A study on polymer blending microrheology: Part IV. The influence of coalescence on blend morphology origination

Abstract The influence of shear induced coalescence on the origination of morphologies in polymer blending processes is investigated both theoretically and experimentally. In the theoretical part a route is proposed to estimate the fraction of collisions between disperse phase domains in simple shear flow that result in an actual coalescence. It was shown that under polymer blending conditions this “coalescence probability” is only substantial if the polymer/polymer interfaces exhibit a high degree of mobility. In the experimental part, the phenomenon of gravity induced droplet/planar interface coalescence is utilized to show the high degree of mobility of molten polymer interfaces. Seoul experiments on the relation between domain size and disperse phase concentration in polymer blends prepared on a single screw extruder were carried out. For extremely low concentration (<½ %) the domain size could be predicted satisfactorily by means of Taylor's classical criterion for Newtonian liquids, while at higher concentration coalescence increased the average domain size manifold.