A group of 2x4 SPF samples was tested for bending stiffness in the Western laboratory of Forintek and then re-tested in the Eastern laboratory . Another group of 2x4 SPF samples was tested for bending stiffness in the Eastern laboratory and then re-tested in the Western laboratory. The bending stiffness tests were conducted on test machines set up in accordance with ASTM Standard D198-02. Additional bending tests were done according to ASTM D4761-02A using the “portable bending” machine in the Western laboratory and a modified Metriguard 312 bending machine in the Eastern laboratory.
Results from ASTM D198-02 bending stiffness tests showed a differences between the laboratories of 2.1% for the sample originating from the Western Laboratory and 1.5% for the sample originating from the Eastern Laboratory. The MOE bending test results were not adjusted to account for any increase or decrease in the moisture content of the specimens.
In this study, we conducted systematic experiments on air permeability of aspen veneer and glueline in terms of panel compression ratio (or applied platen pressure), degree of glue cure (or pressing time), veneer type (sapwood or heartwood veneer) and glue spread level. We also compared the air permeability data of aspen veneer and veneer-ply (2-ply veneer panel) to aspen solid wood and aspen oriented strandboard (OSB). Based on this study, the following conclusions were drawn:
For laminated veneer lumber (LVL) and plywood panels, the compression ratio is the most important factor affecting the panel permeability, followed by veneer type (sapwood or heartwood veneer), glue spread and degree of glue cure (or pressing time). The air permeability of the glueline decreases in the course of glue curing; however, its order of magnitude remains the same as that of uncured glue. The reduction in panel permeability mainly results from small densification of each veneer ply instead of the sealing effect of the glueline. Therefore, during LVL/plywood hot-pressing, the glueline does not serve as a main barrier to the gas and moisture movement as commonly speculated. However, due to the substantial change in the magnitude of panel permeability merely within a 5% compression ratio, the convection effect on heat and mass transfer is considered to be very limited.
The air permeability of sapwood veneer is about twice that of heartwood veneer without compression. However, with compression, the air permeability of heartwood veneer drops much faster than that of sapwood veneer. The permeability of a sapwood veneer panel is 5.5 ~ 7.0 times higher than that of a heartwood veneer panel merely with a compression ratio in the range of 2.5% ~ 5%. In practice, it implies that 1) panels made from sapwood veneer are more treatable with preservatives; and 2) by controlling panel permeability through veneer incising, proper panel lay-up and densification, mills could reduce blows/blisters during hot-pressing.
The air permeability of aspen wood or veneer is not affected by wood density. The air permeability of aspen LVL/plywood panels is 1.5~ 2 times larger than that of aspen solid wood due to the existence of lathe checks, but is significantly lower than that of aspen OSB at the same density level of the panel. On average, commercial LVL/plywood panels have almost the same magnitude of air permeability as commercial OSB. However, due to the absence of voids and small horizontal density variation, LVL/plywood panels will be less permeable than OSB.
One of Forintek’s most valued services to the oriented strandboard (OSB) members is our use of computer modeling tools to assist members optimize their manufacturing processes and quantify the potential benefits of new technology developments This project substantially upgraded our hot pressing model and added two new models to Forintek’s suite of modeling tools.
Forintek’s 2-D hot pressing model describes the relationship between hot pressing schedules and panel attributes. In this project the 2-D hot pressing model was upgraded to a 3-D model. The 3-D model improves the prediction accuracy of heat and moisture transfer and vertical density profile during the hot pressing process. The model can be used to quantify the costs of current hot pressing processes and predict the potential cost implications of changes to schedules and equipment. It can also be used to assess the need for, and impacts, of developing new pressing technology.
Two new models were developed: one for continuous pressing and one that predicts the mechanical properties of panels from specific manufacturing options. Continuous pressing is an emerging technology which is increasingly used by the composite board industry. This project marks the completion of our first model for continuous pressing. The model simulates the distributions of temperature, moisture content, gas pressure and density profile along the press during pressing based on input data that describe panel structure, layer structure, flake geometry and pressing schedule. While the modelling tool provides many insights into the continuous pressing operation, some basic laboratory tests and mill trials are still needed to optimize individual members’ pressing operations.
The first model to predict the mechanical properties of OSB end products from manufacturing process attributes has been completed. The model predicts end product panel modulus of elasticity (MOE) from density profile, flake geometry, strand orientation, fines content and layer structure.
The models completed in this project will be used as a guide for research and development of new products and process optimization for existing products. Use of these models results in significant savings in R&D costs and higher efficiency in problem solving for members.
This report summarizes the results of laboratory tests, conducted during the period April 1/03 to March 31/04, that were designed to assist mills in implementing super-critical speed sawing. The general characteristics of saw behaviour in the super-critical speed region is discussed and measured saw deviations are presented that illustrate the effect on cutting accuracy of increasing saw and feed speeds. Results are presented for guided spline-arbor saws with diameters of 17", 19" and 24". In each case it was found that feed speeds currently in use could be increased by increasing blade speed.
