In this study, the structures and thermal stability of pure urea-formaldehyde resin (PR) and modified urea-formaldehyde (UF) resin are investigated by differential thermal gravity (TG/DTG), and differential scanning calorimetry (DSC) supported by data from Fourier transform infrared spectroscopy. FTIR analysis indicate that the modifiers such as polydimethylsiloxane, dicyclohexylcarbodiimide and phenol have actively participated in the curing reactions. TG/DTG and DSC curve of UF resin show that its pyrolysis process is conducted in three steps: desiccation and dehydration, flash pyrolysis and slow decomposition. Compared with pure urea-formaldehyde resin (PR), modified UF resin exhibited good thermal stability. The activation energy (E) of modified UF resin acquired by Kissinger and Ozawa method was higher than that of PR. ΔH > 0, ΔS > 0 and ΔG > 0 in the thermal decomposition process of UF resin means that the decomposition reaction of UF resin before and after modification is a process of unnatural decalescence and entropy increase.
Keywords: modified UF resin; thermal properties; TG/DTG; thermodynamics; thermal decomposition kinetics