传统非涂布不含机械浆的高级文化纸的生产过程中,添加混合阔叶材高得率浆取代阔叶木漂白硫酸盐浆明显地降低纸张的白度稳定性.讨论了在浆料中添加沉淀碳酸钙(PCC)填料和荧光增白剂(OBA)在纸张表面施胶中的应用.结果表明:高得率浆的使用导致纸页明显的光诱导返黄,但对纸页的热诱导返黄没有明显影响.分别使用OBA和PCC都可以起到抑制返黄、改善白度的作用.在加入PCC填料情况下,使用OBA-HYP和把OBA应用于表面施胶均能消除由于HYP取代对纸张白度稳定性的影响,且能够产生积极的协同作用.在同时使用45%PCC和每面0.18g/m2OBA表面施胶用量的情况下,几乎可以达到100%BKP生产的纸张的白度.     

羊毛织物的蛋白酶改性对墨滴铺展及颜色性能的影响

为探讨羊毛织物经蛋白酶改性后表面性能变化对喷墨印花中常用活性染料墨滴铺展和颜色性能影响,使用蛋白酶Savinase 16L处理羊毛织物,观察了墨滴在织物表面变化。借助接触角测量仪、冷场发射扫描电子显微镜和X射线光电子能谱对未处理和蛋白酶处理后织物的润湿性能、物理形貌和化学组成进行分析。结果表明:蛋白酶改性后织物表面鳞片被刻蚀,纤维结构变得疏松,润湿性能提高;相对于未改性羊毛,改性后羊毛表面不同颜色活性染料墨滴铺展时间和铺展面积均明显减小,以浅红色墨滴为例,铺展时间和铺展面积分别减小了54.8%和19.1%;此外,蛋白酶处理导致纤维表面蛋白质显现程度增加,使得更多的活性染料分子同纤维表面氨基基团共价结合,织物表观得色深度和色彩鲜艳度提高。     

从北方混合阔叶材制浆前绿液中提取半纤维素的酸预水解

林业生物质对于未来生物燃料和生物制品来说是很重要的资源。从化学制浆前经过碱处理（绿液处理）提取的半纤维素可以生产pH中性值的半纤维素低聚衍生物。经过一段时间后,这种低聚物可水解为可发酵的单糖。把北方阔叶材木片和含有3%浓度的氧化钠绿液混合后在蒸煮温度为160℃的回转式蒸煮器内蒸煮110 min。蒸煮液中绿液质量约为去皮木材质量的11.4%,这就导致了低聚半纤维素糖类的稀释。半纤维素低聚物水解之后经过蒸发使其浓度增加。水解条件为：温度为（100~160）℃,硫酸浓度为2%~6%,保温时间为2~258 min。在这种水解条件下,蒸发过程中当质量浓度为10.7 g/L时可以得到发酵性糖,最高可获得90.7%。预水解的结果表明：水解温度和时间是非常重要的影响因素。对提取物的影响因素有反应时间、温度和酸浓度,实验结果表明：合理的控制这三个影响因素可以有效地控制糖的总产量。     

Comparison between heat treated sapwood and heartwood from Pinus pinaster

Sapwood and heartwood samples of Pinus pinaster were treated in an oven at 190 and 200 °C for 2–6 h. Dimensional stability, measured as Anti Shrinking Efficiency (ASE) between 0 and 65 % relative humidity, durability against fungi, mechanical resistance (MOE and MOR), hardness and chemical composition were determined for treated and untreated sapwood and heartwood. Radial ASE reached 52 % for sapwood and 50 % for heartwood, while tangential ASE reached 50 and 40 %, respectively. MOE increased slightly at the beginning of the treatment, decreasing afterwards. No significant differences were found between sapwood and heartwood. MOR decreased by 50 and 30 % for sapwood and heartwood, respectively. A significant increase in durability against Rhodonia placenta was found for both heartwood and sapwood at the higher temperature (200 °C), but at the lower temperature (190 °C) only heartwood showed good results.     

Measurement, modelling and prediction of equilibrium moisture content in Pinus radiata heartwood and sapwood

Pinus radiata heartwood and sapwood specimens was measured and modelled statistically under conditions of adsorption and desorption over a range of values of temperature and humidity typically encountered in in-service use. Two mathematical models (Day and Nelson 1965; W. Simpson 1971) were fitted to the data using non-linear least squares. To obtain statistically valid estimates and predictions, a logarithmic transformation was needed. Re-parameterisations of the models are given which reduce the correlations between parameters to reasonable levels, reduce the number of parameters needed to accommodate the different wood types and sorption conditions, and make it possible to fit the model to limited size datasets. Predictions from the model are estimated to have a relative error of 0.6% (about 10 times more accurate than the raw data) of the predicted value for wood with properties similar to the samples tested. The results are compared to the USDA Wood handbook (USDA Forest Service 1974) values for sitka spruce and some differences noted.