A wear test was conducted on two Cermet and one tungsten carbide tool materials when cutting green western red cedar. Three 4.35-inch diameter sawblades were custom manufactured for the KT125 (Cermet), KT195 (Cermet) and K3030C (tungsten carbide) tool materials with a 0.140-inch kerf. The Cermets were successfully braised using a copper interface between the saw tip and saw body, high silver content solder and limited heat application. The cutting test was conducted on a Delta vertical single-spindle shaper using a bite of 0.026 inches. Wear measurements by impression method were taken at 0, 5000, 10000, 15000 and 20000 lineal feet of cutting. The KT125 grade Cermet fractured early in the test after 140 lineal feet of cutting and would not be considered appropriate for green western red cedar. At the completion of the test, the tungsten carbide tool material had reached the end of its useful life. Measurements showed substantial wear. The KT125, on the other hand, showed significantly lower wear and remained in a running condition after 20000 lineal feet of cutting. Since the KT125 did not reach its end of life, it is difficult to estimate its wear advantage over the tungsten carbide. Based on the wear rate measurements of recession, width and diameter and making several comparative assumptions, a preliminary estimate of the wear advantage may be obtained. It is projected that the wear advantage of KT195 is 1.7 to 4 times beyond that of K3030C under the conditions in this test. Validation of this wear advantage and the determination of the optimum operating conditions for Cermets will require more extensive testing and sawmill trials.
Les tests effectués dans le cadre de ce projet ont généré des résultats sur l’efficacité des opérations manuelles au poste du chariot, de délignage et d’éboutage. Des simulations ont également démontré l’impact de l’utilisation d‘optimiseurs conçus pour évaluer la forme d’une bille ou d’un sciage sur l’efficacité de ces postes de travail.
L’évaluation des opérations manuelles a mis en lumière une fréquence élevée d’erreurs, tant au poste du chariot qu’au poste de délignage et d’éboutage. Il existe une grande variabilité entre la performance des opérateurs et ils ont généralement tendance à mettre l’emphase sur le volume au détriment de la valeur. L’élimination complète de ces erreurs pourrait générer des revenus supplémentaires de l’ordre de 200 000 dollars pour le poste du chariot, et de 500 000 à 700 000 dollars pour le poste de délignage et d’éboutage d’une scierie produisant annuellement 10 MMpmp.
La majorité des pertes encourues au chariot pourraient être récupérées avec l’installation d’un système d’optimisation 3D au chariot et ainsi permettre un retour sur investissement inférieur à deux ans. Ces calculs ne tiennent pas compte du gain en productivité qui résulterait de l’installation d’un tel système.
La situation est différente pour l’optimisation d’un poste de délignage et d’éboutage. Compte tenu que la technologie actuelle ne permet pas l’identification des défauts d’apparence, une partie seulement des pertes pourraient être récupérées suite à l’installation d’un optimiseur à ces deux postes de travail. Les résultats indiquent que l’optimisation d’un poste de délignage et d’éboutage basée strictement sur la flache devrait permettre de récupérer respectivement 25.3 % et 2.3 % des bénéfices globaux escomptés. Ces pourcentages représentent des revenus additionnels de 126 000 dollars pour le délignage et de seulement 15 400 dollars pour l’éboutage pour une scierie de 10 MMpmp.
La possibilité d’intervention de l’opérateur pour modifier la décision de l’optimiseur n’a pas été prise en considération lors de l’évaluation des échantillons. Les bénéfices reliés à l’installation d’un optimiseur au poste de délignage et d’éboutage devraient donc se situer entre les gains générés par l’optimisation selon la flache et ceux générés en tenant compte de tous les défauts. Cependant, considérant le coût d’achat et d’installation de ces équipements (jusqu’à 800 000 dollars), l’intérêt pour ces systèmes est diminué. Dans ce contexte, seuls certains postes de délignage nécessitant une productivité accrue pourront tirer avantage de cette technologie pouvant fonctionner à une vitesse dépassant les 25 pièces/minute.
Des essais en laboratoire et en usine ont été réalisés sur un humidimètre diélectrique commercial (Wagner, modèle L612) et la sonde accessoire pour utilisation dans les piles de bois (Wagner, modèle L712). Ces essais avaient pour but de caractériser et de quantifier les différents facteurs qui influencent la précision des mesures de teneur en humidité effectuées avec ce genre d’appareil. Les essais en laboratoire visaient à déterminer les propriétés du bois et les facteurs externes exerçant un effet sur les lectures. Les essais réalisés sur de l’épinette noire dont la teneur en humidité variait de 9 à 18% montrent la nécessité d’établir un nouveau facteur de correction pour cette essence. Les auteurs ont constaté que le gradient d’humidité, la température du bois, l’état de surface et la largeur des pièces affectent la lecture de l’humidimètre. Bien que non négligeable, l’effet de la température du bois ne représente qu’environ la moitié de ce qui a été observé dans le cas des appareils à résistance. La présence de nœuds ou de bois de compression dans la zone d’essai influence aussi les lectures. La température de séchage n’a par contre aucun effet détectable.
Des essais industriels réels et simulés ont permis de valider les différentes corrections établies lors des essais en laboratoire. Dans le cas de l’épinette noire, il s’est avéré possible d’améliorer la mesure de la teneur en humidité par l’emploi d’un nouveau facteur de correction pour l’essence et, selon l’application considérée, par l’emploi de facteurs de correction pour la température du bois, l’état de surface, etc. Certains essais ont également porté sur la sonde d’échantillonnage. Même dans les conditions bien contrôlées du laboratoire, il a été difficile d’obtenir une bonne corrélation entre les lectures prises à l’aide de la sonde et celles obtenues directement avec l’humidimètre portable ou par dessiccation au four. La sonde a généralement pour effet de sous-estimer la teneur en humidité du bois. Les lectures se sont avérées plus précises et plus uniformes lorsqu’elles ont lieu dans les piles de bois de température uniforme.
