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     

Water resistance properties of kenaf core binderless boards

Abstract Binderless boards were prepared from kenaf core under various manufacturing conditions and their water resistance properties were evaluated. The board properties evaluated were retention ratios of modulus of rupture (MOR) and modulus of elasticity (MOE), internal bonding strength after water treatment (IB), thickness swelling (TS), water absorption (WA), and linear expansion (LE). These values were then compared with those of boards bonded with urea-formaldehyde (UF), urea melamine formaldehyde (UMF), and phenol-formaldehyde (PF) resins, and their water resistance properties were assessed. We found that pressing temperature was one of the most important conditions for the improvement of water resistance properties. The retention ratios of MOR, MOE, and IB of kenaf core chip binderless boards (pressing temperature 200°C, target density 0.8g/cm³, and the three-step pressing of 6MPa for 10min, then 4MPa for 3min, and 2MPa for 3min) were 37.1%, 49.9%, and 55.7%, respectively, compared with values for UMF-bonded boards of 22.5%, 27.1%, and 40.7%, and values for PF-bonded boards of 42.8%, 41.8%, and 54.1%, respectively. The results showed that the water resistance properties of binderless boards were higher than those of UMF-bonded boards and almost as high as those of PF-bonded boards. Part of this article was presented at the 53rd Annual Meeting of the Japan Wood Research Society, Fukuoka, March 2003     

Effects of alkali,mild steam,and chitosan treatments on the properties of pineapple,ramie, and sansevieria fiber bundles

This study focused on the effects of treatments of alkali, mild steam, and chitosan on the surface morphology, fiber texture, and tensile properties of pineapple, ramie, and sansevieria fiber bundles. The fibers were treated with NaOH (2%), mild steam (0.1 MPa), and chitosan solutions (4% and 8%). The properties of these treated fibers were characterized and compared with the untreated fibers. Field emission scanning electron microscopy (FE-SEM) was used to observe the surface morphology of those fibers. X-Ray diffraction (XRD) spectroscopy was used to observe the fiber textures. Tensile properties of the treated and untreated fibers were also recorded. SEM micrographs showed that the surfaces of the NaOH-treated fibers were more damaged than those of the steam-treated fibers. The 4% chitosan solution covered the fiber surface more uniformly than the 8% chitosan solution. The steam-treated fibers had higher values of degree of crystallinity, crystallite orientation factor, and crystallite size than the NaOHtreated fibers. Ramie fiber showed greater mechanical properties than the other fibers. The values of tensile strength, Young’s modulus, and toughness of the steamtreated fibers, which were similar to those of the 4% chitosan-coated fibers, were higher than those for the other treatments.     

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。     

Development of high-performance UF-bonded reed and wheat straw medium-density fiberboard

Urea formaldehyde resin-bonded reed and wheat straw fiberboards were produced from the fibers made under different steam cooking conditions in refining processes at densities of 500 and 700kg/m³. The effect of steam cooking conditions on the board properties was examined. The steam pressure and cooking time for reed and wheat straws were 0.4MPa/10min and 0.4MPa/5min, respectively, and 0.6MPa/3min and 0.6MPa/10min for both straws. The effect of steam cooking treatment before the fiber refining process on the wettability and weight losses of the straws was also investigated. The results indicated that the mechanical properties and linear expansion of the straw medium-density fiberboard (MDF) were improved with increasing steam cooking pressure and time during the refining process, whereas the thickness swelling (TS) did not vary much. The wettability of the straws was improved by cooking treatment. The steam cooking conditions had little effect on the wettability of the straw surfaces. For reed and wheat straws, the weight losses increased with increasing steam pressure and cooking time. In addition, it was found that the properties of MDF were significantly higher than those of particleboard, especially the internal bond (IB), where the IB values of MDF were more than 10 times higher than those of particleboard. All the properties of the straw MDF, except the TS of wheat board, can meet the requirement of JIS fiberboard standard. The high performances of MDF could be due to the improved wettability and the removal of extractives during the refining process.     

