بررسي امكان توليد چسب تانن - فرم آلدييد از پوست درختان چهارگونه پهن برگ

Investigation on the Production of Tannin Formaldehyde Adhesive from the Bark of Four Hardwood Species

In this study, the possibility of making tannin-formaldehyde adhesive from the bark of oak, beech, alder and hornbeam was investigated. The bark mixture was extracted using polar and non-polar solvents. Samples of tannin-formaldehyde and phenol formaldehyde adhesives were prepared at pH 9.5 with molar ratio 1 :2, and the viscosity of the samples were measured following D2556 ASTM standard method. By measuring the shear strength of plywoods made with new formulations, the strength of the products was evaluated, following Iranian Standard No.3492. The experimental results show that quantitatively, 1 % NaOH solution is the most efficient extracting solvent. However, the purity of tannins and phenolic compounds is highest when extracting solvent is ethanol. Also, the shear strength of adhesives soluble in alkali is better than adhesives soluble in other solvents. The shear strength of the samples could be doubled when adding 25% phenol to tannins compared to urea-formaldehyde adhesive.