Acidic deep eutectic solvent as a novel catalyst for urea–formaldehyde resin curing

Abstract

ABSTRACT The effect of a novel catalyst, acidic deep eutectic solvent, on the characteristics of urea–formaldehyde (UF) resins-bonded particleboard was studied in this research work. Methyltriphenyl-phosphonium bromide–protocatechuic acid (MTPPBr–PCAT) as a DES was added to the UF resin at different percentages (1%, 2%, and 3% by weight). Then, the prepared resin was used for manufacturing particleboards. Based on this research finding, DES appears to be an effective UF resin catalyst. Increasing the MTPPBr–PCAT–DES level from 0 to 3 wt% caused a decrease in pH but still within the limits acceptable to international standards requirements, and also it caused a shorter gel time and acceleration of resin curing. Wood particleboard prepared with only 1 wt% DES had higher mechanical strength and dimensional stability and lower formaldehyde emission compared to the controls bonded with UF resins catalyzed with 2 wt% NH4Cl. Under scanning electron microscopy, acidic deep eutectic solvent catalyzed UF resins-bonded panels presented a smooth and monotonous appearance. DESs as UF acidic catalysts present advantages, such as being non-toxic, being able to catalyze resin cure similarly or more effectively than the acid itself, and being recyclable as well.