热压法制备速生杉木集成材工艺

采用脲醛树脂胶粘剂，运用热压胶合工艺，对速生杉木进行指接与侧拼胶合后制成集成材，并进行横向静曲强度和弹性模量测试：分析热压法制备速生杉木集成材的工艺可行性，讨论侧拼压力、胶合时间与热压温度对速生杉木集成材横向静曲强度与弹性模量的影响，为速生杉木集成材的热压法生产提供理论依据。试验结果表明，在本研究试验条件内，采用脲醛树脂作为胶粘剂，运用热压法制备速生杉木集成材是可行的。     

Effects of sealed pressing and ozonization on properties of styrene-butadiene rubber and polyethylene glycol adhesive bonded board produced by two-stage pressing

Boards were produced by using SP adhesive, which contains styrene-butadiene rubber and polyethylene glycol as major constituents. The use of polyethylene in place of clay, which is also a generally used constituent of SP adhesive, was confirmed to improve board properties. In general, the properties of boards are poorer when produced by two-stage pressing, in which mats are first processed by temporary adhesion and then processed into boards by permanent adhesion; however, the properties of boards produced by two-stage pressing were improved when polyethylene was added to the SP adhesive. In addition, internal bond strength and thickness swelling was greatly improved when boards were produced from ozonized wood and by sealed pressing. Thus, the properties impaired by two-stage pressing were improved by ozonization and sealed pressing.     

Comparison of the pressing behaviour of wood particleboard and strawboard

To improve the understanding of strawboard manufacturing processes, mat pressing behaviour of wood particleboard and strawboard bonded with urea formaldehyde resins were experimentally investigated and compared in terms of mat compressibility, transverse permeability, mat pressure, core temperature, core gas pressure and vertical density profile. The results have shown that straw particles are much more compressible and therefore require less platen pressure for pressing. Compared to wood particle and refined straw particle mats, hammer milled straw mats have low permeability and subsequently show high core gas pressure and high maximum core temperature during hot pressing, in addition to large differential densities between surface and core layers in the final pressed boards. It is recommended that a slower press closing rate and longer press opening time be used to develop the strawboard pressing schedule.     

广宁县竹香骨下脚料制备竹碎料刨花板及其复合改性研究

采用竹香骨下脚料为原料,以脲醛树脂和三聚氰胺改性脲醛树脂胶粘剂制备竹碎料刨花板,并与木纤维复合改性,检测并分析了内结合强度、静曲强度、弹性模量和吸水性。结果表明,在热压温度为160℃时,竹碎料板和竹木复合碎料板的物理力学性能均满足国标规定在干燥状态下使用的普通用板要求。当木纤维与竹碎料复合后,复合板材的静曲强度和弹性模量有一定程度提高,但内结合强度降低。     

化学转化木材为热塑性材料

木材是不溶不熔的材料。近年来研究发现通过适当的化学改性反应特别是经典的纤维素酯化和醚化反应对木材进行化学改性，可使木材转化为可溶可熔的新型热塑性高分子材料。这些热塑性木材可单独或与合成高聚物共混热压加工成型为各种形状的类塑料产品，或利用其热熔性制造自粘合型纤维板、微粒板或木板材。这些新发现为扩大木材的加工方法、劣废木材资源更有效的综合利用及提高木材的应用价值开辟了全新的途径，故已成为近１０多年来木材综合利用新技术研究开发的热点之一。本文综述了该领域的研究开发现状。     

Properties of particleboard manufactured using an air-injection radio-frequency hot press

A hot press was used to manufacture particleboards (H boards). A radio-frequency hot press (for RH boards) and an air-injection radio-frequency hot press (for ARH board) were also used, and the effects of air injection on preventing blowout and board properties were analyzed. The thicknesses and densities of manufactured boards were 10 and 30 mm, and 0.6, 0.7, and 0.8 g/cm³, respectively. The investigation ascertained the effects of air injection in preventing blowout when a radio-frequency hot press is used. The increasing order of temperature was ARH board > RH board > H board during the final pressing stage. For the 30-mm-thick boards, the temperature of H board increased to 100 °C and remained constant at 100 °C even when the pressing time was extended. The temperature of the RH board increased to 100 °C more quickly than in the case of the H board and remained constant at 110–118 °C. The temperature of the ARH board increased linearly to 130–142 °C. For both the 10- and 30-mm-thick boards, the internal bond strength of the RH board was almost the same as that of the ARH board at densities of 0.6 and 0.7 g/cm³. In contrast, the internal bond strength of the RH board was lower than that of the ARH board at a density of 0.8 g/cm³. For the 10-mm-thick boards, the thickness swelling in the RH board was almost the same as that in the ARH board irrespective of the density. However, for the 30-mm-thick boards, the thickness swelling in the RH board was higher than that in the ARH board. The low plasticization of particles due to air injection presumably results in a high degree of thickness swelling.     

