3种不同处理方法对木材渗透性影响的研究

本文通过对长白鱼鳞云杉和臭冷杉生材分别进行普通气干处理和酒精置换处理以及对其气干材进行水浸处理,研究了这３种不同处理方法对木材气渗透性的影响及其影响机理。研究结果表明,长白鱼鳞云杉边材、心材和臭冷杉心村的生材经普通气干处理后,其气体渗透性较低,分别约为０．１１４、０．０４５和０．１１１ｄａｒｃｙ;长白鱼鳞云杉边材、心材和臭冷杉心材的生材经酒精置换处理后,其气体渗透性分别约为１１．７１３、０．０７４和０．１４４ｄａｒｃｙ,比普通气干处理对照组试样的平均渗透性分别增加约１０１．５倍、６２％和３０％,ｔ检验表明,前者差异非常显著,但后两者差异不显著;已气干１８个月的长白鱼鳞云杉边材、心材和臭冷杉心材经水浸处理后,其平均气体浸透性较处理前分别增加约８５％、４９％、６５．５％,ｔ检验表明差异均显著。长白鱼鳞云杉生材边材经     

汽蒸处理对木材渗透性的影响

试样（２×２×５ｃｍ）在温度１２０℃和１００℃两种饱和水蒸汽条件下分别汽蒸处理８小时，然后置于大气中干燥至含水率为１０％左右时，采用水上升置换气流法进行渗透性测定。汽蒸试样的渗透性分别与其纵向相邻接的未汽蒸、含水率约１０％的对照比较，并进行成对比较分析ｔ检验。试验结果表明，各树种的木材性质不同，汽蒸作用引起木材解剖上、化学上的变化也不同，因而汽蒸处理对木材渗透性的影响各异。红松气干边材、心材经１２０℃和１００℃汽蒸处理后渗透性分别较未汽蒸者提高约６０、９０％和４０、１３０％；长白鱼鳞云杉生材边材经１２０℃汽蒸后和气干心材经１００℃汽蒸后渗透性分别较未汽蒸者约提高３２６和８０％；成对比较分析ｔ检验，汽蒸试样与未汽蒸试样渗透性之间差异可靠性为９０－９９．９％；汽蒸试样渗透性获得提高的原因均系汽蒸后纹孔膜和纹孔塞发生开裂的结果。但汽蒸长白鱼鳞云杉生材心材、气干边材和心材及臭冷杉生材心材、气干边材和心材的渗透性则未获得提高。     

两种难浸注木材的显微和超微构造及其与渗透性的关系

详细介绍了长白鱼鳞云杉、臭冷杉木材的显微和超微构造特征及其对木材渗透性影响,两树种的心材管胞具缘纹孔膜和管胞胞壁各层纤丝中丰富的无定形物质的沉积是心材渗透性差的解剖方面的主要原因。     

纹孔塞位置回弹对改善长白鱼鳞云杉木材渗透性作用初探

本文通过对难浸注的长白鱼鳞云杉气干5年心材进行水浸泡处理,探讨了纹孔塞位置可否回弹以提高木材渗透性的可能性。试验结果表明,气干5年长白鱼鳞云杉心材经水浸泡11周并用有机溶剂置换干燥后,平均气体渗透性增加了110%,但经成对比较试验t检验,以可靠性95%计差异不显著。表明气干5年后心材通过水浸泡处理,平均气体渗透性虽有增加,但偏移的纹孔塞可能并未重新回弹到中央位置使其渗透性获得真正的提高。     

长自鱼鳞云杉木材渗透性及苯-乙醇浸提对其影响的研究

本研究采用水上升置换气流法测定了长白鱼鳞云杉木材渗透性,并利用苯-乙醇对其进行浸提处理,探明浸提物对渗透性的影响及改善其渗透性的可能性。试验结果表明,长白鱼鳞云杉气干心材的气体渗透性为0.02872达西(darcy),属渗透性低、浸注难树种;苯-乙醇浸提对其心材气体渗透性的影响高度显著,浸提后渗透性得到明显改善,渗透性平均增加75%,而且可以增加渗透的均匀性。     

黄花落叶松木材超微结构及其对渗透性的影响

本文详细地介绍了黄花落叶松木材超微结构特征及其对木材渗透性的影响,心材和边材管胞具缘纹孔的超微结构及其在不同部位和不同处理方法中的变化;晚材管胞具缘纹孔超微结构的变化;细胞壁各层次中的微纤丝及其周围的基质和结壳物质等的渗入或沉积性状。同时还针对黄花落叶松木材渗透性差,及一些晚材具缘纹孔少闭塞或不闭塞的原因,从木材的超微结构特点进行了较详细的探讨。     

不同干燥方法对杉木人工林木材浸注性的影响

采用高频真空干燥、常规窑干和高温干燥3种方法对杉木人工林木材的心、边板材进行干燥处理,用毛细管上升法评价干燥后试样的浸注性能,用半薄切片法测定干燥试样具缘纹孔的闭塞率,最后用扫描电子显微镜观察干燥试样微观构造的变化,比较分析3种干燥方法对杉木人工林木材浸注性的影响机理.结果表明:对于杉木边材,经高频真空干燥后试样的浸注性显著高于常规干燥和高温干燥后试样的浸注性,后2种干燥方法对试样浸注性影响的差异并不显著;对于杉木心材,高频真空干燥与高温干燥后试样的浸注性存在显著差异,而高频真空干燥与常规干燥之间、高温干燥与常规干燥之间对试样浸注性的影响差异均不显著;3种干燥方法处理后,杉木边材的浸注性均显著高于心材的浸注性;具缘纹孔的闭塞率较低以及部分具缘纹孔周缘破裂是高频真空干燥后木材浸注性提高的主要原因.     