---

P. radiata wurde gemessen und statistisch modelliert unter den Bedingungen der Adsorption und Desorption in einem Temperatur- und Feuchtebereich, wie sie typischerweise im Gebrauch vorkommen. Zwei mathematische Modelle wurden an die Daten angepasst nach einer nicht-linearen Methode der kleinsten Fehlerquadrate. Um statistisch gesicherte Sch?tzwerte und Vorhersagen zu erhalten war eine logarithmische Transformation n?tig. Durch die neuen Parameter des Modell wurde folgendes erreicht: Reduzierung der Korrelationen zwischen den Parametern auf ein vernünftiges Ma?, Reduzierung der Anzahl der Parameter, die n?tig sind, um das Modell an die verschiedenen Holztypen und Sorptionsbedingungen anzupassen, Anpassung des Modells auch bei vorliegen von begrenzten Datens?tzen. Der relative Fehler der Vorhersagen des Modells wird auf ca 0,6% gesch?tzt (etwa zehnfach sicherer als die Rohdaten), wenn das Modell auf Holz mit ?hnlichen Eigenschaften wie die Proben angewendet wird. Die Ergebnisse werden verglichen mit Listen des USDA-Handbuchs für Sitkafichte. Dabei ergaben sich einige Unterschiede.

     

Measurement, modelling and prediction of equilibrium moisture content in Pinus radiata heartwood and sapwood

heartwood and sapwood specimens was measured and modelled statistically under conditions of adsorption and desorption over a range of values of temperature and humidity typically encountered in in-service use. Two mathematical models (Day and Nelson 1965; W. Simpson 1971) were fitted to the data using non-linear least squares. To obtain statistically valid estimates and predictions, a logarithmic transformation was needed. Re-parameterisations of the models are given which reduce the correlations between parameters to reasonable levels, reduce the number of parameters needed to accommodate the different wood types and sorption conditions, and make it possible to fit the model to limited size datasets. Predictions from the model are estimated to have a relative error of 0.6% (about 10 times more accurate than the raw data) of the predicted value for wood with properties similar to the samples tested. The results are compared to the USDA Wood handbook (USDA Forest Service 1974) values for sitka spruce and some differences noted.     

The use of sensor array technology for rapid differentiation of the sapwood and heartwood of Eastern Canadian spruce, fir and pine

The quality of the pulp and paper produced in eastern Canada is affected by the proportions of black spruce (Picea mariana), balsam fir (Abies balsamea) and jack pine (Pinus banksiana) present in the wood chips used. A rapid analytical method capable of differentiating the wood of these three species of conifer is a prerequisite to developing a procedure to determine these proportions. This differentiation was achieved through the use of an electronic nose made up of an array of conductive polymer-carbon black composites-based sensors. The procedure is rapid and involves training and validation of the e-nose using reference wood samples followed by identification of unknown samples. Principal Component Analysis is performed on the smell-prints obtained during the training phase. Complete discrimination of the sapwood and heartwood of the three conifers was achieved. The reference and the unknown samples must be measured under identical conditions.     

Surface roughness in sapwood and heartwood of Blackwood (Acacia melanoxylon R. Br.) machined in 90-0 direction

The resulting surface roughness is studied for Blackwood (Acacia melanoxylon) during peripheral milling of sapwood and heartwood samples. It is known that the surface roughness is sensitive to a change in cutting conditions, tool wear, cutting geometry and direction change, but also when some material parameters vary like the species, moisture content and wood density. The bite or better the mean chip thickness is strongly related to the resulting surface quality as well as to the needed cutting forces, whereas other studies have shown these relationships with regard to changing cutting conditions. The aim of this paper is to evaluate and quantify the resulting surface roughness for Acacia melanoxylon considering a change in the mean chip thickness for both types of wood: sapwood and heartwood, and to evaluate the results considering changes in the rotational speed and the feed speed.     

Plasma treatment and bleaching to remove blue-stain from lodgepole pine sapwood

The hypothesis that a combination of plasma treatment and bleaching will be more effective than bleaching alone at removing stain from blue-stained lodgepole pine sapwood was tested. Blue-stained wood was pre-treated with glow-discharge plasma in vacuo for different times, immersed in a concentrated aqueous solution of sodium hypochlorite for 30 s and air-dried. The colour of dry samples before and after plasma treatment and also after bleaching was measured with a spectrophotometer. Prolonged plasma treatment (without bleaching) removed some blue-stain, but the effect was small. In contrast, the combination of plasma treatment and bleaching removed most of the blue-stain. It was concluded that vacuum plasma pre-treatment and bleaching shows promise as a way of removing blue-stain. Further research should be done to examine whether more practical (atmospheric) plasma pre-treatments can increase the effectiveness of hypochlorite bleach at removing blue-stain.     

Antitermitic activity of extracts from Chamaecyparis obtusa branch heartwood

The antitermitic activity of extracts from the branch heartwood of Chamaecyparis obtusa (hinoki) against Japanese termites (Reticulitermes speratus) was compared with that of the trunk. Samples of branch and trunk heartwood were extracted with n-hexane, ethyl acetate, and methanol successively. n-Hexane extracts of branch and trunk heartwood were strongly antitermitic, and branch heartwood contained greater quantities of active n-hexane extracts than trunk heartwood. Germacra-1-(10), 5-dien-4β-ol, t-cadinol, α-cadinol, hinokiresinol, and hinokinin were separated from the branch extracts and the termiticidal and antifeedant activity of these compounds was tested by no-choice and dual-choice test methods. The sesquiterpenoids, germacra-1-(10), 5-dien-4β-ol, t-cadinol and α-cadinol were strongly termiticidal. The norlignan hinokiresinol and lignan hinokinin had weak termiticidal, and strong antifeedant and repellent activity. High concentrations of germacra-1-(10), 5-dien-4β-ol and hinokiresinol were present in branch heartwood. These compounds protect hinoki branches from termites and other harmful organisms. Hinoki branch heartwood, which is usually unused, is a potential source of active antitermitic compounds.