异氰酸酯定向结构板试验

在实验室内压制异氰酸酯定向结构板,研究用胶量和板子密度对物理力学性能的影响。结果表明,异氰酸酯作为制造定向结构板的胶粘剂具有许多独特的优点。     

定向结构板热物理特性的研究

采用热脉冲法测定杨木定向结构板的热物理特性,研究板材的密度、含水率对其热物理特性的影响,获得了绝干、气干及高湿度状态下各种不同密度的定向结构板的热导率、热扩散率、比热容的变化规律,以此为建筑热工设计提供依据。通过对不同材料建筑物的采暖能耗的对比分析得出,定向结构板具有良好的保温隔热性能,用作墙体材料可达到节能目的。     

定向结构板的应用定向结构板系列讲座之五

定向结构板的应用定向结构板系列讲座之五南京林业大学定向结构板工程研究中心１概述定向结构板与其他人造板相比，其特点是强度高，纵、横方向的静曲强度和弹性模量有明显差异。定向结构板的用途也充分体现了板材的力学性能特征，即主要应用于有一定承载要求的场所。国内...     

定向结构板概论：定向结构板系列讲座之一

定向结构板概论定向结构板系列讲座之一南京林业大学定向结构板工程研究中心１前言定向结构板（ＯｒｉｅｎｔｅｄＳｔｒｕｃｔｕｒａｌＢｏａｒｄ或者ＯｒｉｅｎｔｅｄＳｔｒａｎｄｂｏａｒｄ，缩写为ＯＳＢ）是一种新型结构板材。当前，ＯＳＢ与ＭＤＦ一起为世界范围内发...     

定向结构板的特殊处理定向结构板系列讲座之四

定向结构板的特殊处理定向结构板系列讲座之四南京林业大学定向结构板工程研究中心１概述定向结构板以其特有的用途（比如建筑、车船制造和混凝土模板等）要求产品具有相应的特性，归纳起来有四，即阻燃特性、低甲醛释放特性、耐久性和尺寸稳定性。按照正常工艺制造的定向...     

定向结构板制造工艺 定向结构板系列讲座之二

定向结构板制造工艺定向结构板系列讲座之二南京林业大学定向结构板工程研究中心１概述世界范围内可以提供定向结构板成套设备的制造公司不算很多，典型制造商主要集中在德国，比如申克公司、比松公司和辛北尔康普公司。我国赣州第二木材厂和南京木器厂就分别从比松公司和...     

蔗髓含量对蔗渣碎料板性能的影响研究

研究了蔗髓含量（质量分数）分别在10%、20%、30%、40%4种不同情况下蔗渣碎料板的密度、静曲强度、弹性模量、内结合强度、吸水厚度膨胀率和板面握钉力等物理力学性能的变化规律.结果发现，随蔗髓含量的增加，板材的密度增加，弹性模量和板面握钉力下降；在蔗髓含量低于20%以下时，蔗髓的存在对板材的静曲强度无明显影响，而随蔗髓含量增加，吸水厚度膨胀率影响显著上升；在蔗髓含量高于20%以上时，蔗髓的含量增加使板材静曲强度明显下降，而对吸水厚度膨胀率无影响；蔗髓的含量对板材的内结合强度影响不明显.     

定向结构板生产国产化的研究

本研究介绍了国家“八五”科技攻关项目“国产化定向结构板生产线”的特点和工艺流程。已建成年产１万ｍ３和１５万ｍ３生产线，运行良好。产品符合欧共体定向结构板标准的要求。介绍了国外定向结构板发展状况，分析了中国发展定向结构板的有利条件和趋势。     

定向结构板生产的关键主机：定向结构板系列讲座之三

定向结构板生产的关键主机定向结构板系列讲座之三南京林业大学定向结构板工程研究中心１概述定向结构板生产线上的主机包括：刨片机、干燥机、分选机、拌胶机、定向铺装机和热压机。尽管以上设备配置与普通渐变结构刨花板生产线颇为近似，但围绕着如何制备有特殊长宽厚尺...     

定向结构板推广前景与经济分析定向结构板系列讲座之六

定向结构板推广前景与经济分析定向结构板系列讲座之六南京林业大学定向结构板工程研究中心１概述定向结构板作为一种新型结构材料能否在我国得到稳定的发展，主要取决于以下因素：①在日益激烈的市场竞争中，产品的应用范围能否定位并展现独特的优势；②产品的性能和质量...     

