Production and properties of Japanese oriented strand board I: effect of strand length and orientation on strength properties of sugi oriented strand board

Oriented strand boards (OSB) were made using sugi wood strand with different lengths at different free fall distance conditions. Strand alignment and mechanical properties of sugi OSB were evaluated. Results obtained can be summarized as follows. The alignment angle distribution was greatly affected by both free fall distance and strand length. It was found that the standard deviation of the angles can be a measure for predicting the distribution when employing the von Mises distribution function with concentration parameter. The Monte Carlo simulation showed an agreement between the theoretical considerations and the experimental results on the strand alignment. The mechanical properties as affected by both strand length and layer structure were determined. Bending properties could be equal in both directions at 25% face layer ratio. Young's modulus obtained by the in-plane vibration method showed almost linear relation to the face layer ratio. No significant differences or only a slight difference was observed for the internal bond strength, plate-shear modulus, and nail resistance properties. Further studies are necessary.     

分子筛前驱体对定向刨花板性能的影响

人造板阻燃研究中常将分子筛用作阻燃添加剂或协效剂,但合成分子筛通常使用水热方法,耗能大、流程复杂.本研究采用LTA型分子筛的合成前驱体浸渍处理刨花并制备阻燃定向刨花板(OSB).通过热重分析(TGA)和极限氧指数(LOI)测试对浸渍处理刨花的热分解行为和燃烧性能进行考察,采用锥形量热测试和力学性能测试探究了分子筛前驱体...     

Manufacture and properties of high-performance oriented strand board composite using thin strands

Three-layered composite oriented strand boards were manufactured using very thin hinoki (Japanese cypress, Chamaecyparis obtusa Endl.) strands oriented in the faces and mixtures of sugi (Japanese cedar, Cryptomeria japonica D. Don.) and hinoki particles in the core. The boards were composed of two density levels, with 1:8:1, 0.5: 9 : 0.5, and 0: 10 : 0 face: core: face ratios. Polymeric and emulsion type isocyanate resins were used. The resin contents for the strands in the face and particles in the core were 10% and 5%, respectively. The steam-injection press was applied at 0.62MPa (160°C), and the steam-injection time was 2min. The mechanical and physical properties of the boards were evaluated based on the Japanese Industrial Standard. The parallel moduli of rupture and elasticity along the strand orientation direction and the wood screw retaining force increased with increasing face/core ratios. Incorporation of 10%–20% of thin strands in the face of the boards improved the parallel moduli of rupture and elasticity by 47%–124% and 30%–65%, respectively. In addition, the thickness swelling after water-soaking at 20°C for 24h, and the parallel linear expansion after boiling for 2h and water-soaking at 20°C for 1 h, of the three-layered composite boards were below 8% and 0.15%, respectively, despite a short steam-injection press time. The thickness swelling of the boards decreased with increasing face/core ratios. In contrast, the presence of face strands seems to have a minimal effect on the moduli of rupture and elasticity along the perpendicular direction of the three-layered composite boards. A similar trend was observed for the internal bond strength, hardness, and linear expansion along the perpendicular direction.This paper was presented at the 47th annual meeting of the Japan Wood Research Society, Kochi, April 1997     

Flexural strength and stiffness of southern pine plywood

Summary New information is presented that concerns flexural strength and stiffness of southern pine plywood and verification of a method developed by the U. S. Forest Products Laboratory for predicting properties of plywood. This method can predict, with sufficient accuracy, properties of southern pine plywood despite the large natural variability of veneer of this species and other variables. Strength and stiffness between 3-ply and 5-ply plywood with face grain parallel to span are compared. In addition, strength and stiffness between plywood and unidirectionally laminated veneer with same number of plies and total thickness are compared.This research was supported jointly by Federal funds under the McIntire-Stennis Cooperative Forestry Reserach Act (P.L. 87-788), Alabama Project No. 910 and Alabama State appropriated research funds.     

