A Unique Double Percolated Polymer Composite for Highly Efficient Electromagnetic Interference Shielding

This study has developed a carbon nanotube (CNT)/ethylene vinyl acetate (EVA)/ultrahigh molecular weight polyethylene (UHMWPE) composite with a unique double percolated conductive structure, in which only 20 wt% of CNT enriched EVA is needed to form a continuous conductive network. Compared with conventional double percolated conductive polymer composites (CPCs) which require filler-enriched polymer content up to 50 wt%, the low CNT/EVA content gives rise to an unprecedentedly increased effective CNT concentration in the CNT/EVA/UHMWPE composite. The double percolated composite exhibits electrical conductivity comparable to that obtained in CNT-loaded single EVA composite with five times of CNT content. Only 7.0 wt% CNT gives the composite an electromagnetic interference (EMI) shielding effectiveness of 57.4 dB, much higher than that of mostly reported CNT and graphene based CPCs. Absorption is demonstrated to be the primary shielding mechanism due to the numerous interfaces between UHMWPE domains and CNT/EVA layers facilitating multiple reflection, scattering, and absorption of the incident microwaves. The construction of unique double percolated structure in this work provides a promising strategy for developing cost-effective and high-performance CPCs for use as efficient EMI shielding materials.