Prediction of droplet size in dispersed phase of immiscible polymer blends during molten mixing

From a theoretical background similar to that of Ghodgaonkar's, using a general description of breakup and the Smoluchowski theory of coalescence of droplets, a relation has been derived for estimating the dispersed phase droplet size during mixing of polymer blends in the steady state. The influences of dispersed phase concentration, shear rate and elasticity of polymers are studied. In a less concentrated system, the diameter of the droplets increases linearly with their concentration. In a more concentrated system, the coalescence effects become increasingly important, the simultaneous collisions of three and more droplets should be considered and the drop diameter versus concentration dependence becomes more complicated. In PS (dispersed)/PP(matrix) blend system, it was observed that the drop diameter continued to decrease up to a maximum shear rate of 128 s(-1). In PS(matrix)/PP (dispersed) blend system, however, as the shear rate increased, the drop diameter initially decreased. At a critical shear rate, the diameter reached a minimum value, and beyond it, the diameter increased with shear. The elasticity of polymers plays a crucial role.