毛竹无胶粘剂蒸爆板的制造和特性研究

研究了22、26、33 kg/cm2爆破压力,5 min蒸煮时间对毛竹无胶粘剂蒸爆板的制造和特性的影响,结果表明,无胶板的静曲强度、弹性模量和内结合强度与板材密度普遍呈紧密的线性正相关。爆破压力26 kg/m2、蒸煮时间5 min的蒸爆条件有利于产生高强度的弹性和内结合力。无胶板密度超过1.1 g/cm3时,24 h浸泡处理水分吸收率不超过30%,几乎所有压制成的无胶板的24 h浸泡处理厚度膨胀率不超过10%。     

Effect of thermo-mechanical refining on properties of MDF made from black spruce bark

The effects of thermo-mechanical refining conditions on the properties of medium density fiberboard (MDF) made from black spruce (Picea mariana) bark were evaluated. The bark chips were refined in the MDF pilot plant of Forintek Canada Corporation under nine different refining conditions in which preheating retention time was adjusted from 3 to 5 to 7 min and steam pressure was set at either 0.6, 0.9 or 1.2 MPa. The resulting bark fibers were blended with 12% UF resin (based on oven-dry fiber weight) using a mechanical blender. The resinated fibers were manually formed into fiber mats and hot-pressed into MDF panels using consistent parameters. Two panels for each refining condition were produced, resulting in a total of 18 panels. Analysis of variance (ANOVA) was used to analyze the significance of factors. Regression coefficients and 3D contour plots were used to quantify the relationship between panel properties and the two test factors. The results from this study indicated that the preheating retention time was a significant factor for both modulus of rupture (MOR) and modulus of elasticity (MOE), the steam pressure was a significant factor for internal bond strength (IB), MOR and MOE, whereas both factors were insignificant for thickness swelling, water absorption and linear expansion. The properties of MDF panels were quadratic functions of retention time and steam pressure. Compared to the ANSI standard for 120-grade MDF, most panels with a nominal density of 950 kg/m³ had very high IB (>1 MPa) and acceptable MOR, MOE and dimension stabilities. These results suggest that black spruce bark residues can be considered as a potentially suitable raw material for manufacturing MDF products.     

Improvement on the properties of gypsum particleboard by adding cement

Gypsum particleboard (GPB) has high thickness swelling (TS), high water absorption (WA), and low mechanical properties compared with cement-bonded particleboard. The properties of GPB were improved by adding cement. The experimental results showed that GPB with the added cement had good physical and mechanical properties compared with those of gypsum particleboard with no added cement. The TS and WA of gypsum particleboard with added cement were reduced by 10%. The mechanical properties of GPB, such as internal bond strength (IB), modulus of rupture (MOR), and modulus of elasticity (MOE), increased when the GPB was made with added cement. The properties of GPB improved relative to the quantity of cement added. With an increase of cement content from 5% to 10%, the TS and WA were reduced, and the IB, MOR, and MOE were increased. In contrast, the TS and WA increased and the IB, MOE, and MOR decreased when the cement content was increased from 15% to 30%. Thus the physical and mechanical properties of GPB were successfully improved when the added cement content was 10%.An outline of this paper was presented at the 47th Annual Meeting of the Japan Wood Research Society in Kochi, April 1997     

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.     

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     

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.     

Effects of five additive materials on mechanical and dimensional properties of wood cement-bonded boards

There is a growing desire to improve the properties and use of nonwood plant materials as supplements to wood materials for wood cement-bonded boards (WCBs). This study was conducted to determine the comparative properties of WCBs containing various amounts of discontinuous inorganic fiber materials, such as alkali-resistant glass fiber, normal glass fiber, mineral wool, and nonwood plant materials such as retted flax straw and wheat straw particles. Tested cement-bonded boards were made at wood/additive compositions of 100/0, 90/10, 80/20, 70/30, 60/40, and 50/50 (weight percentages). Seventy-eight laboratory-scale WCBs were produced. Various board properties, such as the modulus of rupture (MOR), internal bonding strength (IB), water absorption (WA), thickness swelling (TS), and linear expansion (LE), were studied. The test results showed that three types of discontinuous inorganic fiber used as reinforcing materials in composites significantly enhanced and modified the performance of WCBs. The mechanical properties and dimensional stability of cement-bonded board were significantly improved with increasing amounts of the additives. MOR and IB were increased; and WA, TS, and LE of boards were reduced by combination with the inorganic fiber materials. The results also indicated that combination with retted flax straw particles only slightly increased the MOR of boards, and wheat straw particles led to marked decreases in all the mechanical properties and the dimensional stability of WCBs.Part of this report was presented at the 50th Annual Meeting of the Japan Wood Research Society, Kyoto, April 2000     

