Tunable Electromagnetic Interference Shielding Properties of Binary Thermoplastic Composites Prepared by Reactive Microencapsulation

Thermoplastic composites integrating carbon nanotubes (CNT) and micron-sized metal particles dispersed in polymer matrices can address emerging multifunctional needs, (EMI) shielding combined with easy processing and affordable costs. Herein, an approach based on reactive microencapsulation is reported to prepare polyamide 6 (PA6)-based composites comprising binary loads of CNT and Al, Cu, or Fe particles. The microencapsulation is performed by activated anionic polymerization of epsilon-caprolactam in solution, in the presence of the metal/ CNT loads. The resulting hybrid microparticles are compressionmolded into plates containing effective metal/CNT loads in the range of 12-17 wt %. Among the materials synthesized, the one containing Al/CNT binary load (3:7 wt %) displays the highest EMI shielding effectiveness (SE) of 43.5 dB at 12 GHz, with a 2 mm thickness and an electrical conductivity Sigma dc of 6.61 x 10-3 S/cm. A synergetic effect is observed in all of the metal/CNT PA6 samples in terms of both Sigma dc and SE increase. Evidently, the presence of metal particles well dispersed in the conductive CNT network contributes to the mobility of the carriers and thus to the effective attenuation of the electromagnetic waves. Therefore, the binary composites of this study can be efficient thermoplastic EMI shielding materials.