Shape memory driving thickness-adjustable G@SMPU sponge with ultrahigh carbon loading ratio for excellent microwave shielding performance

Shape memory driving thickness adjustable graphite (G) micro-flakes@shape memory polyurethane (G@SMPU) sponge was fabricated by two-step dipping separately in G-dispersed aqueous solution and SMPU/THF solution for high-performance microwave shielding. The sponge exhibited an ultrahigh G loading ratio (G/sponge, wt/wt) up to 490 wt%. For the first time, dipping coating of SMPU onto the sponge was proposed, and the obtained G@SMPU sponge exhibited a good recovery effect at least above 90% after thorough compression. And also, the thickness could be adjusted by utilizing its shape memory property. For microwave shielding, G-9@SMPU and G-18@SMPU sponges achieved the shielding effectiveness over 20 and 30 dB, respectively. Moreover, varying thickness or compressing repeatedly even up to 100 times would not obviously decrease the shielding effect of the G@SMPU sponge. This suggests the steady distribution and adhesion of G micro-flakes inside the three-dimensional sponge substrate due to the fixing of SMPU.