Dependence of the Average Size of Particles Formed during Steady Mixing on their Concentration in Immiscible Polymer Blends

A linear increase in the size of ethylene-propylene rubber particles with its content in polypropylene matrix at steady mixing in a batch mixer was observed. This type of the dependence is predicted by the theory of dynamic equilibrium between the droplet breakup and coalescence. However, theoretical calculation of droplet radius extrapolated to zero concentration of EPR and slope of the dependence of droplet radius versus concentration, based on the effective shear rate (related to mixing conditions), are in strong disagreement with the experimental results. Reasons for these discrepancies between theories and experimental results are thoroughly elucidated.