The hydrophobic and water-repellent properties of wattle bark extractives

Summary Based on the fact that bark is an almost perfect water barrier and assuming that bark is impregnated with materials which aid in rendering it impermeable to water, the hydrophobic and water-repellent properties of several bark extractives were investigated. Products obtained after extraction with polar and non-polar solvents showed widely different properties. Some were extremely hydrophobic and water-repellent with a water-solid-air contact angle higher than 100°. These were the products obtained from extraction with benzene and mineral turpentine. Alcohol and acetone extractives had contact angles as low as 23° but coatings from some of these materials nevertheless had a high efficiency as water barriers. The efficiency of the various extractives as water repellents or water barriers was determined by coating wood with 10 per cent solutions of the extractives in different solvents and determining the extent to which water could be prevented from being absorbed and causing swelling of the wood and thereby reduce the dimensional changes of the wood. The extractives obtained with nonpolar solvents were extremely efficient as true water repellents while the polar aleohol extracts were far better than could be expected from their almost hydrophilic properties. Nature has therefore provided for hydrophilic film-formers combined with hydrophobic materials which act as a double line of defence against water absorption. The hydrophilic extractives, in addition, act as a bridging agent between the strongly hydrophobic extractives and the hydrophilic cell wall material.Since some of the extractives from wattle bark have excellent hydrophobic properties, and since this bark is available in large quantities as a waste product after tannins have been extracted, the utilization of certain wattle bark extractives as water repellents could be economically attractive.     

长白落叶松提取物对木材防腐作用的研究

以长白落叶松心材、边材及树皮为原料,分别用乙醚、氯仿、丙酮、甲醇和水5种溶剂对其进行提取,采用滤纸片法研究了不同溶剂提取物分别对白腐菌和褐腐菌的抑菌性能,发现心材的甲醇提取物和丙酮提取物对白腐菌有较好的抑制效果,树皮的水提取物对2种菌都有较好的抑制效果.并研究了这两种提取物在室内对木材的防腐性能,借助扫描电子显微镜(SEM)照片观察了木材腐朽后菌丝生长的情况,与常用木材防腐剂酸性铬酸铜(ACC)进行了对比,结果显示:心材的甲醇提取物对白腐菌的抑制效果较好;而树皮的水提取物对褐腐菌抑制效果较好.     

Swelling of acetylated wood I. Swelling in organic liquids

To investigate the affinity of acetylated wood for organic liquids, acetylated yezo spruce wood specimens were soaked in various liquids, and their swellings were compared to those of untreated specimens. The acetylated wood was rapidly and remarkably swollen in liquids having low hydrogen bonding power such as benzene and toluene in which the untreated wood was swollen only slightly or very slowly. On the other hand, the swollen volume of wood in water, ethylene glycol, and alcohols remained unchanged or slightly decreased after the acetylation. The effect of acetylation was greater in liquids having smaller solubility parameters. The easier penetration of aprotic organic liquids into the acetylated wood was considered to be due to the reduction of polarity and the scission of hydrogen bonds in the amorphous wood constituents where the hydrophilic hydroxyl groups were substituted by hydrophobic acetyl groups.     

Extractives of muirapiranga (<Emphasis Type="Italic">Brosimun</Emphasis> sp.) and its effects on the vibrational properties of wood

The potential of muirapiranga (Brosimun sp.) as a substitute material for violin bows was estimated in terms of vibrational properties, and the influence of extractives on the vibrational properties was examined. The loss tangent of muirapiranga was somewhat higher and the specific dynamic Young’s modulus was rather lower than the respective values for pernambuco, which is regarded as the best material for violin bows. Therefore, muirapiranga is a poorer bow material in terms of vibrational properties. Impregnation of crude extractives from muirapiranga decreased the loss tangent of other wood specimens. The main compounds of the extractives were identified as xanthyletin and luvangetin. Impregnations of isolated xanthyletin and commercially available methoxsalen, which was tested as an analogue of luvangetin, markedly decreased the loss tangent of other wood specimens. Methoxsalen and xanthyletin differ from conventional loss tangent-decreasing substances, namely protosappanin B and hematoxylin, in terms of water insolubility and the absence of hydroxyl groups. From the similarity in molecular characteristics of loss tangent-decreasing substances found so far, restriction of molecular motion due to an impregnated substance in the wood matrix is suggested as one loss tangent-decreasing mechanism.     

