Morphology formation in polypropylene impact copolymers under static melt conditions: A simulation study

In this article, the equilibrium morphology of a typical polypropylene (PP) impact copolymer (ICP) system is investigated by numerical self‐consistent field simulations. The ICP was fractionated using temperature rising elution fractionation (TREF) to obtain the data necessary to define the simulation parameters. The results demonstrated the formation of a stratified droplet structure, in which ethylene content decreases from the center of the droplet toward the PP interface. This structure is shown to be in accordance with observations from transmission electron microscopy, scanning electron microscopy, and atomic force microscopy. The components are confined to a narrow layer whose position is primarily determined by its ethylene content. Leakage into a neighboring layer occurs to a degree that is determined by the component molecular weight and the difference in ethylene content between the layers. Simulations for a range of droplet sizes enable calculation of the interfacial tension. A typical drawback of TREF involves the inability to fractionate the amorphous part, leading to a large difference in ethylene content between the matrix and its neighboring layers. Although this effect is shown not to have a significant influence on the stratified structure, it is shown to have a significant influence on the derived interfacial tension. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012