Manufacture of Light-weight Composite Panel from Kenaf

Light-weight composite panels were manufactured using kenaf core particles as core material and kenaf bast fiber-woven sheets as top and bottom surfaces. Methylene diphenyldiisocyanate （MDI） resin was used as the adhesive with the resin content of 4% for core particles and 50 g/m^2 for bast fiberwoven sheets. The target board densities were set at 0.35.0.45 and 0.55 g/cm^3. The composite panels were evaluated With Japanese Industrial Standard for Particleboards （JIS A 5908- 2003）.The results show that the composite panel has high modulus of rupture and internal bonding strength. The properties of 0.45 g/cm^3 density composite panel are： MOR 20.4 MPa. MOE 1.94 MPa, IB 0.36 MPa, WA142%, TS 21%. Kenaf is a good raw material for making light-weight composite panels.     

Manufacture and properties of ultra-low-density fiberboard

Low-density fiberboards with densities ranging from 0.05 to 0.50g/cm³ were manufactured with steam injection pressing. Bond-type and foam-type isocyanate compound resin adhesives were used separately at 10% and 30% resin content levels. Two types of different-size fibers from softwood were used. Mechanical, dimensional, thermal, and sound insulation properties of the fiberboards were tested. The results are as follows: (1) Bond-type isocyanate adhesive showed higher mechanical and dimensional properties of low-density fiberboards than the foam-type adhesive. (2) Fiberboards produced from small fibers have better mechanical and dimensional properties than those made from large fibers. (3) Thermal conductivity of fiberboards depends more on the board density than on the type of resin or fiber dimension. At a board density lower than 0.2 g/cm³, the thermal conductivity is almost equivalent to those of thermal insulation materials such as polystyrene foam and rock wool, (4) Generally, the sound absorption coefficient of low-density fiberboards tends to increase at higher sound frequency. As the board thickness increases, low-frequency sounds are more readily absorbed by boards.Part of this report was presented at the 46th annual meeting of the Japan Wood Research Society, Kumamoto, April 1996     

Binderless fiberboard from steam exploded Miscanthus sinensis

Miscanthus sinensis was pretreated and used to produce fiberboard with no synthetic binders. The lignocellulosic material was steam exploded with a thermomechanical aqueous vapor process in a batch reactor. The effect of the pretreatment and the pressing conditions on the physicomechanical responses of the fiberboard was evaluated and the conditions that maximize the responses were found. Response surface methodology with a central composite design was used. The variables studied and their respective variation ranges were: pretreatment temperature, 196–236°C; pretreatment time 1–6 min; pressing temperature, 130–230°C; pressing time, 1.6–18.4 min. The boards obtained were of very good quality (modulus of elasticity up to 6070 MPa, modulus of rupture up to 48 MPa, internal bond up to 2.9 MPa, thickness swelling up to 4% and water absorption up to 8%) and more than satisfy the requirements of the relevant standard specifications. The effect of the pretreatment influence on the lignin, cellulose and hemicelluloses content was also determined by a fractionation of the previous experimental design. The decrease in hemicelluloses is clearly related to the increase in the dimensional stability of the boards.Abbreviations MOE Modulus of elasticity - MOR Modulus of rupture - IB Internal bond - TS Thickness swelling - WA Water absorption - Tr Pretreatment temperature - tr Pretreatment time - Tp Pressing temperature - tp Pressing time     

生物酶预处理对秸秆中密度纤维板性能的影响

针对稻草和麦秸原料的特点,分别用木聚糖酶、漆酶／碳源系统(LCS)和脂肪酶对原料进行生物酶预处理用机械磨浆方法制备纤维,以木质纤维板用脲醛树脂作胶黏剂,压制秸秆中密度板,并探讨酶处理对秸秆纤维板性能的影响。结果表明:各种生物酶预处理对稻草和麦秸纤维板的性能都有一定的改善,同软化处理相比,经三种生物酶处理后的长纤维的比例明显增加,而细小纤维的含量则明显降低,IB均有不同程度的改进,其中木聚糖酶对此两项指标的改进效果更好。经木聚糖酶预处理后压制的密度达到0．8 g／cm3以上的纤维板的性能如下:麦草纤维板的IB为0．75 MPa,MOE为3 960 MPa,MOR为37．60 MPa,TS为21．29％。除TS外,均优于GB／T11718-1999标准要求。而稻草纤维板的IB为0．73 MPa,MOE为2 618 MPa,MOR为21．35 MPa,TS为21．19％,其中MOR与TS均离标准要求还有一定的差距。     

