Strategy for constructing electromagnetic interference shielding and flame retarding synergistic network in poly (butylene succinate) and thermoplastic polyurethane multilayered composites

Fabricating electromagnetic interference (EMI) shielding materials with excellent flame retarding properties is significant to attenuate undesirable electromagnetic waves caused by electronic devices and simultaneously improve the flame safety of the electronic components. Herein, a novel EMI shielding composite with multilayered structure was fabricated at a low particle loading via layer-multiplying coextrusion technology. Especially, within the multilayered composites, poly (butylene succinate) (PBS) filled with carbon nanotubes (CNTs) was used to construct conducting layer while thermoplastic polyurethane (TPU) filled with intumescent flame retardants (IFRs) and CNTs was used to construct synergistic flame-retarding layer. The content of CNTs and IFRs in the whole system were below 4 wt% and 20 wt%, respectively. Morphological observation demonstrated the alternating multilayered structure and the selective distribution of IFRs and CNTs. Besides, by tailoring the layer numbers, the composites showed tunable EMI shielding and flame retarding performances. With regard to EMI shielding performance, the absorption-dominated average EMI shielding effectiveness (SE) values of both 8- and 16-layer specimens exceeded 30 dB in the range of 8.2-12.4 GHz. Furthermore, superior flame retardancy with prompt self-extinguishment and anti-dripping was achieved in these specimens owning to the production of continuous and foaming carbonaceous structure among layers. Especially the 8-layer specimen, the UL-94 rating was categorized in V-0. Consequently, this work provided a promising and facile route to fabricate polymeric composites simultaneously possessing excellent EMI shielding and flame-retarding properties to fulfill the stringent requirements in practical application.