脲醛树脂改性木材的研究

文中介绍了将缓冲式脲甲醛溶液浸注到木材人部后聚合而形成固化脲醛树脂的木材改进性方法。通过实验，研究分析了处理材抵抗干燥收缩、吸湿膨胀和吸水膨胀的效果。结果表明，脲醛树脂改性处理可显著提高木材干燥、吸湿和吸水时的尺寸稳定性，并对木材有明显的增硬作用。     

纳米复合涂层用于竹制品表面的抑菌防霉效果

为考察复合纳米涂层的抗菌防霉作用,以纳米TiO2及纳米ZnO为原料,制备不同配方的复合涂层,通过电子显微镜观察复合材料的微观形态,以纸片法考察涂料的抑菌效果,以培养皿法测试涂料的防霉效果.结果显示,本复合涂层有较强的抑菌防霉效果,其中10%纳米ZnO的抑菌效果最强,纳米TiO2和纳米ZnO混合物的防霉效果最强.实验证实,纳米TiO2及纳米ZnO的复配处方有抑菌防霉作用,有望应用于竹制产品的表面抑菌及防霉.     

Environment-friendly short-term protection of palm wood against mould and rot fungi

Felled palm trunks are susceptible to fungi as long as their moisture content is above fibre saturation. During this period, palm wood has to be protected against mould and rot fungi. The study was aimed at testing environment-friendly organic acids for their protecting efficiency. Small samples of date palm (Phoenix dactylifera) and oil palm (Elaeis guineensis) wood were treated with weak organic acids and subsequently infected by moulds and wood-decay fungi. Short dipping of the samples in solutions of 5% acetic acid and propionic acid, respectively, protected all samples for two months from colonization by Aspergillus niger, Penicillium sp., Cladosporium sp. and by a natural infection. Boric acid (4%) used in practice for protection was ineffective. Decay tests with the white-rot fungus Pleurotus ostreatus, the brown-rot species Coniophora puteana and the soft-rot fungus Chaetomium globosum showed that both acids prevented most samples from fungal colonization for three weeks and reduced the decay considerably during two months.     

Modelling elastic and shrinkage properties of wood based on cell structure

Summary In a previous article of the authors a model was developed for estimating elastic and shrinkage properties of a softwood cell-wall. In the present article this model is enlarged to simulate the elastic properties of defect-free softwoods. The wood model consists of earlywood, latewood and ray cells, each of which have a different cell-wall structure. In the model the ratio of earlywood to latewood is defined by a given wood density. The calculated elastic properties are in good agreement with test results.     

植物精油对木材霉变菌的抑菌效力研究

【目的】植物精油是一类安全环保且具有抑菌特性的天然产物,在木材霉变防治领域的应用潜力很大。开展植物精油对我国常见木材霉菌及变色菌的综合抑菌效力的研究,可为天然环保型木材霉变防治剂的开发提供重要依据。【方法】配制经植物精油修正的马铃薯葡萄糖琼脂培养基,通过评价霉变菌在培养基中的生长状况,对比分析19种植物精油对6种木材霉变菌的抑菌效力。【结果】在体积分数为0.05%的条件下,19种植物精油对黑曲霉Aspergillus niger、桔青霉Penicillam citrinum、绿色木霉Trichoderma viride、可可球二孢Botryodiplodia theobromae、串珠镰刀菌Fusarium moniliforme和链格孢霉Alternaria alternata的抑菌效力分别为0~100%、0~100%、0~100%、0~100%、11%~100%和20%~100%。聚类分析表明,肉桂、丁香花和百里香精油的综合抑菌效力最高,在体积分数0.05%的条件下对6种霉变菌的抑菌效力均达到100%,而尤加利、甜橙和松树精油的综合抑菌效力最低。相关分析表明,植物精油对6种霉变菌的抑菌效力之间均表现出显著相关性(P=0.01),其Pearson相关系数为0.777~0.959。【结论】不同植物精油的抑菌效力之间表现出较大差异,肉桂、丁香花和百里香精油是可以用于木材霉变防治的较优品种。     

DETERMINE ON INITIAL DIMENSIONAL STABILITY OF CHEMICAL MODIFIED WOOD

Strain development along radial direction was continuously determined by D—200Linear Variable Differential Transformers(L.V.D.T).When a wood specimen was put into waterand begin to swell from absolute dry moisture content to the maximum.Experiment results showthat the differences of swelling with soaking time between untreated and treated wood specimens dueto uptaking water.It would also give an indication to the effectiveness of various chemicals on thedimensional stability of modified wood.ASE of modified wood samples with SA-EP,EP and SA were found to be better than MA-AGE.SA-EP had got the best effetiveness on dimensional stabili-ty in reducing the swelling.     

