The Co-rotating Disk Plasticating Processor

Sections 9.2 and 9.3 discussed the elementary steps that make up the important and widely used screw extrusion process. The common and outstanding feature of all the elementary steps taking place in the screw channel is that they are induced by drag brought about by a single moving surface—that of the barrel. Solids are conveyed and compressed by the 

In screw extruders, as we have seen, the processing takes place in the helical channel formed between the screw and the barrel. In a co-rotating disk processor (CDP), on the other hand, processing takes place in flat doughnut-shaped processing chambers formed by two neighboring disk surfaces, the inner surface of the barrel, the shaft to which the disks are attached, and the channel block attached to the barrel, with very small clearance to the disk surfaces. It thus blocks the channel and separates inlet from outlet, as shown in Fig. 9.44. Processing chambers can be connected in series, parallel, or any other 

The CDP was developed by the Farrel Corporation in Ansonia, CT, and sold under the trade name Diskpack. Although over a dozen machines were manufactured, sold, and used in industry, the line was discontinued. A retrospective analysis of this development, which is instructive regarding the uphill battle of many engineering innovations that radically depart from the traditional practices, is given in Z. Tadmor, Machine Invention, Innovation and Elementary Steps, Adv. Polym. Technol, 21, 87-97 (2002). 

A 350-mm 12-chamber machine is shown in Fig. E9.7b. Unlike the case in the SSE described in the previous section, the journey of a polymer particle in a multichannel CDP is more predictable. Not only do the particles proceed through a sequence of chambers that is predetermined in the design stage, but in addition, each chamber is dedicated to a specific elementary step, as indicated in Example 9.7. This, of course, makes modeling and simulation easier. 

Plasticating First we observe that, in a CDP, there is no solids conveying section or chamber, because the disks are heated and the pellets that come in contact with the rotating disks quickly melt. The solids are compressed into a solid bed as in the SSE, occupying 2ne of the circumference, as shown in Fig. 9.46. 

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