Polymers are widely used in different industries because of their wide range of applications. The use of polymer combinations as blends is common because one single polymer alone does not provide the desired properties required for some specific applications. There are two methods for preparation of polymer combinations: chemical (copolymerization) and physical (blending). Polymer combination leads to better performance, physical and mechanical properties while it reduces the cost effectively. Mixing of polymers is usually difficult because the entropy of mixing is low, and induces phase separation in polymer blend. The properties of polymer blends are affected through phase separation. The properties of polymer blends are associated with their morphology and affected by the miscibility of components and phase separation mechanism. Phase separation in polymer blends can be explained by a combination of kinetic and thermodynamic effects. The physical origin of phase separation is due to fluctuations that include different mechanisms such as nucleation, diffusion, growth and coalescence. So it is of utmost importance to know the governing mechanisms and the factors affecting the phase separation. There are many ways to identify this phenomenon, among them the rheological measurements are the best. This article provides a comprehensive view of the field of phase separation in the polymer blends, the dominant mechanisms, the effective parameters and the methods of determining the phenomenon.
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