Effects of strand length and layer structure on some properties of strandboard made from bamboo

Strandboard panels were experimentally produced from moso bamboo (Phyllostachys pubescens) using various strand lengths and layer structures to evaluate the effects of manufacturing parameters on panel properties. The strandboard was fabricated in a laboratory using diphenylmethane diisocyanate (MDI) resin and laboratory-made strands of four lengths and four different structures. Strand alignment distributions and concentration parameter (k) values were greatly affected by strand length. A linear correlation was found between the value of k and the modulus of rupture (MOR), with correlation coefficients of 0.81 and 0.93 for unidirectional boards and three-layer boards, respectively. This correlation may be used to predict the strength properties of boards. Bending properties were significantly affected by both the strand length and the layer structure of the bamboo strandboard tested. Elasticity data from unidirectional boards and random boards can be used to predict the elastic properties of three-layer boards. The linear expansion (LE) of the random boards increased with decreasing strand length. The difficulty in mat forming and resin distribution for longer strands could cause deviation in modulus of elasticity (MOE) and LE, especially in strand lengths around 80 mm.     

Formation of the density profile and its effects on the properties of particleboard

Summary Two types of particleboards bonded with an isocyanate resin, one with uniform vertical density profile (homo-profile), and the other with conventional U-shaped profile, were fabricated to various density levels using lauan (Shorea spp.) particles. The fundamental relationships between the density profile and the board properties were determined, and the results are summarized as follows: 1. In homo-profile boards, the moduli of rupture (MOR) and elasticity (MOE), internal bond (IB) strength, and screw withdrawal resistance (SWR), are highly correlated to the board mean density. 2. The bottom limit of the board density is estimated to be ca. 0.25 g/cm³, based on the correlation regressions between mechanical properties and mean density. 3. At equal mean density level, the MOR and MOE of the conventional particleboards are higher than the homo-profile boards, due to the higher density near the faces. However, the reverse is true for IB, owing to the presence of the low density core in the former. 4. The net impact of peak density on MOR and MOE is greater at higher mean density level while raising the core density results in more pronounced improvement in IB at lower density. 5. In addition to the compaction ratio, the dimensional stability of the board is also affected by the peak area and mat moisture content. Received 9 January 1997     

竹木复合定向刨花板强度性能研究

本文论述了竹材、意大利杨复合定向刨花板的强度性能,就胶种、刨花厚度、竹材所占比率、板密度、板坯结构、施胶量等诸因子对板材强度性能的影响进行了探讨。结果表明:(1)胶种对竹木复合定向刨花板的强度影响不大;(2)降低刨花厚度或提高板密度均可使板材强度提高;(3)单层结构的复合定向刨花板强度最高;(4)提高板材中竹材的比率可使板子强度明显改善;但竹材比率过高时,板材强重比反而下降,呈开口向下的抛物线型变化;(5)酚醛树脂定向刨花板的强度随原料酸性增大而降低。     

Effects of peeling and steam-heating treatment on mechanical properties and dimensional stability of oriented <Emphasis Type="Italic">Phyllostachys makinoi</Emphasis> and <Emphasis Type="Italic">Phyllostachys pubescens</Emphasis> scrimber boards

Epidermal peeling treatment (EPT) and steam-heating treatment (SHT) are two popular pretreatments for bamboo processing. This study examined the effects of EPT and SHT on strength properties, profile density distribution, internal bond strength (IB), rate of springback, nail withdrawal resistance, and dimensional stability of oriented bamboo scrimber board (OBSB) made of moso bamboo (Phyllostachys pubescens Mazel) and makino bamboo (P. makinoi Hayata) strips. Results obtained using non-destructive testing (NDT) revealed that EPT for moso bamboo in the processing of OBSB caused lower ultrasonic-wave velocity (V_u) and dynamic modulus of elasticity (DMOE_u) parallel to the fiber direction, but higher V_u and DMOE_u perpendicular to the fiber direction. However, EPT slightly affected variations in modulus of elasticity (MOE) and modulus of rupture (MOR) of moso bamboo. In contrast, the effects of SHT on V_u and DMOE_u were inconsistent and insignificant among the OBSB samples. On the other hands, SHT caused increasing in MOE and MOR of OBSB, but leads to decrease in MOE and MOR of OBSB comprising bamboo strips after EPT. Both EPT and SHT contributed to more uniform profile densities in OBSB and had a positive impact on nail withdrawal resistance. EPT increased IB of moso bamboo and SHT enhanced IB of makino bamboo with epidermis only. Bamboo strips after SHT resulted in significant decrease in water absorption of all OBSB specimens. Reduction in swelling as a result of SHT not only improved the dimensional stability of OBSB but also enhanced strength.     