Physical and Mechanical Properties of Flakeboard Reinforced with Bamboo Strips

The objective of this study was to investigate the physical and mechanical performance of flakeboard reinforced with bamboo strips. The study investigated three different bamboo strip alignment patterns and an experimental control. All panels were tested in static bending both along parallel and perpendicular to the lengths of the bamboo strips. Internal bond strength (IB), thickness swelling (TS), linear expansion (LE), and water absorption (WA) were also examined. As expected, modulus of rupture (MOR) and modulus of elasticity (MOE) were substantially greater for all three experimental panel types as compared to the control group. LE was also improved for all three experimental panel groups. The bamboo strip alignment patterns had no significant effect on TS, WA and IB. The sample means for MOR, MOE and LE tested perpendicular to the bamboo strip lengths yielded slightly lower mean values than corresponding samples tested parallel to the bamboo strips lengths. This difference in mechanical properties is largely attributed to low panel density in the failure zones.     

Strength,decay and termite resistance of oriented kenaf fiberboards

The development of oriented fiberboards made from kenaf (Hibiscus cannabinus L.) and their suitability as a construction material has been investigated. Three different types of boards consisting of five layers with individual orientations were prepared using a combination of low molecular weight and high molecular weight phenol-formaldehyde (PF) resin for impregnation and adhesion purposes. Additional boards with the same structure were prepared using high molecular weight PF resin only. The mechanical properties of the boards have been examined as well as their resistance against fungal decay and termite attack. All kenaf fiberboards showed elevated mechanical properties compared with medium-density fiberboard made from wood fibers, and showed increased decay and termite resistance. Differences in the decay and termite resistance between the board types were caused by the presence of the low molecular weight PF resin for the impregnation of the fibers. No significant difference was found for the mechanical properties. The effect of the PF resin for impregnation was much clearer in fungal decay resistance than for termite resistance; however, fiber orientation had no effect on both decay and termite resistance of the specimens.     

改性胶粘剂对稻壳-木材复合材料性能影响的研究

稻壳的外表面覆盖有二氧化硅膜,使用传统的脲醛树脂(UF)和酚醛树脂胶(PF)生产的100％的稻壳板难以达到木质刨花板的质量指标。本研究采用以异氰酸酯(ISO)改性的脲醛树脂和酚醛树脂胶制造稻壳-木材复合材料。稻壳与木片的混合比例为1:1,施胶量为7％,设计密度0.8g/cm3。试验结果表明,3:4的ISO/UF、2:5的ISO/PF、改性胶粘剂制备的板材的物理力学性能达到国标刨花板二等品的要求;用3:4的ISO/PF改性胶粘剂制备的板材达到优等品的要求。     

Bond durability of kenaf core binderless boards II: outdoor exposure test

An outdoor exposure test was conducted on kenaf core binderless boards (pressing temperatures 200°, 180°, and 160°C; pressing pressure 3.0 MPa, time 10 min, target board thickness 5 mm, target board density 0.8 g/cm³) to estimate their bond durability. Modulus of rupture (MOR), modulus of elasticity (MOE), internal bonding strength (IB), thickness change, weight loss, Fourier transform infrared (FTIR) spectra, and color difference (ΔE*) by the CIE L^*a^*b^* system were measured at various outdoor exposure periods up to 19 months. These values were then compared with those of a commercial medium-density fiberboard (MDF; melamine-urea-formaldehyde resin; thickness 9.0 mm, density 0.75 g/cm³). Generally, dimensional stability and the retention ratios of MOR, MOE, and IB after the outdoor exposure test increased with increased pressing temperature of binderless boards. The MOR retention ratio of the kenaf core binderless boards with a pressing temperature of 200°C was 59.5% after 12 months of outdoor exposure, which was slightly lower than that of the MDF (75.6% after 11 months of outdoor exposure). Despite this, the bond durability of the kenaf core binderless boards should be viewed as favorable, especially when considering the fact that the retention ratio of 59.5% was achieved without binder and without obvious element loss. Part of this report was presented at the International Symposium on Wood Science and Technology, IAWPS2005, November 27-30, 2005, Yokohama, Japan