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Clay distribution and crystalline structure evolution in polyamide 6/montmorillonite composites prepared by activated anionic polymerization



Nanostructured polymer composites (NPC) based on polyamide 6 (PA6) are prepared by activated anionic ring-opening polymerization (AAROP) of mixtures of ε-caprolactam (ECL) and organically treated montmorillonite (o-MMT). The polymerization is performed in bulk, at 165°C, i.e., below the melting point of the resulting APA6, the reaction time being in the range of 10–15 min. The o-MMT content is varied in the 0.5–10% range. X-ray diffraction (XRD) and transmission electron microscopy (TEM) show that exfoliated NPC can be produced with clay loads of 0.5–1.0%. Larger clay amounts lead to various degrees of intercalation of the MMT layers. FT-IR imaging proves that all NPCs contain MMT aggregates with sizes in the 10–20 µm range. The formation of the matrix crystalline structure is followed directly by performing AAROP of an activated ECL/o-MMT blend in a synchrotron beamline. Irrespective of the o-MMT type and concentration, it is the α-PA6 that forms first and in larger amounts. The γ-PA6 polymorph can be found in predominating amounts only after melting and recrystallization of the already produced polymer matrix. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1228-1238, 2013