Effects of water soaking and outdoor exposure on modulus of rupture and internal bond strength of particleboard

Phenol–formaldehyde resin-bonded particleboard (PF board) and isocyanate resin-bonded particleboard (MDI board) were soaked in water at 40, 70 and 100 °C, and the relationships between soaking conditions and board properties were analyzed. The relationships between the deterioration of board properties resulting from water soaking and those arising from outdoor exposure were also analyzed. At 100 °C, the modulus of rupture (MOR) and internal bond strength (IB) of the PF board decreased significantly within the first hour, and subsequently constant values were shown with increasing soaking time. This low constant value was defined as the lower limit. At 70 °C, both the MOR and IB decreased with increasing soaking time, and reached the lower limit. At 40 °C, however, neither decreased significantly with increasing soaking time and neither reached the lower limit. The MOR of the MDI board showed the same trend as the PF board. However, the IB of the MDI board showed a different trend to the PF board, that is, the lower limit of IB required extensive soaking, even at 100 °C. The MOR and IB of both the PF and MDI boards reached the lower limit when thickness change peaked. On the other hand, the MOR and IB for outdoor exposure were lower than those for water soaking, even at the same thickness change. The MOR and IB of water soaking decreased owing to the collapse of the bonding points caused by board swelling. On the other hand, the board properties of outdoor exposure decreased owing to the collapse of the bonding points, and biodegradation also added to the decrease.     

竹材刨花板热压工艺的研究

利用正交试验法研究了竹材刨花板热压曲线中各因素与极材的静曲强度，弹性模量及平面抗拉强度间的关系。结果表明，第一阶段压力是影响竹材刨花板力学性能的最主要因素，热压温度及采一阶段时间对力学性能也有较大的影响。根据试验结果确定竹材刨花板的最佳热压工艺参数。     

Evaluating the durability of wood-based panels using internal bond strength results from accelerated aging treatments

In this study, the durability of wood-based panels was evaluated by comparing the internal bond (IB) strength retention after five different laboratory-based accelerated aging tests with the IB retention after 5 years of outdoor exposure in Shizuoka City. In each accelerated aging test, the IB retention of MDI-bonded panels showed high retention compared to other panels. Outdoor exposure in Shizuoka City resulted in an IB retention value for particleboard (PF) and oriented strandboard (aspen) of less than 10% after the 5-year exposure period. Medium-density fiberboards maintained their initial IB strength over the same period. Calculation of the mean IB retention for all board types allowed comparison of the severity of aging between the accelerated test methods and outdoor exposure. The ASTM six-cycle test method was the most severe among the standard treatment cycles applied.     

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     

Reducing resin content and board density without adversely affecting the mechanical properties of particleboard through controlling particle size

Density and resin content are two factors that have a signifi- cant effect on the production cost of wood composite. However, particle size affects resin content and density, which suggests that the interaction of these three factors can be manipulated to reduce the board density and resin content of particleboard without adversely influencing its mechani- cal properties. Some mathematical functional forms based on resin con- tent, board density and slenderness ratio were regressed and an appropri- ate form was chosen. According to analysis of the results using SHA- ZAM 9 software, the exponential function best fit the experimental data. Finally, "indifference curves" of mechanical properties were illustrated and analyzed. The results indicated that negative effects of density or resin content reduction on mechanical properties could be compensated for by controlling particles’ slenderness ratio. Interestingly, increases in slenderness ratio compensated for the negative effects of decreases in resin content or board density on module of rupture (MOR) and module of elasticity (MOE). Moreover, this "compensation ratio" intensified as resin content or density decreased and/or as the MOR or MOE increased. On the other hand, reduction in slenderness ratio indicated a comple- mentary effect on reducing internal bond (IB) strength, a result of de- creases in resin content or density. Moreover, this "complementary ratio" was intensified as resin content or density decreased and/or as IB strength increased.     

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.     

玻璃纤维束增强刨花板的研究

采用玻璃纤维束增强刨花板的试验结果表明,随着玻璃纤维束施加量的增加,刨花板的强度和刚度（ＭＯＲ和ＭＯＥ）有显著的提高,但施加量达到一定程度后,升高趋势逐渐平缓;随着玻璃纤维束间距的减小,刨花板的强度和刚度（ＭＯＲ和ＭＯＥ）呈直线上升,而内结合强度（ＩＢ）变化规律不明显,当间距小到一定程度后,ＩＢ很难达到德国室外用刨花板标准ＤＩＮ ６８７６３ Ｖ１００的要求;随着琉璃纤维束在刨花板厚度方向上的位置由     

Durability characteristics of cement-bonded particleboards manufactured from maize stalk residue

Cement-bonded particleboards of 6 mm in thickness were manufactured using maize stalk (Zea mays) particles of uniform sizes at three levels of board density and additive concentrations respectively. The bending strength and dimensional properties were assessed. Increase in board density and additive concentration caused increase in Modulus of rupture (MOR), Modulus of elasticity (MOE), and decrease in Thickness swelling (TS) and Water absorption (WA). The MOR, MOE and TS of the boards were significantly affected by board density except for WA, but additive concentration affected all the boards’ properties examined at p ≥ 0.05. Strong and dimensional stable cement-bonded boards could be manufactured from maize stalk particles with Portland cement as the binder after hot water treatment. Although the dimensional stability and mechanical strength properties of the boards were affected by the board density and additive concentration, the study revealed that cement-bonded particleboards could be manufactured from maize stalk (Zea mays) particles. However, the increase in board density and additive concentration could cause the increase in MOR and MOE, and cause the decrease in TS and WA of boards.     

