Effect of manufacturing parameters on the linear expansion and density profile of particleboard

Particleboards were fabricated in the laboratory with different board densities and resin contents to evaluate linear expansion when exposed to both vapor and liquid water. Density profiles were measured to determine the relation to the elastic constants and to the dimensional properties of the boards. It was found that density profiles were affected by the board density and resin content applied. The high-density layer formed in the thickness direction affected the elastic constant measurements. A model introduced to predict the linear expansion closely matched the data during exposure to water. Under conditions of 40°C and 90% humidity, linear expansion increased with increasing board density. An increase in resin content from 6% to 12% slightly increased the linear expansion and decreased the thickness swelling. A linear relation was found between board density and linear expansion per unit of moisture content change.     

Effects of press closing time on mat consolidation behavior during hot pressing and on linear expansion of particleboard

Mat consolidation behavior was investigated at various press closing times (PCTs) using hinoki (Japanese cypress) particle mats. The temperature in the core layer of the mat, press pressure, and platen distance were measured. At the plateau stage during hot pressing, the core temperature decreased with increasing PCT. The core temperature did not increase before the platen distance equaled the target board thickness in the PCT range of 4–50 s and rose slightly when the PCT exceeded 100s. There was a linear relation between the logarithm of PCT and the maximum press pressure. The density profile across board thickness was strongly affected by the PCT. As the PCT increased, the position of the peak density (PD) moved toward the core layer as the PD itself decreased. The effect of PCT on the linear expansion (LE) of the board is discussed in relation to the density profile. There was no difference in LE after high relative humidity treatment in the PCT range 4–50s. LE appeared to be related to the low density and the precured region of the board surface. The LE after drying treatment was around –0.1%, and the thickness swelling after high relative humidity and drying treatments increased with increasing PCT.Part of this report was presented at the 51st Annual Meeting of the Japan Wood Research Society, Tokyo, April 1988     

Behavior of acoustic emission generation during tensile tests perpendicular to the plane of particleboard II: effects of particle sizes and moisture content of boards

Particleboard specimens with various particle sizes were conditioned into two ranges: low and high moisture content. One set was investigated for internal bond (IB) strength and acoustic emission (AE) events during tensile tests perpendicular to the plane and the other for ultrasonic wave transmission characteristics in the thickness direction. The particleboard structural mechanics were changed as a result of the moisture effect. Specimens conditioning to higher moisture content had lower IB strength and lower cumulative acoustic emission event counts (T _AE). The decrease in IB strength indicated that the irreversible thickness swelling was seen when recovery forces of the particles exceed the restraining action of the adhesive. This was attributed to stress release, which resulted in internal failure of the board. The change in the internal structure caused an increased stress level at the initiation of AE generation. No events were recorded before this stress level, obeying theKaiser effect. The decrease inT _AE was not only related to the decrease in IB strength but was also affected by the transformation (attenuation) of the AE signals during IB tests according to the mesh size used.Part of this paper was presented at the 45th and 50th Annual Meetings of the Japan Wood Research Society, Tokyo and Kyoto, 1995 and 2000, respectively     

刨花板厚度偏差对板式家具精度的影响

在家具制造过程中，刨花板厚度偏差对板式家具尺寸精度有明显影响。因此控制板材厚度偏差是目前刨花板生产中亟待解决的一个重要问题。     

ANALYSIS OF COMPUTER VISION ON RESIN EFFICIENCY IN PARTICLEBOARD

Particleboardcanbedefinedasaproductthatismadefromwoodornonwoodparticles(flakes,chips,particle-s,etc)andadhesives(l).Theblendingamongparticlesandresinsisoneoftheimportantprocessingstagesinparticlebo-aldmanufacturing,whichhastheobjectthatmakestheliquidadhesiveswelldistributeovertheparticlesurfacesbysomekindsofblenders.Theemciencyofparticleboardmanufacturingdependstoagreatextentontheblending(2).Thebestresinemciencyshouldbethemaximumuti1izationofadhesivesandgetthebestbondingstrengthofparticleboard…     

碳水化合物作添加剂制木质刨花板的研究 Ⅱ糖的作用机理

本研究通过对以糖蜜为助粘剂制造的木质刨花板中木材糖基组成和糖蜜中游离单糖在热压条件下的转化情况和含量变化的研究,解释了糖在木质刨花板中产生胶合作用的方式。结果表明,在热压过程中木材表面化学活性增加,部分纤维素和半纤维素水解。这些水解单糖与糖蜜中的游离单糖均能转化成糠醛,与活化了的木素发生键合作用,生成树脂类化合物,从而达到胶合的目的。经红外光谱测定,在热压后,刨花表面化学基团发生变化,亲水性羟基官能团减少,僧水性羰基官能团增加,说明了糖蜜压制的刨花板具有良好耐水性的原因。这一结论为开发人造板的“无胶”技术提供依据。     

