Epoxy/layered double hydroxide nanocomposites: investigating the influence of preparation method on mechanical properties

This study investigates the macro- and micromechanical properties of epoxy-based nanocomposites containing Mg-Al/NO₃ layered double hydroxides (LDHs), with a comparative evaluation of two preparation routes: solvent-exchange and direct drying from an aqueous LDH slurry.,LDHs were characterised using atomic force microscopy (AFM), scanning transmission electron microscopy, and X-ray diffraction methods. Tensile tests and AFM nanomechanical mapping were used to obtain the macro- and micromechanical properties of LDHs/epoxy nanocomposites, respectively. Both preparation methods resulted in nanocomposites with comparable mechanical performance. Young’s modulus exhibited a significant increase at lower LDHs loadings. The ultimate tensile strength remained largely unchanged compared to pure epoxy. However, a notable reduction was observed at higher content of LDHs, which is attributed to the aggregation of the particles, as shown by scanning electron microscopy and energy-dispersive X-ray spectroscopy. The mechanical response and stiffness maps obtained by the peak force AFM nanomechanical mapping revealed that nanocomposites prepared using the solvent-exchanged LDHs samples exhibit significantly narrower interface widths and higher stiffness compared to those made by the conventional approach, indicating improved interfacial bonding and mechanical performance.