Except the exothermic peaks addressed to the curing
reaction of UF adhesives, the Figure 4 also shows
the presence of endothermic reaction occurring at the
temperatures between 135 and 140 °C. Since the DSC
measurements were conducted under the pressure, the
apparent phenomenon might be addressed to a certain
amount of degradation of the urea polymer, as this
temperature level coincides with the melting temperature
for urea. In earlier research, the endothermic reaction
at 137 °C was addressed to decomposition of urea
rings [18].