Unraveling the Localization Behavior of MWCNTs in Binary Polymer Blends Using Thermodynamics and Viscoelastic Approaches

Using thermodynamics and viscoelastic approaches, the present work evaluated the localization of multi-walled carbon nanotubes (MWCNTs) in binary polymer blends with matrix/dispersed morphologies from pairs of poly(methyl methacrylate) (PMMA), polystyrene (PS), and polypropylene (PP). Thermodynamic predictions suggested that the MWCNTs should preferentially localize at the blend interface for all the nanocomposite samples. However, viscoelastic measurements showed that the MWCNTs localize elsewhere in the binary blend samples, either in the matrix, the droplets, or both; this suggests that the thermodynamic parameters were not the only ones at work. Linear viscoelastic experiments showed that the affinity toward the individual polymers was in the following order PS >> PP >PMMA. Furthermore, it was shown that the dispersive mixing of the MWCNTs in the blend components was mainly controlled by the rheological properties. This was further confirmed by start-up experiments, electron microscopy, and dynamic mechanical analysis. Therefore, the kinetic parameters needed to be considered in determining where the MWCNTs eventually ended up in the binary polymer blends. (C) 2016 Society of Plastics Engineers