Integrating Electrical Insulation, EMI Shielding, and Thermal Conductivity: A Silicone Rubber Composite from Recycled Pyrrhotite for Electronic Thermal Interface Applications

Effective thermal management and electromagnetic interference (EMI) shielding are critical for the reliability of miniaturized electronic devices. However, developing multifunctional composites using sustainable, low-cost mineral fillers remains a challenge due to their intrinsically limited phonon transport and dielectric loss capabilities. In this study, we innovatively proposed and achieved the phase transformation of pyrrhotite from the monoclinic (mPyr) to the hexagonal (hPyr) structure at 450 °C for the first time. Unlike the mPyr, the hPyr phase possesses a more ordered and stable crystal structure, which significantly suppresses phonon scattering and enhances intrinsic thermal conductivity (TC). To validate this, hPyr was modified with polysulfide bonds and incorporated into a silicone rubber (RTV-2SR) matrix. At a loading of 35 wt %, the hPyr/RTV-2SR composite achieved a remarkable 625% improvement in TC (1.46 W/(m·K)) over pure RTV-2SR and a 18.7% enhancement compared to mPyr/RTV-2SR (1.23 W/(m·K)), proving the superiority of the phase transformation strategy. Simultaneously, the hPyr/RTV-2SR composite possessed a resistivity exceeding 1013 Ω·cm while delivering a high EMI shielding performance of 39.6 dB primarily attributed to absorption loss. The incorporation of conductive mineral phases combined with optimized filler distribution endowed the composite with effective EMI shielding capability. In addition, the stress–strain analysis revealed that the hPyr/RTV-2SR composite achieved a tensile strength of 2 MPa. This work presents a promising strategy for the high value utilization of vulcanized mineral tailings while contributing to the development of multifunctional and sustainable materials.