Analysis of electromagnetic shielding performance of waste rubber powder-based flexible composites

Waste tire management has escalated in recent years with the continuous increase in automobile production. Every year, ~ 1.5 billion tires are produced worldwide, and an equal number of tires are removed, thus leading to its crude dumping. The abundant waste tires construct stockpiles at landfills that cover large volumes and 75% of void space. Also, these dumps can self-ignite and may cause long-lasting fires. Besides, the inventories of used tires raise serious environmental, health, and landfills problems. Thus, reusing or recycling of waste tires could mitigate this problem. Therefore, extensive research projects have been carried out how to use waste tire rubber powder in different applications. One of the possible solutions for the waste tire rubber powder is to incorporate as a reinforcing material in composites. Thus, here, rubber extracted from the discarded automobile tires has been reused and converted into flexible composites against electromagnetic interference shielding. For the development of flexible rubber composites, carbon conductive fillers such as expanded graphite, natural graphite, and multi-walled carbon nanotubes were incorporated into rubber powder followed by the compression and molding technique. The effect of conductive fillers content (5 wt% and 10 wt%) and thickness (1 mm and 2 mm) of composites on the electromagnetic interference (EMI) shielding effectiveness was measured in the X band (8.2–12.4 GHz) frequency region. It is found that incorporation of conductive fillers significantly improved the electrical conductivity of composites and higher conductivity leads to superior total shielding effectiveness, dominated by the absorption mechanism. The total shielding effectiveness (SE T ) of ~ 45 dB and ~ 50 dB was achieved for 10.0 wt% of CNTs reinforcement into 1-mm- and 2-mm-thick rubber composites. Additionally, the carbon rubber composites exhibited an enhancement in the dielectric parameters (ɛ′ and ɛ′′), and it improved by increasing the filler content and thickness of the composite. This approach of re-using waste rubber as flexible electromagnetic shielding material could assist the development of next-generation flexible electronic devices and equipment in transport systems by tailoring the properties.