Effects of the chemical treatment conditions of the narrow-leaved ash ( fraxinus angustifolia vahl. Ssp pannonica soo & simon) on the lap shear strength

Abstract

The effect of chemical treatment on wood tissue leads to changes in the chemical composition of wood, thereby changing its wetability and its chemical reactivity with adhesive. In this study, wood samples of narrow-leaved ash (Fraxinus angustifolia Vahl. ssp. Pannonica Soo & Simon) were treated with water and with the aqueous solutions of acetic acid and sodium carbonate at the temperatures of 100 and 120 degrees C, and for a period of 60 min. The addition of acetic acid and sodium carbonate was 0.03, 0.06 and 0.09 g.g(-1) dry matter of wood. The effects of the applied treatments on the lap shear strength were evaluated by the standard test method using urea-formaldehyde adhesive. The entire sample series treated with the sodium carbonate have shown the significant increase of the shear strength when compared to the control sample series (17.5 to 49.6 %). In addition, the increase of the shear strength corresponded to the increase in the concentration of the sodium carbonate solution. On the other side, the acetic acid and the water treatments have not caused any significant changes to the shear strength of the samples. The increase in the concentration of the acetic acid solution has showed a tendency to decrease the shear strength, but this effect could not be confirmed statistically. Finally, the results of the shear strength for all the treated sample series have not been significantly affected by the applied temperature.