Phase‐separation of heterophasic polymer in solution: A model case of impact‐resistant polypropylene copolymer

Impact‐resistance polypropylene copolymer (IPC) has been well known as commercial heterophasic polymer in which ethylene–propylene random copolymer (EPR) domain is dispersed in the homo‐polypropylene matrix. The phase‐separation of those phases is one of the keys to control the polymer properties. However, especially in the solution, there is rarely report that addresses to the phase‐separation of the IPC due to the difficulties in the investigation; i.e., (i) the proximity of the refractive indices of those phases and (ii) the small size of the EPR droplet. Here, the phase‐separation of the commercial IPC in xylene is traced by the in situ small angle X‐ray scattering which the phase‐separation temperature is clearly revealed. The results also show that the evolution of the EPR domain is strongly depended on the polymer composition. Moreover, the migrations of the copolymers are evidenced, and this could be a model for other heterophasic systems. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45069.