Des comparaisons ont été effectuées entre les lectures des deux types d’humidimètre portable (diélectrique et résistance) en rapport avec la teneur en humidité mesurée au four de pièces de bois séchées en laboratoire et en usine. La proportion de lectures comprise dans une plage d’erreur donnée s’avère légèrement supérieure dans le cas de l’appareil à résistance. Il est possible d’établir une corrélation entre les lectures de l’humidimètre diélectrique et celles de l’appareil à résistance indépendamment des facteurs de correction utilisés.
This second report for project entitled “Reduction in Folded strands to Improve OSB Properties” contains studies of flaking yellow birch to reduce strand folding plus additional studies carried out on aspen to further understand the basic mechanisms of strand folding.
In this report, the impacts of wood temperature and counter knife angle were investigated. The effect of flaking parameters on strand tensile strength, flaking energy and strand size distribution was also investigated. Different ways to reduce strand folding were tested, including: flaking birch wood with different knife projections and with different knife clearance angles, drying strands at different temperatures; longitudinal flaking at different rake angles, microbevel angles and different strand lengths. In addition basic flaking studies were carried out to evaluate tangential flaking of aspen wood from different locations with different moisture contents, different counter knife thicknesses and different tilt angles. Strands with different curl indexes were correlated with panel performance in order to study the impact of strand folding on panel properties.
A key finding was that birch strands were more liable to yield folded strands compared to aspen strands. Counter knife angles of 78° and wood temperature of 21°C tended to yield the lowest birch strand folding. Increasing strand thickness and decreasing knife clearance angle decreased the folding of both birch and aspen. Flaking birch strands with a large rake angle and microbevel reduced strand folding.
Strand folding was also dependent on strand drying temperature and strander knife clearance angle. Drying wood at different temperatures resulted in different levels of strand folding. The impact varied among wood species with birch being more prone to folding than aspen.
Longitudinally flaking birch strands shows that an increase of strand length increased strand curl.
Among the following variables, changing wood moisture content, changing the distance between counter knife edge to strand knife edge (edge distance), adjusting strand drying temperature, adjusting knife sharpness angle, and adjusting rake angle, increasing rake angle was the most effective way to reduce strand folding. The effect of wood drying temperature is worthy of further investigation.
Making panels with furnish containing large amounts of folded strands resulted in panel delamination or low IB. Further investigation of the relationships between strand folding and panel properties is needed to develop a more complete understanding of the full impact of strand folding.
These studies indicated that by combining higher wood temperature, larger counter knife angle and larger rake angle with certain microbevel, it will be possible to reduce strand folding, fines and energy consumption.
Whether you are drying 2 x 4 studs or high-quality hard maple for furniture stock, the range of available kiln systems has grown considerably over the past few years. Anyone considering the addition of new drying equipment would be well advised to consider all the options before making a final decision. Some drying systems offer the ability to dry products that were previously impossible to dry properly, or to achieve unprecedented product quality levels. Without considering all options up front, you could end up selecting a system that limits your ability to respond to current or future market opportunities.
This is the second report on wood hardening technologies. In this report, the performance for flooring based on wood treatability, chemical retention, dimensional stability, wear resistance, pull-off strength, and hardness were investigated in Douglas fir, western hemlock, hard maple, aspen, and Amabilis fir treated using two different processes. Tests were also conducted on wood modified with nanoparticles with sol-gel method, wood hardened by different methacrylates formulations, and wood impregnated with MUF resin and polymerized with hot press compression.
On the basis of the wood samples treated at Mill A, it was concluded that hard maple sapwood had the best treatability. Western hemlock and Douglas fir had very good treatability. Aspen and Amabilis had poor treatability. Chemical treatments at both Mill A and Mill B increased the density of the five tested wood samples, compared with control samples. Under the same treatment conditions, Amabilis fir and western hemlock had the highest chemical retention. Hard maple had the lowest chemical retention.
Generally, chemical treatments at both Mill A and Mill B improved the dimensional stability and water absorption property of five tested wood samples, compared with control samples. Under the same treatment conditions, western hemlock had the highest anti-swelling efficiency in radial and tangential direction and the greatest improvement in water absorption. Chemical treatments did not improve the wear resistance of all treated wood samples. But both Mill A and Mill B treatments improved the wear resistance of hard maple and western hemlock, compared with untreated controls. Hard maple had lower wear index than western hemlock, but western hemlock had greater wear resistance improvement than hard maple.
Chemical treatments at both Mill A and Mill B improved the hardness of the samples of five tested wood species, compared with untreated controls. Western hemlock treated at Mill B was the hardest and had the greatest improvement in hardness. Compared with untreated hard maple, western hemlock and Douglas fir treated at Mill B were harder. Chemical treatments at both Mill A and Mill B improved the pull-off strength of tested wood species, compared with controls. Of all the samples, hard maple treated at Mill B had the greatest pull-off strength. Western hemlock and Douglas fir both treated at Mill B had greater pull-off strength than untreated hard maple. They also had the greatest pull-off strength improvement.
On the basis of two Chinese wood species tested, the sol-gel method can be selectively applied to wood to improve wood hardness. One of the factors that determined the level of hardness improvement in wood was chemical retention.
Different methacrylates had different impacts on modified hard maple. Monomer retention by volume in treated hard maple was similar regardless of formulation combinations, but monomer retention by weight was different than formulation combinations because of differences in monomer densities. Methacrylates in wood enhanced wood hardness and hardness modulus. The Brinell hardness correlated highly with hardness modulus. Different methacrylates resulted in different wood water absorptions and had different effects on treated wood dimensional stabilities in tangential direction.
