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.