In this project, a comprehensive experiment studied the impact of wax type, wax content, wax heating temperature and wax molecular weight on OSB panel performance. It shows that to allow tall oil, hydrogenated soybean wax, linseed oil, and low density polyethylene (LDPE) to be used for OSB, further work is needed. We need to add wax in the OSB process; otherwise panel dimensional stability will be ruined. There is an optimal wax content of around 1% in OSB production. The wax content in OSB panel did not need to be higher than 1%. With the waxes tested, wax heating temperature should be higher than 90°C. At a fixed wax heating temperature, optimal wax molecular weight is 520 Daltons for OSB application. Applying high molecular weight wax (600 Daltons) on panel surface may help to improve panel bending strength.
The experiment shows that partial substitution of slack wax with LDPE at the OSB panel surface layer may be feasible.
Experimental results also show that using contact angle and surface tension tests may help us to screen waxes for OSB panel application.
Based on the experimental data, one should handle different waxes in different ways. By engineering wax application parameters one can develop a cost effective way to produce composite panels to meet dimensional stability requirement. Further testing on the feasibility of using contact angle and surface tension to differentiate wax should be conducted. Emulsifying low density polyethylene should be further investigated. Further research is also needed to verify how wax operational parameters affect panel strength.
A pilot plant apparatus was built to electrostatically spray phenolic resin on strands. To evaluate the resin distribution on these strands, an image analysis method was developed. The experimental conditions in this study made it difficult to compare electrostatic treatments to control (non- electrostatic) treatments. Although not statistically significant, there were notable differences between these treatments which indicate that electrostatic resin application may improve panel properties and is therefore worth further investigation. First of all, the electrostatic treatment produced panels with a 10% higher internal bond than the control. Secondly, the resin distribution results show that the electrostatic spray, on average, covered a 30% greater area of the strands than the control even though both treatments applied resin at the 2% resin solids level. Further experiments using alternative test procedures are planned to compare electrostatic treatments to control treatments that simulate industrial conditions.
A prototype scanning system successfully demonstrated the capability of real-time, log pocket monitoring that can be used to alert operators of improper pocket filling practice.
Several previous FPInnovations studies have shown that the log pocket filling is often poorly controlled resulting in poor log alignment and/or incomplete filling that adversely affects both flake quality and strander productivity. Until now there have been no systems available to automatically measure the alignment of logs being fed into the strander or measurement of the actual filling of the strander pockets. An automated monitoring system is needed to signal operators when the log pocket is improperly loaded. This feedback can allow operators to maintain proper log filling procedure to maximize flaking quality.
In March 2013 a machine vision scanning system comprised of a camera, 2 line lasers and computer with image analysis software, was tested for two days at the Peace Valley OSB mill (PVOSB) in Fort Saint John, BC. The scanner’s camera and lasers were mounted 13 feet above the center of the log pocket base. Images of pocket filling were acquired and analyzed for pass/fail conditions. Two image groups were selected for analysis, one of full pocket, aligned logs (pass) and the other containing misaligned logs and/or insufficient pocket fill (fail). For all pocket scans, scanner measurements were compared to manual visual classification.
Approximately 50 different pockets were scanned with results and images saved for analysis. For fill height and vertical log alignment measurement, the scanner correctly identified >95% of all the pockets examined. However, log alignment measurement in the horizontal x-y plane did not function as intended due to poor image contrast that could not be resolved during the mill trial. This technique has been shown to work well in previous pilot plant tests (Groves, 2012) which confirms that the underlying measurement fundamentals are sound. It is recommended that only minor lighting adjustments are required for the scanning system to work well in a mill setting.
Implementing this technology in OSB mills should help to reduce the occurrence of poor pocket filling that can adversely affect strand quality. It should be noted that even small improvements to strand quality and productivity can yield significant cost benefits. It is estimated that reducing fines by a modest 1% and improving productivity by 1% can return in excess of $1 million/year based on an average size Canadian OSB mill.
There are six species of poplar native to Canada's forests. One of the most abundant and widely used of the species is the aspen poplar (populus Tremuloides). Aspen has become the most desirable species for the production of oriented strandboard (OSB). Certain sections of Alberta and British Columbia have considerable stands of aspen. The aspen stands also contain varying amounts of balsam poplar (populus balsamifera) and black cottonwood (populus trichocarpa) and various hybrids of the three species. Forintek Canada Corp's Technical Advisory Committee (TAC) was asked by the B.C.Ministry of Forests to establish whether cottonwood could be a suitable furnish for the production of OSB, since it represented a sizeable potential resource in British Columbia. The poplar species are loosely identified by several names and to confirm the actual species we were referred to Mr.Bob Brash, District Manager, Dawson Creek Forest District. Mr.Brash confirmed that the species in question was in fact balsam poplar (populus balsamifera). Balsam poplar is also known as black poplar and balm poplar. An extensive literature search was conducted on the use of balsam poplar/cottonwood in the production of OSB. The literature review and a summary are reported here.