A vapour phase preservative treatment of manufactured wood based board materials

Summary The preservative treatment of four different wood based board materials using an esterified borate applied in the vapour phase was investigated. Under optimum conditions complete impregnation via the board faces was achieved in all boards treated. Board moisture content and treatment time had a major influence on retention and depth of penetration of the borate vapour.     

The effects of chemical components and particle size on the mechanical properties of binderless boards made from oak (<Emphasis Type="Italic">Quercus</Emphasis> spp.) logs degraded by shiitake fungi <Emphasis Type="Italic">(Lentinula edodes</Emphasis>)

Binderless boards are composite boards that rely on self-bonding mechanisms for inter-fibre bonding. Quercus acutissima and Quercus serrata logs degraded by Lentinula edodes (shiitake fungi) were used in this study to investigate whether physical and chemical changes induced by shiitake fungi can enhance board mechanical properties. Binderless boards were manufactured with 0.8 g/cm³ target density, 220 °C pressing temperature, 5 MPa pressure, and pressing duration of 10 min. Boards made from logs degraded for ≥?26 months were stronger than control boards and met modulus of rupture (MOR) and internal bonding (IB) requirements for fibreboards. Chemical composition and particle size distribution of the wood powder used to make the boards were determined to elucidate the drivers of board mechanical properties. The proportion of small particles (<?150 µm) showed a strong positive correlation with MOR for both species and hot water extractives showed a strong positive correlation with IB for Q. acutissima boards. Introduction of shiitake fungi pre-treatment to the production process may enhance the mechanical strength of binderless boards.     

Preparation and crosslinking of oligoesterified woods based on maleic anhydride and allyl glycidyl ether

Summary Oligoesterification of wood was investigated by alternately adding esterification reactions of wood with maleic anhydride and allyl glycidyl ether. The products obtained consisted of acetone-insoluble and soluble parts. The insoluble parts were novel oligoesterified woods with oligoester chains having polymerizable double bonds. The oligoester chain length showed a tendency to decrease with increase in wood content in feed. The soluble parts were free oligoesters which were not linked with the wood matrix. The products (the oligoesterified wood-containing mixtures), when subjected to hot-pressing in the presence of a peroxide, gave plasticized crosslinked wood boards whose surfaces are smooth, glossy, and plasticlike. In this case, the free oligoesters which were hardening worked as a plasticizer for the wood components and were combined, by the crosslinking, with the oligoesterified woods, resulting in the formation of the network structure. The crosslinked wood boards exhibited outstanding properties in heat distortion temperature (>165°C) and compressive strength (ca. 1,600–2,300 kg/cm²).     

Chemical changes of kenaf core binderless boards during hot pressing (II): effects on the binderless board properties

To provide basic information on self-bonding in kenaf core binderless boards, a series of chemical analyses was conducted on binderless boards and their chemical changes during hot pressing were examined in our previous study. In this study, binderless boards were manufactured under conditions that may accelerate the supposed chemical changes to investigate their effect on the board properties. First, to investigate the influence of the chemical bonds formed by carbonyl compounds on self-bonding, the influence of acetic acid addition prior to board manufacturing was studied and the effect of methanol extractives (containing the carbonyl compounds) was also examined. Second, the influence of the condensation reaction in lignin was discussed from the viewpoint of board density. Last, to examine the influence of thermal softening of lignin, the influences of temperature condition and moisture content, as well as those of microwave pretreatment, were investigated. As a result, the estimated chemical changes were suggested to influence the binderless board properties.     

