SUPERCRITICAL FLUID (SCF) TREATMENT: ITS EFFECT ON BENDING STRENGTH AND STIFFNESS OF PONDEROSA PINE SAPWOOD

Adverse effects on mechanical properties from using a supercritical fluid (SCF) to increase preservative penetration of refractory woods were evaluated by treating small ponderosa pine sapwood specimens with supercritical carbon dioxide at 64 combinations of temperatures (35 to 80 C), pressure (1,000 to 4,000 psig), and time (0.5 to 2 h). Thereafter, the treated and identical untreated specimens were equilibrated to constant moisture content and tested for bending strength and stiffness. The SCZFtreated and untreated specimens were not significantly different in modulus of rupture (MOR) or modulus of elasticity (MOE). Temperature, pressure, and time had no significant effect on MOR, there were interacting effects of these variables on MOE, although these interactions had no meaningful patterns.