Production and markets of modified wood in Russia

Understanding the state of market for modified wood as well as the forces that affect its future development will be essential for those seeking to enter the Russian market. Information on modified wood from websites of companies, research and development organisations, woodworking-oriented magazines and forums, and official Russian statistics were explored, and finally verified by personal contacts with experts. A number of modification methods have been either researched, developed or pre-commercialised during the past 15 years, but only few of them have been adopted by users. Mostly, the modification methods have been copied, further developed and commercialised from variations of thermal modification originally introduced in Western Europe. Modified wood products are still considered premium goods among Russian consumers. Political initiatives aim at increasing the share of wood in construction and renovation but also at import minimisation, which reduces the penetration of foreign producers into the markets. There are approximately 20 producers of thermally modified timber (TMT) with an overall annual capacity of 60,000–65,000 m³. The current annual market for TMT is estimated to be approximately €35–40 million. In contrast to the European mainstream end uses of TMT, there is also a market for massive and glued thermally modified logs in Russia.     

A mathematical model of mould growth on wooden material

Summary A mathematical model for the simulation of mould fungi growth on wooden material is presented, based on previous regression models for mould growth on sapwood of pine and spruce. Quantification of mould growth in the model is based on the mould index used in the experiments for visual inspection. The model consists of differential equations describing the growth rate of the mould index in different fluctuating conditions including the effect of exposure time, temperature, relative humidity and dry periods. Temperature and humidity conditions favourable for mould growth are presented as a mathematical model. The mould index has an upper limit which depends on temperature and relative humidity. This limiting value can also be interpreted as the critical relative humidity needed for mould growth depending also on the mould growth itself. The model enables to calculate the development of mould growth on the surface of small wooden samples exposed to arbitrary fluctuating temperature and humidity conditions including dry periods. The numerical values of the parameters included in the model are fitted for pine and spruce sapwood, but the functional form of the model can be reasoned to be valid also for other wood-based materials. Received 18 May 1997     

Modelling wood formation and structure: power and limits of a morphogenetic gradient in controlling xylem cell proliferation and growth

Key message

The emergence of the characteristic tree-ring pattern during xylogenesis is commonly thought to be controlled by a gradient of morphogen (auxin, TDIF peptide...). We show that this hypothesis accounts for several developmental aspects of wood formation, but not for the final anatomical structure.

Context

Wood formation is a dynamic cellular process displaying three generic features: (i) meristematic cell proliferation is restricted to the small cambial zone, preventing exponential xylem radial growth along the growing season; (ii) developmental processes result in a stable zonation of the developing xylem; (iii) the resulting mature wood cells form the typical tree-ring structure made of early and late wood with a gradient of cell sizes, an important trait for wood functioning in trees and for lumber quality. The mechanisms producing these spatial-temporal patterns remain largely unknown. According to the often-cited morphogenetic-gradient hypothesis, a graded concentration profile of a signalling molecule (e.g. auxin, TDIF) controls xylogenesis by providing positional information to differentiating cells.

Aims

We assessed the predictions of the morphogenetic-gradient theory.

Methods

We developed a computational model of wood formation implementing hypotheses on how a morphogen flows through the developing xylem and controls cell division and growth and we tested it against data produced by studies monitoring wood formation in conifers.

Results

We demonstrated that a morphogenetic gradient could indeed control xylem radial growth and wood-forming tissue zonation. However, it failed to explain the pattern of final cell sizes observed in tree-rings. We discussed the features that candidate additional regulatory mechanisms should meet.

