Electrochemical impedance spectroscopy (EIS): An efficiency method to monitor resin curing processes

Electrochemical impedance spectroscopy (EIS) is widely used to characterize the charge carrier transfer and charge storage process. Charge carrier transfer process may be affected by the media viscosity. Here, EIS was used to monitor the curing processes of epoxy/amine blends for the first attempt, and a new equation was proposed to character the curing process and estimate the curing degree of resins, while, resins, curing agents and the curing processes have significant effect on product properties. Monitoring curing processes of certain resin/curing agent system is very helpful to design an appropriate formulation. The epoxy/amine blends, the model system, were prepared with Diglycidyl ether of bisphenol-A as epoxy resin and different ratio of phenalkamine modified with cardanol as curing agent. The curing processes of epoxy/amine were also investigated by differential scanning calorimetry (DSC), which was employed as a comparative method to verify the EIS results. A good agreement is obtained between the two methods, especially under higher curing temperature condition, which demonstrates the great promise to monitor the curing processes using EIS. The EIS results were also modeled to equivalent electrical circuits (EEC) by ZSimpleWin software for the further analysis. These results might provide some insights on optimizing the epoxy/amine ratio and the performance of cured epoxy resin and monitoring some process related to viscosity change.