Highly thermally conductive carbon nanotubes pillared exfoliated graphite/polyimide composites

In this work, carbon nanotubes pillared grew on exfoliated graphite by the microwave-assisted method is utilized as thermally conductive fillers (CPEG) in polyimide (PI) to fabricate CPEG/PI thermally conductive composites with the combining ways of in-situ polymerization, electrospinning, lay-up, and hot-pressing. The prepared CPEG/PI composites realized the maximum thermal conductivity (lambda, 1.92 W m(-1) K-1) at low CPEG amount (10 wt%), much higher than that of pure PI (0.28 W m(-1) K-1). The lambda of CPEG/PI composites show almost no change after 1000 cycles of heating and cooling at the temperature of 25-100 degrees C. The finite element analysis simulates the nano-/microscale heat transfer in CPEG/PI composites to reveal the internal reason of the lambda enhancement. The improved thermal conductivity model and empirical equation could better reflect the actual lambda change trend of CPEG/PI composites. The actual application test shows the CPEG/PI composites could significantly reduce the operating temperature of the CPU in mobile phone.

Automated summary

In this study, carbon nanotubes pillared on exfoliated graphite by the microwave-assisted method are used as thermally conductive fillers in polyimide to fabricate composites with significantly improved thermal conductivity. The composites show high stability even after repeated heating and cooling cycles, and finite element analysis reveals the internal mechanism of the enhanced thermal conductivity. Actual application tests demonstrate the composite's capability to reduce the operating temperature of mobile phone CPUs.