Performance of Bead Mills

Performance of Bead Mills Materials processed in stirred-media mills are listed in Table 20-17. Variables affecting the milling process are listed below. 

A mathematical analysis of the action in Kady and other colloid mills checks well with experimental performance [Turner and McCarthy, Am. Inst. Chem. Eng. J., 12(4), 784 (1966)], Various models of the Kady mill have been described, and capacities and costs given by Zimmerman and Lavine [Co.st Eng., 12(1), 4-8 (1967)]. Energy requirements differ so much with the materials involved that other devices are often used to obtain the same end. These include high-speed stirrers, turbine mixers, bead mills, and vibratoiy mills. In some cases, sonic devices are effec tive. 

Among new mill developments, annular-gap bead mills and stirred bead mills are being used. These have a high cost, but result in a steep particle-size distribution when used in multipass mode [Kolb, Ceramic Forum International, 70(5), 212-216 (1993)]. Costs for fine grinding typically exceed the cost of raw materials. Produces are used for high-performance ceramics. 

The above assumption [78] was convincingly confirmed in a stirred media mill with a perforated stirrer disc of given size (V = 5.54 1) at a constant energy input per unit mass, E/pV = 103 kj/kg. In batch-wise performed measurements, the kinetic energy of the beads has been varied by the tip speed of the perforated disk stirrers as well as by the density of the grinding media (glass, steel) and, in particular, by the bead diameter (dM = 97-4 000 pm). 

Powder samples of 10u average diameter were prepared by air jet micronization of polymeric or composite chunks. Composite materials were prepared by melt mixing of polymer and carbon black. Carbon black was added to the surface by milling the polymer powder and carbon black with glass beads for an hour, and subsequently heating the particles to tack the carbon black to the particle surface. Static resistivity measurements were performed on packed powders in a procedure similar to ASTM D257. 

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