木材流体可渗性有效毛细管半径和数量的研究

论述了测定木材具有流体可渗性有效毛细管半径和数量的方法和原理，研究了长白鱼鳞云杉、红松和白桦木材具有流体可渗性有效毛细管结构，讨论了它在生产实践中的应用可能性。结果表明，长白鱼云杉和红松木材纵向气体渗透性与平均压力为线性关系，表明流体在这两种针叶材中流动阻力主要来自纹也膜微孔，具有流体可渗性平均有效纹孔膜微孔半径分别为０．６１和０．９８μｍ，单位面积上具有流体可渗性有效纹孔膜微孔数为１２１８和６０     

长白鱼鳞云杉和臭冷杉的木材及其抽出物化学组成的研究

研究长白鱼鳞云杉、臭冷杉的木材及其抽出物化学组成，并分析生材与气干材、心材与边材中各种化学组成变化的规律。同时检测出抽出物中弱酸性物质、中性物质和强酸性物质的含量及弱酸性物质中树脂酸和脂肪酸的组成含量。     

木材可压缩流体渗透中滑流的研究

在气体平均压力倒数为1.4-48atm~(-1)范围内测定了长白鱼鳞云杉和红松木材可压缩流休渗透中滑流效应及影响滑流的因素,论述了木材中流体流动形态和机理。研究表明,两种木材可压缩流体渗透中均产生滑流,但长白鱼鳞云杉中滑流高于红松。前者滑流渗透性与真渗透性百分比、比名义渗透性与真渗透性比、滑流因素分别为69.39％、1.69、0.356atm;后者分别为37.64％、1.376、0.197atm。滑流的大小与木材有效毛细管半径、真渗透性和气体平均压力有高度紧密相关。木材有效毛细管半径愈小,真渗透性愈低,或气体平均压力愈低,则滑流效应愈大。     

杉木冷冻干燥材和气干材液体浸注性的比较研究

A comparative study was conducted on liquid penetration of the freeze-drying and air-drying sapwood and heartwood lumber of plantation Chinese fir （Cunninghamia lanceolata）. The maximum amount of dyeing solution uptake by the capillary rise method was used to evaluate the liquid penetration properties of the treated wood. The pit aspiration ratio was determined by semithin section method. Changes in wood microstructure were investigated using scanning electron microscopy. The results showed that compared with air drying, the freeze drying had a significant effect on liquid penetration of sapwood and heartwood of Chinese fir. The liquid penetration of sapwood is significantly higher than that of the heartwood for both drying treatments. Low pit aspiration ratio and cracks of pits membrane of some bordered pits are the main reasons for increasing liquid penetration after freeze drying treatment.     

Variability of the chemical composition of pit membranes in bordered pits of gymnosperms

Summary The pit membranes of the bordered pits in about one hundred coniferous wood species were investigated in regard to their chemical composition, in particular to the aromatic compounds. In many species pit membranes, even in the sapwood, contain phenolic substances. In heartwood, normally lignification takes place besides the development of other polyphenols. The variability of these compounds, both in sapwood an in heartwood, may be considerable not only between species but also within the same species and even between neighbouring tracheids and pits respectively.We are thankful to Prof. Dr. W. Liese for his support and his frequent discussions.     

Relations Between Permeability and Structure of Wood

The permeability and the structure of heartwood and sapwood of the solvent-exchange dried and the air-dried green-wood of Chinese-fir(Cunninghamia lanceolata(Lamb.)Hook.)and masson pine(Pinus massoniana Lamb.) were measured in order to study the relations between the permeability and the structure.The results showed that the permeability of sapwood of both the air-dried and the solvent-exchange dried wood was higher than that of heartwood,and the permeability of the solvent-exchanged a bigger number of flow path per unit area of the wood perpendicular to the flow direction resulted from a bigger number of unaspirated pits per unit area and a bigger number of effective pit openings per membrane,and on the other hand,a smaller number of tracheid in series connection per unit length parallel to flow direction resulted from a longer tracheid longth and an effective tracheid length for permeability.     

Peroxidase activity, isoenzymes and histological localisation in sapwood and heartwood of Scots pine (Pinus sylvestris L.)

