Evaluation of the arrangement of wood strands at the surface of OSB by image analysis

 The objective of this paper is to evaluate the arrangement of wood strands at the surface of oriented strand board (OSB) by image analysis. Two-dimensional image analysis enables the number of strands and the area of each strand to be computed. In addition, the fiber direction of each strand may be measured manually by recording the acute angle between the fiber direction and the longitudinal axis of the specimen. The image analysis results suggest the following: the average strand area is proportional to the reciprocal of the number of strands. Samples containing many smaller strands exhibit a larger variation in strand size. The average strand area does not correlate with the distribution of the strand area represented by the coefficient of variation. However, there is a reasonable correlation between the number of smaller strands in the range 0 to 1 cm² and the coefficient of variation of strand area. At low average fiber orientations, i.e. better orientation with the principal panel axis, there is smaller variability in orientation. The upper side and lower side of OSB exhibit a different relationship between average fiber orientation and strand area. The upper side of the specimens contains larger strands and exhibits better fiber orientation than the lower side. This is thought to be a function of the production process. The lower side strands fall on a smooth moving substrate, whereas the upper side strands fall on a stable substrate of strands. The number of strands is lower on the upper side of the OSB panel because small size strands tend to migrate to the lower side of the OSB during production. The small particles tend to be vibrated through the strand mat to the lower face before pressing. Received 29 March 1999     

Fast Fourier Transform and Filtered Image Analyses of Fiber Orientation in OSB

The objective of this paper is to investigate the relationship between resolution of images and measurement of fiber orientation in oriented strand board with the ultimate aim of optimising the fiber orientation and quality of the manufactured product. An important consideration has been the capture of images from a distance of 2 meters corresponding to conditions on an OSB production line. In this paper, Filtered Image Analysis (FIA) was used to measure fiber orientation at different resolutions, and results were compared with those for strand grid models. These grid models were adopted to investigate how the FIA technique measures orientation. A two-dimensional Fast Fourier Transform (FFT) analysis was also investigated as a comparative method for measuring fiber orientation. The following conclusions can be drawn: the FFT analysis measures the periodicity of lines and indicates the orientation of lines. The FIA measures the orientation of zones surrounded by lines and shows the orientation of the zones. Hence, the FFT analysis and the FIA analysis measure orientation differently. Both methods are able to measure the fiber orientation of the OSB from a high resolution image. In addition the FIA technique could also measure the fiber orientation from low-resolution images and from a distance of 2 meters. In conclusion, whilst the FFT method is able to analyse high resolution images successfully, the FIA method is superior for analysing low resolution images and the orientation of OSB strands under production condition. Received 16 November 1999     

Monitoring fiber orientation in OSB during production using filtered image analysis

The orientation of oriented strand board (OSB) mats has been practically measured on a commercial factory production line to demonstrate the practical capabilities of the filtered image analysis (FIA) technique. Samples have been cut from OSB panels at a range of angles to the panel axis and these samples have been tested in bending. The factory data and the experimental data have been compared in order to investigate the relationship between the practical condition of fiber orientation in the factory and the bending properties as a function of orientation. The following conclusions can be drawn. Fiber orientation in the production line is good and stable irrespective of position across the width of the production line, time of day and changing line speed. The average value for the orientation angle of the forming mat on the production line is approximately 25°. The general shape of the fiber orientation distribution is similar to a normal distribution, however, at the centre of the fiber mat the sharpness of the distribution is greater than a normal distribution. The average orientations of fibers in commercial board lie at 25° and 60° to the longitudinal and perpendicular directions, respectively. The results suggest that there is potential to improve the mean fiber orientation angle of commercial OSB to improve longitudinal values of MOR and MOE, especially where perpendicular properties are not critical. Received 31 March 2000     

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。     

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.     

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.     

