Crystallization of s-polypropylene from the glassy state:: Indications for a multistage process

Annealing of sPP after a rapid quench from the melt to a temperature below T-g (--3 degreesC) leads for an annealing temperature T-c = 0 degreesC to a trans-rich mesomorphic phase, for T-c = 25 degreesC to the helical crystalline phase, and for T-c = 2 degreesC to a mixture of both phases, SAXS experiments show that the layer thickness and the long spacing are always the same; i.e., they are independent of the inner structure of the lamellae. This can be understood as indicating that the crystals form only in a second step, subsequent to an initial formation of mesomorphic layers.