Peroxidase activity and isoenzymes of fresh wood samples of the third shoot of 12-year old trees and from the sapwood, transition zone and heartwood of c. 60-year old stems of Scots pine (Pinus sylvestris L.) were investigated. Wood samples were ground at −30°C, extracted, and the extracts concentrated c. 20-fold for peroxidase activity assays (guaiacol method) and for IEF-PAGE. At least 11 major isoenzymes could be found in the gels. Even the heartwood contained some peroxidase isoenzymes. Isoenzyme patterns of the juvenile wood did not change with the season. However, juvenile wood showed the highest peroxidase activity at the end of the growing season. Peroxidase activity decreased from the outer sapwood towards the heartwood. Thin sections of different wood zones stained for peroxidase revealed activity in ray parenchyma and resin canal epithelial cells. Intensive staining was localised in the bordered pits of vertical and ray tracheids, and in the end walls of ray parenchyma cells.     

Profile of bordered pit aspiration in Cryptomeria japonica using confocal laser scanning microscopy: pit aspiration and heartwood color

Nine trees of Cryptomeria japonica from six elite tree clones with a broad range of heartwood colors were selected. The profiles of pit aspiration percentage (ASP) of earlywood and latewood from pith to bark for green and air-dry conditions were determined to study the relationship between heartwood color and pit aspiration. Confocal laser scanning microscopy (CLSM) observations showed that the ASP of earlywood was low in sapwood and high in heartwood in the green condition. Pit aspiration increased in intermediate wood when compared with sapwood. On the other hand, latewood pits did not aspirate during heartwood formation. Comparing the air-dry condition with the green condition, sapwood pits aspirated during drying in both earlywood and latewood; however, there was no significant difference in pit aspiration of heartwood. There was no significant difference between samples with red and black heartwoods for ASP. The difference in ASP between individual trees was larger than that by heartwood color. The general advantage of CLSM over light microscopy is that serial optical sections along the Z axis can be obtained for any moisture condition, without the need for thin sectioning or embedding.     

Impregnation of radiata pine wood by vacuum treatment II: effect of pre-steaming on wood structure and resin content

Radiata pine sapwood and heartwood were dried using high-temperature, conventional-temperature, and air drying schedules with and without pre-steaming. They were then impregnated by vacuum treatment with double-distilled water, toluidine blue, and fluorescein dye. For sapwood, there were only minor differences in uptake between drying methods and when pre-steaming was used. Using microscopy, the primary flow pathways in sapwood were found to be the resin canal network and ray parenchyma cells, which provided conduction without large resistance. In heartwood, uptake was strongly influenced by pre-steaming the green lumber. After pre-steaming heart-wood, there was an increase in uptake from all surfaces but especially from the radial surfaces. Lower extractive contents, disruption of epithelial and ray parenchyma cells, and alteration of the condition of bordered pits were also associated with pre-steaming. It was therefore possible to classify flow paths in radiata pine heartwood five ways, according to uptake values and wood anatomical features.This research was presented in part at the 48th annual meeting of the Japan Wood Research Society, Shizuoka, April 1998.     

Effect of different drying methods on liquid penetration of Chinese fir plantation wood

Chinese fir plantation sapwood and heartwood boards were treated by three drying methods: radio frequency-vacuum drying (RFVD), conventional kiln drying (KD) and high temperature drying (HTD). The maximum amount of dyeing solution uptake by the capillary rising method was used to evaluate the liquid penetration of the treated wood. The pit aspiration ratio was determined by a semithin section method. Changes in wood microstructure were investigated using scanning electron microscopy. The results show that liquid penetration of Chinese fir sapwood after RFVD is significantly higher than that after KD and HTD. Liquid penetration of Chinese fir heartwood after RFVD is higher than that after HTD. Liquid penetration of Chinese fir sapwood is significantly higher than that of heartwood after three drying treatments. Low pit aspiration ratio and cracks of some bordered pits are the main reasons for the increase in liquid penetration after RFVD treatment. __________ Translated from Scientia Silvae Sinicae, 2006, 42(10): 85–90 [译自: 林业科学]     

Unexpected experimental results for capillary suction in wood: Analysis on the fibre level

Abstract

A series of simple experiments on capillary water uptake in rectangular sticks of Scots Pine (Pinus sylvestris L.) gave some unexpected results. Sticks of sapwood and heartwood with lengths of 100, 200 and 300 mm, with the four long sides sealed, were used in the experiments. The samples were allowed to suck water, one group for 1000 h and one group for 1900 h. After exposure, as anticipated, the heartwood samples had a moisture content (MC) distribution with high values at the bottom and steeply decreasing values towards the top. The sapwood samples, in contrast, had moisture distributions with high MC at the bottom and the top, and low MC in the middle. Additional experiments to study flow paths and timescales of the process were performed using dyed water. A Fickian approach is discussed in some detail. It is clear that the process represented by the experimental results cannot be explained within a Fickian framework. The analysis has to be done on the fibre level, where an explanation is proposed. The influence from bordered pits is of significant importance and their resistance dominates the timescales. A key factor in the proposed explanation is the high lateral capillary conductivity within the saw-damaged top surface. However, some questions remain unanswered.