Effects of dispersion techniques of carbon nanofibers on the thermo-physical properties of epoxy nanocomposites

The influence of the dispersion states of carbon nanofibers (CNFs) on the structure and thermo-physical properties of the epoxy nanocomposites has been investigated. Two main different methods for dispersion of nanoreinforcements into an epoxy matrix have been tested: (1) directly mixing the CNFs and the epoxy monomer and (2) previous addition of CNFs to a solvent to produce a stable suspension which later was mixed with the epoxy resin. For it, solvents of different nature were tested. Also, several dispersion techniques were evaluated, such as high shear mechanical stirring and sonication at high frequency. In order to improve the compatibility with epoxy matrix, CNFs were amino-functionalizated through the acid-thionyl chloride way.It was found that the experimental conditions applied for CNFs dispersion are critical to obtain homogeneous nanocomposite. It was probed that it is necessary to carry out several stages of CNFs dispersion, including the chemical modification and functionalization of CNFs, the dilution of non-cured epoxy/CNF mixture into a relative polar solvent and to combine different dispersing techniques (magnetic stirring, high shear mixing and sonication) for relative long periods of time at high temperature. In this way, homogeneous nanocomposites were manufactured with important increases of storage modulus.