Flexible, High Thermal Conductivity, and EMI Shielding Performance Thermoplastic Polyurethane Composites through Reinforced-Orientation Carbon Fiber

The thermal management fields are witnessing growing interest in flexible polymer composites that exhibit high thermal conductivity and effective electromagnetic interference (EMI) shielding. Anisotropic thermally conductive thermoplastic polyurethane (TPU) composite films with high EMI shielding performance were prepared by solution blending and hot-pressing through an enhanced orientation of pitch-based carbon fibers in the in-plane direction. The influence of film thickness and filler content on the thermal conductivity of composite films was systematically investigated. The TPU composite films presented an in-plane thermal conductivity of 15.11 W/(m K) and an EMI shielding effectiveness above 29 dB at 8.2–12.5 GHz with film thickness of 0.2 mm and filler content of 30 vol %. Furthermore, laminated composite films were fabricated through a layer-by-layer stacking followed by hot-pressing (namely, laminated hot-pressing) at different number of layers. The in-plane thermal conductivity of laminated composite films increased with the laminated number due to the reinforcement orientation of pitch-based carbon fiber, with the highest in-plane thermal conductivity being 17.69 W/(m K) for ten-layer laminated films. In addition, these laminated composite films exhibited good EMI shielding effectiveness at 8.2–12.5 GHz with a film thickness of 0.2 mm (all above 29 dB), service stability, and mechanical properties. This work paves the way for fabricating multifunctional flexible polymer composites, enabling advancements in thermal management and EMI shielding.