防腐后处理工艺对竹集成材耐久性的影响

以两种水载铜基防腐剂季铵铜和铜唑对竹集成材进行防腐处理,分析了不同药剂和载药量对竹集成材耐腐性能的影响,以及不同干燥温度对处理材抗流失性能的影响,以筛选适宜的竹集成材防腐后处理工艺,显著提高处理材的耐久性.结果表明,经防腐处理后,竹集成材的耐腐性能大幅度提高,当季铵铜载药量≥2.6 kg/m3或铜唑载药量≥1.3 kg/m3时,竹集成材可以达到强耐腐等级;处理材的铜固着率随着载药量的增加而提高,不同干燥温度对铜的抗流失性能影响不显著.总体上看,防腐后处理工艺能够满足提高竹集成材耐久性能的要求,但其防腐剂的抗流失性能有待提高.     

新防腐剂TWP橡胶木防腐试验

TWP防腐剂对木腐菌的毒性剂量为2.2—3.2kg/m~3,毒杀双钩异翅长蠹初龄幼虫的剂量为1.0kg/m~3,抑制蓝变菌和霉菌的毒性浓度分别为1％及1.5—2.0％,对雄性小鼠口服半致死剂量(LD_(50))为1301mg/kg,使用时对人、畜和环境比较安全,并保持木材原有色泽。生产性应用试验结果表明,橡胶木生材用2.0—2.5％TWP,满细胞法或振荡加压法处理,净药保持量4±0.7kg/m~3,防腐效果相当干硼酚合剂12kg/m~3,并优于进口防腐剂。     

防腐前处理对竹集成材力学性能的影响

以季铵铜(ACQ)和铜唑(CuAz)加压浸渍处理的毛竹精刨竹条为单元,以酚醛树脂为胶黏剂,制作防腐竹集成材,并测试其力学强度,分析了药剂种类和载药量对竹集成材抗弯弹性模量(MOE)、抗弯强度(MOR)和胶层剪切强度的影响.结果表明,防腐处理前后,竹集成材的MOR、胶层剪切强度差异不显著,MOE差异性显著(0.05水平);防腐剂种类对竹集成材MOE影响显著,载药量水平对MOE影响不显著;总体上看,防腐竹集成材的MOE和MOR略有下降或保持不变,胶层剪切强度略有提高.     

落叶松非结构集成材加工工艺的研究

以短周期工业材落叶松为原料生产非结构集成材，解决了劣材优用问题，提高了木材利用率，为家具制造和室内装修提供了理想的优质材料。     

后干燥处理对防腐木材性能的影响初步研究

试验初步研究了后干燥处理对加铬砷酸铜(CCA-C)、季铵铜(ACQ-C和ACQ-D)三种防腐处理木材中铜的流失影响。结果表明:随着流失次数的增加,CCA-C、ACQ-C、ACQ-D三种防腐处理木材的铜流失量都呈降低趋势,最终降至非常低。随着处理温度的升高,3种防腐材的铜流失量都有所增大。CCA-C型木材防腐剂的抗流失性优于ACQ型木材防腐剂。在同等条件下,ACQ-D防腐材的铜流失率高于ACQ-C防腐材。     

防腐处理竹材的室内抗腐性试验

选用经五种防腐药剂处理过的淡竹进行室内抗腐性试验,同时选用毛竹做室内天然耐腐性试验。结果表明:用热冷槽法,浓度为5%的“BB”和3%的“BBF”防腐效果较好,采用浸渍法,浓度为5%的“BP”、“CCB”“FCAP”均具有防腐效力,浸渍时间19天为宜。毛竹的天然耐腐性较差,与木材相比毛竹在较低的重量损失率(20%)下就丧失使用价值。而木材在同等重量损失率范围内则属于稍耐腐或耐腐等级。     

木材的汽相硼处理—木材防腐处理新方法

木材的汽相硼处理──木材防腐处理新方法陈允适译编硼的汽相处理是从传统木材防腐处理技术基础上发展起来的一种全新的处理方法，它不依靠溶剂，而是使防腐剂的有效成分成汽相直接进入木材。该方法５年前由新西兰林业研究所和英国皇家学院联合研究开发。在新西兰，用硼来...     