竹胶合板——混凝土模板的构造与应用的研究

竹胶合板是我国最近开发的一种轻质、高强的代木材料。它的种类很多,其中用经纬编席坯板作胶合板的奇数间板,以帘吊内簧坯板作填层组合热压而成的毛竹经帘交压层积板,可以制作混凝土工程面板,以代替木材面板、钢面板以及其他材质面板。它既可与木材、钢材、工程塑料组成多种规格的模板体系;也可制成全竹胶普通模板。竹胶模板适应各种类型建筑工程的施工使用,安全轻便,装拆劳动强度小、工效高,施工经济效益好。     

木材表面的热平整技术

本文介绍了热平整技术的理论基础和滚筒热平整技术。采用热平整和辊压的方法 ,木材受热后表面的绒毛状纤维被塑化而固定 ,木材表面变得密实和光亮 ,且没有粉尘 ,有望替代现在的砂光工序。文章还介绍了在电加热平整中 ,把平整工具置于锯切工具后 ,利用锯切工序后产生的切削热平整家具的加工表面和侧面。试验发现高频机械振动和超声波平整不同材料的效果良好 ,因其具有宽广的频域和功率的调整量范围 ,可望广泛应用于多种场合     

国外薄型刨花板生产技术现状

本文介绍了薄型刨花板的生产工艺和产品的性能与特点。就力学强度检测方法的改进和薄型刨花板的成本分析及应用前景阐述了看法。结合我国刨花板工业的具体情况,作者针对国内应如何发展薄型刨花板问题提出了建议。     

Reaction wood drying kinetics: tension wood in <Emphasis Type="Italic">Fagus sylvatica</Emphasis> and compression wood in <Emphasis Type="Italic">Picea abies</Emphasis>

The drying kinetics of reaction woods in Picea abies (compression wood) and Fagus sylvatica (tension wood) in comparison with their corresponding normal woods was investigated under constant convective drying conditions. Moisture profiles along the thickness of small flat-sawn boards taken from reaction and opposite wood zones were evaluated using a polychromatic X-ray system, a non-destructive method. The results revealed substantial differences in the drying behavior between the reaction and opposite woods. Both reaction woods represented slower drying rate than their matching normal woods mainly during the period of free water loss. However, the reaction and opposite woods reached the final moisture content (MC) of about 12% at the same time due to higher initial MC in the opposite woods. In the case of reaction wood, it took a longer time for the moisture profile to become approximately uniform. Overall, a more striking difference was observed in the drying behavior of compression and opposite wood in P. abies. Some important anatomical differences like the cell and pit dimensions and their proportion give some explanations for these drying behaviors.     

Recent research and development work on wood composites in Japan

Summary This paper highlights a number of articles on research and development on wood composites. The coefficient of variation in the mechanical properties of wood components tends to decrease when the thickness of the wood elements decreases. This finding was utilized in the manufacture of hollow cylindrical columns of laminated veneer lumber (LVL) from Cryptomeria plantation thinnings. In the future, the marketing of wood composite boards will tend toward two types: thick boards with low density properties and thin boards with fiber orientation. For the production of thick boards, fundamental parameters and application of steam-injection pressing have been studied, and continuous steam-injection pressing has been developed. For thin board production, generation principles of aligning torque in high-voltage system and the application has been studied. A new oriented mat former with electrodes positioned only at the reverse side of a forming belt has been developed. Various synthetic resins of low-molecular weight have been applied to improve dimensional stability of laminated products, such as LVLs and particleboards. Acetylation and formalyzation of fibers and particles were investigated to provide stabilized panels. High pressure steam treatment during pressing of wood composites has been studied and the process has been found effective and promising.The authors wish to thank Mr. Dwight A. Eusebio for his help in the preparation of this paperThis paper was presented at the IUFRO All Division 5 conference in Nancy, France, on August 15, 1992     

Effects of air injection on properties of particleboard manufactured using a radio-frequency hot press

