轻质无胶蔗渣板的研究

以蔗渣为原料,不采用合成树脂,而是加入少量环保型添加剂(有机酸或糖)压制轻质无胶蔗渣板。探讨了板的密度,以及防水剂的有无对轻质无胶蔗渣板的物理力学性能及热学性能的影响。采用X射线衍射仪(XRD)、傅里叶变换红外光谱仪(FTIR)初步分析了加入添加剂、防水剂对板的物理力学性能及胶合机理的影响,结果表明:随着密度增大,板的导热性能,MOR值和TS值上升;加入添加剂后,板的纤维素结晶度增大;加入少量防水剂(石蜡)后,板的纤维素结晶度没有明显变化,—OH吸收峰强度下降,TS下降明显;在研究范围内,板的导热系数达到国家林业行业标准LY/T 1718-2007所要求的保温材料的要求。本研究既扩大了人造板生产的原料来源,又解决了人造板产品的游离甲醛释放问题。     

Chemical changes in steam-pressed kenaf core binderless particleboard

The effects of chemical changes in kenaf core binderless particleboards on the bonding performance and thickness swelling of boards were investigated by chemical and spectroscopic analyses. Mild steam-injection treatments (0.6–1.0MPa) caused significant degradation of hemicelluloses, lignin, and cellulose. Conventional hot pressing caused a lower degree of degradation of the chemical components. The hot-pressed kenaf core board without any binders showed poor bonding performance. Thus, it was found that partial degradation of the three major chemical components of the kenaf core by mild steam-injection treatment increased the bonding performance and dimensional stability of the binderless boards, and gave better quality binderless boards than those made by hot-pressing treatments.Part of this report was presented at the 4th International Wood Science Symposium, Serpong, Indonesia, September 2002; and at the 53rd Annual Meeting of The Japan Wood Research Society, Fukuoka, March 2003     

Development of binderless particleboard from kenaf core using steam-injection pressing

Binderless particleboards were successfully developed from kenaf core using the steam-injection press. The effects of board density, steam pressure, and treatment time on the properties of the board were evaluated. The target board densities were relatively low, ranging from 0.40 to 0.70g/cm³. The properties [i.e., moduli of rupture (MOR) and elasticity (MOE) in both dry and wet conditions, internal bonding strength (IB), and water absorption (WA)] of the boards increased linearly with increasing board density. Steam pressure and treatment time also affected the board properties. The bending strength and IB were improved with increased steam pressure. A long steam treatment time contributed to low thickness swelling (TS) values and thus better dimensional stability. The appropriate steam pressure was 1.0MPa, and the treatment time was 10–15min. The properties for 0.55g/cm³ density boards under optimum conditions were MOR 12.6MPa, MOE 2.5GPa, IB 0.49MPa, TS 7.5%, and wet MOR 2.4MPa. Compared with the requirement of JIS 5908, 1994 for particleboard, kenaf binderless boards showed excellent IB strength but relatively poor durability.Part of this report was presented at the 19th Annual Meeting of the Japan Wood Technological Association, Tokyo, October 2001     

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     

Manufacture and properties of low-density binderless particleboard from kenaf core

Low-density binderless particleboards from kenaf core were successfully developed using steam injection pressing. The target board density ranged from 0.10 to 0.30g/cm³, the steam pressure used was 1.0MPa, and the steam treatment times were 7 and 10min. The mechanical properties, dimensional stability, and thermal and sound insulation performances of the boards were investigated. The results showed that the low-density kenaf binderless particleboards had good mechanical properties and dimensional stability relative to their low board densities. The board of 0.20g/cm³ density with a 10-min treatment time produced the following values: modulus of rupture 1.1MPa, modulus of elasticity 0.3GPa, internal bond strength 0.10MPa, thickness swelling in 24h water immersion 6.6%, and water absorption 355%. The thermal conductivity of the low-density kenaf binderless particleboards showed values similar to those of insulation material (i.e., rock wool), and the sound absorption coefficient was high. In addition, the boards are free from formaldehyde emission. Kenaf core appears to be a potential raw material for low-density binderless panels suitable for sound absorption and thermally resistant interior products.Part of this report was presented at the 52th Annual Meeting of the Japan Wood Research Society, Gifu, Japan, April 2002     

