Influence of clay mineral structure and polyamide polarity on the structural and morphological properties of clay polypropylene/polyamide nanocomposites

Abstract

The influence of the clay mineral structure and of the polyamide dispersed phase polarity on the structure and morphology of polypropylene/polyamide blends filled with clay mineral nanoparticles was investigated. Two polyamides (PA) were used: a polar PA6 and a less polar PA12. The clay mineral nanofillers used were either organically modified montmorillonite (Mt) or synthetic talc (ST), having preferential affinity towards PA dispersed phase. For all clay polymer nanocomposites (CPN), a decrease of PA nodule size was observed. However, the mechanisms governing the morphology establishment were shown to depend mainly on the clay structure, and also on the polyamide polarity. Mt nanoparticles were shown to be mostly located at the interface, forming a nanocomposite interphase. The decrease of PA nodule size induced by Mt nanoparticles was attributed to coalescence inhibition by steric repulsions, mediated by the interphase, which is more developed in the case of PA6. Besides, the interphase was shown to play a key role in the change from a nodular to a non-nodular morphology, even at low Mt fractions. ST particles were shown to be exclusively dispersed within PA nodules. In this case, nodule size reduction was attributed to the presence of some larger ST particles, exhibiting numerous structural defects, which favor the nodule break-up, especially in the case of PA12.