Composite aerogel with oriented structure of polyimide@ polypyrrole /MXene for effective shielding against electromagnetic waves and insulation

Although the rapid evolution of electromagnetic wave technology make much progress to society, but has also caused electromagnetic pollution, which poses risks to health, information security, and disrupts communication and device operation. The development of new Electromagnetic Interference (EMI) shielding materials, especially those that are lightweight, easy to process and high shielding efficiency, has become the key to overcoming this challenge. In this study, MXene nanosheets with few layers were fabricated by chemical etching with lithium fluoride (LiF) and hydrochloric acid (HCl). Subsequently, the unidirectional freeze-drying method and vacuum-assisted impregnation method were applied to fabricate polyimide@ polypyrrole/MXene (PI@PPy/MXene) composite aerogel with oriented structure. The electromagnetic shielding properties of the oriented PI@PPy composite aerogel were modulated by changing the polymerization time of PPy to control its conductivity. When the polymerization time was set as 7 h, the oriented PI@PPy composite aerogel showed the highest EMI efficiency, the value of EMI SE was 19.36 dB. With the introduction of MXene, the EMI SE of the PI@PPy/MXene composite aerogel was increased compared to PI@PPy and reached to 32.64 dB. The improvement in electromagnetic shielding performance was attributed to the co-enhancement among the PI aerogel with oriented structure, PPy and MXene, which is the result of the synergisic effect of Multiple reflection losses and polarization losses within the aerogel. The infrared thermography at 200°C showed that with increasing PPy polymerization time, the external temperatures of the samples are 40.3°C, 44.8°C, 51.4°C, 55.4°C and 48.6°C, demonstrating the excellent thermal insulation properties.