The curing behavior of urea-formaldehyde adhesive in the presence of chemically treated narrow-leaved ash

Abstract

The influence of Narrow Leaved Ash (Fraxinus angustifolia Vahl. ssp. Pannonica Soo & Simon) pre-treatments on the curing behavior of urea-formaldehyde (UF) adhesive was studied. Differential scanning calorimetry (DSC) was used to monitor the curing reaction of UF adhesive mixed with non-treated wood flour (control series) and wood flour of Narrow leaved Ash obtained after different pre-treatments of wood particles. Three different pre-treatments were applied, one with sodium carbonate solution (0.03 g/g of dry wood), one with acetic acid solution (0.06 g/g of dry wood) and one with distilled water. The curing reaction of different adhesive systems showed no apparent differences in peak temperature values, and there were no significant differences in the enthalpy of the reaction. However, it was assessed that the activation energy has lower values for the UF systems with alkaline and acid treated wood flour (76.64 and 76.92 kJ/mol) in regard to the UF systems with control (untreated) wood flour and water treated wood flour (79.28 and 79.14 kJ/mol). In addition, the application of iso-conversional models have shown different curing behavior of UF adhesive systems.