EMI Absorption Shielding Effectiveness, Vulcanization, and Mechanical Properties of NBR ‐Based Composites Filled With Ferrites and Carbon‐Based Fillers

ABSTRACT Magnetic soft powdery ferrites, nickel‐zinc ferrite, manganese‐zinc ferrite, and their combinations were incorporated into acrylonitrile‐butadiene rubber. The total amount of magnetic fillers was maintained at a constant level of 300 phr. Graphite or graphene were added to the rubber compounds alongside ferrites in a fixed amount of 25 phr. A sulfur curing system was used to cross‐link the composites. The study was aimed at examination of fillers' influence on the vulcanization process, mechanical properties, conductivity, and absorption shielding performance of the composites. The findings showed a strong correlation between permittivity, conductivity, and absorption shielding. Enhanced conductivity corresponded with increased permittivity, which consequently diminished absorption shielding effectiveness. Concurrently, this relationship led to the lowering of frequency at which the composites provided absorption shielding. Composites containing ferrites and graphene demonstrated higher conductivity and permittivity compared to those based on ferrites and graphite, resulting in narrower effective absorption frequency ranges. Additionally, ferrite‐graphene composites absorbed electromagnetic radiation waves at lower frequencies. Increasing the proportion of nickel‐zinc ferrite in the magnetic fillers' combination broadened the absorption frequency bandwidths for both types of composites, indicating superior absorption shielding capabilities of nickel‐zinc ferrite. The best absorption shielding performance was shown by the composite based on graphite and 300 phr of nickel‐zinc ferrite showing the lowest conductivity. The magnetic fillers' composition exhibited minimal impact on mechanical properties, which were more influenced by the type of carbon‐based filler. Graphene provided a stronger reinforcing effect, leading to higher tensile strength, modulus, and hardness of the corresponding composites.