Relations between structure and property of polyamide 11 nanocomposites based on raw clays elaborated by water-assisted extrusion

Bio-based polymers and polymer nanocomposites have known an increasing interest during the past few years. This work is focused on the elaboration and the characterization of bio-based nanocomposites made from polyamide 11 (PA11) and nonorganomodified montmorillonite. To elaborate these materials an original elaboration process, consisting in injecting water during the extrusion, was used. Results show that thanks to this process, a well exfoliated morphology is obtained for clay contents as high as 10% wt. This was explained on the one hand by the fact that the clay is soluble in water and on the other hand by the fact that water and PA11 are miscible at high pressure and high temperature. Moreover, the morphology analyses have revealed that from 10% wt of clay, the platelets were not totally randomly distributed but they were rather organized at a mesoscopic scale. The obtaining of such clay's dispersion involves an enhancement of thermomechanical properties. For example, for a clay content of 10% wt, the Young's modulus of the material can be doubled and its degradation temperature increased. The role of the elaboration conditions on the morphology and subsequent properties of the nanocomposites are also carefully analyzed. Finally, it has been evidenced that the presence of the filler infers on both the crystalline form induced and the crystallization kinetics. In summary, this study demonstrates that, in the case of PA11 nanocomposites, the water-assisted injection process leads to the achievement of an exfoliated morphology for clay contents as high as 10% wt that allows to obtain high performance materials and to be free from using organomodified clays. (c) 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013