THE MECHANICAL-PROPERTIES OF BOARDS TREATED WITH VAPOR BORON

Several mechanical properties of medium density fiberboard (MDF), part icleboard, and oriented strandboard (OSB) were investigated after the boards were treated to two retention levels of boric acid applied with a vapor-phase system. The test retentions represented levels appropri ate for protection against biological attack and fire. The treatment h ad no significant effect on modulus of rupture (MOR), internal bond st rength (IB), or bond durability in any board type when compared with u ntreated boards. Stiffness was increased by treatment. At fire-retarda nt loadings, MOR, IB, and bond durability properties were not signific antly affected in any board, although in OSB and particleboard the IB strength and bond durability showed a small but statistically signific ant increase. Treatment reduced impact resistance by statistically sig nificant amounts in all board types with the greatest reduction at the higher retention. In MDF, the treatment had a much greater effect on impact resistance when long treatment times were used instead of short times to achieve flame-retardant retentions. Conclusions are that vap or boron treatment resulted in either positive or neutral effects on m ost of the mechanical properties of wood-based boards, except for a ge neral reduction in impact resistance at the higher boric acid retentio n. The possible mechanisms for these effects are discussed.