DETERMINATION OF STATIC AND DYNAMIC DIFFUSION COEFFICIENTS OF MOISTURE IN PARTICLEBOARDS

The static and dynamic diffusion coefficients are important coefficients todescribe the moisture transfer processes in particleboard.In this paper,the formula ofculculating the static and dynamic diffusion coefficients were deduced.At first,the staticdiffusion coefficients of four kinds of particleboards were determined by using diffusion cupmethod.The results demonstrated that the static diffusion coefficients parallel to panelsurface were 10-20 times as large as that of perpendicular to panel surface for test boards.To determine both dynamic diffusion coefficients and surface emission coefficients ofmoisture in particleboards in one experimental period,specimens in four different thickness-es of each kind of particleboard were used in the experiment.Then the method ofregression was used and the dynamic diffusion coefficients and surface emission coefficien-ts were determined based on the slope and intercept of the regressive line.     

定向刨花板剪切模量和弹性模量动态测试

【目的】研究定向刨花板(OSB)的各向异性,探讨OSB面内剪切模量动态和静态测试方法,以提供一种快速、简便、重复性好、精度高的动态测试方法测量和分析OSB弹性常数。【方法】应用ANSYS程序计算OSB自由板和悬臂板试件的振形系数,给出振形系数依赖于板长宽比和宽厚比的关系式,通过仿真计算、动态试验和方板静态扭转试验验证其正确性。动态试验测试OSB剪切模量试件从一块整张OSB上下料制作,分为3个方向,即沿整板纵向下料制作的试件(0°或x向)、横向方向下料制作的试件(90°或y向)和沿与纵向呈45°方向下料制作的试件;方板扭转试验测试OSB剪切模量试件沿整板纵向或横向下料制作;动态测试OSB纵向、横向和45°方向弹性模量以及面内剪切模量和45°方向剪切模量。【结果】OSB实测纵向弹性模量是横向弹性模量的2.89倍,45°方向剪切模量小于面内剪切模量。正交各向异性材料方板扭转试验测试剪切模量推算公式需用±45°方向应变测量值的差值进行推算,将其用于OSB,测得的静态剪切模量与动态测试的剪切模量相当吻合。【结论】OSB弹性模量具有方向性,纵向最大,横向最小,45°方向介于二者之间;自由板扭转振形法和悬臂板扭转模态法适用于动态测试OSB面内剪切模量,其正确性得到方板扭转试验验证;0°和90°OSB动态测得的剪切模量几乎相等,可作为OSB面内剪切模量Gxy的估计值;OSB不宜按单向复合材料处理,在理论分析时宜按正交各向异性处理,OSB45°方向的剪切模量G45°相似文献   

Evaluation of the arrangement of wood strands at the surface of OSB by image analysis

 The objective of this paper is to evaluate the arrangement of wood strands at the surface of oriented strand board (OSB) by image analysis. Two-dimensional image analysis enables the number of strands and the area of each strand to be computed. In addition, the fiber direction of each strand may be measured manually by recording the acute angle between the fiber direction and the longitudinal axis of the specimen. The image analysis results suggest the following: the average strand area is proportional to the reciprocal of the number of strands. Samples containing many smaller strands exhibit a larger variation in strand size. The average strand area does not correlate with the distribution of the strand area represented by the coefficient of variation. However, there is a reasonable correlation between the number of smaller strands in the range 0 to 1 cm² and the coefficient of variation of strand area. At low average fiber orientations, i.e. better orientation with the principal panel axis, there is smaller variability in orientation. The upper side and lower side of OSB exhibit a different relationship between average fiber orientation and strand area. The upper side of the specimens contains larger strands and exhibits better fiber orientation than the lower side. This is thought to be a function of the production process. The lower side strands fall on a smooth moving substrate, whereas the upper side strands fall on a stable substrate of strands. The number of strands is lower on the upper side of the OSB panel because small size strands tend to migrate to the lower side of the OSB during production. The small particles tend to be vibrated through the strand mat to the lower face before pressing. Received 29 March 1999     

Water vapour diffusion through historically relevant glutin-based wood adhesives with sorption measurements and neutron radiography

In this work, the sorption and moisture diffusion behaviour of historically relevant glutin-based adhesives (i.e. bone glue, hide glue, fish glue) is characterized. The adhesive’s sorption isotherms were assessed on thin film samples revealing fundamental differences between the glutin-based adhesives and the synthetic reference adhesive (polyurethane). Furthermore, the water vapour diffusion parallel to the fibre was examined by means of neutron imaging on bonded two-layer samples of Norway spruce wood. In contrast to previous studies using neutron imaging, a new evaluation approach is presented, which allows for nonzero initial moisture conditions and takes into account and compensates for the geometry changes in the sample caused by swelling and shrinkage, thus allowing for a characterization of the diffusion behaviour within the glue line. The diffusion coefficients determined with neutron imaging were interpreted in terms of a theoretical model which takes into account the glue line microstructure. Although the diffusion coefficients were on average larger values for the glutin-based adhesives compared to the reference polyurethane adhesive, the significant variation observed in the sorption measurement is not reflected. This can partially be ascribed to excessive penetration of the adhesives into the wood substrate in fibre direction, which impedes a continuous adhesive layer. Furthermore, deformation and densification of the wood structure was assessed in the vicinity of the adhesive joint. This effect can be ascribed to the surface roughness, which results in very high local stresses leading to buckling and deformation of the tracheids. This situation is similar to that found for adhesive joints in or close to the fibre direction such as finger or butt joints.     

