Characterization of carbon nanotube dispersion and filler network formation in melted polyol for nanocomposite materials

• CNTs were dispersed in melted polyol without solvent by ultrasonication.
• CNTs with highly porous microstructure show improved nanoscale dispersion.
• CNTs with lower bulk densities show improved microscale dispersion.
• CNTs with high aspect ratio and good nanoscale dispersion form strong 3D networks.
• Network quality can be probed by rheology, thermogravimetry and sedimentation.

Different grades of carbon nanotubes (CNTs) were dispersed in poly(tetramethylene ether glycol) (PTMEG) without any solvent in the presence of a block copolymer dispersing agent by ultrasonication at a temperature well above the melting point of the PTMEG. The state of CNT dispersion at different length scales was evaluated by using optical microscopy, UV–Vis spectroscopy, rheological measurements, differential scanning calorimetry, thermogravimetric analysis and sedimentation tests. Optical microscopy can be used to characterize the state of dispersion and CNT network formation on a micrometer scale, whereas UV–Vis provides useful information about the dispersion of individual CNTs at nanoscale. Furthermore, the strength and quality of the network formed can be assessed using different modes of rheological measurements. Dispersion at nanoscale also affects the crystallization behavior of PTMEG, while network formation strongly influences suspension thermal stability and sedimentation behavior. The results obtained using different methods indicate equivalence between UV–Vis spectroscopy, rotational rheometry and PTMEG crystallization behavior for probing the CNT state of dispersion at nanoscale, while an analogy in detection of CNT network formation and strength is observed between oscillatory rheometry, thermogravimetric analysis and sedimentation tests.

Figure optionsDownload as PowerPoint slide