External field induced high speed sintering of dynamically cross-linked polydimethylsiloxane: Mechanical properties and electromagnetic wave absorption

External field induced high speed sintering (HSS), is one kind of powder bed fusion 3D printing technology, which significantly enhances the printing rate using infrared light area-scanning instead of laser point-scanning and fusion. HSS printing needs to develop new materials with rapid melting-solidification kinetics to adapt to its rapid sintering process. Here, the polydimethylsiloxane (PDMS) covalent adaptable networks (CANs) with dynamic imidazolium bonds were synthesized and further pulverized to make the elastomer powders for HSS 3D printing. The high-quality PDMS elastomer parts with good dimension accuracy and mechanical strength can be HSS-printed through the optimization of printing processing parameters. A post-treatment process with vacuum impregnation and heating can further improve the surface appearance and mechanical strength. The printed PDMS parts exhibit a tensile strength of 4.24 MPa and can be healed multiple times with an efficiency of nearly 100 %. A surprising finding is that the HSS printed parts have a good ultra-broadband electromagnetic wave (EMW) absorption function, which also can be tuned by altering the printing parameters. The sub-microscopic layered structures of the inkjet-printed carbon black particles used as infrared absorbers of HSS printing were formed during the printing process, which can induce the multiple reflections and refractions of EMWs, significantly attenuating their intensity. At a specimen thickness of 28.3 mm, an effective absorption bandwidth (EAB) of 14 GHz (4–18 GHz) can be achieved. The simulation results indicate that polarization loss, conduction loss, and quarter-wavelength interference are responsible for the electromagnetic waves' energy dissipation.