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Publication: Forest Products Journal
Authors: Anderson Matthew E|Leichti Robert J|Morrell Jeffrey J
Reference ID: 50(11/12):85-93
Publish Year: 2000
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Title: The effects of supercritical CO2 on the bending properties of four refractory wood species
Description:
The effects of three supercritical fluid (SCF) treatment parameters on the bending properties and development of treatment defects were studied in Douglas- fir, yellow-poplar, western red cedar, and Engelmann spruce Two rates of pressurization (0.34 and 3.44 MPa/min.), two treatment pressures (10.34 and 20.69 MPa), and two venting rates (0.34 and 3.44 MPa/min.) were examined on small, clear specimens of each species, using one treatment temperature (60°C) and one treatment time (30 min.). Supercritical treatment of yellow-poplar produced no significant reductions of bending properties. Bending properties of Douglas-fir appeared to increase after SCF treatment, but these increases were due to differences in mean specific gravity between treatments. Bending properties in western red cedar and Engelmann spruce were reduced significantly after SCF treatment. Western redcedar specimens showed up to 23.1 percent reduction of modulus of rupture (MOR), 13.7 percent reduction in modulus of elasticity (MOE), and 31.0 percent reduction in work-to-maximum-load (WML) after SCF treatment. Engelmann spruce properties declined 10.8 to 21.6 percent in MOR, 16.0 to 21.4 percent in MOE, and 7.2 to 29.0 percent in WML after SCF treatment. Rapid rates of venting produced the most significant reduction in bending properties for western redcedar, while Englemann spruce was affected by both slow and rapid rates of pressurization and venting. The results indicate that SCF treatments, while effective for treating refractory wood species, must be used with some caution to avoid negative effects of bending properties.

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