Densification,screw holding strength,and Brinell hardness of European beech and poplar oriented strand boards

In this study, selected mechanical properties of beech and poplar oriented strand board such as screw holding strength (SH) and Brinell hardness (BH) as well as the relationship of stress and strain under compression for both species under two temperatures (180°C and 220°C) were examined. Poly methylene diphenyl diisocyanate resinated laboratory-scale boards in different design and density of both species (650 and 720?kg/m³) were prepared. The results showed that density has a positive effect on SH and BH of panels. It was also observed that wood species (beech or poplar) and size of strands (normal or fine size) also effect on SH. Both species showed a specific behavior regarding the lapse of stress and strain during compression.     

Prediction of oriented strand board properties from mat formation and compression operating conditions. Part 2: MOE prediction and process optimization

A model to predict the bending modulus of elasticity (MOE) of oriented strand board (OSB) panels produced by batch processing is presented. The approach developed herein is unique in its comprehensiveness since the MOE is determined from information on the panel structure, temperature and moisture profiles and vertical density profiles obtained from the mat formation and compression models presented in Part 1. Comparison of predicted MOE values with those measured from 24 commercially produced panels shows good agreement considering some of the uncertainties involved. Simulations show that the MOE can be increased by any of the following changes: reduced fines content, increased panel density, better flake alignment in each of the three layers within a panel, increased flake length and a larger difference between the density of the face and core layers. The model was also used in a genetic algorithm to carry out an optimization study of batch OSB manufacturing. This analysis showed that by combining the appropriate reduction in the amount of flakes used, increase in fines content, improvement in flake alignment within each of the face and core layers and shortening of the batch time, a significant theoretical profit increase from the base case scenario can be obtained.     

Thermal degradation modeling of flexural strength of wood after exposure to elevated temperatures

Abstract

Wood is being used heavily in single-family residential dwellings. Therefore, it is important to categorize their response when exposed to elevated temperatures for a sustained period of time. An important aspect of structural fire design is to assess postfire residual strength of existing structures. This study addresses this issue by developing models to predict strength degradation of wood after exposure to elevated temperature. The objectives were to (a) study the effect of exposure time on bending strength [Modulus of Rupture (MOR)] of wood at elevated temperatures, (b) interpret any relationships between different temperature and time of exposure using kinetics and a statistical approach, and (c) compare the two approaches. Two hundred thirty-two samples in total were tested in flexure as a function of exposure time and several temperatures. MOR of wood decreased as a function of temperature and exposure time. Rate of degradation was higher at higher temperatures. These results were fit to a simple kinetics model, based on the assumption of degradation kinetics following an Arrhenius activation energy model with apparent activation energy of 37.4 kJ/mol. A regression-based statistical model was also developed. The kinetics-based model fit the data better with one less parameter and predictions consistently matched the observed values, making the model preferred over the regression approach.     

不同阻燃剂对胶合板胶合强度和燃烧性能影响

选用3种自制阻燃剂浸渍思茅松单板,通过测试胶合板的胶合强度、氧指数和烟密度,分析阻燃剂对胶合板的胶合强度和燃烧性能的影响.研究结果表明:工业制备阻燃胶合板的胶合强度、氧指数、烟密度等级满足国家标准GB/T 17657和GB 8624-2006的要求,说明工业生产阻燃胶合板是可行的.与对照试件相比较,阻燃胶合板的氧指数提高了75.8％～149.8％、烟密度等级降低了15.4％～60.5％、胶合强度降低了43.9％ ～ 56.1％;其中阻燃剂FR-B对胶合板氧指数影响最大,阻燃剂FR-A对胶合板的烟密度影响最大,阻燃剂FR-C对胶合板的胶合强度影响最小.     

