Multifunctional materials based on iron/iron oxide-filled carbon nanotubes/natural rubber composites

This work describes the synthesis, characterization and study of properties of novel multifunctional composite materials obtained by natural-rubber latex and a special kind of multi-walled carbon nanotube (CNT), in which the cavities are filled by magnetic species. To prepare stable aqueous dispersions of CNTs, two approaches have been employed, based on a mixture of the surfactant sodium dodecyl sulfate or a previous treatment with a mixture of acid solutions. The composites have been characterized by infrared and Raman spectroscopy, X-ray micro-tomography, transmission and scanning electron microscopy, and atomic and magnetic force microscopy. A good adhesion between the CNTs and the polymer matrices was obtained. Several samples have been prepared containing different amounts of CNTs (from 0.01 to 10 wt.%), and the effect of carbon nanotubes in the electrical, mechanical, chemical and thermal properties of the composites was evaluated by thermogravimetric analysis, resistivity measurements, stress–strain mechanical tests and solvent sorption measurements. The occurrence of networks of CNTs in the polymeric matrices provided significant increases in all of these properties. Additionally, because of the species encapsulated in CNT, the composites exhibit magnetic behavior, confirmed by magnetic force microscopy. This approach results in novel multifunctional material with great potential for further applications.