Flexible and High-Performance Electromagnetic Shielding Materials from Waste Polyurethane Foams

Abstract

In the modern society, polymer composites utilizing various wastes for electromagnetic interference (EMI) shielding are of great economic and social significance. Herein, we report that waste polyurethane foams (WPUF) can be facilely converted into high-performance EMI shielding materials via surface coating of carbon nanotubes followed by hot pressing. The merit of this work lies in the novel skin-core segregated structure from the complete three-dimensional skeleton of WPUF, which is well retained after compression molding. The uniform distribution of multiwalled carbon nanotubes (MWCNTs) on the polyurethane skeleton surface assisted by cellulose nanofibers (CNFs) provides the material with remarkable electrical conductivity, leading to excellent EMI shielding properties. The resultant composite (WPUF-MC) achieves a high EMI shielding effectiveness (SE) of 63.2 dB at a low loading of MWCNTs (6.6 wt %), far surpassing the values for many early reported shielding materials of this kind. Moreover, the WPUF-MC also exhibits sufficient flexibility and reliable EMI shielding performance. Even if bent or twisted 1000 times, it can still maintain EMI SE at a fairly high level. This work not only offers an effective strategy for high-value utilization of WPUF but also may expand the application potential of flexible shielding materials.