Morphology, reorganization and stability of mesomorphic nanocrystals in isotactic polypropylene

Density of heterogeneous and homogeneous crystal nuclei in poly (butylene terephthalate)

“…In other words, within a rather narrow temperature-range, on increasing the supercooling, the nucleation density increases by a factor of 10 9 which suggests a qualitative change of the mechanism of primary crystal nucleation from heterogeneous nucleation at low supercooling to homogeneous nucleation at high supercooling. Similar increases of the nucleation density and rate on increasing the supercooling of the melt have been obtained for iPP [55,56], PA 6 [24,25], and PA 11 [13]. However, in all of these examples, the increase of the nucleation density on crystallization at high supercooling is paralleled by a change of the crystal structure.…”

Synthesis, molecular characterization, evaluation of polymorphic behavior and indentation response in isotactic poly(propylene-co-1-heptene) copolymers

“…As already reported for other propylene based copolymers, the formation rate of this mesophase can be easily tailored by varying either comonomer composition or length of counit at a given mol content [16,30,31]. Thus, the mesomorphic phase in iPP homopolymer is obtained under very fast quenching conditions [30,49,50] (i.e., cooling rates higher than 100°C/s) and from the stretching of the c polymorph [51] in metallocene iPP, whereas the cooling rate is becoming much smaller when either comonomer content increases at a given copolymer or length in chain branching is enlarged at an almost constant molar content [30,31].…”

Vitrification and crystallization of poly(butylene-2,6-naphthalate)

“…In kinetic and also technical aspects, the mesophase of iPP is obtained by the cooling from the melt at a rate faster than ca.100 K/s, preventing the crystallization which is initiated by the heterogeneous nucleation [5,24,25]. Furthermore, cooling at a rate faster than 1000 K/s also prevents the mesophase formation in iPP, which is initiated by the homogeneous nucleation, and consequently the glassy amorphous iPP is obtained [24,26].…”