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.     

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     

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     

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     

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     

Bond durability of kenaf core binderless boards I: two-cycle accelerated aging boil test

A two-cycle accelerated aging boil test was conducted on kenaf core binderless boards to estimate their bond durability. This is one of the methods to estimate the bond quality of kenaf core binderless boards, as stipulated by Notification 1539 of the Ministry of Land, Infrastructure, and Transport, October 15, 2001, for the Building Standard Law of Japan. Generally, retention ratios of modulus of rupture (MOR), modulus of elasticity (MOE), and internal bond (IB) strength after the boil test increased with increased pressing temperature. In particular, the MOR retention ratio of boards with a pressing temperature of 200°C (average 106.4%) was higher than that of a commercial medium-density fiberboard (MDF) (melamine-urea-formaldehyde resin) (average 72.7%), and the value sometimes exceeded 100%. The durability of kenaf core binderless boards with a pressing temperature of 200°C compared favorably with that of the commercial MDF (melamine-urea-formaldehyde resin), having almost the same retained strength values after the boil test. Part of this article was presented at the International Symposium on Wood Science and Technology, IAWPS2005, November 27–30, 2005, Yokohama, Japan     

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.     

The lamination influence on properties of agro-based particleboard

Abstract

Response surface methodology (RSM) based on a three-level, three-variable central composite rotatable design was applied to evaluate the effects of the parameters such as ratio of rice straw (Oryza sativa)/poplar (Populus deltoids) wood particle bonded with urea-formaldehyde resin in panels, species of wood veneer coating these panels and amount of adhesive in glue line on the modulus of rupture (MOR), internal bonding (IB), and thickness swelling (TS) of panels. Mathematical model equations were derived by computer simulation programming to optimize the properties of the particleboard. These equations that are second-order response functions representing MOR, IB, and TS were expressed as functions of three operating parameters of panel properties. Predicted values were found to be in a good agreement with experimental values (R ² values of 0.96, 0.98 and 0.98 for MOR, IB, and TS, respectively). This study has shown that the RSM could efficiently be applied for modeling panel properties. It was found that the variables affected the properties of panels. Straw usage up to 30% in the mixture did not cause a significant decrease in MOR, IB, and TS. Using beech veneer and 190 g/m² glue line had the highest MOR and lowest TS.     

Manufacture of plywood bonded with kenaf core powder

Kenaf (Hibiscus cannabinus L.) core powder was used as a binder to manufacture three-ply plywoods of sugi (Cryptomeria japonica D. Don) by conventional hot pressing under various manufacturing conditions: hot-pressing conditions (pressure, temperature, and time) and powder conditions (grain size, spread volume, and moisture content). The adhesive shear strength and wood failure of plywoods were measured in accordance with the Japanese Agricultural Standard (JAS) for plywood. The result showed that fine kenaf core powder played a role as an effective binder when plywoods were pressed at high pressure, which caused extreme compression of veneer cells. In addition, the adhesive shear strength of plywoods in dry conditions was high regardless of pressing temperature and time, but it was sensitive to pressing temperature and time in wet conditions. The highest adhesive shear strength was obtained from plywoods manufactured with kenaf core powder (grain size 10 μm, spread volume 200 g/m², moisture content 8.6%) under hot-pressing conditions (pressure 5.0 MPa using distance bars 4 mm thick, temperature 200°C, time 20–30 min). However, the plywood could not meet the requirement for the second grade of plywood by JAS because of its low water-resistance properties. Part of this article was presented at the 58th Annual Meeting of the Japan Wood Research Society, Tsukuba, March 2008, and the 10th World Conference on Timber Engineering, Miyazaki, June 2008     

Influence of the chemical composition of kenaf bast and core on the alkaline pulping response

The bast and core of kenaf,Hibiscus cannabinus L., have markedly different chemical components and alkaline cooking responses. The bast had about double the hot-water extractives content and only about half the lignin content of the core. The core contained a large amount of hemicellulose, mostly composed of xylan. The lignin structures of bast and core were also quite different: The former had a significant abundance of syringyl structures. Evidence showed that the bast was much more easily delignified than the core. When the bast and core were cooked together in alkaline condition, the pulp yields at the same kappa number were higher than those of the individual pulpings of bast and core. The bast-core pulping gave a positive effect on the yield of bast pulp in the sodaanthraquinone and kraft pulpings. On the other hand, kenaf was abundant in the hot water extractives. These extractives consumed alkali during cooking to a relatively large extent but acted as a protector of hemicellulose and slightly increased the pulp yields.Part of this paper was presented at the 48th and 49th Annual Meetings of the Japan Wood Research Society, Shizuoka, April 3–5, 1998 and Tokyo, April 3–5, 1999     

