Viscoelastic behavior of nanotube-filled polycarbonate: Effect of aspect ratio and interface chemistry

A combined experimental and modeling study on the solid-state rheology of multi-walled carbon nanotube (MWNT)/polycarbonate composites as a function, independently, of MWNT aspect ratio and interface chemistry was carried out. Shorter aspect ratio nanotubes lead to greater broadening of the loss modulus peak in frequency space, but there was no effect of aspect ratio on the glass transition temperature. The breadth of the loss modulus peak was found to correlate with the free space parameter, a measure of the spacing between the MWNTs. A new model that accounts for the aspect ratio and distribution in a representative volume element was developed to study these parameters in a controlled setting where morphology was precisely known. Micromechanics modeling was found to correlate well with experimental data. These results shed light on the separate impacts of aspect ratio, dispersion, and interface modification on the solid-state rheology of nanofilled polymers.