Polyimide-based composites reinforced by carbon nanotube-grafted carbon fiber for improved thermal conductivity and mechanical property

This paper describes a method to improve the thermal conductivity, mechanical properties and thermal dimensional stability of polyimide-based composites by rationally introducing carbon nanotubes (CNT) chemically-grafted-carbon fiber CF into the polyimide matrix via an ice-templating strategy followed by hot-pressing. The grafted CNT onto CF surface (CNT@CF) significantly increased the roughness of the smooth surface of carbon fiber, improving the interfacial compatibility between CNT@CF and PI matrix and resulting in improved thermal conductivity and tensile strength as well as the dimensional stability. Typically, the PI/CNT@CF20 composite containing 20 wt% CNT@CF exhibits an in-plane thermal conductivity of 4.25 W m−1 K−1, 1134% enhancement compared to the pure matrix (0.34 W m−1 K−1). Meanwhile, the PI/CNT@CF20 composite also presents an increased tensile strength (130 MPa), ∼18 MPa and ∼58 MPa higher than that of PI/CF20 composite (102 MPa) and pure PI (72 MPa), respectively. Besides, the resulting composites exhibit a gradually reduced coefficient of thermal expansion (CTE), which decreases from 66.7 ppm K−1 to 24.7 ppm K−1 as the content of CNT@CF increasing from 0 to 20 wt%. Interestingly, the PI/CNT@CF composites also show good Joule heating performances at low driving voltages. Accordingly, the developed polyimide-based composites demonstrate high potential as advanced thermal management materials with excellent mechanical properties.