Ternary composites of polypropylene, elastomer, and filler: Analysis of phase structure formation

Abstract Investigation of the morphology and properties of ternary composites of polypropylene, ethylene‐propylene‐diene terpolymer, and filler has shown that in such systems two kinds of structures can be formed: separate dispersion of the components or encapsulation of the filler by the elastomer. A thermodynamic analysis of the two structures revealed that encapsulation is the thermodynamically favored process. The final structure is determined by the stability of the encapsulated units, which depends on the relative magnitude of adhesion and shear forces. The former depends on the reversible work of adhesion and on the particle size of the filler, while the latter depends on the viscosity and shear rate. Surface treatment of the filler decreases the work of adhesion, resulting in extensive de‐encapsulation. The developed tentative explanation is in agreement with the observed phenomena and experimental results.