Structural and morphological development in polypropylene/poly(propylene‐1‐octene) in‐reactor alloy due to the competition between liquid–liquid phase separation and crystallization

Abstract

Relationship between phase separation and crystallization of polypropylene/poly(propylene-1-octene) in-reactor alloy (iPP/PPOc) were studied using optical microscopy, scanning electron microscopy, and differential scanning calorimetry. Optical microscopy was used to monitor nuclei density and spherulite growth rates, providing complementary information about the effect of liquid-liquid phase separation (LLPS) on crystallization behavior. We found that LLPS process had a retardation effect on crystallization rate and had a dominant effect on the final crystalline morphology of the iPP/PPOc alloy. By simply changing the LLPS time or temperature, we could control the size and the distribution of the elastomer phase that dispersed in the iPP spherulites. The growth rate of the spherulites significantly depended on the degree of LLPS. Higher degree of phase separation reduced nuclei density and the growth rate of spherulites. However, it was helpful to the formation of more perfect spherulites. But surprisingly, there seemed to be little variation of crystallinity between the two quenching procedures (i.e., single quench vs. double quench). Overall, the competition between LLPS and crystallization significantly influenced the structural and morphological development of the iPP/PPOc alloy. By controlling the interplay between LLPS and crystallization of iPP/PPOc alloy, it was possible to control the structure and morphology as needed in applications.

Regulation of Phase Separation in PP/EPR In-Reactor Alloy and Its Effect on Crystallization Kinetics

“…The PP/EPR in-reactor alloy is typically a multicomponent system containing crystalline components. In such a system, phase separation may occur in its melt and plays an important role on its crystallization, morphology and thus the final mechanical properties. − As a result, it is of great importance to study the effect of phase separation on crystallization and morphology of PP/EPR in-reactor alloy. However, although many researches have been conducted on PP/EPR in-reactor alloys, the effect of phase separation on crystallization and morphology is rarely reported, as compared with the blends containing a crystalline component.…”

Polymer crystallization at liquid‐liquid interface

“…The majority of work on the coupling of these processes has focused on polymer blends . With the origin of the binodal, spinodal, and melting lines discussed, it is worth noting how they can be determined experimentally and what limitations arise with these phase diagrams.…”