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The crystallization behavior of a polyamide 6/organo‐modified montmorillonite (PA 6/OMMT) nanocomposite has been investigated by scanning chip calorimetry and wide‐angle X‐ray scattering, with emphasis placed on the evaluation of the effect of supercooling/cooling rate on the crystal/mesophase polymorphism of the PA 6 matrix. Presence of OMMT has negligible effect on the kinetics of formation of α‐crystals of PA 6 at low cooling rate while there is observed enhanced nucleation of γ‐mesophase on fast cooling. Furthermore, addition of OMMT leads to a distinct increase of the cooling rate required to completely vitrify the amorphous state. The performed experiments demonstrate that the nucleating effect of OMMT in PA 6/OMMT nanocomposites is of particular importance at cooling conditions relevant in polymer processing. magnified image

Polypropylene (PP) is a widely used thermoplastic and polymorphic polymer. Three different types of PP were prepared, namely non-nucleated, -and -nucleated PP. These materials were pressed using different cooling rates to influence the degree of crystallinity within the materials, which was determined by differential scanning calorimetry (DSC). The materials resistance against stable crack propagation was described by R-curves. The J d -a curves were determined using the instrumented Charpy impact test (ICIT) to apply single edge notch bending specimens (SENB) with a high loading velocity. The results show not only the influence of the cooling rate on the degree of crystallinity but also a correlation between the degree of crystallinity and the materials resistance against stable crack propagation. The lower the cooling rate of the material is the higher is the degree of crystallinity and the higher seems to be the materials resistance against stable crack propagation.

The aim of this work was to characterize the fracture behavior of polyamide 6 (PA6) and PA6 reinforced with clay (organically modified montmorillonite) [PA6/OMMT] at different temperatures and under higher loading rate. Pure PA6 and PA6 with different amounts and two types of OMMT were investigated. The structure and morphology of the nanocomposites were analyzed by X-ray diffraction technique and transmission electron microscopy. The fracture behavior was evaluated using the instrumented Charpy impact test at different temperatures starting from À30 C up to 50 C. To determine the fracture toughness K Id at higher temperatures, the equivalent-energy concept was used. Based on the J-value versus temperature diagrams, the brittle-to-tough transition temperature T BTT of the materials was determined. It was found that the crack toughness as a function of temperature and the T BTT are influenced by the content of OMMT and the morphology. There are indications that at low OMMT contents, the deformation behavior is dominated by the matrix properties. With increasing filler content, the influence of the nanostructure on T BTT increases. The crack toughness of the nanocomposites with an intercalated morphology is higher than that of exfoliated ones, due to additional energy-dissipating mechanisms.

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