Cement-bonded particleboard with a mixture of wheat straw and poplar wood

We investigated the hydration behavior and some physical/mechanical properties of cement-bonded particleboard (CBPB) containing particles of wheat straw and poplar wood at various usage ratios and bonded with Portland cement mixed with different levels of inorganic additives. We determined the setting time and compression strength of cement pastes containing different additives and particles, and studied the effects of these additives and particles on thickness swelling, internal bond strength and modulus of rupture of CBPB by using RSM (Response Surface Methodology). The mathematical model equations (second-order response functions) were derived to optimize properties of CBPB by computer simulation programming. Predicted values were in agreement with experimental values (R2 values of 0.93, 0.96 and 0.96 for TS, IB and MOR, respectively). RSM can be efficiently applied to model panel properties. The variables can affect the properties of panels. The cement composites with bending strength > 12.5 MPa and internal bond strength > 0.28 MPa can be made by using wheat straw as a reinforcing material. Straw particle usage up to 11.5% in the mixture satisfies the minimum requirements of International Standard, EN 312 (2003) for IB and MOR. The dose of 4.95% calcium chloride, by weight of cement, can improve mechanical properties of the panels at the minimum requirement of EN 312. By increasing straw content from 0 to 30%, TS was reduced by increasing straw particle usage up to 1.5% and with 5.54% calcium chloride in the mixture, TS satisfied the EN 312 standard.     

Characterization of bagasse binderless particleboard manufactured in high-temperature range

This paper describes the features of binderless particleboard manufactured from sugarcane bagasse, under a high pressing temperature of 200–280 °C. Mechanical properties [i.e., modulus of rupture (MOR) and elasticity (MOE) in dry and wet conditions, internal bonding strength (IB)] and dimensional stability [i.e., thickness swelling (TS)] of the board were evaluated to investigate the effect of high pressing temperature. Recycled chip binderless particleboards were manufactured under the same conditions for comparison, and particleboards bonded with polymeric methylene diphenyl diisocyanate (PMDI) resin were manufactured as reference material. The target density was 0.8 g/cm³ for all of the boards. The results showed that the mechanical properties and dimensional stability of both types of binderless boards were improved by increasing the pressing temperature. Bagasse showed better performance than that of recycled chip as a raw material in all evaluations. Bagasse binderless particleboard manufactured at 260 °C had an MOE value of 3.5 GPa, which was equivalent to the PMDI particleboard, and a lower TS value of 3.7 % than that of PMDI particleboard. The MOR retention ratio under the dry and wet conditions was 87.0 %, while the ratio for the PMDI particleboard was only 54.6 %. The obtained results showed the possibility of manufacturing high-durability binderless particleboard, with good dimensional stability and water resistance, which previously were points of weakness for binderless boards. Manufacturing binderless boards under high temperature was effective even when using particles with poor contact area, and it was possible to express acceptable properties to allow the manufacture of particleboards. Further chemical analysis indicated a contribution of a saccharide in the bagasse to the improvement of the board properties.     

Manufacture and mechanical properties of binderless boards from kenaf core

Binderless boards were prepared from finely ground powders of kenaf (Hibiscus cannabinus L.) core under varying manufacturing conditions. This research was designed to investigate their mechanical properties and evaluate the various manufacturing conditions: pressing temperature and time, pressing pressure, board density, board thickness, grain size of raw materials, and addition of furfural. The mechanical properties (i.e., modulus of rupture and elasticity, internal bonding strength) of boards increased with increasing board density and met the requirement for 15 type medium-density fiberboard (MDF) by JIS A 5905-1994. Thickness swelling and water absorption of boards exceeded the maximum permitted levels for 15 type MDF and S20 grade hardboard by JIS A 5905-1994, which indicates the low water-resistant property of binderless boards. In contrast to that in usual wood-based materials, internal bonding strength showed significant correlations with other board properties: modulus of rupture and elasticity, thickness swelling, and water absorption. We confirmed experimentally that the best manufacturing conditions proved to be as follows: pressing temperature 180°C, time 10min; pressing pressure 5.3MPa; board thickness 5mm; board density 1.0g/cm³; average grain size 53µm; and powder with no furfural content.Part of this paper was presented at the 52nd Annual Meeting of the Japan Wood Research Society, Gifu, April 2002     

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     

Physical and mechanical properties of particleboard from roselle (Hibiscus sabdariffa) stalks and eucalyptus (Eucalyptus camaldulensis) wood particles