防腐处理农用木材的大田试验

以经防腐处理的木材作香蕉支撑和育苗大棚的大田试验；在园林建筑方面作应用试验。经过２年多的观察，初步结果表明，经防腐处理的木材未发现腐烂和虫害，经受多次台风袭击仍完好无损。防腐处理木材用于农业和园林建筑，效果良好。     

木材防腐的现状及研究开发方向

对国内外木材防腐、阻燃的研究与产业状况进行了概述,并对我国木材防腐、防蓝变、阻燃技术的研究开发提出了建议,如在低毒对环境无害的防腐剂、防蓝变药剂、抗渗出/抗吸湿阻燃技术的研究开发与推广应用方面.并对国内木材防腐产业的前景进行了分析,如用于建材等领域.     

不同老化试验方法对层板胶合木性能的影响

以层板胶合木为研究对象,比较了不同人工加速老化方法(ASTM D1037、BS EN1087—1、CAN/CSA—0188、ASTM D3434)对层板胶合木构件力学性能的影响。层板胶合木构件在4种不同人工加速老化方法的作用下,通过对静曲强度、弹性模量、剪切强度及木破率等实验指标的比较分析,发现试材的胶合剪切强度下降程度明显高于其他性能的变化程度,建议作为判定层板胶合木构件耐老化性能的重要指标;经分析认为达到相同老化效果BS EN1087—1法更节约时间,是研究层板胶合木耐老化性能较优的人工加速老化处理方法。     

Simultaneous determination of shear strength and shear modulus in glued-laminated timber using a full-scale shear block specimen

A newly developed full-scale shear block specimen was used to simultaneously determine the shear strength and shear modulus of glued-laminated timber. The shear modulus was calculated using the shear strain distribution measured by means of digital image correlation. To obtain the exact relationship between shear modulus and shear strength, the shear strain in the intended shear plane was measured. A relatively high correlation coefficient of 0.75 was found between the shear modulus and nominal shear strength in two types of glued-laminated timber tested: sugi (Cryptomeria japonica) and Douglas-fir (Pseudotsuga menziesii). Good correlation was also found between the density of middle lamina and shear strength. However, the relationships to density showed species dependence, which was not observed in the relationship between shear modulus and shear strength.     

Stochastic model for predicting the bending strength of glued-laminated timber based on the knot area ratio and localized MOE in lamina

The aim of this study was to develop a stochastic model for predicting the bending strength distribution of glued-laminated timber (GLT). The developed model required the localized modulus of elasticity (MOE) and tensile strengths of laminae as input properties. The tensile strength was estimated using a regression model based on the localized MOEs and knot area ratios (KAR) which were experimentally measured for lamina grades samples. The localized MOE was obtained using a machine stress-rated grader, and the localized KAR was determined using an image-processing system. The bending strength distributions in four types of GLTs were simulated using the developed GLT beam model; these four types included: (1) GLT beams without finger joints; (2) GLT beams with finger joints; (3) GLT beams with different lamina sizes; and (4) GLT beams with different combinations of lamina grades. The simulated bending strength distributions were compared with actual test data of 2.4 and 4.8 m-long GLTs. The Kolmogorov–Smirnov goodness-of-fit tests showed that all of the simulated bending strength distributions agreed well with the test data. Especially, good agreement was shown in the fifth percentile point estimate of bending strength with the difference of approximately 1%.     

Property relationships between spruce logs and structural timber

This paper summarises the comparison between log properties and resulting structural timber properties. The establishment of these relationships is a first step to place the grading as early as possible in the production process, if possible directly on the log. To find out what should be detected on the log, the modulus of elasticity (MOE) based on longitudinal frequency, the number of resin pockets and the value for spiral grain were detected. Relationships are established to the corresponding properties on the structural timber produced out of it and to visual log grades commonly used in Austria. This paper discusses advantages and disadvantages of these properties on 85 spruce logs. The MOE based on longitudinal frequency showed high potential whereas the number of resin pockets and the value of spiral grain only helped to identify timber unsuitable for construction.     

Experimental evaluations of material damping in timber beams of structural dimensions

Understanding the inherent damping mechanisms of floor vibrations has become a matter of increasing importance following the development of new composite floor layouts and increased span. The present study focuses on the evaluation of material damping in timber beam specimens with dimensions that are typical of common timber floor structures. Using the impact test method, 11 solid wood beams and 11 glulam beams made out of Norway Spruce (Picea abies) were subjected to flexural vibrations. The tests involved different spans and orientations. A total of 420 material damping evaluations were performed, and the results are presented as mean values for each configuration along with important statistical indicators to quantify their reliability. The consistency of the experimental method was validated with respect to repeatability and reproducibility. General trends found an increasing damping ratio for higher modes, shorter spans, and edgewise orientations. It is concluded from the results that material damping of timber beams of structural dimensions is governed by shear deformation, which can be expressed more conveniently with respect to the specific mode shape and its derivatives.     