Hard maple and poplar impregnated with MUF resin improved wood hardness and dimensional stability in terms of thickness swelling and water absorption, compared with controls. Resin impregnated hybrid poplar was harder than untreated hard maple. Compression had a tendency to decrease chemical retention in poplar. Impregnation together with compression improved hybrid poplar hardness, but had a tendency to decrease the hardness of compressed hard maple. With the experimental parameters used, impregnation of wood with MUF resin caused cracks, especially in compressed wood samples.
Successfully applying wood hardening technologies in the wood flooring industry depends heavily on the processing cost and on marketing. It also relies on empathy for better life, better quality and better environment. Thus, research should be focused on reducing production costs and long-term performance. MUF resin offers an alternative for hardening wood at a relatively low cost. Preliminary test results indicate that impregnating hybrid poplar and hard maple improved the wood hardness and dimensional stability. Impregnation, together with hot press compression, improved the hardness and dimensional stability of poplar. Compression has the potential to reduce chemical retention in wood and reduce process cost without compromising wood hardness and dimensional stability. Thus, impregnation together with hot press compression should be tested in a methacrylates-wood system. A comparison between a methacrylates-wood system and MUF resin-wood system would be very helpful. Further research on MUF resin impregnation and hot press compression should be done on low-density wood species to improve impregnation efficiency and reduce chemical retention. The resin formulation and hot press compression parameters should be optimized. The long term durability of the treated wood should be confirmed.
Laboratory and industrial testing was conducted on a commercial, dielectric moisture meter (Wagner model L612) and an accompanying stack sampling probe (Wagner model L712). The purpose of the testing was to identify and quantify the various factors affecting the accuracy of moisture content (MC) estimates obtained when using this equipment. Laboratory tests were conducted to determine which wood-related properties and environmental factors had an influence on meter readings. Testing of black spruce over a range of MC’s from 9 to 18% identified the need for a new correction factor for this species. Moisture gradient, wood temperature, surface roughness, and board width were found to have an effect on meter reading. Effect of wood temperature is significant but is roughly half the effect previously documented on DC-resistance. The presence of knots or compression wood in the sampling area also influenced meter reading. Temperature that the wood was dried at was not found to have an effect.
Simulated and actual industrial tests were conducted to test the applicability of various corrections identified in the laboratory testing phase. For black spruce, improved estimates of MC were obtainable by applying the newly developed species correction and, depending on the specific tests, other corrections for wood temperature, surface quality, etc. Tests were also conducted using the stack sampling probe. Even under well controlled laboratory conditions, there was not a good correlation between readings taken with the stack sampling probe and either readings with the handheld meter or oven-dry moisture content. Readings taken with the stack sampling probe typically underestimate the actual MC. More accurate and consistent readings were obtained when sampling wood stacks at a uniform wood temperature.
Readings from both dielectric and DC-resistance meters were compared against oven-dry MC for laboratory and industrially dried lumber. The DC-resistance meter performed marginally better when evaluated on the basis of proportion of readings within given error limits. MC estimates from the dielectric meter can be correlated with DC-resistance MC estimates regardless of which correction factors are applied. Dielectric and DC-resistance meters are not used totally interchangeably in the wood industry as each has specific applications where they are advantageous to use. As a result, any small difference in accuracy is not always the determining factor.
This report summarises a research project carried out at Forintek Eastern Laboratory on Investigation of MDF Press Strategies to Reduce Press Time. The scope of the research includes theoretical analysis of MDF hot pressing process, development of a computer simulation model for MDF continuous hot press, parametric study of hot pressing process using the simulation model, and experimental works on microwave pre-heating of the fibre mat. As results of the research project, a comprehensive computer simulation model was developed. The following conclusions can be made based on the theoretical and experimental works of this project:
The computer simulation model is capable of analysing the hot pressing process and predicting the evolution of important pressing parameters including temperature responses, gas pressure, gas density, gas flow velocity, moisture content, load and stress, and density profile development in different location of the fibre mat. The predicted data agree well in trend with the observations from the industrial MDF continuous presses.
The parameters significantly affecting the hot pressing time include panel density, initial fibre moisture content, initial fibre mat temperature, pressing temperature and width of the fibre mat.
Other hot pressing parameters, such as the initial closing speed and the temperature difference among different pressing zones, have no significant effects on the hot pressing efficiency.
Microwave pre-heating of the MDF fibre mat, not only increase the initial mat temperature, but also re-distribute the moisture towards the mat surface.
Microwave pre-heating induces an earlier increase of the core temperature in the MDF fibre mat and a greater rate of temperature increase.
As a result of microwave pre-heating, the pressing time can be substantially reduced, leading to an increase in production efficiency.
This study was conducted to evaluate how wood harvest seasons (winter, spring, summer, fall), species (single, mixture), divisions of the stem (sapwood, heartwood), and test methods (cold water extraction, hot water extraction) affect wood chemical characteristics. Ten wood species, normally used for manufacturing particleboard, medium density fiberboard (MDF), and oriented strand board (OSB), were characterized for pH, buffer capacity (acid, base), acid content (total, soluble, bound), and solubility (water, ethanol-toluene).
