A versatile approach to prepare layered silicates composites: the case of sepiolite nanofibers

The development of high-performance polymer nanocomposites (NCs) requires a strong interfacial interaction between filler and polymer matrix and an optimal filler nanodispersion. Among layered silicates, sepiolite has attracted researcher attention because of its easy availability, low cost, strong mechanical and chemical stability, and anisotropic particle shape. Even if several applications of sepiolite-polymer materials have been proposed in literature, the use of pristine sepiolite as filler in elastomers is very limited due to its hydrophilic surface and to the consequent low affinity towards polymers. To face with these issues, we explored a new approach to prepare rubber NCs based on the use of nano-sized sepiolite (NS-Sep) fibers. Pristine and organically-modified sepiolites were structurally modified by an acid treatment, which provides NS-Sep fibers with reduced particle size and increased silanol groups on the layer surface, preserving the anisotropic features. NS-Sep fibers were used to prepare by ex-situ blending styrene-butadiene rubber (SBR) NCs. Morphological, spectroscopic, thermal and mechanical analyses were performed for a complete characterization of the hybrid materials.