Improvement of capillary penetration of liquids into wood by use of supersonic waves

Summary The effect of supersonic waves on the capillary penetration of liquids into wood was found to be positive or negative depending upon a number of factors. The penetration of non-polar compounds like paraffins and aromatic hydrocarbons was not improved by using supersonic waves. The effect of supersonic waves, however, became positive by introducing one or several hydrophilic groups into straight hydrocarbon chains.Diluting hydrocarbons containing hydrophilic groups with non-polar solvents reduced the positive effect of supersonic waves until it became negative below a certain concentration. Polyfunctional alcohols exhibited an optimum effect at certain concentrations when diluted with water. These concentrations correspond to alcohol-water blends of maximum affinity to the surface of wood.Supersonic waves improved the capillary penetration of water when the surface tension was reduced by using surface active agents.In fields were the rapid and thorough impregnation of wood by various liquids is important, supersonic waves can under certain conditions aid this process and be of practical use.     

Hemmung einiger Ektoenzyme von Fomes annosus (Fr.) Cke. durch Holz- und Bastextrakte aus Picea abies (Karst.)

Inhibition of several ectoenzymes of Fomes annosus (Fr.) Cke. by wood and bark extracts from Picea abies (Karst.). Methanol soluble extractives of sapwood, heartwood and reaction zone from Norway spruce as well as acetone soluble extractives of spruce bark were tested at a concentration of 0.05 percent for inhibition of Fomes annosus enzymes cellulase, pectinase     

桉树纸浆材生长、材性指标近交退化和杂种优势分析

以尾叶桉 (EucalyptusurophyllaS .T .Blake)自交F1子代、尾叶桉株间杂交F1子代、尾叶桉自由授粉F1子代和尾×巨桉 (E .urophylla×grandis)种间杂交F1子代林为试材 ,讨论分析了桉树生长、材性指标的近交退化和杂种优势规律性 .结果如下 :①尾叶桉近交退化现象呈现自交子代比自由授粉子代显著 ,生长性状比材质性状显著的规律性 .②尾叶按自交子代树高、胸径和材积具有显著至极显著的近交退化 ;生材含水率、木材基本密度和树皮厚度无近交退化 .③尾叶桉自由授粉子代树高、胸径和材积有一定程度的近交退化 ,但不甚显著 ;生材含水率、木材基本密度和树皮厚度无近交退化 .④尾叶桉与巨桉种间杂交子代的树高、胸径和材积可获得显著的杂种优势 ,但不同杂交组合的杂种优势率大有差别 ;子代的生材含水率、木材基本密度和成熟材纤维长度无杂种优势 ;子代的树皮厚度和 1%NaOH抽提物含量呈显著性降低     

丙烯酸酯/石蜡共混乳液处理材疏水性研究

针对石蜡和丙烯酸(酯)在木材防水改良应用方面的优势和不足,提出了利用丙烯酸酯乳液共混改性石蜡乳液。探究丙烯酸酯乳液对复合乳液成膜性及其对复合乳液处理材疏水性能的影响。考察了复合乳液粒径、离心稳定性、成膜性以及处理材吸水率、表面润湿性和尺寸稳定性等。研究结果表明:1)复合乳液可被用于木材浸渍改性处理,复合乳液平均粒径约180.0 nm。2)相比于石蜡乳液处理,复合乳液中丙烯酸酯乳液可协助石蜡在处理材内部形成有效疏水膜层,提高木材疏水性和尺寸稳定性。     

Physical and mechanical properties required for violin bow materials II: Comparison of the processing properties and durability between pernambuco and substitutable wood species

Pernambuco (Guilandina echinata Spreng. syn Caesalpinia echinata Lam.), which has been used for a material of violin bows, was compared with substitutable wood species from the viewpoint of processing properties and durability. The properties required for bow material are discussed. The shearing strength of pernambuco was higher than that of the other wood species at the same specific gravity. High shearing strength seems to be effective for preventing damage to the head (top part) of the bow. The presence of extractives affects the thermal softening of wood material, but ease of handling and permanent retention of form are not particularly superior for pernambuco, although it does have a high extractives content. A peculiarly low loss tangent (tan S) of pernambuco can probably be attributed to the large amount of extractives, rather than the mean microfibril angle.Part of this report was presented at the 46th Annual Meeting of the Japan Wood Research Society in Kumamoto, April 1996.     

Wood defects during industrial-scale production of thermally modified Norway spruce and Scots pine

This research investigates wood defects, particularly the formation of surface cracks, during the production of thermally modified wood and its exposure to cyclic moisture changes. Boards of Norway spruce and Scots pine originating from different steps within the production of ThermoWood® were collected and wood defects were investigated at macroscopic and microscopic scale. Subsequently, the wood was exposed to capillary wetting cycles to record its sensitivity towards cracking. After the modification process, typical anatomical defects of conventional kiln-drying became more frequent and severe, with the magnitude being to some extent depending on the presence of defects in the raw material. At microscopic scale, damages to ray parenchyma and epithelial cells as well as longitudinal cracks within the cell walls of earlywood tracheids were evident in thermally modified wood. Despite a lower water uptake and higher dimensional stability, thermally modified wood was more sensitive to surface cracking during wetting cycles than unmodified wood, i.e. at the outside face of outer boards (near bark). For limiting surface cracking of thermally modified wood during service life, the use of high-quality raw material, the exposure of the inside face of the boards (near pith) and the application of a surface coating are considered beneficial.     

