Non-aqueous colloidal processing route for fabrication of highly dispersed aramid nanofibers attached with Ag nanoparticles and their stability in epoxy matrixes

Abstract

Abstract In order to achieve the one-dimensional alignment of Ag nanoparticles (NPs) in epoxy resins, a simple technique to attach Ag NPs on aramid nanofibers (ANFs) and then to disperse the prepared Ag NP/ANF composites in epoxy resins and their processing solvents has been established. To facilitate the attachment of Ag NPs on ANFs and the stabilization of the Ag NP/ANF composites, the surface of the Ag NPs was modified with polyethyleneimine (PEI) and an anionic surfactant that branches into alkyl- and polyethylene glycol-based chains, which improved the stability of the NPs in various solvents and polymers. The prepared Ag NPs were then dispersed into ethanol or toluene and mixed with an ANF suspension prepared in dimethyl sulfoxide (DMSO) with the assistance of ultrasonication. The effect that the solvents and the Ag NPs/ANFs ratio, during the mixing procedure, had on the morphology and stability of the prepared Ag NP/ANF composites was investigated. It was found that Ag NPs could attach on ANFs without forming strong aggregates, when ethanol was chosen as the solvent. An increase in the average diameter of the Ag NPs attached on the ANFs was observed as the relative number of Ag NPs increased; this could be due to the dissolution and reduction of Ag + during the ultrasonication treatment, assisted by the PEI layer on the Ag NPs. The prepared Ag NP/ANFs were found to be dispersible in epoxy/toluene mixtures and epoxy resins, and their long-term stability (>3 days) was ensured when the suspension viscosity was controlled at >1.7 Pa s.