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.
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.
Under current ASTM D-3501 procedures, the only practical method of obtaining compressive properties of wood based panels is to glue two or more plies of the specimen together to provide a compact column cpapble of resisting buckling. It is thought, however, that this method may not provide representative compression strength and stiffness data due to load sharing.
The optimum moisture content of the raw logs used in the manufacturing of oriented strand board (OSB) may be defined by a minimum requirement for fibre conversion and a maximum that will limit the cost of drying the flakes. This criterion could become the mainstay of an effective raw-log purchasing and inventory management program. However, OSB manufacturers have lacked the technology for monitoring whole-log moisture content. FERIC tested several technologies and identified time domain reflectometry (TDR) as an effective means of sampling the moisture content in a large number of logs.
The bending properties of aspen waferboard can be improved by increasing the resin content and/or board density. These options, however have limited effect and are very costly. On the other hand, panels produced with longer, oriented stands have demonstrated significant improvements in bending strength and stiffness. The panel industry has recently used wafers or strands up to approximately 102mm (4in), however, the utilization of much longer material is practical. In addition to more efficient use of the wood resource, structural panels with improved properties can penetrate more demanding applications, particularly as future engineering materials, and overcome some problems experienced with traditional wood composites such as creep. The overall objective of the study was to demonstrate that by using long strands, coupled with appropriate strand alignment, strand thickness, and face-to-core layer ratio, a structural panel can be produced with superior strength and stiffness in the aligned direction while maintaining adequate properties in the cross direction. The specific objective for this year's work was to establish the improved performance using panels produced in structural sizes and under conditions that parallel those of the industry more closely. Manufacturers of oriented strandboard and waferboard can use the information to produce high performance OSB panel products with minimal effects on production parameters and costs.