Influence of heat treatment on antioxidant properties and colour stability of beech and spruce wood and their extractives

Heat treatment of wood in absence of oxygen and under mild conditions allows for obtaining a material with many interesting properties, such as enhanced dimensional stability and increased biological durability. The aim of this work was to study the influence of a thermal treatment on the antioxidant activity of the extractives of two wood species – beech and spruce – by using the DPPH method and quantifying the formation of phenoxyl radicals using ESR as wood and extractives are exposed to light irradiation. The relationship between the kinetics of formation of free radicals in the extracts of heat-treated wood and the antioxidant properties is discussed. Links with colour modification are discussed.     

Genotypic variation in wood properties and growth traits of <Emphasis Type="Italic">Eucalyptus</Emphasis> hybrid clones in southern China

Growth traits, wood properties and bark percentage were assessed for 19 hybrid eucalypt clones at three sites in southern China sampled at age 51 months. Analysis of variance showed that there were significant differences in growth traits and wood properties between clones and sites, and that the clone × site interactions were also significant except for basic density. Coefficients of variation ranged from 8.4 to 27.9% for growth traits, 2.7–11.1% for wood properties and 14.0–23.3% for bark percentage. Repeatability ranged from 0.73 to 0.96 for growth traits, 0.32–0.93 for wood properties and 0.77–0.88 for bark percentage. Strong genotypic correlations between the same traits in clones at pairs of sites indicated that the traits were rather stable across sites. The genotypic correlations between growth traits and basic density ranged from −0.67 to 0.43, and generally favorable negative genotypic correlations between growth traits and bark percentage were also found. The correlations between growth traits and Pilodyn pin penetration were positive, ranging from 0.28 to 0.65 and therefore unfavorable as lower wood density will be associated with higher values of Pilodyn pin penetration and improved growth rate. The correlations between traits assessed using non-destructive field methods and wood property assessment results indicated that Pilodyn and Fakopp microsecond timer tools can be confidently used to indirectly select for fiber width and basic density.     

4种不同类型栓皮栎软木物理力学性能研究

以厚皮深裂、厚皮浅裂、薄皮深裂与薄皮浅裂4种类型栓皮栎(Quercus variabilis)软木为材料,通过测定皮层厚度、密度、含水率、吸湿率、吸水率、硬度、抗压性和压缩回弹性等主要物理力学参数,对软木特性进行比较分析。结果表明,厚皮浅裂型软木的综合性能较优,皮层厚度为0.34 mm;密度为0.26 g/cm^3;含水率为4.91%;吸湿率为3.69%;吸水率为16.24%;硬度为63.42 HA;抗压指数(纵向为3.29 MPa,横向为2.44 MPa);24 h压缩回弹率(纵向为87.50%,横向为87.20%),更适于栓皮栎的培育及深加工利用。     

木材保护剂分散体系及其液体渗透性研究概述

木材保护是节约木材资源、提高木材使用质量的重要手段。为了实现长期、高效的木材保护,通常需要对木材进行整体浸渍处理,即通过木材的多孔结构将包含有效成分的木材保护剂分散体系引入木材内部。随着技术的发展,出现了各种不同类型的木材保护剂分散体系,笔者介绍了其分类以及各类型的定义和基本特性,在此基础上分别对溶液、微乳液、乳浊液、溶胶、悬浊液型木材保护剂分散体系在木材中的液体渗透性方面研究进行了概述。对于水溶型木材保护剂而言,木材构造、木材抽提物及处理药剂的性质是影响其液体渗透性的主要因素;油溶型木材保护剂的液体渗透性在很大程度上取决于其溶剂的性质,轻油溶剂比重油溶剂的渗透性更优;乳浊液的液滴粒径与木材纹孔膜上孔隙尺寸相当,因此其渗透性与液滴粒径、树种密切相关;微乳液比乳浊液更易渗透,甚至可部分进入木材细胞壁;溶胶形成胶体粒子后在木材内的渗透与木材构造、胶体粒子粒径及p H等相关;悬浊液型木材保护剂由于粒径较大,在木材内的渗透性不佳,分布也不均匀。分析了该领域现有研究的不足,提出应系统、深入地开展研究,在此基础上改善分散体系在木材中的液体渗透性,并为木材保护分散体系的开发提供指导。     

Fatty acids triggering coremia formation by Ceratocystis ulmi their occurrence and distribution in elm wood

This paper reports the identification of fatty acids in elm wood and its active extractives triggering coremia formation, their distribution between bark, sapwood and heartwood of elms, and their occurrence in the mycelium of the pathogen.     