     

HTST hydrolysis of wood: Modelling of the kinetics and projections on reactor configuration

Summary We present experimental data on hydrolysis of wood in high temperature short residence time (HTST) and low acid concentration conditions. Effects of temperature, acid concentration, particle size and liquid/solid ratio are discussed. A kinetic model is proposed which accounts for effects of temperature and acid concentration. This kinetic model is used to predict performance of a twin-screw extruder as a hydrolyser which consists of ideal mixed flow or plug flow reactor units in series.Symbols A Acid concentration in liquid phase - A Acid concentration in solid phase - A₀ Initial mass of sulphuric acid, g - C Cellulose content of solid phase, % - d Diameter of wood particles, m - E₁ Activation energy of cellulose hydrolysis, cal. mol^-1 - E₂ Activation energy of glucose degradation, cal. mol^-1 - F Objective function, refers to Eq. (5) - G Glucose yield - G_e Glucose yield at equilibrium - G_{i, exp} Experimental glucose yield (Eq. (5)) - G_{i, th} Calculated glucose yield (Eq. (5)) - G_max Maximum glucose yield - k^* Parameter defined by Eq. (9) - k₁ Rate constant of cellulose hydrolysis, s^-1 - k₂ Rate constant of glucose degradation, s^-1 - k ₁ ^* Apparent rate constant of cellulose hydrolysis, s^-1 - k ₂ ^* Apparent rate constant of glucose degradation, s^-1 - k₁₀ Pre-exponential factor of constant k₁, s^-1 - k₂₀ Pre-exponential factor of constant k₂, s^-1 - K Parameter defined in Table 3 - m Constant - m_g Mass of glucose produced, g - M₀ Initial mass of wood, g - M Mass of saturated steam delivered, g - M Mass of saturated steam delivered after 120 s of reaction time, g - m₀ Initial mass of water, g - n Constant - N Number of reactor units - q_i Volume flow rate in reactor units, m³ · s^-1 - r_g Conversion rate of glucose, s^-1 - R Ideal gas constant, 1.987 cal · mol^-1 K^-1 - t Reaction time, s - T Temperature, K - V_i Volume of reactor units, m³ - W Water content of wood sample, % - X, X Parameters defined in Table 3 - Y, Z Parameters defined in Table 3 - Constant defined in Eq. (4), s^-1 - v Number of experimental points (Eq. (5)) - _i Residence time in plug flow unit, s - _i Residence time in mixed flow unit, s     

The effects of several commercial wood coatings on the deterioration of biological pigments in wood exposed to UV light

This research subjected four wood species pigmented with the red stain of Scytalidium cuboideum and Acer negundo wood pigmented with the tree’s naturally occurring red stain to natural and artificial UV light. Several commercially available coatings were applied to determine the effect of coating on the degradation of both red stains over time. The red stain of Acer negundo was found to be significantly less stable in UV light than the red pigment produced by S. cuboideum on any wood species, even A. negundo. None of the tested coatings significantly increased the pigment retention time of the red stain produced by A. negundo. The red stain of S. cuboideum was significantly affected by both coating and wood species; Populus tremuloides retained pigment significantly longer than Fagus grandifolia or Acer saccharum, and the Danish oil coating retained pigment significantly longer than the lacquer, water-based polyurethane with UV inhibitors, or the uncoated samples. Overall, lacquer increased the degradation rate of the red pigment produced by S. cuboideum, with the most pronounced increase occurring on F. grandifolia. These results indicate that the red-pigmented wood produced by A. negundo may not be appropriate for applications involving UV exposure, regardless of coating utilized. However, P. tremuloides wood pigmented with S. cuboideum may be appropriate for such applications, especially if Danish oil is applied as a coating.     

Effect of growth rate and abnormal growth on wood substance and cell wall density

Summary Fast or abnormal (tumor) growth does not substantially affect wood substance and cell wall density. Consequently, void volume of dry cell walls is also not substantially affected.     

