Micromechanical deformation processes in PA/layered silicate nanocomposites: Correlation of structure and properties

Abstract

AbstractPolyamide/organophilic montmorillonite nanocomposites were prepared from two silicates with different organophilization resulting in strong and weak matrix/silicate adhesion, respectively; uncoated sodium montmorillonite was used as reference. The silicate content of the composites changed between 0 and 10 vol% in seven steps. Composite structure was characterized by X‐ray diffraction and electron microscopy. Micromechanical deformation processes were followed by acoustic emission and volume strain measurements. The structure of the composites is more complicated than usually claimed; they contain individual silicate platelets, tactoids with different degree of intercalation, and larger particles. Elastic deformation and shear yielding dominates during the elongation of the specimens. The matrix polymer and the composites deform according to different mechanisms. Sound is emitted by cavitation in the former, while sound emitting processes are related tactoids and nonexfoliated particles in the composites. Acoustic events are generated mainly by the fracture of the particles. Matrix/silicate adhesion seems to be strong, debonding rarely takes place, and volume increase is initiated primarily by particle failure. The type and amount of the surfactant used for organophilization plays an important role in the determination of deformation processes and properties, since it influences both matrix/filler interaction and the inherent strength of the particles. POLYM. ENG. SCI., 47:1235–1245, 2007. © 2007 Society of Plastics Engineers