Gypsum-bonded particleboard manufactured from agricultural based material

Gypsum-bonded particleboard （GBPB） panels were made from various mixtures of particles of bagasse （Saccharum officinarum L.） and wheat straw （Triticum aestivum L.）, bonded with different ratios of particle/gypsum. This study examined the feasibility of bagasse and wheat straw particles in the production of GBPB. One-layer experimental GBPBs with a density of 1.05 or 1.20 g.cm-3 were manufactured at different ratios of bagasse/wheat straw, i.e., 100%/0%, 93.75%/6.25%, 87.5%/12.5%, 75%/25%, 50%/50%, 25%/75% and 0%/100% using two particle/ gypsum composite ratios, i.e., 1/2.75 and 1/3.25 by weight. Thickness swelling （TS）, water absorption （WA）, modulus of rupture （MOR）, modulus of elasticity （MOE） and internal bond strength （IB） properties of the boards were evaluated and a statistical analysis was performed in order to examine the possible feasibility of these agricultural residues for use in commercial GBPB manufacturing. We determined that WA of panels decreases as the amount of straw increases to 100% and the LR/G （wood/gypsum） ratio decreases to 1/3.25, whereas the TS of panels decreases as the proportion of straw decreases to 0% and the LR/G ratio increases to 1/2.75. The experimental results also show that the MOR and MOE of panels containing 0%, 6.25% and 12.5% wheat straw with a LR/G ratio of 1/2.75 were higher than those of panels made from 25%-100% wheat straw with a LR/G ratio of 1/2.75, as well as those from all other percentages of straw with a LR/G ratio of 1/3.25. On the other hand, the IB of panels containing more than 12.5% straw with LR/G ratios of 1/2.75 and 1/3.25 were lower than those of panels made from 0-12.5% straw also with both LR/G ratios. Panels consisting of 0%, 6.25% and 12.5% wheat straw with LR/G ratios of 1/2.75 and 1/3.25 met the minimum EN standard requirements of mechanical properties for general purposes. All of the panels containing 0-100% wheat straw with a LR/ G ratio of 1/2.75 or 1/3.25 met the required level of TS for 24-h immersion.     

Properties of kenaf core binderless particleboard reinforced with kenaf bast fiber-woven sheets

Kenaf composite panels were developed using kenaf bast fiber-woven sheets as top and bottom surfaces, and kenaf core particles as core material. During board manufacture, no binder was added to the core particles, while methylene diphenyldiisocyanate resin was sprayed to the kenaf bast fiber-woven sheet at 50 g/m² on a solids basis. The kenaf composite panels were made using a one-step steam-injection pressing method and a two-step pressing method (the particleboard is steam pressed first, followed by overlaying). Apart from the slightly higher thickness swelling (TS) values for the two-step panels when compared with the one-step panels, there was little difference in board properties between the two composite panel types. However, the two-step pressing operation is recommended when making high-density composite panels (>0.45 g/cm³) to avoid delamination. Compared with single-layer binderless particleboard, the bending strengths in dry and wet conditions, and the dimensional stability in the plane direction of composite panels were improved, especially at low densities. The kenaf composite panel recorded an internal bond strength (IB) value that was slightly low because of the decrease of core region density. The kenaf composite panel with a density of 0.45 g/cm³ (one-step) gave the mechanical properties of: dry modulus of rupture (MOR) 14.5 MPa, dry modulus of elasticity (MOE) 2.1 GPa, wet MOR 2.8 MPa, IB 0.27 MPa, TS 13.9%, and linear expansion 0.23%.     

