EFFECT OF CLAY MODIFICATION ON THE MECHANISM OF LOCAL DEFORMATIONS IN PA6 NANOCOMPOSITES

Dominkovics, Zita and Naveau, Elodie and Jérôme, Christine and Hári, József and Renner, Károly and Móczó, János and Alexandre, Michaël and Pukánszky, Béla (2013) EFFECT OF CLAY MODIFICATION ON THE MECHANISM OF LOCAL DEFORMATIONS IN PA6 NANOCOMPOSITES. MACROMOLECULAR MATERIALS AND ENGINEERING, 298 (7). pp. 796-805. ISSN 1438-7492

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Abstract

PA nanocomposites were prepared from clays organophilized with a phosphonium and an ammonium salt, respectively. Sodium montmorillonite was used as reference. The composites were homogenized by twin-screw extrusion followed by the injection molding of specimens. The clay content of the composites changed from 0 to 7 vol% in 7 steps. Micromechanical deformations were characterized by volume strain and acoustic emission measurements and the mechanism of local deformation was studied by SEM. The analysis of mechanical and micromechanical properties revealed that several micromechanical deformation processes occur in the PA/MMT composites investigated. The matrix cavitates at relatively small stress. Processes related to non-exfoliated clay structural units, particles or tactoids, are initiated at larger stresses. Sound is emitted mainly by the fracture of particles, but debonding may also occur with the emission of sound. The plastic deformation of the matrix dominates at larger stresses and deformations. The various local deformations are independent of each other and composite properties are not determined by silicate related processes, but by the deformation of the matrix. The modification of clay influences all processes in smaller or larger extent, the key factors are exfoliation and interfacial adhesion, a proper combination of which leads to considerable reinforcement.

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