Manufacture and properties of binderless particleboard from bagasse I: effects of raw material type, storage methods, and manufacturing process

Binderless particleboards were manufactured from sugarcane (Saccharum officinarum L.) bagasse by steam-injection pressing and by using hot pressing as a reference method. The inner layer (core/pith) and the outer hard fibrous layer (face/rind) of bagasse were used as raw materials. The effects of bagasse type, manufacturing process, and storage method on the mechanical properties of binderless particleboards were investigated. The results showed that the bagasse pith particles provided better board properties than bagasse rind particles. It seemed that bagasse pith particles were more easily deformed than bagasse rind particles, enlarging the bonding contact area. The severe conditions of steam-injection pressing caused delamination on the bagasse pith binderless boards with densities of 0.6 g/cm³ or higher, and gave poor bonding quality. However, steam-pressed boards showed relatively higher board properties than hot-pressed boards. The storage method of sugarcane bagasse affected the chemical composition and the board properties. It was shown that the extent of self-bonding formation depends on the chemical and morphological properties of lignocellulosic materials, as well as on the manufacturing conditions. Part of this paper was presented at the 5th International Wood Science Symposium, Kyoto, Japan, September 2004     

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。     

Manufacture and properties of high-performance oriented strand board composite using thin strands

Three-layered composite oriented strand boards were manufactured using very thin hinoki (Japanese cypress, Chamaecyparis obtusa Endl.) strands oriented in the faces and mixtures of sugi (Japanese cedar, Cryptomeria japonica D. Don.) and hinoki particles in the core. The boards were composed of two density levels, with 1:8:1, 0.5: 9 : 0.5, and 0: 10 : 0 face: core: face ratios. Polymeric and emulsion type isocyanate resins were used. The resin contents for the strands in the face and particles in the core were 10% and 5%, respectively. The steam-injection press was applied at 0.62MPa (160°C), and the steam-injection time was 2min. The mechanical and physical properties of the boards were evaluated based on the Japanese Industrial Standard. The parallel moduli of rupture and elasticity along the strand orientation direction and the wood screw retaining force increased with increasing face/core ratios. Incorporation of 10%–20% of thin strands in the face of the boards improved the parallel moduli of rupture and elasticity by 47%–124% and 30%–65%, respectively. In addition, the thickness swelling after water-soaking at 20°C for 24h, and the parallel linear expansion after boiling for 2h and water-soaking at 20°C for 1 h, of the three-layered composite boards were below 8% and 0.15%, respectively, despite a short steam-injection press time. The thickness swelling of the boards decreased with increasing face/core ratios. In contrast, the presence of face strands seems to have a minimal effect on the moduli of rupture and elasticity along the perpendicular direction of the three-layered composite boards. A similar trend was observed for the internal bond strength, hardness, and linear expansion along the perpendicular direction.This paper was presented at the 47th annual meeting of the Japan Wood Research Society, Kochi, April 1997     

Review on Closing Steam-injection Pressing Technology

The general steam-injection pressing is mainly used for produce particleboards and medium density fiberboard. However, it is difficult to produce soft fiberboard with desired strength. However, the closing steam-injection pressing that based on the steam-injection pressing could. The wooden frame sealing up the slab could prevent the steam from emitting when the steam injected into the slab. The caloric released by steam condensation make the slab reach high temperature level for a short period. This method is very appropriate for making thick panels in theory, especially for the soft fiberboard. It makes a great leap forward on the hot pressing process that for wood-based panels. Moreover, it will be a meaningful technological breakthrough in developing new products and improving wood utilization.     

喷蒸热压刨花板断面密度分布的研究

通过喷蒸热压工艺与常规热压工艺压制刨花板的试验结果,分析了刨花板断面密度分布情况与刨花板性能的关系,验证了喷蒸热压工艺的优点。     

阻燃型杉木间伐材层压板的制造

探讨了在由双氰胺、磷酸、硼化物等配制的阻燃剂处理的杉木间伐材单板生产阻燃型层压板的工艺和性能.分析了各阻燃处理材的阻燃性能和热压工艺对杉木间伐材层压板胶合强度的影响,并检测了甲醛释放量.结果表明:该阻燃层压板达到了国标难燃一级标准;其胶合强度和游离甲醛两项指标均达到室内用材的要求.     

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。     

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。     

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     

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.     

Density profile relation to hardness of viscoelastic thermal compressed (VTC) wood composite

Density profile relation to hardness of VTC wood composites was evaluated using X-ray densitometry and modified Brinell hardness method using different applied forces. Moreover, surface elasticity was evaluated. Prior to lamination, the low-density hybrid poplar (Populus deltoides × Populus trichocarpa L.) and Douglas-fir (Pseudotsuga menziesii L.) thin boards were compressed to 1.22 or 1.14 g/cm³, respectively. Two different kinds of laminations were made, either single layer of 1.5 mm thickness or two 1.5-mm layers bonded to unmodified wood. The results show that thicker laminate has a great positive influence on Brinell hardness. This study suggests that results from the existing method for Brinell hardness are not comparable, and if applied force is chosen without restraint, the effect on the hardness value is significant for inhomogeneous wood composites.     

喷蒸热压法棉秆无胶碎料板的研制

以棉秆为原料,采用喷蒸热压法研制无胶碎料板,探讨板的密度、蒸汽压力及喷蒸时间对棉秆无胶碎料板的物理力学性能的影响.结果表明:在试验范围内,随着板密度增大,无胶碎料板的静曲强度、弹性模量与内结合强度明显提高;提高蒸汽压力及延长喷蒸时间,能明显降低无胶碎料板的吸水厚度膨胀率.     

