Effects of Heat-Treatment on Screw and Nail Withdrawal Resistance of Nanosilver- Impregnated and Untreated Solid Woods

The present study is aimed at the effect of heat treatment on nanosilver-impregnated Populus nigra, Fagus orientalis, and Abies alba to find out nail and screw withdrawal resistance. Treatments included control, heat-treated, and nano-silver-impregnated heattreated specimens. Empty-cell process was used for impregnation with a 200 ppm aqueous dispersion of silver nanoparticles with the size range from 10 to 80 nm under 3 bars in a pressure vessel for 20 minutes. For heat treatment, both seasoned nano-silver-impregnated and heat-treatment specimens were kept for 24 hours at 135°C. The nails and screws were installed according to ASTM D 1761-88 specifications. Results showed that the maximum nail and screw withdrawal resistance was closely related to the density. The difference between longitudinal and radial withdrawal resistance in both nail and screw was significantly influenced by the species as a softwood or hardwood. Regardless of the species, heat treatment was more influenced by the density rather than species. However, nano-silverimpregnation of the specimens aggravated the effects of heat treatment in hardwoods (more increasing in poplar and more decreasing in beech), but it decreased the withdrawal resistance in fir.