First, it was observed that wood harvest season affected the chemical properties of jack pine, black spruce, white spruce, and balsam fir. The extent of seasonal influence on wood chemical properties depended on individual species. In general, wood harvested in fall and summer yielded lower pH values than wood harvested in winter and spring. Winter-harvested balsam fir had significantly higher acid buffer capacity (followed by summer and spring) than other species during the same seasons. Most species yielded higher total and soluble acid contents when harvested in summer compared with winter, and yielded higher water solubility when harvested in winter compared with summer. Higher ethanol-toluene solubility and lower levels of bound acid were observed for jack pine and black spruce, respectively, compared with other species harvested in winter and/or summer seasons.
The wood chemical properties of spruce (black and white), jack pine, and balsam fir (SPF) mixes did not follow the “ideal mixture behaviour” predicted by simply averaging values for individual species (only winter season was examined). This phenomenon could be attributed to the interaction between chemical compounds of wood extractives of the different wood species. Such interactions would either offset or reinforce each other in terms of wood chemical properties between different wood species. An increase in the percentage of balsam fir (from 20 to 60%) in the SPF mix increased pH, acid buffer capacity, and soluble acid content, but decreased the bound acid content. A higher spruce content in the SPF mix resulted in lower water solubility and lower ethanol-toluene solubility.
Wood pH and buffer capacity differed between sapwood and heartwood for SPF species (only fall harvest season was examined). All species except for balsam fir had higher pH and lower acid buffer capacity for heartwood than for sapwood. Sapwood and heartwood yielded higher pH and acid buffer capacity than the whole tree of each species. Differences in wood pH and base buffer capacity between sapwood and heartwood were also observed for five hardwood species and one softwood species—southern yellow pine (only fall harvest season was examined). Aspen and white birch heartwood had higher pH values than the sapwood, while yellow birch, red maple, southern yellow pine (SYP), and sweet gum heartwood had lower pH values than the sapwood. Heartwood and sapwood had an opposite effect on wood base buffer capacity than they did on pH value for these species.
In jack pine, wood chemical characteristics such as pH and acid buffer capacity were influenced by extraction time and temperature, wood quantity in titration, and wood particle size. Increased extraction time and decreased particle size in hot water extraction resulted in slightly lower pH values and a higher acid buffer capacity. Increased extraction time and decreased particle size in cold water extraction seemed to slightly decrease both wood pH values and acid buffer capacity. However, compared to extraction temperature, extraction time and particle size (between 60 and ¼ meshes) had much less influence on wood chemical properties. Hot water extraction resulted in lower pH values and acid buffer capacities than with cold water extraction; this was attributed mainly to different water temperatures (100oC vs. ambient condition) and quantities of wood (25 vs. 3 g of OD wood flour) used in extraction. In addition, hot water extraction might yield more acidic soluble materials than cold water extraction.
Oriented strand board (OSB) is widely used in house construction in North America. In Canada, OSB panels are commonly made of aspen strands and are susceptible to mould and decay when they get wet. Building envelope failures due to mould, decay or poor construction practices can negatively impact the image of wood. This can lead to product substitution that in turn can affect the wood industry’s overall competitiveness. To ensure durability of OSB panels, the most important consideration is the use of mould- and decay-resistant panels to prevent fungal attack. Using low environmental impact technology to improve the durability of OSB products could have market-related advantages over using chemical protection products. This project aimed to develop technologies for protecting OSB raw materials from biodegradation and to explore biological pre- or post-treatments to increase the durability of panels so they would better resist mould, stain and decay.
The project was divided into three parts. Part one involved developing a biological technology to protect OSB raw materials from biodegradation. In this part, aspen, red maple and yellow birch trees, which are commonly used to make OSB in Canada, were felled in May and cut into 4-foot logs. These logs were then equally divided into two groups (16 logs each) with one group keeping its bark and the other having it removed. These debarked and “bark-on” logs were further divided into two groups, each containing 8 logs. One group of logs was treated with a bioprotectant and another group served as a control. The treated and untreated logs were stored separately in Forintek’s yard. Two inspections were conducted, one at the end of the growth season (in October after a 5-month storage period) and the other after one year. During each inspection, four logs from each test group were examined for fungal degradation (mould, stain and decay), and then cut into strands to be used for manufacturing panels. The panels’ physical and mechanical properties and mould resistance were evaluated.
The second part involved developing a biological pre- or post-treatment technology by using naturally resistant wood species to increase the durability of panels so they would better resist mould, stain and decay. In this part, a series of tests were conducted using various wood species. These tests included a) determining the antifungal properties of bark from various wood species; b) using white cedar to improve panel durability; c) optimizing manufacturing conditions for producing durable panels with white cedar; d) using other wood species to produce mould-resistant panels; and e) post-treating panels with extracts of durable wood species.
The third part consists of developing a biological pre- or post-treatment technology by using fungal antagonists to increase the durability of panels against mould, stain and decay. This part will be conducted in the 2004-2005 fiscal year, and results will be included in next year’s report.
The results of the first part on the protection of raw materials showed that all untreated logs, with or without bark, were seriously degraded by moulds, stain and decay fungi after a summer storage period of five months. The logs with bark were more degraded than the debarked logs, and the log ends were more degraded than the middle sections. After summer storage, 55% to 83% of the wood was degraded in untreated logs. The biological treatment was effective, only 4% to 16% of the wood in treated logs was affected by various fungi after a five-month storage period. Furthermore, the biological treatment was more effective on logs without bark than logs with bark, and more effective on yellow birch and aspen than on red maple. After one year in storage, the total infection rates of untreated logs ranged from 68% to 91%, whereas the rate for biologically treated logs ranged from 27% to 49%. Among these treated logs, the logs ends were degraded from 31% to 62%, whereas the middle sections were degraded from 7% to 26%. Strands cut from untreated logs contained 50% to 75% of grey or blue stained strands, whereas those cut from biologically treated logs contained 10% to 25% of such strands. Panels made using biologically treated logs had the lowest TS and WA values compared with panels made using fresh-cut logs and untreated stored logs. The other physical and mechanical properties of the various panels made for this test were comparable.
