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1.
Low-density sandwich panels of veneer-overlaid fiberboards of 12 mm thickness for structural use were manufactured at densities of 0.3–0.5g/cm3 using an isocyanate compound resin adhesive and steam injection pressing method. The effects of board density, veneer thickness, and resin content on the fundamental properties of sandwich panels were examined, with the following results: (1) The dry moduli of rupture and elasticity in the parallel direction of sandwich panels with thicker veneers were superior. The dry moduli of rupture and elasticity in the parallel direction of sandwich panels with 2.0 mm thick veneer at densities of 0.4–0.5 g/cm3 were 40–60 MPa, and 5–8 GPa, which were two and four times as much as those of homogeneous fiberboards, respectively. (2) The higher-density panels exhibited tensile failure at the bottom veneer surface during static dry bending in a parallel direction, whereas lower-density panels experienced horizontal shear failure in the core. (3) The dimensional stability of sandwich panels had good dimensional stability, with negligible springback after accelerated weathering conditions. (4) The thermal insulation properties of sandwich panels were found to be much superior to other commercial structural wood composite panels.Part of this report was presented at the 47th annual meeting of the Japan Wood Research Society, Kouchi, April 1997 相似文献
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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. 相似文献
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We studied the effects of nanoparticles of organo-silane(NOS) compounds in the size range of20–80 nm on physical and mechanical properties in medium density fiberboard,and used NOS at four consumption levels of 0,50,100,and 150 g kg-1dry wood fibers.Density of all treatments was kept constant at 0.67 g cm-3.The water-repellent property of organo-silane significantly reduced water absorption(WA) and thickness swelling but mechanical properties declined due to the reduced proportion of wood-fiber as organo-silane was added to the matrix:the compression ratio of MDF panels and the integrity among wood-fibers both declined,resulting in reduced mechanical properties.We recommend use of 50 g of NOS/kg wood-fiber to improve WA and thickness swelling while retaining acceptable mechanical properties. 相似文献
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Woodceramics (WCS) are new porous carbon materials that have been shown to possess many excellent properties, but the chemical
mechanism during pyrolysis has not been reported yet. In order to investigate this process, pyrolysis of medium density fiberboard
(MDF) was analyzed by thermogravimetry coupled with Fourier transform infrared spectroscopy (TG-FTIR) in this study. The results
showed that the pyrolysis consisted of three stages up to 700°C. The first stage of the pyrolysis occurred below 240.0°C and
was mainly due to moisture evaporation. The second stage between 240.0° and 390.2°C accompanied the main mass loss. The maximum
pyrolysis speed (mass loss) was about 3.79% per minute at 313.2°C. This was believed to coincide with the cleavage of ether
bridges between the wood material and phenol-formaldehyde (PF) resin, and pyrolysis of carbohydrate. At higher temperature,
the pyrolysis of PF resin and lignin was the main reason for the mass loss in the third stage. The microcosmic environments
of both the MDF and PF resin in the MDF treated with PF resin were different from the untreated MDF and PF resin, so that
the temperatures at which their pyrolysis occurred and the quantities of evolved gases were different. During the process
of WCS preparation, the rate of temperature increase should be very slow before it reaches 700°C, especially at around 313.2°C,
at which point violent pyrolysis occurs. Such temperature control should allow uniform sintering of the sample and should
reduce flaws in the product. 相似文献
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Surface chemical characteristics of straw fiber have a great effect on the properties of interfacial conglutination between
straw fiber and adhesives. In our study, straw was treated by four different methods—hot water, acetic acid, sodium sulfite
and sodium hydrid sulfite. Our results show that the main chemical group of straw fiber, under the four different treatments,
has not changed significantly. The acetic acid treatment reduces pH values of straw fibers and has a significant effect on
the internal bonding strength of straw fiberboards. The modulus of rupture and modulus of elasticity did not clearly improve
with the four different treatments. The thickness swelling of straw fiberboard treated in different ways is higher than that
of standard values. It is concluded that acid treatment is optimal for producing good quality straw fiberboard.
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Translated from China Forest Products Industry, 2006, 33(4): 24–26 [译自: 林产工业] 相似文献
7.