木塑复合板主要工艺对材料性能的影响

研究了木粉与聚丙烯为主要原料的复合材料的主要力学性能和尺寸稳定性.实验结果表明:热压时间对复合材料的力学性能有一定的影响,加压时间为9min,复合板的力学强度较优,吸水厚度膨胀率小;木塑配比对复合材料的力学性能有较大的影响,随着配比的增加,板性能呈现逐渐下降的趋势;配比对吸水厚度膨胀率影响明显,木粉的比例越高,吸水厚度膨胀率越高.     

细木工板作装饰材料的应用

介绍了细木工板的特点及选择其作装饰材料时应遵循的原则。     

覆塑竹帘胶合板"冷-热-冷"胶合新工艺的研究

针对覆塑竹帘胶合板现有的"冷-热-冷"胶合工艺存在能耗高、用水量大的缺点,将胶合工艺改进为先在热压机内采用"热-热"工艺胶合成板,然后在冷压机内进行冷却定型的新工艺。实验室研究表明:新工艺不仅可以节能、节水,而且板材的胶合质量与表面性能都可以满足相关标准的质量要求。     

木粉加入量对木／塑复合材料性能影响的研究

研究了聚丙烯与木粉以不同比率复合而成的材料的物理力学性能和复合形态特征。结果表明：不同混合比率的聚丙烯与木粉进行复合后所得的复合材料，除冲击强度有所降低外，其它力学性能均比纯聚丙烯的有较大幅度的提高。木粉表面的酯化处理可以改善木塑界面之间的相容性和复合材料的均匀性。在木塑复合过程中木塑之间发生镶嵌现象使木塑之间产生物理结合。     

Influence of pressing parameters on mechanical and physical properties of self-bonded laminated beech boards

Abstract

Five-ply self-bonded boards were obtained by pressing beech veneers parallel to the grain without additional adhesives, steam or pre-treatment. Fifteen different combinations of pressing parameters were tested, including temperature (200°C, 225°C and 250°C), pressure (4, 5 and 6 MPa) and pressing time (240, 300 and 360 seconds). Due to severe pressing conditions, the new product showed a higher density and different properties compared to a conventionally glued laminated wooden board. The self-bonding quality was assessed through dry shear strength tests, through a three-point bending test and a water-soaking test at 20°C. The dimensions in the cross section of the boards were measured after soaking in water. Results show that the choice of pressing parameters affects all the mechanical and physical properties tested. A statistical analysis revealed that the pressing temperature is the most influential parameter. Boards pressed at 200°C delaminated rapidly in water, whereas boards pressed at 225°C delaminated only at core-positioned layers after 48 hours and boards pressed at 250°C did not delaminate at all in water. Compared to panels pressed at lower temperatures, boards pressed at 250°C had the highest density, a higher shear and bending strength and a lower water absorption.     

Thermal insulation properties of wood-based sandwich panel for use as structural insulated walls and floors

Thermal insulation and warmth-keeping properties of thick plywood-faced sandwich panels with low-density fiberboard (plywood-faced sandwich, PSW), which were developed as wood-based structural insulation materials for walls and floors, are comprehensively clarified. The properties focused on were thermal conductivity (λ), thermal resistance (R), and thermal diffusivity (D). The results for PSW panels were compared with those for commercial wood-based boards, solid wood, and commercial insulators. The λ values were measured for PSW panels and their core and face elements. As a result, the composite theory of λ was found to be appropriate for PSW composites, because the calculated/experimental λ ratios were approximately 90%. The λ values for PSW panels with densities of 340 kg/m³ (PSW350) and 410kg/m³ (PSW400) were 0.070 and 0.077W/mK, respectively. The R values for PSW350 and PSW400 were 1.4 and 1.2m²K/W, and the D values were 0.00050 and 0.00046m²/h, respectively. Consequently, the PSW provided thermal insulation properties superior to those of the boards and in terms of warmth-keeping properties were greatly advantageous over the insulators. These advantages were due to the moderate densities of PSW panels. The PSW panel with sufficient thickness showed remarkably improved thermal resistance compared with those of the boards.     

Performance of three-layer composites with densified surface layers of Nothofagus pumilio and N. antarctica from Southern Patagonian forests

Nothofagus pumilio and N. antarctica forests of Southern Patagonia, Argentina are currently being managed for production of saw logs with fast growing conditions. The result of these management strategies is faster growing forests, but also an increase in the percentage of low-density wood. The motivation for this study was to find a way to valorise this low-density wood. Surface and bulk densification treatments were applied these wood species and were then applied as face layers in three-layer composites. The mechanical properties of three-layer composites were studied. The modulus of elasticity, modulus of rupture, and modulus of hardness were improved compared to many types of structural composite lumber. This increase in mechanical properties of N. pumilio and N. antarctica wood opens the possibility for its use in structural composites and added value to these otherwise underutilised and undervalued species.     

Mechanical properties of natural fiber composites produced using dynamic sheet former

ABSTRACT

Composites formed from wood fibers and man-made cellulosic fibers in PLA (polylactic acid) matrix, manufactured using sheet forming technique and hot pressing, are studied. The composites have very low density (due to high porosity) and rather good elastic modulus and tensile strength. As expected, these properties for the four types of wood fiber composites studied here improve with increasing weight fraction of fibers, even if porosity is also increasing. On the contrary, for man-made cellulosic fiber composites with circular fiber cross-section, the increasing fiber weight fraction (accompanied by increasing void content) has detrimental effect on stiffness and strength. The differences in behavior are discussed attributing them to fiber/ fiber interaction in wood fiber composites which does not happen in man-made fiber composites, and by rather weak fiber/matrix interface for man-made fibers leading to macro-crack formation in large porosity regions.