Stability condition energy dissipate

This model was introduced by Neville and Hunter (13,14) for the case of sterically stabilized dispersions which have undergone reversible flocculation. It is assumed that the major contribution to the excess energy dissipation in such pseudoplastic systems comes from the need to provide energy from the shear field to separate contacting particles. Under these conditions, the extrapolated yield value is given by the expression (13,32,33),... 

From the multi-scale point of view, the total energy dissipation Nj can be grouped into three portions, namely, Nsurf, Nturb, and Nbreak- The last portion is generated from bubble breakage and finally dissipated in the process of bubble coalescence. While Nsurf and Nln rb are considered to be directly dissipated on micro-scale, Nbreak is counted as a kind of meso-scale energy dissipation. Therefore, the stability condition can be either expressed with the minimization of micro-scale energy dissipation Nsurf + Nturb 7 min or conveyed as the maximization of meso-scale energy dissipation Nbreak max. 

As mentioned earlier, both chemical (catalyst, surfactants, stabilizers) and physical (fluid dynamics, energy dissipation rates, circulation time and so on) factors control the performance of the suspension polymerization reactor. It is first necessary to examine the available experimental data to clearly understand the role of these chemical and physical factors. The available data indicates that the yield of usable polymer beads in laboratory scale reactor is more than 85%. Laboratory experiments were then planned to examine the sensitivity of the yield to various parameters of the polymerization recipe under the same hydrodynamic conditions. These experiments showed that the yield is relatively insensitive to small deviations in the chemical recipe. Analysis of the available data on pilot and plant scale indicated a progressive decrease in the yield of usable polymer beads from laboratory to pilot to plant scale. This analysis and some indirect evidence suggested that it may be possible to re-design the plant-scale reactor hardware to generate better fluid dynamics and mixing to increase the yield of particles in the desired size range. 

Dissipation as an organizing factor can only occur under certain conditions, necessary prerequisites are energy input (open system), nonlinear dynamics and stabilization far away from thermal equilibrium i.e. beyond the regime of linear irreversible thermodynamics (vid. the requirements of Chapter I). 

The photochemistry of 2-hydroxyphenylbenzotriazoles has not been studied extensively, but it is clear that the 2-hydroxy phenyl substituent is essential for light fastness and hence stabilizing potency [135]. Moreover, it has been shown that the quantum yields of fluorescence and of chemical reactions of 2-aminophenylbenzotriazoles are much lower than those of the corresponding meta or para isomers that have no internal hydrogen bond [136]. This has been attributed to the hundred-fold more rapid conversion from excited state to ground state in the former case in those conditions most of the energy is dissipated thermally. 

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