Effect of matrix polymer viscosity on nanofiller exfoliation during compounding

The functionality of carbon nanotube (CNT) composite materials relies on good CNT dispersion within the polymer matrix. Current CNT dispersion enhancement methods involve the use of organic solvents. However, the mass production of polymer-CNT composites requires more cost effective and environmentally friendly methods. Specifically, the defibration and dispersion of CNTs via the dry kneading process is a promising alternative approach. This study investigated the effect of the viscosity of the matrix polymer (polycarbonate, PC) on CNT defibration and dispersion during the dry processing of a polycarbonate-CNT composite. The importance of shear force and wettability as factors affecting CNT dispersion in the polycarbonate-CNT composite were evaluated. The results suggested high conductivity in PCs with low molecular weight and low viscosity, and the defibration of CNTs proceeded predominantly. Consequently, the wettability was more important for the defibration of CNT than the high shear force, and the CNT defects increase on account of the high shearing force in PCs with high viscosity. Further, this study established the pretreatment of the PCs and CNTs using supercritical CO2 as a promising alternative to organic solvent-based pretreatments. The results provide a guideline for the selection of the CNT matrix and increase the number of CNT matrix options.