Intermaterial area generation

Figure 8.5 Intermaterial area generation by mixing (a) top view of lamellar structure formed by miscible polymer B in polymer A (b) droplets of immiscible polymer B dispersed...

Intermaterial area generation in materials with passive interfaces is termed distributive mixing. Mixing of misdble liquids or soluble pigments as in Figure 8.5a and d is distributive mixing. On the other hand, mixing with intermaterial... 

The application of chaotic flows leads to much smaller droplets than allowed by the equilibrium between the shear and interfacial forces [204-206] and than those obtained in some commercial mixers. The smaller size of droplets can be directly traced back to their precursor thinner flbrils as the droplets originate from the fibrils by capillary instability and breakup. The exponential stretching encountered in chaotic mixers subdues the growth of interfacial instabilities in both lamellas and fibrils and consequently smaller diameter fibrils are produced. In some cases, fibrils with an aspect ratio as high as 1000 are produced [204]. In addition, the chaotic mixing conditions have been shown to slow down the rate of coalescence of droplets [207]. Another study utilized the rapid intermaterial area generation in chaotic flows to promote chemical reactions in the synthesis of thermoplastic polyurethanes [140]. 

Relevance of Intermaterial Area Generation to Dispersive Mixing... 

Dispersive mixing of two immiscible polymers or particulate fillers in a polymer benefits greatly from intermaterial area generation. The increased intermaterial area promotes wetting and homogenization of fillers by polymers and also leads to rapid deformation and breakup of minor component polymers. The interfadal reactions can still occur, but the reaction products - the molecules of the new polymer - stay at the interface and compatibilize the domains. 

Mixing Flow and Kinematics of Mixing 372 Intermaterial Area Generation in Miscible Fluids 374 Relevance of Intermaterial Area Generation to Dispersive Mixing 381... 

Repeated stretching and folding generate intermaterial areas... 

Breakup of large size domains into smaller ones generates intermaterial areas. Mixing of immiscible polymers up to the point of breakup is distributive mixing, but breakup of domains occurs by dispersive mixing... 

In chaotic mixing, rapid generation of intermaterial areas in both distributive and dispersive mixing is obtained. This is illustrated in assodation with simple shear flow as in Eq. (8.11), and also in Figure 8.9. 

The observed scaling of p has an important physical interpretation Once p approaches the characteristic invariant and statistical distributions generated by the global invariant manifold, it then evolves everywhere at the same rate as the mean density. In other words, if the mean intermaterial area density is doubled, the local density is doubled everywhere. This is important, because it means that the time evolution of time evolution of p at aU locations of the chaotic flow (i.e., intimacy of mixing improves everywhere by the same factor). Similarly, the striation thickness both locally and globally ... 

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