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本文提出利用定压力、环形点、表面接触式探头、以单板表面电阻为表征其含水率参量,配合计算机系统,实现单板含水率及其分布特征的快速、无损检测新方法。 相似文献
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IntroductionA new type contact dryer with non-metal flexibleplaten was patented in 1998 in China, which specialstructure and material solved the problem of low productivity in platen drying. The machine was similar tohot press. Direct contact betWeen wood and heatedplaten allows rapid heat transfer by conduction (Sandoe 1983). Though the flexible screen conducts heatslower than metal platen does, it transfers massmuch fast6r. So water removing rate decides veneerdrying rate in the new machin… 相似文献
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辊压连续式单板干燥机的设计 总被引:1,自引:0,他引:1
单板干燥机是单板及胶合板生产过程中的主要设备之一,单板干燥质量直接影响贴面板、胶合板产品质量。辊压连续式单板干燥机的设计,主要是利用国际上最新的加压接触式单板干燥技术,其主要工作原理是:单板在上下两条钢带的夹持下经过预热管的预热使钢带和单板温度趋于一致,而后进入干燥滚筒之间进行快速干燥。由于钢带与滚筒之间具有一定的压力,使单板在被夹持的状态下进行连续干燥,因此可以使干燥后的单板平整、含水率均匀,干燥质量和干燥效率得到很大提高;并且具有高温滚筒与湿单板直接接触传热,热效率高,热损失小,大大减少热能损耗的特点。 相似文献
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《Wood material science & engineering》2013,8(3):198-211
Abstract A shortcoming of the laminated bending process is that the products may become distorted after moulding and during use. In this study, we have examined the influence of different UF-adhesive systems, adhesive distribution, and veneer properties such as species, moisture content, and fibre orientation. Two different species were studied: beech (Fagus silvatica L.) and birch (Betula pubescens Ehrh.). Distortion was determined directly after moulding and after storage in a changing relative humidity. The aim of the work was to study how the above-mentioned material and process parameters influence the distortion. The results show that the material and process parameters and the storage in a changing relative humidity had a clear impact on distortion. Fibre orientation, differences in moisture content between veneers, and the moisture gradient in the final product are identified in this study as being the most important parameters influencing the distortion and shape stability of laminated veneer products. 相似文献
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Productive test of a newly drying technology of veneer: intermittent-contact drying of veneer with flexible screen belt 总被引:1,自引:0,他引:1
A newly drying technology, intermittent-contact drying of veneer with flexible screen belt (ICD-fbs), was invented and used in poplar veneer drying. Productive test was carried out for validating the practical use of this drying method. The test result shows that to dispose flexible screen belts on the two sides of hot board could help steam discharge remarkably. The veneer dried using ICD-fsb method had smooth and level surface, less deformation and warping, even moisture content, and high utilization rate. The time for opening hot board to discharge steam,which, early or late, is a key to obtain good drying result, was determined at the time when the core‘s temperature of veneer reaches 100℃ (vaporization). Using ICD-fsb method, the shrinking rates in tangent of veneer were from 1.90% to 2.26% for veneer of 0.4 mm in thickness,2.49% to 4.50% for veneer of 1 mm in thickness and 1.34% to 3.30% for veneer of 1.7 mm in thickness, which are much lower than the results obtained by other drying methods. The method of ICD-fsb offers a reliable technological guarantee for solving the deformation problem of veneer drying, especially the deformation of wood from quick-growing plantation. 相似文献
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对福建省主要桉树木材材性及其旋切单板厚度偏差、背面裂隙率进行检测分析,探讨木材旋切单板的适应性和制造胶合板的工艺并采用正交法优选最佳工艺参数。结果表明:尾叶桉单板背面裂隙率和单板厚度变动系数比尾巨桉小,尾叶桉用于旋切1.5 mm厚度单板质量较佳。尾叶桉木材制造胶合板较佳工艺参数:热压温度为130℃、单位压力为1.4 MPa、热压时间为1.35 min·mm-1、涂胶量为320 g·m-2。工艺条件对板材性能均有影响,桉树木材龄级对板材性能影响显著,随着桉树龄级的增大,板材性能有较大幅度提高,特别是静曲强度、弹性模量影响最为明显。 相似文献
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Summary The purpose of this paper was to clarify the gluability and adhesion mechanism of polypropylene as a hot melt wood adhesive for plywood bonding. The gluability of plywood glued with nonpolar and modified polypropylene satisfied approximately the specification of the Japan Agricultural Standard, Designation Types 1 and 2. The moisture content (8 to 25 %) of the core veneer had no recognizable effect on gluability. The durability of polypropylene and that of modified polypropylene were the same as that of melamine-formaldehyde resin. Molten polypropylene made good contact with veneer surface, and penetrated into the lumina of wood cells and other spaces. In the separated glue lines, casts of glue which had penetrated into the vessels had many mushroom-like projections which had filled the bordered pit cavities. It was indicated that the anchoring effect of polypropylene which had penetrated into various wood elements and spaces in the veneer contributed dominantly to the gluability.Part of the paper was presented at the IUFRO-Working Party of Wood Gluing, October 2–9, 1977, Merida, Venezuela. 相似文献
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Summary The objective of this research is to study the moisture deformation of densified in technological pressing wooden composite materials. By generalizing Cosserat's couple-stress theory a structural model for determination of mid-surface strains and curvatures of composite board taking into account asymmetric structure and nonuniform distribution of moisture as well as nonlinear swelling functions of the wooden stuff and dependence of strain characteristics on moisture content is developed. On the basis of a laminate analogy the optimum flake or veneer alignment in board has been estimated for the real composite production process. According to analysis performed, the optimum alignment for hygromechanical properties may not coincide with that for mechanical properties, and for every type of loading, material with a definite structure should be used. 相似文献
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玉米淀粉改性UF树脂胶合高含水率单板 总被引:2,自引:0,他引:2
采用半酯化的玉米淀粉与脲醛树脂(UF)共聚改性,探讨加入量、脲醛树脂的量比、混合比、热压条件等对胶液的黏度、稳定性、固化时间及胶合质量的影响.结果表明:当单板含水率提高到16%~18%时,用改性UF树脂生产的多层胶合板,其物理力学性能指标达到GB/T 9846.1~12-88中Ⅱ类胶合板的要求,并大幅度地降低了胶合板的制造成本. 相似文献
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柔性电热板加热摞式热压工艺的研究与实践 总被引:1,自引:1,他引:0
在单层大开档压机中,将数块特殊制作的柔性电加热板按一定方式直接置于成摞堆放的板坯中对板坯进行加热加压。板坯为多层胶合板或细木工板。几年的研究与实践证明:与目前通常的刚性压板热压相比,板坯压缩率较小(低于4%),能源消耗也较低,电耗为30~50kWh/m3。在单板含水率为14%~18%的条件下,仍然有十分可靠的胶合,胶合强度均大于1.2MPa。 相似文献
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该研究采用BL-阻燃剂溶液浸渍处理杨木单板,比较分析BL-阻燃杨木与未阻燃杨木的吸湿性和尺寸稳定性的影响。结果表明:①在不同的湿度条件下,阻燃处理后试件的吸潮率递增值明显高于未处理材。②BL-阻燃剂浓度越高的试件吸潮率也越高,相同浓度的试件在不同湿度中,湿度越高,其吸潮率也越高。③阻燃后杨木单板的尺寸变化率明显高于未处理材的,BL-阻燃剂具有较高的吸湿性,其对杨木单板尺寸稳定性的影响规律为:厚度弦向径向。 相似文献
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