Non-isothermal kinetics of thermal degradation of DGEBA/TU-DETA epoxy system

Abstract

A curing agent Thiourea-diethylenetriamine (TU-DETA) was successfully prepared with its structure characterized by Fourier transform infrared spectrum and nuclear magnetic resonance (¹³C-NMR spectrum). The curing agent TU-DETA contained incompletely reacted material diethylenetriamine (DETA) and the polymerization degree (n) of TU-DETA was equaled to either 1 or 3 according to liquid chromatography–mass spectrometry (LC-MS) analysis. Kinetics of thermal degradation of DGEBA (diglycidyl ether of bisphenol A)/TU-DETA epoxy system was investigated with thermogravimetric analysis (TGA) under non-isothermal conditions with heating rates of 5, 10, 12.5, 15, and 20 °C/min. The derivative thermogravimetry curves of DGEBA/TU-DETA epoxy system revealed that the thermal degradation process was only a single weight-loss step. The apparent average activation energy calculated with the Flynn–Wall–Ozawa method was 140.4 kJ/mol. With a combination of the Coats–Redfern and Phadnis–Deshpande methods, it was showed that the most probable mechanism of degradation process of the cured epoxy resin was F1 deceleration type.

Keywords:

• thermal degradation
• DGEBA/TU-DETA epoxy system
• thermogravimetric analysis
• activation energy
• degradation mechanism

Acknowledgments

The authors gratefully acknowledge the financial support from the funding of Ministry of Education Key Laboratory for the Synthesis and Application of Organic Functional Molecules, and the English correction by Dr Jianjia Yu and Mr Shangwen Zha of New Mexico Institute of Mining and Technology of United States of America.