For Polybutylene Terephthalate (PBT) it is known that if you cool it down at fast rates to have an additional melting Peak in DSC-Scans.
Androsch et al. (2015) conclude that this is due to different nucleation mechanisms depending on the cooling rate. If you cool down slowly the Polymer will crystallize at one big Peak at ~225°C. The spherulites are heterogenous. At faster Rates, there is a second nucleation mechanism, thats faster and the nucleation density is also much higher by a factor of 10^9. Thus it is a homogenous crystallisation. If this happens you can see a small but noticeable Peak at temperatures below 225°C (in my case at 140°C).
Androsch et. al state that the smaller Peak has the same crystalline Structure (alpha) as the bigger Peak, so the location of the smaller peak has to come from the nucleation density (spherulite size) mainly.
My Question now is whether there are any known dependencies of the melting Point of a spherulite on its size. Or to put it in another way: Why has the smaller Peak a smaller melting Temperature in DSC-Scans even though it has the same crystalline structure?
Cornelius Betz
Yes, there is a quantitative theory of the relationship between the phase transition temperature and the dispersity of particles (spherulites). By analyzing the dependence of the Gibbs energy on pressure and temperature, one can easily derive an equation relating the melting temperature and the radius of nanoparticles - it is called the Gibbs–Thomson equation.
https://him.1sept.ru/article.php?ID=200901702