High performance differential scanning calorimetry (HPer DSC): A powerful analytical tool for the study of the metastability of polymers

The crystallization and melting behavior of polypropylene (PP), polyoxymethylene (POM) and polyamide-6 (PA6) has been investigated by means of varying the cooling and heating rates using a high performance differential scanning calorimeter (HPer DSC). The influence of the sample mass and scan rate on thermal lag has been sorted out and the importance of making proper corrections is stressed. By varying the cooling rates from 5 to 250 °C/min in combination with one particular heating rate (10 and 300 °C/min have been used) reorganization and especially recrystallization effects in a PP sample have been examined. Recrystallization of the PP can be avoided by using a high heating rate (300 °C/min). The influence of incorporating a stabilizer acting as a comonomer in the POM chain on the kinetics of the crystallization and melting behavior is studied. The influence of the maximum heating temperature in the melt on crystallization of POM and of POM with stabilizer is investigated by self-seeding experiments using high heating and cooling rates. Furthermore, the melting behavior of PA6, where several transitions take place during heating which are up to now not fully understood, is discussed subsequent to cooling at 5–300 °C/min. Throughout it has been made clear that it is important to have the capability of applying proper combinations of low/high and cooling/heating rates in order to examine the metastability of polymer systems and the related kinetics of transitions, to scrutinize the phenomena seen and to arrive at the right explanations.