Stretching induced alignment of graphene nanoplatelets in polyurethane films for superior in-plane thermal conductivity and electromagnetic interference shielding

The rapid innovation of flexible smart electronics has increased the demand for flexible thermally conductive films with the high performance of electromagnetic interference shielding (EMI). This study focuses on graphene nanoplatelets/polyurethane (GnP/PU) films that were fabricated utilizing the solution casting approach. The stretching-induced alignment method was then used to align the GnP sheets horizontally in the PU matrix by uniaxially stretching to a particular degree. The resultant stretched GnP/PU films with 10 wt% GnP loading at a stretching degree of 130% show an excellent in-plane thermal conductivity (λ∥) and EMI shielding effectiveness values of 10.68 W m−1 K−1 and 41 dB in the frequency range of 8–12 GHz which are 679% and 60%, respectively, higher than that of corresponding unstretched ones. The outstanding λ∥ and EMI shielding effectiveness can be ascribed to the horizontal alignment of GnP sheets in the PU matrix. That, in turn, may decrease the interfacial thermal resistance, and facilitate the establishment of effective phonon and electron transfer in the stretched GnP/PU films. The obtained films demonstrated superior heat dissipation and mechanical properties compared to neat PU film. Therefore, the prepared GnP/PU films have great potential as heat spreaders and EMI shielding material in flexible smart electronics.