Constructing fully carbon-based fillers with hierarchical structure to fabricate highly thermally conductive polyimide nanocomposites
Thermal conductivity enhancement of polymer composites by adding single kind of carbon-based fillers is still at the price of reducing mechanical properties. In this study, a novel kind of fully carbon-based fillers (f-MWCNT-g-rGO) is constructed by a reaction between amino functionalized multi-walled carbon nanotubes (f-MWCNT) and graphene oxide (GO) followed by chemical reduction. The highly thermally conductive polyimide nanocomposites (f-MWCNT-g-rGO/PI) are fabricated through the combining method of in-situ polymerization, electrospinning and hot pressing. UV-vis spectrum, Raman, TGA, XPS, XRD, TEM and AFM characterizations all demonstrate the f-MWCNTs-g-rGO nanocomposites have completed hierarchical “line-plane” structure, and f-MWCNT contacts with rGO by chemical interaction. The fabricated f-MWCNT-g-rGO/PI nanocomposites possess outstanding thermal conductivity coefficient (λ), high glass transition temperature (Tg) & heat resistance index (THRI) and excellent mechanical properties. The f-MWCNT-g-rGO/PI nanocomposites reach the maximum λ of 1.60 W/mK and the λ enhancement is about 490% at a low f-MWCNT-g-rGO loading of 10 wt% while the mass ratio of rGO to f-MWCNT is 2:1. In addition, an improved thermal conduction model that more fits the experimental λ is established while comprehensively considering the interfaces, fillers alignment, etc. Owing to the highly thermal conductivities while preserving good mechanical properties and thermal stabilities at low fillers loading, the f-MWCNT-g-rGO/PI nanocomposites expected to be used as thermal pads in LED substrates and liquid crystal displays.