Phase transitions in Nylons 8, 10 and 12 crystallized from solutions

The peculiar structural modifications of Nylons 8, 10 and 12 prepared by crystallization from solutions and reported as α*, were studied by differential scanning calorimetry (DSC) and thermomicroscopy, supported also by some X‐ray diffraction (XRD) measurements. The results indicate that the phase transition shown by the α*‐forms of the Nylon 8–12 series exhibits the characteristics of a melting immediately followed by crystallization into γ‐form, rather than of a α* → γ solid‐solid transition. When the γ‐crystallization is concluded, the melting of this form takes place. DSC and XRD data demonstrate that the α* → γ transition is irreversible. The changes in the DSC traces of the Nylon 8 – 12 series were interpreted as indicative of a gradual stability increase of the α‐form in comparison with the corresponding α*‐form, depending on the increase of the number of methylene groups in the repeating unit.