Droplet Dynamics in Immiscible Polymer Blends

Polymers are frequently mixed or blended in order to optimize some combination of thermal, mechanical, and other properties without the work and expense of designing and synthesizing new polymers with the desired properties. Unusual combinations of 

In drop-breakup experiments with polymers, the shear viscosity is typically shear-rate-dependent. So in plots such as Fig. 9-11, the viscosities are taken to be those of the melts at a nominal shear rate in the mixer. In the experiments of Sundararaj and Macosko, for example, the nominal shear rate y at a given motor speed is estimated from the linear drag flow that is assumed to exist in the narrowest gap of the mixer. 

To use an expression such as Eq. (9-19) for predicting droplet sizes, one also needs a value for the interfacial tension F, which for polymer-polymer interfaces are hard to measure. However, the theory of Helfand and Sapse (1975) allows F to be estimated from the interfacial width A  

From this correlation, Eq. (9-21), the interfacial tension can be estimated if the interfacial width A can be measured in an electron micrograph of a blend (Wu 1987). 

The data of Sundararaj and Macosko (1995) (Fig. 9-13), like those of Elmendorp and van der Vegt, show an increase in the average particle diameter d with increased concentration, as well as an increase in the width of the size distribution, where one standard deviation in Fig. 9-13 is represented by the error bars. Sundararaj and Macosko also show 

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