Miscibility and properties of acid-treated multi-walled carbon nanotubes/polyurethane nanocomposites

Abstract

Nanocomposites based on polyurethane and acid-treatment multi-walled carbon nanotubes (A-MWNTs) are prepared by solution blending. The surface of the MWNTs was modified by acid treatment to incorporated functional groups. The modified MWNTs exhibited improved dispersion in organic solvents and miscibility with the PU matrix. The derivatives of MWNTs were characterized by Fourier transform infrared (FT-IR) spectroscopy, Transmission electron microscopy (TEM) and Raman spectroscopy. The thinning and defects of the A-MWNT from the surface etching of acid treatment can be clearly seen from TEM pictures and Raman spectra, respectively. The interaction and degree of miscibility between the MWNTs and the PU matrix is examined using FT-IR, modulated differential scanning calorimeter (MDSC), TEM and atomic force microscopy (AFM). The hydrogen bonding index (HBI) measured by FT-IR was employed to show the degree of interchange hydrogen bonding. Composites films with higher A-MWNT content exhibit higher HBI and the degree of miscibility is significantly improved. The resultant composites have higher tensile strength, higher Young's modulus and lower elongation at break because of the rigid structure of A-MWNT and the increase in the number of hydrogen bonds among the composites. Incorporating A-MWNT in composites increases the mass of the residue at temperatures over 600°C, according to thermo gravimetric analysis (TGA). An A-MWNT percentage of 20 wt %, the electric conductivity approached 6.2 × 10-2S/cm. © 2006 The Society of Polymer Science, Japan.