Self-assembled rectorite films with remarkable mechanical performance: preparation, structural characterization and properties

Abstract

Cohesive flexible rectorite clay films with good mechanical performance were prepared by a simple casting method through self-assembly of exfoliated natural clay from aqueous dispersions. The multi-layered microstructure of the films consisted of continuous layers of aligned clay platelets parallel to the casting surface. Layers overlap randomly in lateral direction (plane) and join vertically in irregular manner by edge to face cross-linkages (bridging) to form coherent multi-layered nanostructured films with platelet-void microstructure. The films with highest mechanical properties had thickness below 30 µm. Overall films from rectorite clay with monovalent interlayer content exibited a higher experimental tensile strengths ranging up to 44 MPa and Young’s modulus up to 56 GPa. The corresponding experimental values for films with divalent interlayer cations were 23 MPa for strength and 25 GPa for modulus. The highest experimental values for strength and modulus for neat Na-Ca-rectorite films were 25 MPa and 50 GPa respectively. The mechanical property values of the rectorite-based clay films compare favourably with values featured by polymer films typically used for packaging applications.