Effects of drying methods of lamellas used in multilayer parquet manufacturing on surface roughness and bonding strength

Abstract

The objective of this study is to determine surface roughness and bonding (tensile shear) strength of lamellas (top layer of multilayer parquet) which were cut away from green lumber and dried by different types of drying methods. Also, finding out the most convenient manufacturing method as surface roughness, bonding strength properties was aimed by comparing results with surface roughness and bonding strength of lamellas, which were cut away from dry lumber as seen in practice. Flat sawn green lamellas with 5 and 2 mm thicknesses, which were cut away from Iroko lumber by means of thin cutting frame saw, were dried with 3 different drying methods such as drying in lumber drying kiln, jet ventilated automatic veneer roller dryer and veneer press dryer. Effect of drying temperature on surface roughness and bonding strength was also determined by applying 3 different drying temperatures as 60, 100 and 140°C in jet ventilated automatic veneer roller dryer. In addition, lamellas with the same thicknesses were manufactured from dry lumber by means of the same thin cutting frame saw mentioned above. As the result of analysis of variance showed, differences between test groups were determined as surface roughness. Consequently, effect of drying method on surface roughness was found. Also, surface roughness values were determined to be increasing as drying temperature increases when drying in veneer roller dryer. Surface roughness values of lamellas dried in lumber drying kiln were found to be higher than those cut away from the dry lumber as expected. Differences exist between test groups as bonding strength was determined by means of analysis of variance. The biggest bonding strength was found in lamella group which were cut away from dry lumber and mentioned as comparison group. It was found that no relation existed between bonding strength and temperature increase drying in veneer roller dryer. Also, it was determined that no significant relation was found between surface roughness and bonding strength as the result of correlation analysis. Conclusively, it was found that lamella manufacturing method, cutting away from dry lumber, was the most convenient method for obtaining the best bonding strength in multilayer parquet production.

Key words: Drying method, multilayer parquet, surface roughness, bonding strength.