Maddock mixing section

See also Dulmadge mixing section, Maddock mixing section, and cavity-transfer mixer. 

Maddock from Union Carbide published results of experiments with this mixing section [38] since then the mixing section is often referred to as the Maddock mixing section. 

Figure 3.33 Maddock or Union Carbide mixing section.

Figure 8.66(a) The LeRoy mixing section (also called Maddock or UC mixing section)... 

Calculated streamlines in one repeating section of a LeRoy-Maddock dispersive mixing section... 

Figure 12.44 Calculated strain rates (a) and flow number (b) of three particles as they travel through a LeRoy-Maddock dispersive mixing section...

The melting process is the primary mode for mixing in single-screw machines. This concept can be observed from Maddock solidification experiments. Melting as a method for mixing is presented in Section 8.4. 

Figure 8.21 Schematic for Maddock-style mixers a) a mixer with the flutes aligned in the axial direction, and b) a cross-sectional view perpendicular to the screw axis showing the clearance for the mixing flight (courtesy of Jeff A. Myers of Robert Barr, Inc.)...

Although the full history of this screw is unknown, the mixing pins appeared to have been added to the screw after the screw failed to mix and homogenize the extrudate. Pin mixers have been retrofitted to screws for many years as a way to improve the distributive mixing for an extruder. Here the pin mixers would distribute the solid polymer fragments evenly in the extrudate, hut the mixers lacked the ability to trap and disperse them. Pin mixers were clearly the wrong type of mixer to use for this application. Instead, a dispersive mixer such as a Maddock-style mixer would be preferred see Section 8.5.1. 

A Maddock solidification experiment was performed using ABS resin at a screw speed of 60 rpm [30]. Like the solidification experiment for the ET screw of Section 14.2.2, the feedstock resin contained 2% Ti02 compounded into the pellets, and a black-colored masterbatch was added at a letdown ratio of about 220 1. The cross-sectional views of the resin solidified in the channels are shown by Eig. 14.15. The white pellets and unmixed resin are visible in the views as white regions. The regions that are well mixed are an evenly colored dark or black color. 

Fig. 9.43 The Union Carbide Maddock Fluted Mixing Screw Section.

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