Effect of nano-zinc oxid and adhesive type on Physical and Mechanical properties of Laminated Strand Lumber

One of the most widely used wood products applied in wooden buildings as load bearing posts or beams is laminated strand lumber(LSL). Nano-zinc oxide is a chemical that has the potential to be used in the protection of LSL. The use of nano-zincoxide as an additive in LSL may affect its mechanical and physical properties. In this study, the effect of adhesive type(PF and pMDI) and nano-zinc oxide amount(0, 0.5, 1, 1.5 % based on strands weigth) on the physical and mechanical properties of LSL was investigated. For this purpose, lSLs were made from Iranian beech using either a phenol formaldehyde(PF) or a polymeric methylene diphenyl diisocyanat(pMDI) adhesive and four loading levels of nano-zinc oxide. The mechanical and physical properties of the LSLs were then measured according to ASTM-D5456 and modified ASTM-D1037 respectively. The results showed that the interaction between nano-zinc oxide treatment and the adhesive type was significant for MOE and IB while the interaction was not significant for MOR at the alpha level of 5%. Not only did nano-zinc oxide not reduce significantly the mechanical properties of the composites but it also increased partially the studied properties in most cases. Nano-zinc oxide with the lowest loading decreased the thickness swelling and improved the dimensional stability. The higher loadings did not result in any further improvement. In general, it can be concluded that the different levels of nano-zinc oxide can be used in treating laminated strand lumber composites made with PF and pMDI adhesives without having any negative effect on mechanical properties of the composites.