定向刨花板挠度与蠕变试验

采用正交异性的挠度方程计算四边筒支定向刨花板的中心点挠度，并在实验基础上对此进行验证，从而得到满足实际生产的定向刨花板挠度值计算公式，并对６ｍｍ，１０ｍｍ定向刨花板进行蠕变测试，找出持荷时间与挠度之间关系，进一步分析终挠度值与初挠度值之比，静曲强度和弹性模量损失量。     

Veneer strand flanged I-beam with MDF or particleboard as web material IV: Effect of web material types and flange density on the basic properties

The balance of strength between the flange and web parts of veneer strand flanged I-beam was investigated by the following methods: (1) use of different web material types, such as plywood, oriented strand board (OSB), particleboard (PB), and medium density fiberboard (MDF), that have different strength properties; and (2) fabrication of I-beams with low-density flanges using low-density strands with PB web material. Replacing PB or MDF with plywood showed slight significant improvement in the modulus of rupture but not in the modulus of elasticity of the entire I-beam. However, PB and MDF showed competent performance in comparison with OSB, thus strengthening the promising future of the use of PB or MDF as web material to fabricate I-beams. Hot-pressing conditions used for I-beam production exerted slightly adverse effects on the bending properties of PB, but not on MDF, OSB, and plywood web materials. The flange density of 0.60 g/cm³ was considered to be the lower limit that provides I-beams with balanced mechanical properties and dimensional stability.     

Effect of mat structure on modulus of elasticity of oriented strandboard

A model to predict bending stiffness of oriented strandboard (OSB) was tested with pilot plant experimental data. The experimental procedure developed in this study is unique in that it allows the model to be tested for extensive vertical configurations of strand angle distribution. After validation, the model was used to simulate a typical three-layer cross-oriented OSB panel with a vertical density profile and strand angle distribution measured on industrial panels. Analysis of the simulated vertical distribution of modulus of elasticity (MOE) indicated that the layers near the panel surfaces contributed much more to the effective parallel panel MOE than those close to the panel thickness center, with 80% of parallel MOE coming from the top 41% of weight and 32% of thickness. The effectiveness of methods to increase parallel bending stiffness through improving mat structure was evaluated. Increasing face/core weight ratio from 54/46 to 66/34 resulted in a 3.7% increase in simulated parallel MOE. Alignment of strands in face layers was identified having a greater potential to increase parallel MOE. Simulations with three improved strand angle distributions showed gains of 5.7, 12.0 and 19.8% in parallel MOE compared with a typical strand angle distribution of industrial OSB panels.     

铜基防腐剂对竹材定向刨花板性能的影响

选用季铵铜(ACQ)、铜唑(CuAz)及环烷酸铜(CuN)3种铜基防腐剂,考察防腐剂添加对竹材定向刨花板物理力学性能的影响。研究表明,3种防腐剂处理材的物理力学性能,均满足LY/T 1580-2000《定向刨花板》中OSB/3规定;其中,CuAz及CuN各载药量处理材的性能均超过OSB/4的要求,并且综合力学性能优于ACQ处理材。添加2.21 kg/m3的CuAz制作的板材性能略低于对照试板外,其余防腐剂或载药量对板材性能无不利影响。     

Thermal degradation of bending strength of plywood and oriented strand board: a kinetics approach

The construction industry has relied heavily on wood and wood-based composites, such as oriented strand board (OSB) and plywood for timber frame construction. Therefore, it is highly imperative to categorize the response of wood-based composites when exposed to elevated temperatures for a sustained period of time. The essence of fire-resistant structural design is to ensure that structural integrity be maintained during and after the fire, prevent collapse and maintain means of egress. Another aspect is to assess post-fire structural integrity and residual strength of existing structure. The objective of this project was (a) to study the effect of exposure time on bending strength (MOR) of OSB and plywood at elevated temperatures, (b) to interpret any relationships between different temperature and time of exposure using a kinetics model for thermal degradation of strength, and (c) to develop a master curve representing temporal behavior of OSB and plywood at a reference temperature. As much as 1,152 samples were tested in static bending as a function of exposure time and several temperatures. Strength (MOR) of both OSB and plywood decreased as a function of temperature and exposure time. These results were fit to a simple kinetics model, based on the assumption of degradation kinetics following an Arrhenius activation energy model. The apparent activation energies for thermal degradation of strength were 54.1 kJ/mol for OSB and 62.8 kJ/mol for plywood. Furthermore, using the kinetics analysis along with time–temperature superposition, a master curve was generated at a reference temperature of 150°C which predicts degradation of strength with time on exposure at that reference temperature. The master curves show that although plywood has a higher initial strength, OSB performs better in terms of strength degradation after exposure to elevated temperature.     

