AUTHORS: Bouchra Safadi, Rodney Andrews, Frank Derbyshire
Center for Applied Energy Research, University of Kentucky, Lexington, KY 40511-8410
The inclusion of multiwalled carbon nanotubes (MWNTs) in polymer matrices greatly enhances the physical properties and electrical conductivity of the formed composites. In this work, MWNTs were dispersed in matrices of polystyrene (PS) or polyfurfural (PFF) resin at concentrations of up to 7.5 wt$\%$. The tensile strength, elastic modulus, strain to failure and electrical conductivity of the resulting composites were measured for various MWNT loadings. Uniform dispersion of the MWNTs into the matrix proved to be a critical factor, with optimal property enhancement achieved by dispersion in which the nanotube bundles were separated and dispersed.
The PS films were transformed from an insulating to a conductive material, with conductivities approaching 1 ohm$^{-1}$ cm$^{-1}$. The properties of the PFF-MWNT composites were similarly changed. This increase in composite conductivity increased with increasing MWNT loading and nanotube dispersion for both matrices.
The addition of MWNTs to the PS films approximately doubles both the tensile strength and the stiffness at about 5$\%$ MWNT loading. While blank PS samples fail plastically, the MWNTs-PS composites show little plastic deformation on failure, indicating a stiffening of the composite with nanotube inclusion. In contrast, for the brittle PFF matrix, improvements to the polymer flexibility (65$\%$ reduction in flexural modulus) were observed. It is tentatively concluded that the properties of the MWNTs dominate those of the matrix in determining the composite material behavior.