Highly Deformable Porous Electromagnetic Wave Absorber Based on Ethylene-Propylene-Diene Monomer/Multiwall Carbon Nanotube Nanocomposites.

The need for electromagnetic interference (EMI) shields has risen over the years as the result of our digitally and highly connected lifestyle. This work reports on the development of one such shield based on vulcanized rubber foams. Nanocomposites of ethylene-propylene-diene monomer (EPDM) rubber and multiwall carbon nanotubes (MWCNTs) were prepared via hot compression molding using a chemical blowing agent as foaming agent. MWCNTs accelerated the cure and led to high shear-thinning behavior, indicative of the formation of a 3D interconnected physical network. Foamed nanocomposites exhibited lower electrical percolation threshold than their solid counterparts. Above percolation, foamed nanocomposites displayed EMI absorption values of 28-45 dB in the frequency range of the X-band. The total EMI shielding efficiency of the foams was insignificantly affected by repeated bending with high recovery behavior. Our results highlight the potential of cross-linked EPDM/MWCNT foams as a lightweight EM wave absorber with high flexibility and deformability.

Preparation and Characterization of Highly Elastic Foams with Enhanced Electromagnetic Wave Absorption Based on Ethylene-Propylene-Diene-Monomer Rubber Filled with Barium Titanate/Multiwall Carbon Nanotube Hybrid.

Hybrid ethylene-propylene-diene-monomer (EPDM) nanocomposite foams were produced via compression molding with enhanced electromagnetic wave absorption efficiency. The hybrid filler, consisting of 20 phr ferroelectric barium titanate (BT) and various loading fractions of multi-wall carbon nanotubes (MWCNTs), synergistically increased the electromagnetic (EM) wave absorption characteristics of the EPDM foam. Accordingly, while the EPDM foam filled with 20 phr BT was transparent to the EM wave within the frequency range of 8.2-12.4 GHz (X-band), the hybrid EPDM nanocomposite foam loaded with 20 phr BT and 10 phr MWCNTs presented a total shielding effectiveness (SE) of ~22.3 dB compared to ~16.0 dB of the MWCNTs (10 phr). This synergistic effect is suggested to be due to the segregation of MWCNT networks within the cellular structure of EPDM, resulting in enhanced electrical conductivity, and also high dielectric permittivity of the foam imparted by the BT particles. Moreover, the total SE of the BT/MWCNTs loaded foam samples remained almost unchanged when subjected to repeated bending due to the elastic recovery behavior of the crosslinked EPDM foamed nanocomposites.