酚醛树脂制造竹定向刨花板的工艺探讨

竹定向刨花板(BOSB)是将窄长竹刨花经过施胶、定向铺装和热压而成的一种多层结构板材.通过测定竹刨花形态、施胶量、热压工艺等因素对BOSB性能的影响,探索制造BOSB的较佳工艺条件.采用本试验确定的工艺参数试制的样板,主要性能指标可满足林业标准中木质OSB/3类一级品的要求.     

彩色定向结构刨花板的研制

彩色定向结构刨花板（ＯＳＢ）是利用染我后的大片刨花为表层,本色刨花为芯层,施 后一次热压成型,经简单处理后用于有色彩要求的场所。本研究主要探讨染色工艺对刨花表面相对自由基浓度的影响及由此产生的对胶合性能的影响。研究结果表明,不同染料和染色工艺对刨花表面的相对自由基浓度有显著影响,染色对ＯＳＢ无不良影响     

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 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.     

竹材是我国制造OSB的一种潜在原料

定向刨花板(OSB)是近20年人造板家族中发展最迅速的一种板材。国外已呈现原料供应不足状况。我国OSB制造业正在起步阶段,将来也会面临原料资源问题。我国是世界第一产竹大国,通过分析竹材的理化性质和采用毛竹进行压板试验,结果表明竹材极有可能替代木材成为制造OSB的一种新原料。     

Adhesive systems used in the European particleboard,MDF and OSB industries*

In this work, the adhesive systems used today in the European industries of particleboard, medium density fibreboard (MDF) and oriented strand board (OSB) are discussed. The structure of particleboard, MDF and OSB markets in Europe in relation to the types of adhesives and product specifications are presented as well. It is noticeable that new markets for wood-based panels like particleboard and fibreboard, known as non-furniture markets, are growing in Europe at a fast rate. It was concluded that most of the technological changes concerning the adhesive systems applied and additives have been realised from the need for niche panel products, the obligation to reach even lower formaldehyde emissions, and the necessity to decrease production costs due to the stringent competition in the market of wood-based panels.     

Deterioration of wood-based boards subjected to outdoor exposure in Tsukuba

Various types of wood-based boards were analyzed for deterioration after being exposed to an outdoor environment for 5 years in Tsukuba, Japan. In phenol–formaldehyde resin bonded particleboard (PB(PF)) and aspen oriented strand board (OSB(aspen)), longer exposure caused a greater reduction in the modulus of rupture and internal bond strength, an increase in the coefficients of variation, and a decrease in 95 % lower tolerance limit at the 75 % confidence level (95TL). Nail-head pull-through and lateral nail resistance were also reduced by outdoor exposure, but their coefficients of variation and 95TL were not significantly affected. In contrast, methylene diphenyl diisocyanate bonded medium density fiberboard (MDF(MDI)) only showed a slight deterioration of these properties even after 5-year exposure, and the coefficients of variation and 95TL hardly changed. After 5-year exposure, the retention of shear load in one-plane at relative displacement of 1.0 mm was high in MDF(MDI) and OSB(aspen) at 93.5 and 78.5 %, respectively, but low in PB(PF) at 41.1 %. As with PB(PF), OSB(aspen) also showed a sharp decrease in the modulus of rupture and internal bond strength, but only slightly reduced shear load in one-plane.     

Supplementing pine with European beech and poplar in oriented strand boards

Abstract

The objective of the study was to compare the properties of oriented strand boards (OSBs) made from the following mixtures: European beech and poplar, beech and pine, poplar and pine and 100% pine (i.e. the conventional raw material for OSB in Europe). Panels with 50–50% of beech-poplar/beech-pine/poplar-pine at two density levels of 650 kg/m³ and 720 kg/m³ were made with 5% pMDI (poly methylene di-isocyanate) as binder at 180°C and 240s as press conditions. Results showed that panels comprising a mixture of European beech and poplar have higher mechanical properties compared to panels made with mixtures of pine-beech or pine-poplar. In addition, for all panels, when density is increased from 650 kg/m³ to 720 kg/m³, mechanical properties increased. Internal bond values for all designs were in the same range, especially at higher density (720 kg/m³). The pure pine panels showed lower values between different designs. Thickness swelling, an important physical property of OSB, improved when face and core layers consisted of a mixture of beech and poplar strands.     

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.