Castor oil–based waterborne polyurethane/silver nanowire gradient films for electromagnetic interference shielding and thermal management

Plant oil–based waterborne polyurethane (WPU) films with conductive fillers are suitable candidates as elastomers for electromagnetic interference (EMI) shielding and thermal management, conforming to sustainable development. However, the synthesis of the above WPU films is a major challenge. Herein, castor oil–based WPU/silver nanowire (c-WPU/AgNW) films, the integration of high-performance EMI shielding and excellent thermal management, were obtained via designing AgNW gradient distribution. The gradient distribution induced AgNWs to create perfect thermal and electrical pathways at the bottom of the as-prepared films. The c-WPU/AgNW gradient films exhibited excellent electrical conductivity (64.1 S m −1 ), shielding effectiveness (58.1 dB), shielding effectiveness/thickness (1236.2 dB cm −1 ), and in-plane thermal conductivity (1.67 W m −1 K −1 ) when their AgNW content and thickness were 9.1 wt% and 0.47 mm, respectively. The insolation of the 7.0 wt% AgNW-loaded c-WPU/AgNW film after 40 d in the atmosphere maintained 81 % shielding effectiveness of original samples, demonstrating good durability. The fabricated c-WPU/AgNW gradient films have EMI shielding and thermal management applications.