Characterization of crack propagation in particleboard

Summary In this paper the wedge-splitting-method (Tschegg 1986) for mode I-testing was applied to specimens of particleboard. Specimen geometry and loading-device used for this method allow testing under the condition of steady state crack propagation. Therefore the full load-displacement curves can be recorded. Using the loaddisplacement-curves, different ways of evaluation have been carried out to determine relevant fracture properties like the specific fracture energy G_f and the crack resistance R_c of the investigated material for two different orientations.The authors thank Dr. D. M. Tan for conducting the FE-calculations. Financial support by the Fonds zur Förderung der wissenschaftlichen Forschung, Wien is gratefully acknowledged     

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.     

柠檬桉水泥刨花板若干工艺因子的研究

通过对柠檬桉制造水泥刨花板的可能性、水泥/刨花的比率、水泥种类与板材性能关系等因素的研究,结果表明:使用添加剂或对木材进行热水处理可以使柠檬桉成为适宜制造水泥刨花板的树种。     

Modelling of vertical density profile of particleboard,manufactured from hardwood sawmill residue

Abstract

Particleboards are generally made in three layers using softwood as the major raw material. Limitation on natural wood resources and concerns about the carbon footprint of products has created a significant interest in environmentally friendly or ‘green’ building materials. Hardwood sawmill residue, which has been disposed as solid waste, was investigated by authors as the main raw material for producing particleboard at RMIT University, Australia. Physical and mechanical properties of final particleboard were measured and analysed against original materials and process variables. The density of a particleboard along its thickness direction is not uniform, and is called the vertical density profile (VDP) which is dependent upon processing parameters. The VDP influences particleboard properties including flexural strength and its dimensional stability and fastening capacity. It is important to influence the formation of the VDP, altering processing variables, to achieve optimum particleboard properties. This paper presents an attempt to develop a model to predict the formation of the VDP of hardwood residue particleboard compared to processing parameters, using the theory of experimental design. The advantages of such a model in optimising particleboard properties are also discussed.     

Utilization of sweet sorghum bagasse and citric acid for manufacturing of particleboard II: influences of pressing temperature and time on particleboard properties

Development of environmentally friendly particleboard made from sweet sorghum bagasse and citric acid has recently attracted attention. In this study, we investigated the effects of pressing temperature and time on physical properties, such as dry bending (DB), internal bond strength (IB), and thickness swelling (TS) of particleboard. Wet bending (WB), screw-holding power (SH), biological durability, and formaldehyde emission of particleboard manufactured under effective pressing temperature and time were also evaluated. Particleboards bonded with phenol formaldehyde (PF) resin and polymeric 4,4′-methylenediphenyl isocyanate (pMDI) were manufactured as references. Effective pressing temperature and time were 200?°C and 10 min, respectively. It was clarified that DB, IB, and TS satisfied the type 18 requirements of the JIS A 5908 (2003), and were comparable to those of particleboard bonded with PF and pMDI. The WB and SH of particleboard did not satisfy type 18 of JIS. Particleboard manufactured under effective pressing conditions had good biological durability and low formaldehyde emission. Based on the results of infrared spectra measurement, the degree of ester linkages increased with increased pressing temperature and time.     

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.     

Performance of particleboard manufactured using air-injection press I: effects of air-injection press on preventing blowout of board manufactured from low-moisture particles

An air-injection press (AIP) was developed to prevent accidental blowouts of boards during production. In this study, the effects of the AIP on preventing blowouts were investigated by artificially creating a blowout-prone condition, and the press was shown to be effective in preventing blowouts. The modulus of rupture of the boards was almost constant irrespective of pressing time. Longer pressing time resulted in higher internal bond strength when pressed at 170 °C. The thickness swelling of the boards pressed at 170 or 190 °C was almost uniform irrespective of pressing time, and the manufactured boards showed performance similar to those manufactured with an ordinary press. The AIP prevented blowouts sufficiently even when the pressure of the injected air was reduced, and this reduction did not adversely decrease the performance of the boards. Air injection reduced formaldehyde emissions from the board.     

