Graphene Nanoplatelet Exoskeleton on Polyurethane Foam to Produce Flame-Retardant, Piezoresistive, and Electromagnetic Interference Shielding Surfaces

Polyurethane foam (PUF)'s porous structure, light weight, flexibility, and low-cost properties make it useful in various cutting-edge technologies. However, time-consuming, costly, and complicated surface modification methods severely hinder its commercial applications. Herein, an ultrafast, simple, and cost-effective surface modification method based on the evaporation of a low boiling point solvent to prepare a multifunctional graphene nanoplatelet (GNP)-decorated PUF (GNP@PUF) is proposed. Due to the passive heat barrier of GNP sheets, the resulting sponge exhibits excellent flame retardancy by reducing the critical fire retardancy metrics, that is, peak heat release rate, total heat release, and total smoke release by 72%, 50%, and 81%, respectively. In addition, GNP@PUF can function as a piezoresistive sensor and electromagnetic interference (EMI)-shielding material. As a piezoresistive sensor, it exhibits a wide-compressive pressure (2.4-112 kPa)/strain (5-70%) range and ultra-fast response/relaxation time (48/35 ms), wide-stretching strain (5-100%) range, and it can detect minute human motions by being attached to different parts of the human body. Meanwhile, the composite foam displays good absorption-dominant EMI shielding performance (& AP;38 dB), possibly due to conductive dissipation and multiple reflections/scattering of EM waves inside the 3D conductive graphene network. This study provides a simple coating technique for developing multifunctional lightweight foam materials.