Abstract

The objective of this work was to evaluate the performance of particleboard manufactured from roselle (Hibiscus sabdariffa) stalks and eucalyptus (Eucalyptus camaldulensis) wood. The manufacturing parameters were various roselle (Hibiscus sabdariffa) ratios in the mixture (0, 25, 50, 75 and 100%) and press time (3, 5 and 7 min). Modulus of elasticity (MOE), modulus of rupture (MOR), internal bonding (IB) strength values and thickness swelling (TS) after 24-hour water soaking of the panels were determined according to the procedure of European Union (EN) Standard. The results of the study demonstrate that roselle stalks can be an alternative raw material source for particleboard industry. With an increase of roselle particles from 0% to 100%, the TS was reduced, and the IB, MOR and MOE were increased. The highest MOE, MOR, IB strength and TS values of the samples were found as 2754.18, 16.81, 0.89 N/mm² and 15.26% for the panels made using 100% roselle with a 7-min press time, respectively.     

Investigation of a new natural adhesive composed of citric acid and sucrose for particleboard

The development of a natural adhesive composed of materials derived from non-fossil resources is a very important issue. In this study, only citric acid and sucrose were used as adhesive materials for particleboard. A water solution in which citric acid and sucrose were dissolved was used as an adhesive, and the manufacture of particleboard with a target density of 0.8 g/cm³ was attempted under a press condition of 200 °C for 10 min. The optimum mixture ratio of citric acid and sucrose and the optimum resin content was 25–75 and 30 wt%, respectively. The modulus of rupture (MOR) and the modulus of elasticity in bending were 20.6 MPa and 4.6 GPa, respectively. The internal bond strength (IB) was 1.6 MPa, indicating that the adhesive had excellent bond strength. The thickness swelling (TS) after water immersion for 24 h at 20 °C was 11.9 %. The board did not decompose even under more severe accelerated treatments. This meant that the adhesion had good water resistance. The MOR, IB and TS of the board were comparable to or higher than the requirement of the 18 type of JIS A 5908 (2003). Consequently, there is a possibility that a mixture of citric acid and sucrose can be used as a natural adhesive for particleboard.     

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.     

Combination treatment of kenaf bast fiber for high viscosity pulp

The viscosity of kenaf bast fiber has been found to be highly sensitive and variable with different pulping methods; therefore, it is important to choose proper chemicals and conditions for pulping and bleaching of kenaf bast fiber. From several pulping experiments, a nonconventional pulping method with a combination of ammonium oxalate pretreatment followed by soda pulping at normal pressure and then acidic chlorite delignification was developed to obtain high-viscosity pulp (162 centipoise). The optimum level of alkali dosage of soda pulping for high-viscosity pulp was found to be 15% (on pulp as NaOH). Pulps showed linear relations between viscosity and xylose or glucose contents, but the combination pulping method gave extremely high pulp viscosity, beyond the relations. The highest viscosity pulp from kenaf bast fiber demonstrated a tear index about twofold and a folding endurance 6.2-fold higher than those of Manila hemp pulp with comparable tensile and burst indexes. The high-viscosity pulp could be used in the production of high-quality currency paper or longevity paper for special uses.Part of this paper was presented at the 43rd Lignin Symposium, Fuchu, Tokyo, October 26–27, 1998     

Manufacture of oriented board using mild steam treatment of plant fiber bundles

This study investigated the effects of mild steam treatment (0.1 MPa for 2 h) of natural bio-based fibers and orientation (0° and 90°) of those fibers in various fiberboards. Ramie bast, pineapple leaf, and sansevieria fiber bundles were used as materials. The composite fiberboards were prepared using phenol-formaldehyde (PF) resin. To investigate the effect of mild steam treatment on wettability, contact angles of PF resin to the fiber were measured. The mechanical properties of the boards were examined as well as their dimensional stability. The contact angle data showed that mild steam treatment was effective in improving the wettability of fibers. Unioriented steam-treated boards showed better performance of internal bond (IB), moduli of rupture (MOR) and elasticity (MOE), thickness swelling (TS), and water absorption (WA) than other boards. Unioriented steam-treated sansevieria board with longitudinal fiber direction showed higher average values of MOR (403 MPa), MOE (39.2 GPa), and IB (1.33 MPa) and lower values of TS (5.15%) and WA (8.68%) than other boards. The differences in the mechanical properties and dimensional stability of boards were found mainly due to the differences in the ratios of fiber fraction of the boards to the density of the fiber bundles.