The effectiveness of air injection for preventing the blowout of particleboards manufactured using a radio-frequency hot press was investigated by evaluating the board properties under artificially created conditions that were conducive to blowout. For evaluation, 10-mm-thick boards with densities of 0.7 and 0.8 g/cm³ and 20-mm-thick boards with a density of 0.7 g/cm³ were manufactured. Pressing times for the 10-mm-thick boards were 2, 4, 6, and 8 min, and those for the 20-mm-thick boards were 4, 6, 8, and 10 min. Without air injection, blowout occurred in all manufactured boards. With air injection, however, blowout did not occur in the 10-mm-thick boards with a density of 0.7 g/cm³. Moreover, air injection prevented blowout even when the board density and board thickness were increased to 0.8 g/cm³ (for 10-mm-thick boards) and 20 mm (the density was kept at 0.7 g/cm³), respectively. Air-injection radio-frequency pressing reduced the pressing time from 4 to 2 min for 10-mm-thick boards, and from 6 to 4 min for 20-mm-thick boards. Moreover, this reduction in the pressing time was achieved without a large reduction in the internal bond strength of the boards.     

刨花板厚度方向变形研究Ⅰ.尺寸稳定之化学热力学研究初步

本文从化学热力学角度出发 ,理论上分析了人造板尺寸稳定的一些普遍性规律 ,初步证明人造板热压后在变形恢复时 ,蠕变和松弛将会同时发生 ;人造板的尺寸稳定过程是通过释放非膨胀功耗能量和膨胀功耗能量而实现的 ,只有使体系以非膨胀功耗能量释放 ,才能对人造板的尺寸稳定性有利 ;同时为热堆放处理有利于人造板尺寸稳定从化学热力学找到理论根据     

薄刨花高密度人造板生产工艺初步研究

研究以厚度为10—200μm杨木刨花为原材料生产高密度人造板的工艺条件,探讨了热压温度、刨花施胶量、板材密度对产品性能的影响。结果表明,在热压温度155℃,板材密度为0．88g／cm^3,采用UF和MF混合添加,总施胶量为绝干刨花质量12％（其中MF占总施胶量的35％）的工艺条件下生产出的人造板具有良好的物理力学性能,各项指标达到或优于GB／T4897．3—2003,GB／T4897．4—2003刨花板国家标准的要求。     

Chemical changes of kenaf core binderless boards during hot pressing (I): influence of the pressing temperature condition

Self-bonding is the main factor of the performance expression of binderless boards, and therefore its clarification is considered to be an important issue. For this purpose, a series of chemical analyses were conducted on kenaf core binderless boards and their chemical changes during the hot-pressing process are discussed in this article. First of all, binderless boards were prepared from kenaf core powder at different pressing temperatures (without steam-explosion process) and were used for chemical analyses after they were reduced into powders and extracted with methanol. To investigate their chemical changes, lignin, holocellulose, and neutral sugar contents were determined, Fourier transform infrared (FTIR) spectra were recorded, and the nitrobenzene oxidation procedure was applied. As a result, it was found that parts of lignin and hemicelullose were decomposed during the hot-pressing process; however, the contribution of the resulting fractions to selfbonding was not observed. In addition, progress of condensation reactions in lignin and the formation of chemical bonds by low molecular weight conjugated carbonyl compounds in methanol extractives were observed. Thermal softening of lignin is also suggested to play an important role in the expression of board performance.     

Performance of particleboard manufactured using air-injection press II: effects of board density and thickness on the performance of board manufactured from low-moisture particles

Particleboards of different densities (0.6, 0.7 and 0.8 g/cm³) and thicknesses (10 and 20 mm) were manufactured from low-moisture particles using an air-injection press. The effects of the air injection on preventing blowout of the boards of different densities and thicknesses were investigated by artificially creating blowout-prone conditions using metal frames. The effects of the air-injection pressure on the board performance were also investigated. 10-mm-thick boards of 0.8 g/cm³ pressed at 170 °C blew out when air was not injected, but were successfully manufactured by injecting air. 10-mm-thick boards at 150 °C showed constant internal bond (IB), regardless of density, but at 170 °C, IB was higher in boards of higher densities. This was likely due to accelerated hardening of the urea–formaldehyde resin at 170 than 150 °C. At both pressing temperatures, low air-injection pressure did not cause blowout and a reduction in board performance. Air injection also prevented the blowout of thick boards of 20 mm and enabled successful manufacture, showing its effectiveness. The IB of the 20-mm-thick board manufactured using the air-injection press exceeded that of 20-mm-thick board manufactured using an ordinary hot press.