The effect of soft magnetic ferrites and carbon allotropes on EMI absorption shielding performance and mechanical characteristics of NBR-based composites

Nickel–zinc and manganese–zinc ferrites, both individually and in combination, were incorporated into an acrylonitrile–butadiene rubber matrix at a total loading of 300 phr. In subsequent series, these magnetic fillers were combined with 25 phr of carbon allotropes (graphite, carbon black, or carbon fibers) to form multi-component hybrid shielding systems. The results revealed a strong correlation between electrical conductivity, permittivity, and absorption efficiency. The dielectric response was primarily governed by interfacial polarization (Maxwell–Wagner–Sillars effect) and the formation of 3D conductive networks. Composites filled exclusively with ferrites exhibited the most effective absorption-based shielding due to optimized impedance matching. Conversely, the addition of carbon allotropes increased conductivity and permittivity, leading to a decline in absorption efficiency owing to enhanced surface reflection. The carbon black–ferrite systems showed the weakest absorption but the highest mechanical strength, suggesting strong filler–matrix interactions and restricted molecular mobility of the rubber chains. Increasing the nickel–zinc ferrite content systematically broadened the absorption bandwidth, highlighting its superior potential for broadband electromagnetic attenuation through synergistic material design.