Polymer Composites for Flexible Electromagnetic Shields

Abstract

Harmful electromagnetic (EM) interference (EMI) to living beings and various sensitive instruments by EM radiations from electronic and electrical gadgets and mobile towers is increasing rapidly. It inflicts illness, and presumably cancerous growth in human cells. EMI is minimized by wrapping the receiver and/or the emitter gaplessly by an efficient EM shielding sheet. Compared to the widely used and classical metallic shields, 2nd generation polymer composite EMI shields are lighter and more flexible. Conventional polymer composites use conducting polymers and metallic/carbon powders that have conducting electrons to reflect EM waves away. A polymeric binder, curing overnight to a soft and flexible sheet, has presently been selected for making the polymeric composites. We test EM shielding by certain non‐metallic composites. We review results for composites with fine metallic fibers (copper and brass turnings, available as waste from mechanical workshops) or conducting forms of cadmium oxide or ferroelectric materials (PbNb2O6 [o‐PN] & BaTiO3 [BT]) or their mixtures (52 samples). Small pieces of these cloth‐like polymeric sheets have been characterized in a Vector Network Analyzer (VNA), by measuring input power (Pin), the reflected power (Prefl), and the transmitted power (Pout), over five frequency bands in 700 MHz to 40 GHz range to find Shielding Effectiveness (SE) = 10 log (Pout/Pin) and Reflection Effectiveness = 10 log (Prefl/Pin). Success of o‐PN, BT, conducting (fired) Cd‐O, metallic turnings and their combinations has been discussed, highlighting some new observations. Composites, developed in this work, include EMI Shielding materials and potential Radar Absorption Materials.