Phthalonitrile and Cyanate Ester-Based Carbon Foams for Effective Electromagnetic Interference Shielding Applications

Lightweight materials with high electromagnetic interference (EMI) shielding effectiveness (SE) are greatly sought to address the increasing electromagnetic menace, especially in aerospace domain. In this work, lightweight foam-based EMI shielding materials are realized from phthalonitrile (PN), cyanate ester (CE), and a blend of PN-CE resin matrices by infusing into a rigid graphitic board (RGB) template. The low-density (0.3 and 0.4 g/cm(3)) carbon foams have achieved good electrical conductivity of 0.45-0.62 S/cm, high total EMI shielding efficiency of similar to 72-78 dB, specific EMI shielding of 75-195 dB, and thickness-normalized EMI shielding of 150-390 dB, indicating the excellent shielding of incident EM waves. The heterocyclic cross-linked networks formed from the ring formation polymerization of nitrile and cyano moieties are instrumental in conferring high EMI SE to the carbon foams. The primary EMI shielding mechanism is determined to be absorption. A thermal degradation mechanism proposed further confirms the formation of a hybrid graphitic structure conducive for high EMI SE. The polarization effects brought on by the built-in nitrogen-containing cured framework also contribute to the shielding efficiency. These lightweight carbon foams are prospective EMI shielding materials expected to be useful in aerospace, aeronautical, and high-end industrial fields in the future.