Polyurea-formaldehyde resin: a novel wood adhesive with high bonding performance and low formaldehyde emission

摘要

By using polycondensation -> hydroxymethylation strategy, a novel wood adhesive, namely polyurea-formaldehyde resin (PolyUF) was designed and successfully synthesized. Polyurea polymers were firstly synthesized through polycondensations between urea and ethylenediamine with no solvent and catalyst used. After simply removing residual NH3, the polyurea polymers were directly reacted with formaldehyde in different F/U molar ratios to produce hydroxymethylated polyureas. The resulted resins were structurally different from the currently used formaldehyde-based wood adhesive resins. Bonding performance tests indicated that the water resistance of PolyUF resins is good and comparable to that of high-molar ratio UF resin (F/U = 1.6), but the formaldehyde emission of the PolyUF resins was only 20 similar to 30% of UF. The PolyUF resins successfully balanced formaldehyde emission and bonding performance by incorporating polyurea linkages in resin structures which are stable toward hydrolysis.