INFLUENCE OF THE
ACIDITY AND SIZE OF BEECH PARTICLES ON THE HARDENING OF THE UREA–FORMALDEHYDE
ADHESIVE
Sergej Medved
and Jože Resnik
Abstract
Presented work deals with the
influence of acidity of beech particles of different size on the hardening of
the urea–formaldehyde adhesive. The pH value and the milliequivalents
of soluble and total acids were determined upon the method published by
Subramanian et. al. in 1983.
The method is based on the reaction between acids in wood and the aqueous
solution of sodium acetate, where the equivalent quantity of acetic acid is
generated. The quantity of the generated acetic acid was determined by the
titration and presents the total acids in wood. The acetate solution helps to
extract the acids soluble and insoluble in water. We determined that the
particle size does not influence the pH value of particles and the quantity of
the extracted soluble acids, but does have the influence on the quantity of the
extracted insoluble acids. We furthermore determined that the particle size
influences the gel time of the urea–formaldehyde (UF) adhesive. The shortest
gel time was determined at the finer particles.
Key words: beech particles, soluble wood acids, insoluble wood acids, adhesive gel time