Radiation modification and radiation hardness of microwave properties for some polymer nanocomposites under Co-60 gamma irradiation

Nanocomposites, i.e., polymer composites filled with conductive nano-fillers have been shown to be promising materials as broadband microwave absorbers. However, increasing the filler content above a critical value cannot provide further improvements of nanocomposite electromagnetic properties. Herein, the electromagnetic interference shielding efficiency of gamma-irradiated polymer composites was investigated. For that purpose, nine types of nanocomposites based on various polymers and various nanocarbon fillers were prepared and treated with gamma irradiation from Co-60 source by cumulative absorption doses up to 750 kGy. The corresponding electromagnetic properties (reflection, transmission, and absorption) were then measured in the K_a microwave frequency range. The experiments revealed two distinct behaviors, depending on the polymer matrix and the filler: either an improvement of the electromagnetic response under gamma-irradiation of about 90 kGy, or a high tolerance to irradiation up to 750 kGy.