Elastic moduli and stiffness optimization in four-point bending of wood-based sandwich panel for use as structural insulated walls and floors 总被引:1,自引:0,他引:1
Tamami Kawasaki Min Zhang Qian Wang Kohei Komatsu Shuichi Kawai 《Journal of Wood Science》2006,52(4):302-310
Several wood-based sandwich panels with low-density fiberboard core were developed for structural insulated walls and floors,
with different face material, panel thickness, and core density. The elastic moduli with and without shear effect (E
L, E
0) and shear modulus (Gb) were evaluated in four-point bending. Generally, the stiffer face, thicker panel, and higher core density were advantageous
in flexural and shear rigidity for structural use, but the weight control was critical for insulation. Therefore, optimum
designs of some virtual sandwich structures were analyzed for bending stiffness in relation to weight for fixed core densities,
considering the manufactured-panel designs. As a result, the plywood-faced sandwich panel with a panel thickness of 95 mm
(PSW-T100), with insulation performance that had been previously confirmed, was most advantageous at a panel density of 430
kg/m3, showing the highest flexural rigidity (E
L
I = 13 × 10−6 GNm2) among these panels, where E
L, E
0, and G
b were 3.5, 5.5, and 0.038 GN/m2, respectively. The panel was found to be closest to the optimum design, which meant that its core and face thickness were
optimum for stiffness with minimum density. The panel also provided enough internal bond strength and an excellent dimensional
stability. The panel was the most feasible for structural insulation use with the weight-saving structure. 相似文献
8.
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 相似文献
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Jianying Xu Ragil Widyorini Hidefumi Yamauchi Shuichi Kawai 《Journal of Wood Science》2006,52(3):236-243
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 相似文献
12.
Durability of isocyanate resin adhesives for wood I: Thermal properties of isocyanate resin cured with water 总被引:1,自引:0,他引:1
The thermal properties of isocyanate (IC) resin cured with water were studied using dynamic mechanical analysis (DMA) and Fourier transform infrared spectroscopy. The thermal properties of cured phenol formaldehyde (PF) resin were also studied for comparison purposes. The DMA specimens were prepared using a unique technique. The relation between the mechanical and chemical changes of the resin during DMA was clarified. The cured PF resin had better thermal stability than the IC resin cured with water. The improvement of thermal stability in cured IC resin by heat treatment was considered to be less effective. The effect of the heating rate on the mechanical properties was also investigated. The apparent activation energy in the thermal degradation of cured IC resin was calculated based on the results obtained.Part of this paper was presented at the 47th Annual Meeting of the Japan Wood Research Society, Kochi, April 1997 相似文献
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改性脲醛树脂胶低密度稻壳-木材复合材料制造工艺的研究 总被引:4,自引:0,他引:4
采用异氰酸酯(ISO)改性的脲醛树脂胶制造低密度稻壳-木材复合材料。稻壳与木质刨花的混合比例为1:1,施胶量为7%,试验结果表明,异氰酸酯改性的脲醛树脂胶黏剂适用于低密度稻壳-木材复合材料,其物理力学性能明显优于使用传统的脲醛树脂胶黏剂。低密度稻壳-木材复合材料的物理力学性能随着改性剂异氰酸酯用量的增加而提高。密度是稻壳-木材复合材料物理力学性能的重要影响因素,低密度稻壳-木材复合材料的物理力学性能随着密度的增加而提高。在设定密度为0.45g/m~3和0.5g/cm~3的条件下,3:4的ISO/UF的稻壳-木材复合材料的物理力学性能均达到日本刨花板工业标准(JIS A5908)的要求。 相似文献
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ABSTRACTGas permeability and structure of fiberboard mats are essential properties because of their impact on mat internal gas pressure, moisture content and temperature evolution during the hot-pressing process. The objectives of this work were to determine the effect of fiber size and mat density on the intrinsic gas permeability of the mat. For the study of these mat properties, panels with a homogeneous density profile through the thickness were manufactured at five density levels (200, 400, 600, 800 and 1000?kg m?3) for three different fiber sizes. Fiber refining was performed in a disk refiner at three plate spacings. Gas permeability was measured with an in-house built apparatus. The results showed that the fiber sizes studied had no significant effect on the intrinsic permeability. This was likely due to a more significant impact of the internal porous structure of the mat compared to fiber size. Besides, the intrinsic permeability decreased significantly when the panel density increased from 198 to 810?kg m?3. This suggests that the decrease of the intrinsic gas permeability during the last seconds of press closure plays an essential role in the bulk moisture mass transfer through the fiberboard mat. 相似文献
19.
Taking medium density fiberboards (MDF) as samples, the feasibility of the applications of wavelet analysis in a nondestructive
test is discussed in this paper. The main results are as follows: the modulus of elasticity of longitudinal resonance, measured
by wavelet analysis, can replace the conventional static modulus of elasticity. Their correlation coefficient is significant
(p < 0.01). The defect of samples can be judged by wavelet analysis, which is superior because it is a nondestructive test.
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Translated from Scientia Silvae Sinicae, 2006, 42(10): 91–94 [译自: 林业科学] 相似文献
20.
用水性高分子异氰酸酯生产无醛胶合板生产工艺的研究 总被引:3,自引:0,他引:3
用低成本高分子异氰酸酯胶粘剂生产无醛胶合板,其生产工艺与常规脲醛树脂生产胶合板生产工艺相同,成本只有其它非甲醛系胶粘剂的50%,并彻底解决了游离甲醛释放问题。 相似文献