Droplet morphology

Figure 41. The percolation threshold determination for polymer blends undergoing the phase separation. Minority phase volume fraction, fm, is plotted versus the Euler characteristic density for several simulation runs at different quench conditions, /meq- = 0.225,..., 0.5. The bicontinuous morphology (%Euier < 0) has not been observed for fm < 0.29, nor has the droplet morphology (/(Euler > 0) been observed for/m > 0.31. This observation suggests that the percolation occurs at fm = 0.3 0.01.

Thus, one could expect to find a droplet morphology at those quench conditions at which the equilibrium minority phase volume fraction (determined by the lever rule from the phase diagram) is lower than the percolation threshold. However, the time interval after which a disperse coarsening occurs would depend strongly on the quench conditions (Fig. 40), because the volume fraction of the minority phase approaches the equilibrium value very slowly at the late times. 

In the unstable region, the concentration fluctuations are delocalized and there is no thermodynamic barrier to phase growth. Thus, separations that take place spontaneously lead to long range phase separation. This process is called spinodal decomposition (SD). In this mechanism, decomposition starts with a co-continuous structure and gradually shifts to a droplet morphology because of the breakdown of the continuous structure [41]. 

The electro-optic properties of PDLC films are controlled by the types of materials used, the droplet morphology and the method of film construction. Desireable properties include high clarity and transmission of the film in the ON and OFF states, low driving voltage, low power consumption, fast switching times and high film resistance. Since these properties are related, it is usually not possible to change them independently. 

Morphology. The SEM of freeze-fractured System-1 specimens Indicates dispersed droplet morphology In blends containing 5, 75 and 95% PP... 

When the major polymer melts before the minor one, the pellets are deformed into sheets, holes are formed in these sheets (their expansion is controlled by the interfacial tension forces), the hole coalesce, the sheets break up into ribbons and irregular fragments, and eventually the well-known droplet morphology is obtained [Scott and Macosko, 1991]. 

The distinction between different drying stages and respective droplet morphology states can be made by using the following criterion ... 

Film morphology Fibril morphology Droplet morphology... 

Anisotropic morphology has different effects on rheological properties compared to droplet morphology. When there is no interaction between the components in an immiscible multicomponent system, the rheological properties of a blend can be determined by a linear combination of each contribution ... 

The Jakob number is relevant within the transition regime given the violent boiling occurring within the early instants after impact, before the lamella levitates. On the other hand, there is an evident relation of droplet morphology with the Weber number, as shown in Fig. 8.3. 

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