Radial patterns of carbon isotopes in the xylem extractives and cellulose of Douglas-fir

Heartwood extractives (nonstructural wood components) are believed to be formed from a combination of compounds present in the adjacent sapwood and materials imported from the phloem. The roles of local compounds and imported material in heartwood formation could have important implications for the wood quality of species having naturally durable wood. Stable isotope composition (delta(13)C) was analyzed to assess radial variation in sapwood extractives, and to estimate the relative importance of adjacent sapwood extractives and imported photosynthate in the formation of heartwood extractives. Cellulose and extractives from the outer 39 annual rings of six Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) trees were isolated and their delta(13)C composition determined. Although the extractives and the cellulose showed different absolute delta(13)C values, the patterns of change over time (as represented by the annual rings) were similar in most cases. Within an annual ring, carbon isotope ratios of extractives were correlated with the cellulose isotope ratio (R2 = 0.33 in sapwood, R2 = 0.34 in heartwood for aqueous acetone-soluble extractives; R2 = 0.41 in sapwood for hot-water-soluble extractives). These data suggest that some sapwood extractives are formed when the wood ring forms, and remain in place until they are converted to heartwood extractives many years later. Sapwood extractives appear to be important sources of materials for the biosynthesis of heartwood extractives in Douglas-fir.     

木材等离子体改性研究进展

综述了木材等离子体改性研究进展, 包括等离子体表面改性技术、木材亲水性和疏水性、木材表面形貌和表面化学组成、木材胶接性、木材阻燃性、竹材等离子体改性。     

Studies on the material resistance and moisture dynamics of Common juniper,English yew,Black cherry,and Rowan

The overall aim of this study was to provide comprehensive durability characteristics of wood species underutilized but frequently occurring in Central and Northern Europe: Common juniper (Juniperus communis L.), Black cherry (Prunus serotina Ehrh.), English yew (Taxus baccata L.), and Rowan (Sorbus aucuparia L.). Decay resistance was tested against white and brown rot causing basidiomycetes and soft rot causing micro-fungi in terrestrial microcosms. Their wetting ability was determined in terms of capillary water uptake at the end-grain, the liquid water uptake during submersion, the water vapor uptake at high humidity, and the water release during drying. All tests were performed with unleached and leached specimens. Durability classes were assigned based on results from the different tests. Juniper and Yew were classified very durable (Durability class DC 1); Black cherry and Rowan were found to be less durable (DC 3–5). Leaching did not affect the durability classification significantly. Durability characteristics were completed with different indicators for the wetting ability of the four wood species. The combined effect of wetting ability and inherent decay resistance was considered for service life modeling based on a resistance model using dose–response relationships between material climate (dose) and fungal decay above ground (response).     

The influence of chemical factors on the selectivity of Pinus resinosa stumps for Fomes annosus

Compounds such as resins or phenols produced by the host in response to wounding or fungal penetration may play an important role as factors of resistance against Fomes annosus. By extracting stem sections, that were kept for different intervals in a closed chamber, with different organic solvents chloroform produced the most inhibitory extractives against F. annosus. This may explain at least partially the decreasing stump selectivity for F. annosus. Three compounds were isolated from the neutral fractions of chloroform extractives from 24 days wounded wood discs which were found to be different from the compounds in normal and 12 days fractions. Spectrophotometric analyses reveal some characteristics of these isolated compounds, whereas their chemical formula and structure need further investigation.     

Wood properties of juvenile and mature heartwood in Robinia pseudoacacia L.

The aim of this study is to characterise the properties of juvenile and mature heartwood of black locust (Robinia pseudoacacia L.). Content, composition and the subcellular distribution of heartwood extractives were studied in 14 old-growth trees from forest sites in Germany and Hungary as well as in 16 younger trees of four clone types. Heartwood extractives (methanol and acetone extraction) were analysed by HPLC-chromatography. UV microspectrophotometry was used to topochemically localise the extractives in the cell walls. The natural durability of the juvenile and mature heartwood was analysed according to the European standard EN 350-1. Growth as well as chemical analyses showed that, based on extractives content, the formation of juvenile wood in black locust is restricted to the first 10–20 years of cambial growth. In mature heartwood, high contents of phenolic compounds and flavonoids were present, localised in high concentrations in the cell walls and cell lumen of axial parenchyma and vessels. In juvenile wood, the content of these extractives is significantly lower. Juvenile wood had a correspondingly lower resistance to decay by Coniophora puteana (brown rot fungus) and Coriolus versicolor (white rot fungus) than mature heartwood.