Evaluation of surface roughness of laminated veneer lumber (LVL) made from beech veneers treated with various fire retardants and dried at different temperatures

Abstract

in this study the surface roughness of laminated veneer lumber (LVL) treated with various fire-retardants and dried at different temperatures was investigated. Commercially manufactured veneer of beech wood (Fagus orientalis L.) was treated with borax-boric acid, monoammonium phosphate and diammonium phosphate using a full-cell pressure process. Concentration of the chemical solutions was adjusted to provide average retention of 56 kg/m(3). The veneers were than dried at different temperatures (120, 140, 160, and 180 degrees C), and experimental LVL panels were made from these veneer sheets. A stylus method was employed to measure the surface roughness and evaluate the surface characteristics of the samples. According to the results of this study, surface roughness of the LVLs made from untreated veneers was not influenced by different drying temperatures. When the drying temperature was above 140 degrees C, surface roughness of LVLs made from fire-retardant treated veneers was significantly increased as compared to untreated control specimens. Although surface roughness values of the specimens made from treated veneers dried at less than 140 degrees C were also higher than that of untreated specimens, these increases were not statistically significant. No significant difference relative to surface roughness was found among the fire-retardant chemicals used in this study. When each treatment group was individually evaluated, low veneer drying temperatures (120 to 140 degrees C) did not affect surface roughness of the LVLs, while a significant increase was found at high temperatures (160 to 180 degrees C).