Thermal Reactions and Industrial Uses of Bark
Abstract
A kinetic study indicated that the phenolic substances in Douglas-fir and red alder bark can be polymerized by high-temperature heating. Organic extractives that may be leached out by the action of water are condensed to water insolubles. Heat-treated bark is shown to be an appropriate material for the cleaning up of oil spills on water without contributing to high BOD and possible toxieity to fish. The oil absorption of bark, depending on its particle size, is two to seven times its weight.
A vacuum system was developed for hot pressing bark boards, which technnique avoids blister formation caused by the evolution of gases from condensation and dehydration reactions in thick boards. Bark boards made under an appropriate time-temperature schedule have both internal bond strength and bending modulus of rupture similar to bark boards made with 4.5% phenolic resin and subsequently pressed at a moderate time-temperature schedule, precluding polymerization of the bark extractives. Hot stacking increased the internal bond strength of boards.
Dimensional stability is the most significant property of these bark boards. Properly made bark boards have a much smaller thickness swelling and linear expansion than bark boards made with 4.5% phenolic resin after soaking in water for 72 hr.
References
Cnow, S., and K. J. Pickles. 1971. Thermal softening and degradation of wood and bark. Wood and Fiber 3(3): 166-178.nJohnson, E. S., ed. 1956. Wood particle board handbook. N.C. State Coll., Sch. Eng., Raleigh. 302 p.nLevin, E. D., N. D. Barabash, and A. A. Sinorov. 1971. Electron paramagnetic resonance study of the mechanism of semicoke formation. Khim. Drevesiny (Riga) 7:73-77. ABIPC 42:abstr. 2832 (original not seen).n
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