The objectives of this study were to characterize OSB panel permeability in comparison with plywood and low density fiberboard; to determine the effect of panel characteristics on the speed of moisture movement through the thickness of the OSB panels; to create a finite element model of the permeability of OSB; to suggest improvements of the OSB panel structure in function of permeability.
The introduction of current report presents extracts of the theory of moisture transfer in wood materials and introduces the concept of water potential and the instantaneous profile method as adapted to OSB to be used for the determination of the diffusion coefficient (D).
The experimental part is divided into three stages. In the first stage the permeance of the OSB panels, plywood and low density fiberboard is compared according to the dry cup method. The experiments showed that the low-density fiberboard panels’ permeance is more than twice as high as compared with the permeance of the OSB panel; the Western Red Cedar has an approximately equal permeance with the OSB panel, which is in turn higher as compared with the permeance of the Aspen plywood. The Aspen plywood produced with parallel plies shows approximately 30 % higher permeance as compared to the regular plywood.
In the second stage, the effects of density, strand geometry and orientation level, panel density and moisture content on the permeance and on the diffusion coefficient are determined. The experiment is organized based on an experimental design. For the permeability (permeance and diffusion coefficient), the lower the strand thickness, the lower the permeability; the lower the level of strand orientation, the higher the permeability; the larger the strand width and length (surface area), the lower the permeability, the higher the permeability.
During the third stage, the dynamics of moisture movement in the panel is modeled with a finite element model based on an unsteady-state moisture transfer equation and the results from simulations are compared to experimental results in order to validate the model. Ten cases of adsorption and two cases of desorption are considered. Seven of the cases are duplicated with experimental results to serve for validation of the model. The closeness of the experimental and simulation results allow concluding the validity of the finite element model, which can be used to optimize the OSB panel structure by selecting practical layer characteristics leading to desired moisture permeability.
A prediction model for long term creep and creep-rupture behavior of OSB was developed by the late Senior Research Scientist, Dr. L. Palka at Forintek Canada Corporation, Vancouver, BC, Canada. By using one minute destructive ramp load test results, the "Palka Model" allows the prediction of time-to-failure and time-dependent creep deformations under given sustained loads. Verification testing of the model was performed on time-to-failure at the 75% sustained load level and on creep deformation behavior at the 25% and 50% levels. The verification tests gave encouraging results which showed a reasonable agreement between the test results and the Palka Model predictions. The Palka Model is recommended for use as a first approximation prediction tool for long term creep behavior of OSB. The model prediction technique appears ideal to assist in product development decisions and also in evaluation of load duration and creep factors in timber design codes.
The project objective is to identify the wood-rotting fungi causing decay in Canadian buildings, and to provide data for a numerical model which will provide an indication of the time required for initiation of strength loss in wood-based panels when exposed to a range of moisture contents and temperatures.
The MEWS consortium led by the National Research Council's Institute for Research in Construction is developing a computer model to predict the moisture and temperature conditions within a construction assembly in service. By including a damage function calculation for the various building components, the model can predict the consequences of these conditions in terms of strength loss.
Forintek's role is to develop an experimental protocol that will be universally acceptable in the field of wood science, and generate a data set from which one could derive a damage equation for wood decay as a function of time, temperature and moisture conditions. Discussions have established that strength loss in sheathing is the first priority.
A series of proposed test methods were examined. In consultation with members of the consortium task force, a method was selected which was felt would provide suitable strength loss data within the constraints of the funding available. Sheathing samples will be subjected to various combinations of temperature and humidity and repeatedly inoculating with a wood-rotting fungus to represent natural infection. The samples will be monitored using non-destructive testing and then destructively tested when the first test suggests a strength change. The result is a two-stage test at a range of temperatures and humidity levels, giving a measurement of time to strength loss.
An initial pilot study is concerned with development, refining and verification of the method. "Method B" of ASTM 3043 is being evaluated to determine if it will be appropriate. The test is monitoring the bending stiffness and strength of oriented strand board samples, using a 2-point flexure test. The pilot study is underway, with samples exposed to 20°C and a relative humidity of approximately 96%. Problems involving moisture control in the environmental chambers have been resolved, as have questions around the sample size, the number of test specimens required in the pilot study, the time required for conditioning prior to inoculation and the actual bending and strength test procedures. The inoculation protocol is being evaluated. At this time none of the test pieces have shown significant losses in bending stiffness. A number of test conditions remain to be defined, however, and these will be established at the conclusion of the pilot study.