Sorption of copper and lead by citric acid modified wood

The sorption characteristics of citric acid modified wood to remove copper and lead ions from aqueous solution under batch conditions have been investigated. Sorption was pH dependent with increasing uptake at higher pH values. The kinetics of sorption for both ions was rapid with 90% sorption taking place within the first 60 min regardless of its initial concentration. Sorption can be explained by a second-order kinetics model from which the rate constant, the equilibrium sorption capacity and the initial rate were calculated. From these parameters, the predictive models for Cu and Pb sorbed (q _t) in time t and at an initial concentration (C _o) are given by q _t=C _o t[0.31C _o–2.29+(0.04C _o+5.19)t] and q _t=C _o t/[0.06C _o–6.59+(0.01C _o+4.48)t] for Cu and Pb, respectively. Using these models the predicted and experimental uptakes of Cu and Pb were compared and discussed. Maximum sorption capacities of modified wood under present experimental conditions were 23.70 and 82.64 mg/g for Cu and Pb, respectively. However, for untreated wood the corresponding values were 2.56 and 7.71 mg/g indicating a tenfold increase in sorption upon citric acid modification. Ethylene diamine tetraacetic acid and nitrilotriacetic acid complexed with both ions render sorption less favorably. However, salicylic acid had little influence. In a binary system, Pb ions were more favorably sorbed than Cu ions which could be due to the larger ionic radius of the former ions.     

Classification of thermally modified wood by FT-NIR spectroscopy and SIMCA

Quality assessment of thermally modified wood has evolved as one of the major fields in the research on thermal modification of wood. This study investigates NIR spectroscopy in combination with the pattern recognition method of soft independent modeling of class analogies (SIMCA). Focus is put on identifying different treatment intensities of thermally modified samples of beech, ash, and Norway spruce. The results indicate that SIMCA classification based on NIR spectroscopy could be used for quality control of thermally modified wood. The method might be applicable for producers (pre-delivery checks) and customers (reception control). However, transfer from laboratory to industrial conditions needs further investigation.     

Douglas-fir wood quality studies part I: Effects of age and stimulated growth on wood density and anatomy

Douglas-fir trees about 21 years old and growing on a poor site were thinned and fertilized causing accelerated growth. The characteristics of the wood across the 30-year age span were studied for 7 trees from the treated plot. Four trees of nearly uniform ring growth were also studied for some characteristics. Radial and tangential tracheid diameters, tracheid length and percent latewood were correlated quite well with log of age, coefficients ranged from 0.76 to 0.88 on pooled data. All tracheid dimensions when correlated with log of age gave high coefficients on a within-tree basis. The strongest relationship in all age-related factors was between 0 and 12 to 14 years. Specific gravity increased with age in all trees to about 16 to 18 years, then leveled off.Fertilization and thinning caused immediate production of lower density wood with somewhat lower percent latewood, a slight decrease in tracheid diameter tangentially but slightly greater radially, and a small decrease in tracheid length. The effects were mainly in the first 3 to 4 years after treatment, then there was recovery to normal wood density and cell dimensions. Wood from the trees of uniform growth showed no significant change over the same time period in percent latewood, specific gravity, and tracheid length.The research was financed by funds from State of Washington Initiative 171, Institute of Forest Products and the College of Forest Resources, University of Washington, Seattle.     

PF树脂改性速生杨木浸注性分布规律研究

采用低分子量酚醛树脂对速生杨木进行增强浸注,改性后统计分析改性材的质量增加率情况,以了解浸注性的分布规律。结果表明:速生杨木改性后质量增加率的数据整齐,集中在平均数附近。经过假设并检验后得出,速生杨木改性材质量增加率服从均值为41.87%、总体标准差σ为0.069 0的正态分布;并由此计算出速生杨木改性后,质量增加率落在参考区间为35%～55%的概率值。     

栽培基质对风信子生长与开花的影响

研究不同基质配比对3个品种风信子生长与开花的影响,结果表明:泥炭与园土等量配比是最佳栽培基质。在此基质中,风信子出苗更早、更整齐、植株更高;叶片更长、更宽、叶面积更大;花的观赏特性也得到提高;风信子叶片叶绿素含量和可溶性糖含量的积累也得到增加;风信子现蕾时间提前;种球的质量也得到较好保持。该基质提高了风信子的综合观赏价值,可作为其通用栽培基质。