Effect of Urea-Formaldehyde Resin Adhesive Viscosity on Plywood Adhesion

Abstract

This work was conducted to investigate on the effect of urea-formaldehyde (UF) resin viscosity on plywood adhesion. The viscosity of UF resin was controlled either by adjusting the condensation reaction during its synthesis to obtain different target viscosities (100, 200 and 300 mPa.s) at two levels of formaldehyde/urea (F/U) mole ratios (1.0 and 1.2) or by adding different amounts (10, 20 and 30%) of wheat flour into the resins for the manufacture of plywood. When the viscosity of UF resin increased by the condensation reaction, the adhesion strength of plywood bonded with UF resin of 1.2 F/U mole ratio consistently increased, while those bonded with the 1.0 F/U mole ratio resin slightly decreased, suggesting a difference in the adhesion in plywood. However, the adhesion strength of plywood decreased as the viscosity increased by adding wheat flour, regardless of F/U mole ratio. The manipulation of UF resin viscosity by adjusting the condensation reaction was much more efficient than by adding wheat flour in improving the adhesion performance of plywood. These results indicated that a way of controlling the viscosity of UF resin adhesives has a great influence to their adhesion in plywood.

The reduction of adhesive application in plywood manufacturing by using nanocellulose‐reinforced urea‐formaldehyde resin

“…As reported by Réh et al 35 water reacts with UF resin functional groups, for example hydroxymethyl groups and form a three‐dimensional crosslinking network structure which results in the improvement in bonding quality. Studied performed by Hong et al 36 confirmed that adjusting the viscosity is necessary to obtain good adhesion strength.…”

Utilization of Birch Bark as an Eco-Friendly Filler in Urea-Formaldehyde Adhesives for Plywood Manufacturing

“…High viscosity of adhesive resulted in a low flow ability of the adhesive and then consequently a poor penetration into wood veneers [ 91 ]. Another reason is that increasing the addition of WF in the adhesive reduced the amount of UF resin in the bond line which consequently decreased the adhesion strength of veneers [ 92 ].…”

“…The high content of WF absorbs most of the water, which participates in forming a three-dimensional crosslinking network structure [ 31 ]. An increase in viscosity of UF resin adhesive led also to increase in the bond strength which affected the flow ability of UF resin adhesives, and inhibited the resin penetration into wood veneers [ 92 ].…”

Calcium carbonate modified urea–formaldehyde resin adhesive for strength enhanced medium density fiberboard production

“…The MOR of the berboard usually increases with the increase in density. 21 However, the density and moisture content of the berboards prepared in this experiment are basically the same. It can be concluded that CaCO 3 modication on UF resin in this study has no signicant effect on the MOR of the berboards prepared using UF resins.…”