Rheological Properties of Epoxy/Polypyrrole Coating and its Behavior as EMI Material

In this study, we analyze the rheological properties of epoxy/polypyrrole/carbon black coating and its performance as electromagnetic interference shielding efficiency (EMI SE). For this purpose, a commercial epoxy coating was mixed with a conductive polymer, namely polypyrrole. Rheological tests were performed to obtain the flow curve, the storage and loss moduli, the cure time and thixotropic characteristics. Thermal analysis of DSC (cure behavior) and EMI SE were also performed. Epoxy coating showed non‐Newtonian (shear thinning) behavior. The addition of PPy.DBSA reduced the coating fluidity by the increase in consistency index and viscosity. The stress oscillatory amplitude sweep test was performed to determine the linear viscoelastic range. The results of the LVR stress and strain frequency sweep tests were compared to the PPy.DBSA. The results show that LVR and critical crossover change with the percent of Polypyrrole. The cure times obtained by the rheometer and DSC were in good agreement: the addition of polypyrrole reduced the cure time, probably due to the presence of amino groups in the PPy.DBSA, which can react with the oxirane ring in the epoxy resin. The EMI SE attenuation by absorption and reflection mechanism was observed by adding 10 phr of PPy.DBSA. For practical applications, it is necessary to combine polypyrrole with conducting carbon black. The formulation with 1.5 phr of carbon black improves the EMI SE performance to 72%. J. VINYL ADDIT. TECHNOL., 26:348–353, 2020. © 2019 Society of Plastics Engineers