Collision breakage

When the particle inertia overcomes the surface-tension-induced force, the particle will penetrate the bubbles. Recognizing that particle penetration may not lead to bubble breakage, details of bubble instability due to particle collision are given in Chen and Fan (1989a, b). 

Fig. 5. Fragmentation nomenclature of peptides. Bond breakages of all bonds of the peptide backbone have a systematic name (I). When fragmenting multiply charged peptide ions the peptide bond breaks preferentially since it is among the most labile bonds and only relatively low collision energies are involved (II).

This example illustrates that even small impact velocities in collisions between metallic materials (or with hard solids) may lead to plastic deformation or breakage of colliding parts. 

One important parameter contributing to different breakage mechanisms is solids concentration or density in the mill. This directly influences the number of particle-particle or particle-wall collisions and the force of those collisions. Particle density in the mill is controlled not only by feed rate to the mill, but also by mill residence time. Depending on the type of equipment and how it is operated, solids density in the mill can impact both the milling rate and its efficiency so understanding and control of this parameter are important for scale-up. 

For the toothed rotor/stator mills, there are localized areas of high shear where the most energy is imparted to the particles, and breakage is believed to occur, through a combination of shear and collision. Therefore, useful parameters that quantify mill performance will reflect these effects. Three typical parameters used in rotor-stator mill scale up are tip speed (rotation rate of rotor x rotor circumference), shear rate (tip speed/distance between rotor and stator), and shear frequency (rotation rate x number of slots on rotor x number of slots on stator).Rotor-stator types typically differ in the number of rows of teeth and the number of teeth in each row of rotor and stator, though other geometric differences are possible. When rotor-stators of different design are available for study, shear frequency appears to have... 

If the dry milling equipment does not include internal classification, or if a separate classifier is not part of the equipment train, feed particle size may affect milled particle size. Additionally, as one main mechanism for particle breakage in these mills is interparticle collisions, the density of solids in the mill or the solids feed rate can be an important parameter to control to obtain reproducible milling results. 

Reactive cross sections for H abstraction, H elimination mid C-C breakage tis a function of collision energy are presented in Eigure 2. 

C breakage process. The oxyradical receives more energy than the alkyl radical, the latter being barely above its zero point in all cases. In addition, the oxyradical energy increa.ses with collision energj-, a trend akin to that reported for H chrnination. 

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