再谈利用蔗渣生产刨花板必须除髓

目前用蔗渣为原料生产刨花板仍然有不少生产厂家采取不除蔗髓，直接用渣生产刨花板的工艺，实践表明弊多利少，现推荐一种简捷的除髓工艺，既不增加设备，又不扩建，且除髓效果显著.     

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.     

Blowout conditions and properties of isocyanate resin bonded particleboard manufactured from high-moisture particles using an air-injection press

Blowouts of particleboards were artificially induced by increasing the vapor pressure inside the boards. Isocyanate resin bonded boards were manufactured from high-moisture particles, and the blowouts and board properties were analyzed. Boards with a high resin content of 5 % showed high bonding strength and did not blow out when pressed at 190 °C, but blew out at a raised temperature of 210 °C to increase vapor pressure inside the boards, thereby showing that blowout occurred when vapor pressure inside the boards exceeded the bonding strength of isocyanate resin. Boards with a low resin content of 2.5 % had low bonding strength and blew out when manufactured without air injection, but were successfully manufactured with air injection that prevents blowouts. However, the injection of high-pressure air reduced the strength properties of the board and increased the coefficient of variation, likely due to the discharge of isocyanate resin from the boards. Therefore, very small local blowouts occurred inside the boards, which lowered the strength properties of some specimens and led to a large coefficient of variation. When the pressure of injected air was lowered, the strength properties increased and the coefficient of variation decreased. This was possibly because the low-pressure air allowed isocyanate resin to remain in the boards, resulting in virtually no parts showing very low-strength properties.     

Development of binderless fiberboard from kenaf core

Binderless fiberboards with densities of 0.3 and 0.5 g/cm³ were developed from kenaf core material using the conventional dry-manufacturing process. The effects of steam pressure (0.4–0.8 MPa) and cooking time (10–30 min) in the refining process, fiber moisture content (MC) (10%, 30%), and hot-pressing time (3–10 min) on the board properties were investigated. The results showed that kenaf core binderless fiberboards manufactured with high steam pressure and long cooking time during the refining process had high internal bond (IB) strength, low thickness swelling (TS), but low bending strength values. The binderless fiberboards made from 30% MC fibers showed better mechanical and dimensional properties than those from air-dried fibers. Hot-pressing time was found to have little effect on the IB value of the binderless board at the refining conditions of 0.8 MPa/20 min, but longer pressing time resulted in lower TS. At a density of 0.5 g/cm³, binderless fiberboard with the refining conditions of 0.8 MPa/20 min recorded a modulus of rupture (MOR) of 12 MPa, modulus of elasticity (MOE) of 1.7 GPa, IB of 0.43 MPa, and 12% TS under the optimum board manufacturing conditions. Part of this article was presented at the 54th Annual Meeting of the Japan Wood Research Society, Hokkaido, August 3–5, 2004     

Self-bonding characteristics of binderless kenaf core composites

We investigated optimum self-bonding conditions of kenaf core composites manufactured by steam treatment, and discussed on the roles of cinnamic acids in the self-bonding mechanism. The presence of cinnamic acids in the kenaf core and its composites were analyzed by pyrolysis gas chromatography-mass spectrophotometry in the presence of tetramethyl ammonium hydroxide (TMAH/Py-GC-MS). The results showed that the optimum bonding properties of kenaf core composites were achieved under these conditions: steam pressure of 0.8–1.0 MPa and pressing time of 10–15 min were able to provide shear strength of 0.40–0.42 MPa while having 2–5% of weight loss. Lignin analysis showed that steam-treated kenaf core composites had a lower proportion of syringyl- to guaiacyl-derived moieties and also cinnamic acids to guaiacyl-derived moieties than its native counterpart. The results indicated that some parts of the ester-linked cinnamic acids were also cleaved due to the degradation of hemicelluloses and lignin during steam treatment. Based on these results, it was concluded that in addition to three main components, the cinnamic acid was also suggested to participate in the self-bonding mechanism of non-wood lignocellulosic binderless boards.