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.

Silicone Rubber Composites of Differently Fired Cadmium Oxide and Their Positron Lifetime Study

“…Next, their composites with a silicone rubber binder have been formed at different concentrations to get flexible cloth-like composites with the advantages of cadmium oxide. Flexible electromagnetic (EM) shielding [13] has been one of the applications in mind. Current positron lifetime measurements in the composites prove that cadmium oxide enters the free volume of the polymeric binder to form the composites.…”

“…So, the composites are seen to retain the advantage of high electrical conductivity, while providing flexible samples. These composites and other silicone rubber-based composites have been used [12,13] for EM Interference (EMI) shielding applications.…”

“…However, the sintered pellets are brittle and resist any fabrication. So, here we have fabricated [2,12,13] new composites of these differently heat-treated Cd-O solids with an interesting silicone rubber polymer. We have discussed above how cadmium oxide is becoming technologically important.…”

Flexible ultra-wideband cartoon-shaped antenna based on a composite with customizable dielectric properties

“…To ensure that the experiments were conducted successfully, we carefully selected dopants and a uniform doping method. PTFE powder becomes the first choice of the dopants because it has excellent chemical stability and can be used as a filler in the electromagnetic shielding field [25][26][27]. In addition, barium titanate is used as the dielectric substrate to improve antenna performance [28].…”

A Flexible Sandwich Structure Carbon Fiber Cloth with Resin Coating Composite Improves Electromagnetic Wave Absorption Performance at Low Frequency

“…In the past few decades, a lot of research has focused on wave absorbing materials but has been mainly concentrated in the Super High Frequency, the studies of wave absorbing materials below the Super High Frequency have been fewer or not ideal. However, a large number of electronic devices have been used in these lower frequency bands [8], so that the research at the lower frequency bands of wave absorption materials has become very significant.…”