Heterogeneous recycled carbon black derived from pyrolytic waste tire rubber with strong, wideband electromagnetic wave absorption

To contribute to the circular and sustainable economy framework, waste tire rubber reclamation by extracting carbon black through pyrolysis and heat treatment and then ingeniously designing it as an electromagnetic wave absorbing (EWA) material is proposed herein. The results showed that the pyrolysis-recycled carbon black (RCB) was heterogeneous with multiple interfaces, making it suitable for EWA application. The RCB was processed at 500 °C-1000 °C to study the changes in the composite and microstructure as well as the EWA properties. The heterointerfaces, defects and components changed with the pyrolytic temperature, which helped to adjust the conductive loss, polarization loss, impedance matching, and electromagnetic wave (EW) transmission path, thereby obtaining different EWA performances. As a result, RCB500 exhibited a minimum reflection loss (RL_min) of −35.99 dB at a thickness of 2.5 mm with a low filler loading of 40 wt%. Its widest effective absorption bandwidth (EAB) can reach 3.98 GHz at a low thickness of 1.5 mm. For RCB800, the RL_min value can reach −34.47 dB, and the EAB_max value can reach 4.14 GHz at a low thickness of only 1.5 mm with a filler loading of only 30 wt%. The absorption mechanism was deeply studied. The results indicated that the carbon black pyrolysed from waste tire rubber with strong, wideband electromagnetic wave absorption can be considered a promising candidate for designing high-efficiency carbon-matrix EWA materials.