Coalescence behavior of dispersed domains in immiscible polymer blends having broad size distribution

Coalescence process of a immiscible polymer blend having broad distribution of domain size, which is a 1:1 mixture of two pre-sheared polymer blends is compared with those of the two pre-sheared samples having narrow size distributions. Component samples used are polydimethylsiloxane (PDMS: viscosity 27.1 Pa-s) and hydrocarbon-formaldehyde resin (Genelite: viscosity 10.5 Pa·s). The weight ratio of PDMS:Genelite was 7:3 and shear rates of preshear are 2.4 and 4 s^-1. The coalescence process was observed under steady shear flow with 0.8 s^-1. It was observed that the coalescence between large and small domains more frequently occur in the blend sample with broad size distribution than those of similar size domains in the blend samples with narrow size distribution. As a result, initial coalescence rate became faster for the blend with broad distribution than that with narrow size distributions. Moreover, the size distribution after a long time of flow are different for the samples with broad and narrow size distributions, though the average radius are similar, implying that the domain structure of immiscible polymer blends with broad size distribution cannot be well controlled by the flow at low shear rates.