The antifungal properties of bark from six wood species (aspen, red maple, yellow birch, balsam fir, white spruce and white cedar) were investigated in the second part of this research project. Based on the colony growth rate of moulds, stain and decay fungi on bark-extract-agar media, white spruce bark was the best at inhibiting growth of these fungi, followed by red maple bark. White cedar and balsam fir bark somewhat inhibited certain fungi tested. Aspen and yellow birch bark did little or nothing at all to inhibit fungal growth. The research also showed that the white cedar heartwood-extract-agar medium not only inhibited decay fungi growth, but also inhibited the growth of moulds and staining fungi. The bark-extract-agar medium of this wood species was less effective in inhibiting fungal growth than the heartwood was.
Three-layer panels made using white cedar heartwood strands in the face layers and aspen strands in the core layer at a ratio of 25:0:25 were mould and decay resistant, but the panels “blew” easily during manufacturing and their mechanical properties were not satisfying. The overall mould infection rate on white cedar heartwood-faced panels was 0.8, which indicated that the panel was mould resistant. White spruce heartwood-faced panels were highly mould resistant and moderately decay resistant. The overall mould infection rate on white spruce heartwood-faced panels was only 0.2 after 8 weeks of exposure to high humidity environmental conditions. In addition to being mould resistant, white spruce heartwood-faced aspen panels also had better IB, MOR and MOE properties, compared with aspen panels. The panels with black spruce in surface layer had mechanical and mould-resistance properties that were similar to those with white spruce in surface. The panels with surface layer of Eastern larch heartwood were non-resistant to moulds and slightly resistant to decay, but they had better IB, TS and WA properties compared with the other types of panels. The overall mould infection rate on the panel with surface layer of Eastern larch heartwood was 3.7, which was similar to the rate for aspen control panels. Aspen panels (serving as control panels) were seriously affected by moulds with overall mould infection rates ranging from 3.8 to 4.9.
Aspen panels with surface layer from whole-wood strands (using both sapwood and heartwood) from white cedar, in a ratio of 25:50:25 and pressed at 220°C for 150 seconds, were well bonded and had IB, TS, WA and MOE values that were similar to those of aspen control panel, but with a higher MOR. All the panels’ properties met the requirements of the standard. This type of panel also was the least infected by moulds, especially in the face layers which rated a 0.2. The panel sides were moderately infected, rating a 2.6, this occurring mostly in the middle layer of aspen strands. The overall rate of this type of panel was 1.0, which indicated that the panels were resistant to mould infection. This type of panel was also highly resistant to brown rot and moderately resistant to white rot.
Panels made of steam-treated white cedar whole-wood strands and aspen strands at a ratio of 3:7 based on oven-dry weight also had low infection rates: the average face infection rate was 1.2; the side infection was 2.4 and the overall rate was 1.6. Compared with aspen panels, this type of panel also had high MOR and MOE values and low TS and WA values.
In the case of white cedar whole-wood strands faced aspen panels, when the pressing time was increased from 160 seconds to 180 seconds at 200°C, the panels’ IB strength and MOE increased whereas the panels’ TS, WA and MOR decreased. By increasing the pressing temperature from 200°C to 240°C and pressing for 160 seconds, the panels’ IB strength, MOR and MOE increased and the panels’ TS and WA decreased sharply. At a pressing temperature of 240°C and a pressing time of 180 seconds, the panels’ IB strength, MOR and MOE increased significantly and the panels’ TS and WA decreased significantly. These data showed that aspen panels with surface layer from white cedar whole strands at a ratio of 25:50:25 and pressed at 240°C for 180 seconds had the best mechanical and physical properties. All panel samples were slightly infected by moulds on the faces. A fair amount of mould occurred on the sides of panels pressed at 200°C for 160 seconds and 180 seconds and those pressed at 240°C for 180 seconds. The panels pressed at 240°C for 160 seconds were the least infected by mould (with an infection rate of 0.3). Panels pressed at 200°C had a white-yellowish colour, whereas those pressed at 240°C were yellow-brownish and darker than those pressed at 200°C. Panels pressed at 200°C for 160 or 180 seconds and those pressed at 240°C for 160 seconds were highly decay resistant, especially to brown rot. The decay resistance of panels pressed at 240°C for 180 seconds was lower compared with the other panels.
Compared with aspen panels, panels with surface layer from steam-treated white cedar strands and aspen strands at a ratio of 7:3 based on oven-dry weight had higher TS, WA, MOR and MOE values and a similar IB value. Panels with surface layer from steam-treated white cedar strands and aspen strands at a ratio of 4:6 based on oven-dry weight had the highest IB value. A reduction in mould and decay resistance corresponded to a reduction in the proportion of white cedar strands in the face layers. The overall mould growth rate was 1.27 on panels with surface layer from steam-treated white cedar strands and aspen strands at a ratio of 4:6, 0.6 on panels with surface layer from steam-treated white cedar strands and aspen strands at a ratio of 7:3, and 0.4 on panels faced with 100% white cedar whole strands, respectively.
