Crystallization of a polyamide 11/organo-modified montmorillonite nanocomposite at rapid cooling

Abstract

Fast scanning chip calorimetry (FSC) has been used for analysis of the crystallization behavior of a polyamide 11/organo-modified montmorillonite (PA 11/OMMT) nanocomposite. The addition of OMMT leads to a significant increase of the crystallization temperature of the polymer matrix only on cooling faster than about 100 K s–1. In case of slow cooling at rates typically used in standard differential scanning calorimetry (DSC), the nucleating effect of OMMT on crystallization of PA 11 is negligible. The critical cooling rate to suppress crystallization of PA 11 and to completely vitrify the relaxed melt increases at least by one order of magnitude due to the addition of OMMT. Furthermore, the enthalpy of crystallization is nearly independent on the cooling conditions in the analyzed cooling rate range from 10–2 to 2 × 103 K s–1 in PA 11/OMMT nanocomposites. Isothermal crystallization experiments confirmed that the nucleating effect of OMMT on the crystallization of PA 11 increases with supercooling, being therefore of particular importance at cooling conditions relevant in polymer processing. The evaluation of the kinetics of crystallization of the PA 11/OMMT nanocomposite by FSC and DSC in a wide range of cooling rates/supercooling has been completed by analysis of the effect of OMMT on the α/δ’ polymorphism of PA 11 and the spherulitic superstructure.