Concentration‐Dependent Lamellar Organization and Structure–Property Relationships in Melt‐Processed EVA /Cloisite 20A Nanocomposites

Abstract

ABSTRACT The effect of Cloisite 20A content (0–7.5 wt%) on the structural organization and thermomechanical behavior of melt‐processed EVA nanocomposites was systematically evaluated, with emphasis on clay dispersion and lamellar arrangement. X‐ray diffraction revealed a concentration‐dependent shift of the (001) peak, indicating a transition from highly disordered lamellae at low clay loadings to predominantly intercalated structures with partial restacking at higher concentrations. Transmission electron microscopy corroborated this evolution, showing more dispersed platelets at 2.5% and increased tactoid formation at 5.0% and 7.5%, confirming the progressive reorganization of the silicate galleries during processing. Differential scanning calorimetry showed that the EVA melting temperature remained essentially unchanged, whereas crystallinity was strongly influenced by clay morphology. At low and intermediate loadings, restricted chain mobility was observed, whereas at higher concentrations a nucleating effect occurred, associated with increased interfacial density. Thermogravimetric analysis confirmed the preservation of the dual degradation mechanism, with slight shifts in characteristic temperatures due to interfacial effects. Young's modulus increased with clay addition, while tensile strength and ductility exhibited moderate reductions. Overall, the results demonstrate that nanostructural organization governs the balance among stiffness, thermal stability, and toughness, defining an optimal compositional window.