Panels made from 100% white cedar whole-wood strands or a mixture of whole-wood strands of white cedar and aspen (50:50) in the core layer were “blown” after pressing. Panels made from a mixture of white cedar and aspen strands at a ratio of 25:75 in the core layer and aspen strands in the face layers had superior IB, MOR and MOE values than other panels. However, their TS and WA values were also higher than those of white cedar-faced panels. Panels made from a mixture of white cedar and aspen strands at a ratio of 25:75 in the core layer and white cedar strands in the face layers had the worst physical and mechanical properties among all the panels made for this test. The tests results for mould showed that panels made with a mixture of white cedar and aspen strands at a ratio of 25:75 in the core layer and aspen strands in the face layers ware seriously attacked by moulds and had an overall mould growth rate of 4.2. No mould infection was found on panels made from 100% white cedar strands. Panels made from a strand mixture of white cedar (50%) and aspen (50%) in the core layer and white cedar strands in the face layers had little mould infection. The overall mould growth rate on this type of panel was 0.2.
Compared with the control aspen panels, aspen panels with surface layer from white cedar whole-wood strands at a ratio of 15:70:15 had similar IB and TS values, a lower WA value and higher MOR and MOE values. When the white cedar strand proportion in the face layer was increased from 15% to 25%, the panels’ IB strength and WA decreased, but their MOR and MOE values increased. Panels with surface layer from white cedar strands at a ratio of 15:70:15 had little infection from moulds on the face and bottom layers, but had an increased infection rate on all four sides. The average overall infection rate of this type of panel was 0.5. When the white cedar in the panels’ face layer was increased from 15% to 25%, the average infection rate on the panels’ faces was still 0.1, but the infection rate of the panels’ sides dropped from 1.2 to 1.0. The overall rate was 0.4. In terms of decay resistance, panels with surface layer from 25% white cedar strands performed better than those with surface layer from 15% white cedar.
Sixteen fresh and recycled particleboard furnishes were characterized for pH, acid buffer capacity, base buffer capacity and total buffer capacity. Mechanical and physical properties of particleboard prepared from heat-treated (kiln drying) particles were also correlated with the wood chemical properties. It was found that the wood chemical characteristics of both fresh and recycled materials were influenced by heat treatment time (4 minutes and 24 hours), temperature (105o and 150oC), and particle size (coarse face and fine core particles). In general, the recycled material resulted in lower pH values than fresh material at 105oC, which was probably attributed to the residual acids from cured urea-formaldehyde resin in the recycled particles. The pH values of both fresh and recycled materials increased as treatment time increased at 105oC. Increasing the treatment temperature from 105o to 150oC at 24-hour treatment time did not seem to affect the pH of recycled material but reduced the pH of fresh material. The decrease in pH of fresh material at 150oC/24 hours might be related to the release of organic acids from the wood particles via the initial decomposition (hydrolysis and/or pyrolysis) of wood extractives and components. No influence of treatment temperature on the pH of recycled material observed from 105o to 150oC at 24 hours could be resulted from the interaction between wood and cured resin after heat treatment. The acidity of wood due to the initial decomposition of wood extractives and chemical components might offset the alkalinity of wood caused by the generation of ammonium hydroxide via decomposition of cured UF resin. A higher temperature and longer heat treatment time generally resulted in higher acid, base, and total buffer capacities; the extent of the increase depended on face and core particles.
Particleboard was disintegrated using both BTCA (butanetetracarboxylic acid) treatment and cold water soaking (24 hours overnight), combined with hammer milling. BTCA treatment of particleboard resulted in decreased pH values in the particles due to the acid contained in the BTCA solution. Particles disintegrated with 1.0% BTCA solution yielded pH levels similar to the pH levels in particles treated with water soaking. In addition, BTCA treatment of particleboard yielded higher wood acid and base buffer capacities compared to water soaking.
A regression analysis indicated that some correlations existed between wood chemical characteristics and particleboard properties: internal bond (IB) strength strongly correlated with the pH value, but modulus of elasticity (MOE), thickness swelling (TS), and water absorption (WA) correlated with the base buffer capacity of core material. In addition, MOE and TS well correlated with the pH values of face materials, while modulus of rupture (MOR) and formaldehyde emission (FE) well correlated with the base buffer capacity of core material.
A total of 24 hybrid poplar clones grown in Windsor and St-Ours in southern Quebec, Canada, were characterized for chemical properties (pH, acid buffer capacity, and base buffer capacity). This test group of 10-year-old poplar clones (spring of 1993 to winter of 2002) was comprised of 12 clones grown in Windsor and 12 clones grown in St-Ours. At both locations, there were four hybrids: P. deltoides (D); P. deltoides x P. nigra (D x N); P. trichocarpa x P. deltoides (T x D); and P. maximowiczii x P. balsamifera (M x B). Thus, each hybrid included three clones. In addition, 3 replicates of two clones derived from D and D x N hybrids grown in Windsor were tested to examine the block (sub-location) influence of clone type on wood chemical characteristics.