Properties of oriented strand board made from Betung bamboo (Dendrocalamus asper (Schultes.f) Backer ex Heyne)

Bamboo has gained increasing attention as an alternative raw material for use in the manufacture of composite boards. Three-layer OSBs were made using Betung bamboo (Dendrocalamus asper (Schultes.f) Backer ex Heyne) strands to evaluate the effects of strand length and pre-treatment techniques on the physical, mechanical, and durability properties. Three different strand lengths, namely 50, 60, and 70?mm, were prepared. Prior to the manufacture into OSB, the strands were immersed in cold water for 24?h and in 6% acetic anhydrides solution for 48?h. The OSBs were fabricated using 5% MDI resin based on the strand dry weight. The results indicated that MOR and MOE values in perpendicular to the grain direction were much influenced by strand length. The dimensional stability of OSB was slightly improved by immersing the strands in acetic anhydride solution. Immersing strands in cold water and acetic anhydride solution improved the resistance of OSB against subterranean termite (Macrotermes gylvus) attack under the adopted experimental condition. All OSB parameters manufactured in this experiment were better than the minimum requirement of CSA 0437.0 (Grade O–2) standard.     

Prediction of oriented strand board properties from mat formation and compression operating conditions. Part 1. Horizontal density distribution and vertical density profile

A model is presented to determine the horizontal density distribution (HDD) and vertical density profile (VDP) of oriented strand board (OSB) panels produced by batch pressing. The HDD is simulated using input distributions of flake dimensions and orientation from plant measurements. Many previous HDD models rely on assumed distributions, which may not accurately characterize current manufacturing processes. The model predicts the VDP based on the compression behaviour of cellular materials in combination with temperature and moisture profiles calculated using a previously published heat and mass transport model. A novel empirical approach is applied rather than the time–temperature–moisture superposition method commonly used. The model predictions compare favourably with plant data and exhibit trends similar to previously reported experimental results. This work is the first of a two-part publication. The second part is concerned with stiffness property prediction and an optimization of the OSB manufacturing process. This work is novel in that no comprehensive model including HDD, VDP, stiffness property prediction and optimization has been reported in the literature.     

Effect of fire-retardant treatment on plywood pH and the relationship of pH to strength properties

Summary This paper investigates the relationship between wood pH and the strength properties of fire-retardant-treated (FRT) plywood, as it is affected by fire-retardant (FR) formulations, processing variables, and extended high temperature exposure conditions. The objectives of this study were to (1) identify the effect of post-treatment kiln-drying temperature, followed by high temperature exposure, on wood pH; (2) identify the effect of various mixtures of FR components, followed by high temperature exposure, on wood pH; (3) determine if treatment effects on strength and pH are affected by plywood thickness; and (4) quantify the relationship between changes in wood pH and strength loss and whether pH can be used as a predictor of strength loss. Results indicate that the differences in pH resulting from the initial redry temperature became insignificant after extended periods of high temperature exposure. All FR treatments studied caused large, rapid decreases in pH, with the most rapid decreases occurring with formulations containing phosphoric acid. Additions of borate compounds, especially disodium octaborate tetrahydrate (Timbor), produced a measurable buffering effect that slowed or lessened the decreases in pH. No differences in the effect of FRT on the wood pH-strength relationship were noted between the two plywood thicknesses evaluated. A strong relationship was noted between changes in pH of the plywood and reductions in strength and energy-related properties. These findings suggest that the pH of FRT plywood is a good indicator of its current condition and may have potential as a predictor of future strength loss as the plywood is subjected to elevated in-service temperatures. Received 8 January 1997     

Surface characterization of a series of cured polyurethane adhesives by inverse gas chromatography and adhesion strength testing of plywood

Inverse gas chromatography (IGC) was used to determine the surface properties of a series of polyurethane adhesives, A ₁, A ₂, A ₃ and A ₄ cured with water. The weight percentages of isocyanate group (NCO) in polyurethane adhesives were 5.3, 7.0, 13.0 and 19.6%, respectively. Four n-alkanes, C₆, C₇, C₈ and C₉ were chosen as non-polar probes to characterize the dispersive component of surface free energy, $ \gamma_{s}^{d} . $ Acetone, tetrahydrofuran and ethyl acetate were chosen as polar probes to detect the Lewis acid–base parameters, K _a and K _b. The trend of $ \gamma_{s}^{d} $ and K _a and K _b of the series of cured adhesives was also shown in this paper. The cured adhesives were all amphoteric, but predominantly Lewis basic. The adhesion strength of the poplar plywood bonded with polyurethane adhesives was tested. The results showed that the adhesion strength of plywood increased with increasing the NCO content of the adhesives and K _b/K _a of the cured adhesives.     