稻草刨花板制造工艺的初步研究

探讨了以腺醛(UF)胶和以异氰酸酯(PMDI)改性的UF胶制造稻草刨花板的可行性。结果表明,用UF胶很难制造出较高强度的刨花板,以PMDI改性可明显提高UF胶对稻草的胶着力。通过对改性胶的施胶方式、固化利用量与板判性能关系的研究,以及对制板主要工艺参数的正交试俭,提出了制造稻草刨花阪的工艺条件。     

环境温度对刨花板生产质量的影响及改进方法

本项研究对气温(尤其在冬季)是如何影响刨花板生产进行了分析。通过对不同季节时的两种极端情况——较高的板坯芯层温度和较低的板坯芯层温度在热压过程中板坯芯层渴度的变化,进一步说明了芯层温度对热压时间以及刨花板质量的影响,并就如何解决这一问题提出了建议。     

十种树种刨花板制板工艺条件的研究

试验测定了十种树种枝桠材的密度、木材水浸提液的pH值和碱缓冲能力,及刨花堆积密度。通过对树种、板材密度、施胶量、固化剂和石蜡用量与板材性能之间关系的研究,提出了十种树种刨花板的制板工艺条件。     

THE EFFECTS OF WETTING AND REDRYING CYCLE ON PHYSICAL PROPERTIES OF PARTICLEBOARD

INTR0DUCTI0NOvertheyearsmmpresearchershavefoundUFandPFparticleboardstoedsbitsimilarshorttermphysicalpropeniesatlowhumidityandtemperatUre(DeainandOstInan,l983).DifferentbehaviorpatternsbetWeentl1eresinsemefgeasrelativehumidityandtem-peratUrerise,finallycouldresultinthefailureofboards(R0dwell,l99l).AnumberofworkshavequestionedWhetherhydrolysisistheonlyfactorinvolvedinb0ndfailure.Irlereported(l986)thedifferenteffectsofwettingandredryingonthepropertiesofpureUFandPFresinfilms.Soitmaybeim…     

碳水化合物作添加剂制木质刨花板的研究——Ⅰ热压工艺的制定

本研究以杨木为原料,用糖蜜、麦芽糖、啤酒废液等碳水化合物以及它们的水解产物作添加剂压制刨花板。首先从探索差热和热重变化来确定热压曲线,其次用其水解前后产物作添加剂进行压板对照试验,并对反应机理进行初步探讨。最后对添加不同化学助剂改善板材性能的效果进行了测定。结果表明,NH_4NO_3的作用较ZnCl_2的显著,用碳水化合物可以压制出高质量的耐水性刨花板。     

Dimensional stability and strength properties of particleboard produced by a closed-press system

The purpose of this study was to reveal the effects of various levels of mat-moisture content (m.m.c.) and the closed-press system for making single- or three-layer particleboard on the density profile, thickness swelling, specific moduli of elasticity (MOE) and rupture (MOR) and internal bond strength. Internal gas pressure was measured in an enclosed frame; and the larger the m.m.c., the higher the internal gas pressure became. When rising water vapor (steam) struck particles, it plasticized them and cured the adhesive, resulting in improved interparticle contact. The vertical density gradient in the three-layer board was larger than that in the single-layer board. As for thickness swelling by cold-water soaking, the single-layer boards were less affected than the three-layer boards and showed good dimensional stability with increased m.m.c. The open-system boards swelled more than the closed-system boards. The closed-system single-layer board made at high m.m.c. returned nearly to the prime thickness by air-drying after cold-water soaking. Specific MOE and MOR were larger at 15% or 10% m.m.c. than those at other m.m.c. Considerable reductions of specific MOR and MOE of the closed-system three-layer board were observed at 20% or 25% m.m.c.Part of this report was presented at the 45th annual meeting of the Japan Wood Research Society, Tokyo, April 1995 and at the 48th annual meeting of the Japan Wood Research Society, Shizuoka, April 1998     

建筑物框架结构未设置伸缩缝的设计方法

本文论述了某高校食堂全现浇框架结构未设置伸缩缝 ,而采用UEA补偿收缩混凝土的设计方法。通过理论与实践证明 ,此方法是行之有效的。     

THE ANALYSIS OF ADHESIVE DISTRIBUTION ON PARTICLE SURFACE

rnODUCTloNAmathemahcaltheoryandmethodwhichwascalledtheWaveletanalysistheoryhasbeenbroughtupthroughrevoluhon.Inthemathemahciansopinion,theWaveletisthoedtofaharinonicanalysis,whichisamodernFodrieranalysisandanimportansub-jectwhichistheresearcl1workresultduringahalfOfcentUryTheWavelettheoryhasbroughtupimportantbreakthoughtlnthetheoryandmethodoftheimageanalysls.TheWaveletanalysishasmoremeritsthantheFodrieranalysisandithasagoodPropertyin1ocalPOsihoninhmeandfrequencyspace.Atsamehme,ithasanotl…     

