Stability of spherulite growth rate

Spherulite growth rates in thin films of isotactic polypropylene, poly (methylene oxide), and poly (ethylene adipate) have been studied by light microscopy. The growth rate of the parts of spherulites formed from pockets of occluded melt is decreased drastically. The decrease is associated with the negative pressure buildup inside the pockets due to the density change as the melt is converted to spherulites. Material subjected to negative pressure shows a higher melting point of 3–4'C if the pressure is released prior to melting. Slight periodic changes of the growth rate were detected during crystallization of banded spherulites. No changes in growth rate were observed for two spherulites about to impinge or for spherulites growing near a solid obstacle.