Fillers and catalysts effect on the physicochemical properties of urea-formaldehyde resins

Abstract

In the present research the effect of different f illers on the composition of urea-formaldehyde resins (UFR) was studied. The usage of fillers in the composition of urea-formaldehyde resins makes it possible to reduce the resin consumption by 10–20%. Aluminum silicate type of fillers cannot be used conveniently in plywood technology because resin partic les initially agglomerate; then their swelling and hydration lead to the significant visc osity growth of the adhesive especially at a filler consumption rate more than 8% by weight of the resin. Sulfate and carbonate types of fillers can be used more preferable because in this case there are no agglomeration of resin particles and no quick solidification of adhesive composition. Viscosity of the adhesive composition decreases vice-versa with th e adding of silicate type filler into the urea-formaldehyde resin. Combining of different fillers types allows controlling the rheological properties of the adhesive composition. Compounds containing ions of three-valence meta ls are effective catalysts of urea-formaldehyde resins. The usage of such catalysts in plywood technology leads to condensation time reduction of urea-formaldehyde resins at 1.8–2.3 times which opens up additional possibilities for application of low-emission resins with a low formaldehyde content. Gelatination time of adhesive compositions prepared using the new effective catalysts for the condensation process of urea-formaldehyde resins remains for 2–4 hours.