A series of dispersion-resin plywood formulations were prepared in the laboratory and their bond performance assessed on incised spruce veneer at 10% m.c. Excellent bond quality results were achieved in these laboratory experiments as indicated by high average % wood failure values of over 90%. To further develop the plywood dispersion resin, a pilot plant trial at a gluing company was conducted and again excellent bond quality results were achieved. A large quantity of the plywood dispersion resin was prepared and a successful mill trial at Cantree Plywood was carried out. This trial demonstrated that more dimensionally stable panels can be prepared from high m.c. veneer. The waferboard dispersion technology developed in this study helped facilitate a mill trial using high moisture content face wafers.
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.
The new technologies, incising, moisture tolerant phenolic adhesives and steam pressing were evaluated for the manufacture of laminated veneer lumber (LVL). Both 8- and 13-ply incised spruce LVL panels were prepared using these new technologies. The results showed that both steam pressing and self-generated steam from wet face and back veneers accelerated temperature rise in the innermost glueline of 13-ply incised spruce LVL panels. This would help facilitate faster production rates for LVL manufacture. Bond quality and edge bending values were determined for the steam-pressed 8-ply and 13-ply incised spruce LVL panels. In all cases the average % wood failure was above 90% indicating excellent adhesion between the moisture tolerant adhesive and wood. The modulus of rupture and modulus of elasticity values measured for the steam-pressed incised spruce LVL samples compared very favourably with those for a commercial Norway spruce 15-ply LVL product.
The effects of different pressing variables were evaluated for the manufacture of hog fuel board made from western hemlock. In general, the hog fuel boards made at higher temperature and pressure exhibited better dimensional stability and durability properties. Pressing time was reduced with temperature ranging from 20 min at 260 C to 4 min at 315 C. It was demonstrated that good quality hog fuel boards could be produced using a high wood content of 65%. In all cases, the western hemlock hog fuel boards showed an average thickness swelling less than 10% after a 2-hour boil test. After the same treatment, OSB shows 50% thickness swelling and particleboard disintegrates. Preliminary results for bark / hog fuel boards made from three eastern species, white spruce, balsam fir and jack pine showed the boards exhibited excellent dimensional stability and durability properties. In the interests of furthering the preliminary market and economic feasibility investigations of bark board and in co-operation with Dr. A. Kozak and his 4th year marketing class (Dept. of Wood Science, UBC), exploratory analyses were done on four potential end uses. These were flooring, floor underlayment, roof shingles and furniture / cabinets.
The work presented in this report addresses the manufacture of bark board products on Forintek’s 15 x 15 –inch hot press. The properties of these bark board products including fire and decay resistance, fastener and weathering properties, VOC’s and formaldehyde emissions, dimensional stability and strength properties are discussed in the report. Some discussion on the mechanism of bark board chemical reactions is discussed. Results on catalysts to reduce pressing temperature and time, the potential to utilize recycled material as well as a preliminary market evaluation for bark board are also discussed.
Specifically using an optimized pressing schedule on the 15 x 15 – inch hot press at 260°C, spruce bark boards exhibited excellent internal bond strength and dimensional stability.
Results showed that by using 3% by weight of a catalyst, the pressing temperature can be reduced by 40°C in the manufacture of bark board.
Results showed it is feasible to use recycled plywood and OSB trim furnish up to 20% by weight in the manufacture of spruce bark board.
A preliminary marketing study indicated that the positive attributes of bark board showed strong potential of marketing a bark board product not only in North America but also in Japan.
Bark boards made from eastern and western species as well as catalyzed Douglas fir bark all showed substantially lower VOCs emissions compared to commercial unfinished MDF and particleboard panels. These bark boards also showed negligible formaldehyde emissions and were about one hundred times less than the 0.3 ppm emission limit set by the American HUD and voluntarily adopted by the North American Composite Panel Association. The VOCs emissions were driven off the bark boards during the manufacturing process. The higher levels of VOCs emissions during the pressing step would have to be considered when constructing a plant.
By overlaying spruce bark board with thin 1.5 mm birch veneers, the nail-head pull-through load increases by a factor of over four and is comparable to plywood and oriented strandboard.
Based on cone calorimeter test data, one-step birch veneer overlaid spruce bark board would exhibit a flame-spread rating in the range 60 to 70. This compares to a flame spread rating range of 140 to 220 for OSB, 90 to 120 for Canadian softwood plywood and a flame spread rating below 25 for fire-retardant wood. The cone calorimeter test data also showed the time to ignition for one-step birch veneer overlaid bark board is much better than most wood products.
Preliminary results showed that painted western spruce bark board samples showed good weathering properties.
Both Douglas fir and spruce bark boards showed good resistance to brown rot fungi.
The durable, dimensionally stable bark board products are unique compared to all other wood composite products in that they are manufactured without the need for expensive synthetic adhesive.
Six impregnating phenol formaldehyde (PF) resins having low to moderate molecular weight were synthesized and evaluated for their wood veneer penetration and curing properties. Based on the results from the penetration and curing properties studies, a PF resin designated as B-2 was used to impregnate subalpine fir, white spruce and lodgepole pine veneer. LVL panels, 12 x 12 inch, were prepared with these veneers. Both modulus of rupture (MOR) and modulus of elasticity (MOE) were increased by 10 to 15% for the resin-impregnated LVL made from each of the SPF species. Edgewise bending results for specimens cut from 2 x 4 foot white spruce LVL panels showed an increase of 15% both for MOR and MOE for the resin impregnated specimens. As well, the dimensional properties (% edge swelling and % water uptake) of the SPF LVL panels were improved by 50% using the patented Forintek resin impregnation method.
A series of plywood and laminated veneer lumber (LVL) panels were prepared using incised veneers in the second phase of this two year project. The primary purpose of the work was to evaluate the effects of steam injection on the pressing times. A secondary objective was to expand the study of warpage in three-ply and four-ply plywood which was begun in phase one. Thirteen-ply 40 mm (1 5/8 inch) thick panels were evaluated for press times and thin 9.5 mm (3/8 inch) and 12.5 mm (1/2 inch) panels were evaluated for cupping and bowing. Press temperatures of 150 degrees C, 175 degrees C and 204 degrees C were used with a commercial adhesive mix for the LVL study while normal plywood pressing conditions were used for the plywood. For the plywood warpage study, the effect of lathe check orientation and species mix were evaluated. The lathe check orientation had little effect while the surface veneer species had a pronounced effect on the warpage in the plywood. Steam used for injection was heated to 260 degrees C at 450 KPa (65 psi) with a super-heater. All panels were made with incised 3.2 mm (1/8 inch) SPF veneers. The project demonstrated that steam injection can shorten press times by fifty percent if incised veneers are used.