Influence of specimen size during accelerated weathering of wood-based structural panels

ABSTRACT

Wood structural panels are commonly subjected to short-term accelerated weathering (AW) procedures to determine relative moisture durability for quality control and product development purposes. The panel edges contribute heavily to moisture uptake since edges represent the least resistant pathway for moisture intrusion. In full-size panels, the edge area to total surface area ratio is small, and moisture intrusion is primarily limited to panel faces. When small specimens are used, such as those in AW procedures, the ratio of edge area to total surface area increases and moisture intrusion at the edges may dominate, which is referred to as the edge effect. The purpose of this study was to determine if physical and mechanical properties of oriented strand board (OSB) and plywood after AW are influenced by specimen size. Specimen width was varied while thickness and length remained constant to understand if edge effects were present in small specimens with different edge area to total surface area ratios. Three AW procedures were evaluated to determine if the effect of specimen size depends on weathering method. No clear effect of specimen size on physical and mechanical properties of either composite type was found. Differences in flexural properties between specimen widths were observed for unweathered OSB, but similar property retention between specimen widths after AW indicated the same trend as the unweathered control. Plywood results were influenced by natural defects, resulting in high variability and absence of statistically significant differences. Lateral nail resistance connection properties of both OSB and plywood were highly variable for all treatment groups and were unaffected by weathering.     

Diffusion of chemicals into archaeological waterlogged hardwoods obtained from the Thang Long Imperial Citadel site,Vietnam

This study shows a method to easily develop suitable impregnation procedure of chemicals for preserving the archaeological waterlogged wood (WW) using diffusion constant. The steady-state diffusion coefficients of polyethylene glycol 4000 (PEG4000), trehalose, and keratin through eight archaeological waterlogged wood species were obtained from the total amounts of the chemicals diffused through the wood samples. The diffusion coefficients were strongly affected by the anatomical structures of the wood species and degree of wood deterioration. Within the same species of wood, the highest diffusion rates were measured in the longitudinal direction, followed by those in the radial and tangential directions. The longitudinal diffusion coefficients were 1.5- to 8.1-times higher than the radial diffusion coefficients, which were in turn approximately 1.1- to 5.7-times higher than the tangential diffusion coefficients. The diffusion rates were found to be inversely proportional to the molecular weight of the diffusing chemical. The diffusivity of trehalose through the waterlogged woods was found to be higher than those of keratin and PEG4000. This study provides a potential method to easily estimate chemical diffusion coefficients for dip-diffusion treatments.     

OSB在我国的发展前景分析

作为一种成熟的环保建材产品,定向刨花板(OSB)在发达国家已被广泛应用.自2001年我国引进OSB以来,产品的应用领域不断拓展.在分析产品特点、生产工艺以及在国内外生产应用状况的基础上,预测了OSB在我国的发展前景.     

Water vapour diffusion and adsorption characteristics of sugar maple (Acer saccharum,Marsh.) wood polymer composites

Summary Water vapour diffusion characteristics and adsorption isotherms were determined for cell-lumen and cell-wall treated wood polymer composites (WPC). The diffusion coefficients of the cell-lumen WPC were lower than untreated wood and the cell-wall WPC coefficients were lower than cell-lumen. Using the Hailwood and Horrobin sorption model, it was found that the unimolecular layer is formed at lower moisture contents in WPC than in wood. The amount of free dissolved water was reduced only in the cell-wall WPC. The polymer reduces the water vapour accessibility in both types of WPC.     

竹材是我国制造OSB的一种潜在原料

定向刨花板(OSB)是近20年人造板家族中发展最迅速的一种板材。国外已呈现原料供应不足状况。我国OSB制造业正在起步阶段,将来也会面临原料资源问题。我国是世界第一产竹大国,通过分析竹材的理化性质和采用毛竹进行压板试验,结果表明竹材极有可能替代木材成为制造OSB的一种新原料。     

单板的厚度和配置方式对复合定向刨花板性能的影响

研究了单板厚度和配置方式对复合定向刨花板性能的影响。试验发现：１．复反的强度与刚度随着单板配置方向的改变而明显改变。当单板纹理方向与ＯＳＢ定向方向平行时，复合板在平行于ＯＳＢ定向强度与刚度明显增加，而且在纵横两个方向上的差异也增大；而当单板纹理方向与ＯＳＢ定向方向垂直时，复合板在纵横两个方面的强度与刚度趋于均匀。２．本试验中如果单板以纹理方向的与ＯＳＢ定向方向垂直配置，则在单板厚度为０．８５ｍｍ时