Comparison of PA6 and PA66 crystallization using modified FSC

PA66 and PA6 share many comparable properties due to their similar chemical structures. However, their crystallization kinetics differences are not received similar attention as their other properties. With the advent of the modified FSC, non-damaging spectroscopy and morphology characterization can be performed in addition to the calorimetry analysis. The polymorphs, crystallization kinetics, and morphology of two polyamides are studied in a wide crystallization temperature span. Time-temperature-transformation (TTT) diagrams of PA66 and PA6 are built to compare their crystallization behaviors. It is noted that the crystallization rate of PA66 is always faster than PA6 in the entire crystallization temperature range. The nodular–spherulitic morphology transition takes place at a higher temperature of 135°C in PA66 than 120 °C in PA6. The use of the TTT diagram also successfully predicts the impact of different crystallization pathways on their final morphology. With increasing cooling rate from 10K/s to 3000K/s, both polyamide samples experience gradual morphological changes from spherulitic, spherulitic/nodular, spherulitic/amorphous, and full amorphous. The different morphologies are further investigated by μFTIR and calorimetry analyses.