Effects of Nano-Wollastonite on Screw Withdrawal Capacity of Oriented Strand Lumber

The effect of changes of urea-formaldehyde resin content and nanowollastonite content on the withdrawal capacities of sheet metal screws and medium density fiberboard screws from the edge, face, and end surfaces of oriented strand lumber were investigated. The panels were produced with two urea-formaldehyde resin contents (8% and 10%), and two nano-wollastonite contents (10% and 20%). Specimens were prepared and tested according to ASTM standard D 1761-88. Sheet metal screws had a higher withdrawal capacity than medium density fiberboard screws. Withdrawal capacity in the face and edge directions were significantly higher than in the end direction. Changes in urea-formaldehyde resin content had no effect on screw withdrawal capacity in any of the three directions, implying that compaction in the composite panels had higher impact on screw withdrawal strength in comparison to the increase in resincontent from 8% to 10%. However, addition of NW resulted in a decrease in withdrawal capacity values at both resin levels in all directions.