Structural Optimization of Polyimide Foam via Composition with Hyperbranched Polymer Modified Fluorinated Carbon Nanotubes

The key to improve the foam’s performance is to optimize the cellular structure and its bulk-material composition. Here, the hyperbranched polymer modified fluorinated multi-walled carbon nanotube (HPMCNT-F) based on the nucleophilic reactions of MCNT-F was successfully prepared and used to composite with PI foams. The pristine MCNT shows a poor dispersity and weak interfacial interaction with PI matrix. While HPMCNT-F exhibits an excellent dispersity and effectively forms covalent/non-covalent interaction with PI matrix due to the surface-structure engineering, resulting in the enhancement of the PI bulk. Furthermore, HPMCNT-F works as a heterogeneous nucleation agent in PI foam to optimize the cellular structure. The enhancement of PI bulk and the optimizing of cellular structure result in the increase of compressive special strength of composite foam by 58.9% with a low loading of 1.6 wt% HPMCNT-F. Moreover, the hyperbranched polymers effectively prevent the thermal conduction among HPMCNT-F, and the isolated MCNTs effectively block thermal radiation through absorption and reflection the infrared waves. Thus, the thermal conductivity was reduced by 8.0% simultaneously.