Hybrid carbon nanotube-silica/polyvinyl alcohol nanocomposites films: preparation and characterisation

Composites of carbon nanotubes (CNT) in polymeric matrices have attracted considerable attention in the research and industrial communities due to their interesting and unique properties. However, the main intrinsic problem of CNT is their insolubility or very poor solubility in either water or organic solvents. Therefore, the dispersion of CNT has become the focus of many researches. In this study, a simple method based on a chemical process was developed in order to improve the dispersion of CNT. Our method consists in grafting carboxylic acid-functionalized carbon nanotubes (CNT-COOH) onto an amino-functionalized silica particles (SiO2-NH2) surface. Prior to assembly, CNT-COOH were prepared by using a mixture of concentrated nitric and sulfuric acids, while SiO2-NH2 were prepared by a silanization with 3-aminopropyltriethoxysilane (APTES). The hybrid carbon nanotube-silica (CNT/SiO2) was dispersed in polyvinyl alcohol (PVA) with 1, 3 and 5 wt% (by weight). Techniques including scanning electron microscopy (SEM), transmission electron microscopy (TEM) and differential scanning calorimetry (DSC) measurement have been employed to study the dispersion state in the polymer matrix. The results indicated a good and uniform dispersion of hybrid fillers. Indeed, it was shown that the silica particles play the role of dispersing agents. In addition, a decrease of the resistivity of the composite films was observed as the concentration of CNT-silica fillers in the PVA increases, reaching 3.4 x 10(3) Omega.m when the hybrid fillers concentration is equal to 5 %.