Results showed that both hybrid and geographic location affected wood chemical characteristics, based on the average values of the same hybrid. In general, the fast-growing poplar clones (as determined by tree diameter) in St-Ours showed higher pH and acid buffer capacity, but lower base buffer capacity than those grown in Windsor. For clones within the same hybrid, observations showed that clone type had more influence on acid and base buffer capacities than on pH value, and the extent of the influence depended on each individual hybrid. In terms of variations in wood chemical properties within the same clone, replicate measurements of two clones (one from D hybrid and one from D x N hybrid) showed greater variations in base buffer capacity than in pH and acid buffer capacity. This study implies that differences in the wood chemical properties examined depend not only on wood genotype, but likely also on site quality, which correlates well to wood physical properties such as tree diameter, basic wood density and fiber length.
The objectives of this project were to develop and validate a finite element (FE) model of the hygroscopic warping of OSB panels and to suggest panel structures that ensure a higher level of stability during the storage, handling and use of panels.
A modification of the methodology developed at Université Laval for solid wood and already applied to MDF panels at Forintek Canada Corp. was used for the determination of diffusion coefficients in OSB. An existing finite element model developed jointly by Forintek Canada Corp. and Université Laval for the evaluation of MDF warping was adapted to the characteristic OSB structure. The finite element model was based on an unsteady-state moisture transfer equation, a mechanical equilibrium equation, and an elastic constitutive law. The experimental inputs were the mechanical properties E1, E2, E3, G12, G13 and G23 all as a function of moisture content, density and strand orientation; the expansion properties b1, b2 and b3 as a function of density and alignment; sorption isotherms and diffusion coefficient generated by producing a total of 50 laboratory OSB panels: 18 one-layer panels without density profile and strands oriented through the entire thickness (6 x 500 kg/m³, 6 x 625 kg/m³, 6 x 800 kg/m³), 24 three-layer panels with density profile (16 panels with density 625 kg/m³, aligned strands in surface, random strands in core, and 8 panels with density 625 kg/m³, different alignment in the two surface layers, random strands in core) and 8 panels with density 625 kg/m³, random strands. The panels had dimensions after trimming of 838 mm x 838 mm x 10.5 mm (33 in x 33 in x 7/16 in). To validate the model, warp was initiated and its dynamics was monitored by submitting 2 panels from each group to an 80% relative humidity.
The results showed that for all one-side sealed panels, the MC-increase in the zones close to the surface at the early exposure stages caused rapidly a convex deformation towards the exposed surface. When MC gradually homogenized across thickness, most of the panels returned close to their original flat shape. For panels with a flat density profile, the higher the average panel density, the higher the level of warp due to the effect of density on the expansion and swelling properties. Panels with oriented strands experienced higher strain differential and therefore developed stronger warp compared to panels with random strands. Panels with a one-layer structure experienced higher warp compared to panels with a three-layer structure. When the sealed surface layer was thicker than the exposed surface layer, or when the alignment in the sealed layer was higher than the alignment of the exposed layer, the panels continued to distort and their warp became negative, instead of stabilizing close to their original flat form.
The agreement between the experimental results and the finite element results confirmed the validity of the proposed model in the conditions and the OSB properties considered in this work. Simulations with the finite element method were performed corresponding to specific industrial applications and allowed the creation of a large database of results, which served for building the software package WarpExpert.
Cette étude vise à quantifier la précision des différentes technologies de scanneur de billes (2 axes et 3D) utilisées dans l’industrie et cherche à démontrer leur impact sur les performances des scieries canadiennes de bois résineux. L’analyse considère à la fois la configuration des équipements et les erreurs de débitage qui s’y rattachent.
La précision du scanneur optique 3D s’est avérée meilleure que celle du système de 2 axes à rideau de lumière. L’écart-type des erreurs de lecture du scanneur 3D est de l’ordre de 3 mm, comparativement à 6 mm pour le 2 axes. De plus, ce dernier a tendance à surévaluer le diamètre des billes de 1 mm, soit l’équivalent de la moitié de sa résolution.
Un échantillon de billes de 8’ à 16’ de longueur (73 dm³/bille) représentatif de l’approvisionnement typique des scieries de bois résineux, a été simulé avec Optitek pour quantifier les rendements volumique (pmp/m³) et économique ($/m³) des divers scénarios élaborés. Des lignes de sciage équipées d’un système d’alimentation de type DLI (entrée double longueur), SLI (entrée simple longueur), ainsi qu’une 4 faces ont été comparées en fonction du type de scanneur, tout en incorporant différents niveaux d’erreurs de débitage. Les erreurs de rotation ont été considérées comme étant la principale source d’erreur. Des erreurs de rotation de 10°, 25° et 45° d’écart-type ont été simulées pour s’apparenter à la réalité des scieries.
Le système DLI équipé de 2 scanneurs 3D permet d’obtenir de meilleurs rendements, cependant les erreurs de débitage et de lecture des scanneurs réduisent sa performance économique d’au moins 5 %. Le rendement sciage théorique qui se chiffre à près de 300 pmp/m³ selon le calcul des solutions optimales incluant l’optimisation de la rotation (1er scanneur), s’abaisse aux alentours de 280 pmp/m³ lorsque les erreurs sont ajoutées. La performance d’un système SLI utilisant un scanneur 3D, sans optimisation de la rotation est inférieure de 1 % à celle d’un système DLI. Le système 4 faces affiche quant à lui une performance nettement inférieure d’environ 10 %, mais est toutefois désavantagé par le volume et la longueur des billes. On retrouve habituellement des systèmes 4 faces sur des lignes de sciage qui transforment essentiellement de plus petites billes.
Les gains économiques réels attribuables à utilisation de la technologie des scanneurs 3D s’élèvent en moyenne à 0,5 % comparativement au système 2 axes.