泡桐木材防变色处理配方优选试验研究

为防止泡桐材的变色降等，采用防变色剂、耐光剂、渗透剂组成的防桐木变色剂配方处理桐木板材，观察其对色度ａ＊、ｂ＊、色差ＤＥ＊、明度Ｌ＊的影响。通过正交试验选择最佳工艺参数。处理后的泡桐板材可达到出口一级品之指标，颜色纯洁，保持木材天然本色。     

Modeling internal temperature changes of timber poles during ACA treatment

Summary The temperature-time-location relationships during steam conditioning and pressure treatment of timber poles using ammoniacal copper arsenate (ACA) have been studied and a new mathematical model that incorporates both the thermal properties of the poles and the parameters of the treatment process is discussed. Prediction equations and charts are presented that show the minimum required steaming time to satisfy the 1982 Rural Electrification Authority (REA) purchase specification, i.e. a center temperature above 150 °F (65.5 °C) for 2 hours. A six hour steaming time, commonly used for ACA treatment, has been found to be too short to bring poles with diameters larger than about 40 cm to the required sterilization conditions. Therefore longer steaming times, predicted using the methods given here, are recommended. The temperature of the preservative used does not appear to be a major factor in determining the maximum temperature achieved at the center of a pole, but it can influence the length of time the pole is above 65.5 °C.Symbols D pole diameter, cm - k₁ rate of surface temperature change during vacuuming, °C/h - K₂ rate of surface temperature change early in the pressure period, °C/h - J₀ Bessel function of the first kind of order zero - J₁ Bessel function of the first kind of order one - r radial location in a pole measured from the center, cm - R pole radius, cm - T interior temperature of a pole during preservative treatment, °C - T_f final preservative temperature, °C - T_mid average of the steam and the final preservative temperatures, °C - t₀ initial temperature of a pole, °C - T_s temperature of the steam used for conditioning the poles, °C - T₁ surface temperature at the end of the vacuum period, °C - t time measured from the opening of the steam valve for steaming, h - t_above time the center of a pole remained above 65.5°C during preservatives treatment, h - t_c1 total time required for the surface temperature to reach T_f, °C - t_pr time elapsed at which initial vacuuming stops and pressure is applied, h - t_stm minimum required steaming time used, h - t_vc time elapsed at which initial vacuuming starts, h - thermal diffusivity, cm²/h - _n Roots of a particular characteristic equation - _d the time delay period between initial flow of steam and surface temperature response, h     

Effects of early re-spacing on the physical and mechanical properties of Sitka spruce structural timber

The effects of early re-spacing on the physical and mechanical properties of Sitka spruce (Picea sitchensis [Bong.] Carr.) structural-dimensioned timber were studied using material from a fully replicated 57-year-old trial located in Northern Ireland, which had been thinned at age 11 years. Basic density, distortion (spring, twist and bow), modulus of elasticity (MOE) and modulus of rupture (MOR) in bending of structural timber from four different re-spacing treatments (1.83 m × 3.66 m, 3.66 m × 3.66 m, 3.66 m × 5.49 m and 5.49 m × 5.49 m) were compared with those of timber from a control (1.83 m × 1.83 m). Re-spacing intensity had a significant effect on both modulus of elasticity (p = 0.006) and modulus of rupture (p = 0.009), but not on basic density (p = 0.379) or distortion (p > 0.200). Timber from the two widest re-spacing treatments failed to meet the requirements for the C14 strength class, while timber from the control met the requirements for the C16 strength class. Both MOE and MOR were significantly and negatively associated with knot size and frequency, which in turn increased with re-spacing intensity. Overall, re-spacing intensity only explained approximately 10% of the total amount of variation in both MOE and MOR, with most of the variation due to inter- and intra-tree differences within a treatment. Based on these results, re-spacing of Sitka spruce to a residual stand density of less than 900 trees/ha (3.33 m × 3.33 m) is not recommended if the goal of management is to produce C16 structural timber.