Image analysis and bending properties of model OSB panels as a function of strand distribution,shape and size

The technique of image analysis has been used to assess the quality of model oriented strand board panels by investigating the relationships between shape and size of strands, the distribution of strands and bending properties. A batch of commercial strands was analysed by image analysis and the distribution of the shape and size of strands was quantified. The strands were categorised into five strand types as a function of size and aspect ratio. In general, strand shapes were observed to be mostly rectangular and there was also a wide variation in strand dimensions in commercial material. Bigger area strands had low aspect ratios and small strands had high aspect ratios. Half of the commercial strands were longer than 100 mm.Model OSB panels were manufactured in the laboratory by hot pressing strand mats formed from each of the five strand types. Strands were laid up by hand into the forming mat and following pressing the orientation and shape of strands was evaluated by image analysis and the panels were tested in a three point bending. Large area (type 3) strands with high aspect ratios produced model panels with optimum strand orientation and mechanical properties.Type 3 panels were also fabricated from strands dropped through a slotted forming device in order to simulate the delivery of strands to the forming line under factory conditions. As the height of strand delivery increased from 0 to 100 to 200 mm the disorientation of strands in the pressed panels progressively increased and as a result mechanical properties in bending were reduced.Image analysis is therefore a powerful tool for evaluating the distribution of commercial strand shapes and the relationship between strand geometry, strand orientation and the mechanical properties of oriented strand board.     

Effect of nanoclay on some applied properties of oriented strand board (OSB) made from underutilized low quality paulownia (Paulownia fortunei) wood

In this study, the effect of nanoclay on some applied properties of oriented strand board (OSB) made from underutilized low quality paulownia wood was investigated. Organo-modified montmorillonite (MMT) at four levels (0, 1, 3 and 5?%) was added to urea formaldehyde (UF) resin. Some chemical properties of paulownia wood (holocellulose, cellulose, lignin and ash contents, pH value and hot and cold water solubility), mechanical [modulus of rupture (MOR), modulus of elasticity (MOE), internal bond strength, screw and nail withdrawal strengths], physical (water absorption and thickness swelling) properties and formaldehyde emission of the strand boards were evaluated. Mechanical properties of all panels complied with the general-purpose OSB minimum property requirements of European Norm. With increasing 5?% nanoclay to UF resin, mechanical and physical properties of the resulting panels improved and formaldehyde emission decreased. However, none of the panels satisfied the thickness swelling and water absorption requirement. The results of X-ray diffraction and transmission electron microscope analysis confirmed the good dispersion of nanoclay in the resulting OSBs. Using paulownia as a fast-growing underutilized species not only can sustain the forests but also can supply raw material to countries facing shortage of wood.     

Combustion gas toxicity,hygroscopicity, and adhesive strength of plywood treated with flame retardants

Summary The results of tests of combustion toxicity, hygroscopicity, and adhesive strength for fire retardant-treated plywood are described. The plywood was prepared from veneers treated with diammonium phosphate and ammonium bromide, and from glue mixed with poly (ammonium phosphate). Furthermore, the plywood boards were coated with boric acid. High ammonium phosphate and low or 0 ammonium bromide contents with the boric acid-coatings gave the greatest improvement in the combustion toxicity. Influence of almost all the treatments on the hygroscopicity was not significant. In all treatments the dry adhesive strength and the cyclic boil adhesive strength were slightly and considerably reduced, respectively.     

Prediction of timber bending strength on basis of bending stiffness and material homogeneity assessed from dynamic excitation

The potential of utilizing resonance frequencies corresponding to edgewise bending modes for predicting the bending strength of timber is investigated. The research includes measurements of axial and transversal resonance frequencies, laboratory assessment of density, static bending stiffness and bending strength of 105 boards of Norway spruce of dimensions 45?×?145?×?3,600?mm3. It is shown that E _b,1 , (MOE based on the resonance frequency of the first bending mode) gives a higher coefficient of determination to the bending strength than what E _a,1 (MOE based on the first axial resonance frequency) does. It is also shown that resonance frequencies corresponding to higher bending modes can be used in the definition of a new indicating property, the measure of inhomogeneity (MOI). This is a scalar value representing the lack of fit between the true, measured resonance frequencies and the expected (assuming homogeneity) resonance frequencies of a board. The results show that using the MOI as a third indicating property, in addition to E _b,1 and density, increases the coefficient of determination with respect to bending strength from R ²?=?0.69 to R ²?=?0.75.     

