Preparation of flexible and elastic thermal conductive nanocomposites via ultrasonic-assisted forced infiltration

Flexible and elastic thermal conductive polymer composites are of urgent demand in the microelectronics, thermal management systems, and energy industry. In this work, high thermal conductive carbon nanotubes (CNTs) buckypapers were prepared using vacuum filtration technique. Polyurethane (PU) matrices with different isocyanates and isocyanate index R were then polymerized by semi-prepolymer method. Finally, flexible and elastic PU/CNTs nanocomposites were fabricated via ultrasonic-assisted forced infiltration. Owing to the forced infiltration effect of high power (2 kW) and high frequency (20 kHz) ultrasonication, PU matrix with high viscosity can complete infiltrate the compact CNTs buckypaper within seconds. The CNTs are evenly embedded in the PU matrices and still overlap with each other to keep the 3D network after forced infiltration. PU/CNTs nanocomposite film, with a thickness of 70 μm, presented excellent mechanical stability (211.7% elongation at break, 5.97 MPa tensile strength, and 360° bending available) and superior thermal conductivity (6.028 W/mK), which can dissipate the heat accumulation effectively. This facile and robust method of ultrasonic-assisted forced infiltration provides a new strategy to design and fabricate highly thermal conductive composites and other functional polymer composites.