Research progress of filled-type high-thermal-conductivity flexible polyimide composites: a review

Polyimide (PI) has been widely used to manufacture flexible films in aerospace, electronics and other fields because of its flexibility, thermal resistance, etc. However, the thermal conductivity of PI is relatively low, restricting the wider applications of PIs. This review discusses the research progress during recent five years in the preparation of filled-type PI composites with high thermal conductivity and flexibility. In addition, this review introduces four types of fillers, including boron nitride, graphene (or graphite oxide), carbon nanotubes and carbon nitride, as well as four popular preparation methods, the arrangement and surface modification of fillers, the microstructure design of composites and the synergistic effect of different fillers, and explicitly explains the different action mechanisms between them. These methods provide suggestions to balance the relationship amongst thermal conductivity, flexibility and mechanical properties of preparing filled-type PI composites. In addition, this article also introduces the current application status and future prospects of PI composite materials in advanced materials.