Heterogeneous UPR composite film with adjustable serrated structure for flame retardant and electromagnetic interference shielding

Reasonably controlling the structure of a polymer-based composite film is crucial for optimizing flame retardant and electromagnetic interference (EMI) shielding performance. Herein, an adjustable serrated structure was designed into a heterogeneous unsaturated polyester resin (UPR) composite film to enhance interfacial adhesion between organic and inorganic components, thereby boosting the overall performance of the composite film. First, halloysite nanotubes (HNTs) serve as fillers, incorporated into the UPR matrix to enhance flame retardancy and thermal stability. Meanwhile, HNTs could endow the film (UPR/HNTs) with an adjustable serrated structure, which provides conditions for MXene deposition. Subsequently, due to the dual action of physical interlocking and chemical bonding, MXene was deposited onto the serrated interface of the UPR/HNTs film for EMI shielding, flame retardant, Joule-heating, and infrared stealth performance. Consequently, the optimized composite film (UPR/10 %HNTs-MXene) exhibits significantly improved flame retardant performance. The peak heat release rate (PHRR), total heat release rate (THR), peak smoke production rate (PSPR), and total smoke production (TSR) of the composite film were reduced by 53.87 %, 45.45 %, 53.03 %, and 57.06 %, respectively, compared to pure UPR. Moreover, due to the high conductivity and low reflectivity of MXene, UPR/10 %HNTs-MXene has good Joule heating and infrared stealth performance. Benefiting from the serrated interface structure, which induces synergistic multiple reflections, interfacial polarization, and heat-dissipation losses, the optimized film exhibits a superior EMI shielding performance of 40.17 dB. These findings not only provided a scalable approach to designing other advanced films but also promoted the application of multifunctional films in electronic devices.