Tensile strength of thermally modified laminated strand lumber and laminated veneer lumber

Laminated strand lumber (LSL) and laminated veneer lumber (LVL) were thermally modified as a post-treatment at 140°C, 150°C, 160°C, 170°C, and 180°C. The tension modulus of elasticity (MOE) of LSL was not significantly impacted by the treatments, with the 180°C treatment group exhibiting the highest tension MOE (11.8?GPa). The LVL also experienced minimal impacts, with the 150°C treatment group having the highest tension MOE (19.4?GPa) and the 160°C treatment group exhibiting the lowest (17.1?GPa). The maximum tensile strength (MTS) of the LSL and LVL significantly decreased with increasing temperatures, with the control and 180°C treatment groups experiencing the highest and lowest MTS, respectively. The lowest MTS for LSL was 10.8?MPa (180°C treatment), which was 70% lower than the controls. The lowest MTS of the LVL was 24.4?MPa (also at the 180°C treatment), which was a 49% decrease compared to the controls. These results suggest that thermal-modification post-treatments minimally impact tension MOE, but can significantly reduce MTS at higher treatment temperatures. Combined with previous work improving the moisture properties and equilibrium moisture content of thermally modified LSL and LVL, it may be possible to optimize the treatment technique(s) to yield products with desirable properties.     

Study on sheet material made from zephyr strands V: Properties of zephyr strand board and zephyr strand lumber using the veneer of fast-growing species such as poplar

Zephyr strand board (ZSB) and zephyr strand lumber (ZSL) were produced using zephyr made from poplar veneer to investigate the greater utilization of low-density poplar as a structural material. These materials were then compared to ordinary plywood, laminated veneer lumber (LVL) from poplar veneer, lauan plywood, and particleboard. The bending properties (moduli of rupture and elasticity) of ZSB proved superior to those of poplar plywood: and ZSL produced from poplar veneer zephyr had bending properties greater than ordinary LVL from poplar veneer. Apparently, the conversion of the poplar veneer into zephyr material had a positive effect on bending properties. Additionally, poplar ZSB had bending properties superior to those of lauan particleboard and equal to those of lauan plywood. The internal bond strength of poplar veneer ZSB was nearly two times greater than that of lauan particleboard.Parts of this report were presented at the international symposium on the utilization of fast-growing trees, Nanjing, China, October 1994. Report IV appeared inMokuzai Kogyo 49:599, 1994     

Effect of board density on bending properties and dimensional stabilities of MDF-reinforced corrugated particleboard

We investigated the bending properties of composite boards produced by reinforcing both sides of corrugated particleboard with medium-density fiberboard (MDF). Thickness swelling and linear expansion (LE) were measured to assess the dimensional stabilities of the composite board. Although the apparent density of the composite board was 0.48g/cm³, its strength was found to be equivalent to that of 18-type particleboard as described in JIS A 5908. The boards parallel/perpendicular anisotropy in strength was 0.9. The modulus of rupture (MOR) of the composite board increased with board density only up to a certain density, beyond which the MOR was constant. On the other hand, the thickness swelling of both corrugated particleboard and the composite board was smaller than that of flat-type particleboard, satisfying the JIS A 5908 standard of 12%. Linear expansion (soaking in water of ordinary temperature for 24h) of corrugated particleboard was 0.7%–0.9% in the parallel direction and 2.1%–3.1% in the perpendicular direction; hence, anisotropy in linear expansion existed in the corrugated particleboard. The linear expansion of the composite board was 0.6%–0.9% in the parallel direction and 1.8%–2.5% in the perpendicular direction. Although the LE of the composite board was lower than that of corrugated particleboard, it is necessary to improve the LE of composite board for practical use.