Medium-density fiberboard performance as affected by wood fiber acidity, bulk density, and size distribution

The properties of medium-density fiberboard (MDF) panels as affected by wood fiber characteristics were investigated. Wood chips from three softwood and one hardwood species were refined under the same refining conditions to make four different types of fibers. The resulting fibers were characterized by fiber size distribution, bulk density, pH value, and buffering capacity. Using the same resin system and hot-pressing parameters, MDF panels were produced and evaluated for internal bonding (IB), modulus of rupture (MOR), modulus of elasticity (MOE), thickness swelling, and linear expansion. The pH values and alkaline buffering capacities of raw materials were reduced considerably after refining. IB was strongly related to the pH value of fibers. The mechanical properties increased with alkaline buffering capacity. IB, MOR, and MOE increased with the bulk density of fibers. Increased proportions of coarse fibers had negative effects on the panel mechanical properties.     

半干法石膏纤维板工艺研究：Ⅰ.原料配比,密度等对板材性能的影响

本研究是建立在我国资源和工业技术基础之上,探讨利用木纤维以半干法制造石膏纤维板（ＧＦＢ）的生产工艺;提出了半干法石膏纤维板的工艺方案,并建立了密度、木膏比、水膏比与板材性能的数学模型。结果表明：密度（Ｄ）增加,板材力学性能显著提高,木膏比（Ｗ／Ｇ）、水膏比（Ｈ／Ｇ）有效强的交互影响。木膏比增大,板材反弹率和吸水厚度膨胀率（ＴＳ）增加,纤维形态,蒸煮工艺对板材静曲性能无显著影响,纤维形态对内结合强度     

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%.     

烟秆/木材刨花板的初步研究烟秆

初步探讨了实验室条件下烟秆/木材刨花板的生产工艺,研究了热压时间、施胶量、密度、木刨花加入量等因素对板材的静曲强度、内结合强度、吸水厚度膨胀率的影响.实验结果表明,烟秆/木材刨花板的静曲强度和吸水厚度膨胀率较纯烟秆刨花板有所提高,内结合强度相差不大.     

木材-橡胶功能性复合材料制造工艺主要影响因素的交互作用和相关性(英文)

确定聚异氰酸酯(PMDI)与脲醛胶(UF)混合胶黏剂胶接木材与废旧轮胎橡胶制备功能性复合材料工艺的可行性;研究木材-橡胶功能性复合材料制备工艺的主要影响因素(密度、热压时间和温度)对复合材料力学性能:内结合强度(IB)、静曲强度(MOR)、弹性模量(MOE)作用的相关性。采用Design-Expert的响应曲面法分析各主要因子密度、温度、时间对力学性能影响的变化规律,优化各因子,并揭示相互影响和作用机制。结果表明:密度对材料的力学强度有显著性的影响,热压温度与时间的交互作用同样对材料的力学性能影响显著;采用低成本的PMDI/UF混合胶黏剂能够很好地胶结木材和橡胶制备功能性复合材料;获得木材-橡胶复合材料最佳优化工艺:密度1000kg·m-3、热压时间300s、热压温度170℃。利用电子扫描电镜(SEM)揭示了木材-橡胶功能性复合材料的微观结构,并进行界面结构分析。对PMDI/UF胶黏剂胶接橡胶和木材的物理化学胶合机制进行全面系统的分析。     

Preparation of composite board using foil-laminated and plastic-laminated liquid packaging paperboard as raw materials

We investigated the properties of composite board formed using base sheets of aluminum foil-laminated and polyethylene (PE) plastic-laminated liquid packaging paperboard (LP) as an alternative to recycling these items in wastepaper stream. Boards of different specific gravities ranging from 0.55 to 0.75 were made by pressing shredded LP blended with urea resin having resin content of 6%–10% at 180°C. Subsequently, we also prepared mixed particleboard [wood (WD) particles and LP mixed], three-layered particleboard (LP as the middle layer, WD in the upper and lower layers), and wood particleboard all having resin content of 10% and various specific gravities. Static bending and internal bonding strengths and thickness swelling of the specimens were determined to examine their properties. At the same specific gravity, the properties of LP particleboards were affected by their resin content. The modulus of rupture (MOR), modulus of elasticity (MOE), and internal bond strength of the LP particleboards increased with increasing specific gravity of the boards at the same resin content, but thickness swelling of the LP particleboards showed the reverse trend. The average MOR of the LP particleboards approximated that of the mixed particleboards and was greater than those of the three-layered particleboards and wood particleboards. Internal bond strength and thickness swelling of the LP particleboards were smaller than those of the other particleboards. Based on the above observations, we deemed that LP can be made into composite boards with adequate properties either alone or mixed with wood particles.     

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     

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。