Urea formaldehyde resins (UF) are commonly used in the production of particle boards due to their relatively low price and possibilities to maintain in the wide range conditions of condensation to get boards of good quality. However said boards are not resistant for the influence of changeable environment conditions, and especially high moisture. Therefore are carried out attempts to improve properties of boards on the way of modification of UF resin. In presented materials are results of investigations of possibilities to modify UF resin with the use of mixture of alkylo-phenols, resorcine, and its alkylo derivatives. The said compounds were introduced to UF resin in form low-molecular resins of the rezol type in quantity from 5 up 15%.
The further increase of said quantities decreased solubility in water of obtained resins.
With the use in such way modified resins, were produced particle boards for further investigations. Tested were following properties of those boards: static bending strength, tension perpendicular to the planes, absorbability and swelling in water after 24 hours.
Besides that, bending strength of particle boards has been determined directly after 24 hours of soaking in water, and after their conditioning through 7 days in normal climate.
To determine the effect of the modifying substances upon the resistance of resins against water, were carried out tests of glue line strength upon shear accordingly to the DIN 68602 Standard.
Results of presented investigations have shown that the modification of resin with the used modifying substances have had caused essential improvement of physical and mechanical properties of glue line, and water resistance.
It was found that the greater was the percentage of introduced modifiers, the greater was water resistance of glue line.
Key words: urea resins modification, particle boards.
Correspondence: Janina Lecka, Akademia Rolnicza, Wydzial Technologii Drewna, Katedra Chemii, Wojska Polskiego 75, Poznan 60-637, Poland