Kinetics of the condensation reaction of urea and furfural in a heterogeneous phase leading to difurfurylidenetriurea: A calorimetric study

•The reaction of urea and furfural occurs at relatively low temperatures.•DSC experiments revealed the superposition of two thermal events.•Reaction heat is released at the interface of urea crystals causing their melting.•Kinetic parameters and reaction heat were evaluated.•Mechanism of reaction is proposed to occur in four steps.