刨花形态,树皮含量及石膏质量与石膏刨花板性能的关系

对刨花形态、树皮含量及石膏粉质量与石膏刨花板性能之间关系的研究结果表明:保持一定的刨花长度有利于提高石膏刨花板的静曲强度;石膏刨花板的静曲强度随着木刨花中树皮含量的增加而下降,但把树皮作为填料加入石密刨花板能使板子强度得以提高,不同产地的石膏粉制成的石膏刨花板性能差异很大,按建筑石膏粉标准测定的性能指标及相组成与石膏刨花板的性能之间无显著的相关关系。     

Effects of mat moisture content and press closing speed on the formation of density profile and properties of particleboard

Isocyanate resin-bonded 0.5 and 0.7 g/cm³ lauan (Shorea sp.) particleboards were produced from mats with uniform and distributed moisture content (MC) distributions, using three hot press closing speeds. The effects of these processing variables on the formation of density profile in particleboard and board properties were analyzed statistically. A definition of the density profile was introduced, and the correlations among the various defining factors were established. The results are summarized as follows. (1) The peak density (PD) of particleboard could be increased, with a slight reduction in the core density (CD), using mats with different MC distributions. (2) In a conventional density profile, CD and PD are highly dependent on the board mean density (MD); and the gradient factor (GF), peak distance from the faces (Pdi), and peak base (Pb) are significantly correlated to each other, at the 99% significance level. (3) Greater press closing speed reduces Pdi and Pb, with an increase in GF. (4) Greater press closing speed could increase the PD in board of low MD, with minimal effect on CD. (5) The modulus of elasticity (MOE) of particleboards from mats with high MC near the faces were consistently higher than those from mats with uniform MC, irrespective of the press closing speed, whereas their modulus of rupture (MOR) became indifferent at higher MD under slow and fast closing speeds. (6) Sanding does not improve the MOR and MOE of particleboard significantly.     

基于RS和GIS的吉首市城市扩展动态研究

以RS和GIS技术为支撑,基于多时相Landsat遥感数据,采用监督分类中最大似然方法提取湘西自治州吉首市城市空间特征信息,通过影像叠加分析及重心转移分析,结合扩张速度指标和吉首市独特的人文因素研究表明：吉首市城区1987-2005年19a间面积翻了1．3倍,年平均增长率为4．511％;城区扩展空间主要集中在西南方向;在此基础上,以影响城市扩张视角多元化为出发点,通过分析社会经济因子、人口因子、政策导向性因子等因子对城区扩张的影响,得出在政策导向性的前提下,社会经济（GDP）和人口增长是吉首市城市扩展的核心影响因子。     

Effect of buffers on gypsum particleboard properties

The paper recounts how buffers affect the physical and mechanical properties of gypsum particleboard (GPB) and the initial curing time (IC) of gypsum. The acidic buffers were better than alkaline buffers for prolonging the IC of gypsum and affecting the properties of GPB. Weak acids were advantageous for curing gypsum. When suitable amounts of citric acid and trisodium citrate were added, high performances could be achieved and the IC of gypsum could be prolonged to about 2h. When alkaline buffers such as sodium carbonate were added, the 1C of gypsum was still short but the internal bond strength (IB), modulus of elasticity (MOE), and modulus of rupture (MOR) of GPB were obviously decreased. Citric acid was the best among the four buffers used; and the GPB had a good IB, MOE, MOR, and adequate IC when citric acid of 0.1% was added. Sodium carbonate was not suitable owing to low performance and short IC. Gypsum curing is an endothermic reaction.Part of this paper was presented at the 11th Annual Meeting of the Chugoko Skikoku Branch of the Japan Wood Research Society, Matsue, September 1999     

沙柳的材性对刨花板生产工艺的影响

论述了沙柳的材性对刨花板生产工艺和产品质量的影响，并根据分析结果讨论了目前沙柳刨花板的生产工艺，测试了沙柳刨花板的物理力学性能，针对测试结果提出了改善刨花极性能的措施。     

Interaction analysis between slenderness ratio and resin content on mechanical properties of particleboard

The interaction between particle size and resin content is one of the most important structural parameters that can influence the accuracy of predictions about wood-composite properties. We developed three kinds of equation (linear, quadratic, and exponential) for each mechanical property of particleboard based on slenderness ratio and resin content at a constant density (0.7g cm -3 ). Results from SHAZAM software (version 9) suggested that the quadratic function was not significant, but the linear and exponential functions were significant. The interaction between particle size and resin content was analyzed by Maple 9 software. The results indicated that an exponential function can better describe the simultaneous effect of slenderness and resin content than a linear equation. Under constant resin content, particles with higher slenderness ratios increased more in modulus of rupture (MOR) and modulus of elasticity (MOE) than did particles with lower slenderness ratios. Edge withdrawal resistance (SWRe) values did not increase with increasing slenderness ratio.