Modular co-rotating twin screw extruder

S. Bawiskar and J. L. White, A Composite Model for Solid Conveying, Melting, Pressure and Fill Factor Profiles in Modular Co-rotating Twin Screw Extruders, Int. Polym. Proc., 12, 1331 (1997). 

Figure 1.15 Meskat-Pawlowski modular co-rotating twin-screw extruder [86].

This conclusion seems to be confirmed by various studies on the addition of compatibilizing agents, which reduce the interfadal tension and make phase morphologies finer [92,93]. Wu [93] - based on a study of the system (polyamide-6,6) / (ethylene propylene copolymer) and [poly(ethylene terephthalate)]/(ethylene propylene copolymer), prepared in a modular co-rotating twin-screw extruder - suggests that final morphology may be correlated by using ... 

The modular co-rotating twin-screw extruder is the most widely used of all twin-screw extruders. There is probably no application for twin-screw extruders to which it has not been applied. Applications include all aspects of compounding and blending of thermoplastics with particulates, oils, and other polymers. The machine is also widely used for removal of liquids, that is, devolatilization and for reactive extrusion. The modular co-rotating twin-screw extruder has also been used for both polymerization and for grafting reactions. 

Basic experimental studies of flow in modular co-rotating twin-screw extruders began with Erdmenger [95,103], who observed the flow in the screw elements moved along the screw channels in a figure-8 motion but did not flow between the screws (Fig. 9.25). The more complex motions in the kneading disc blocks were noted. 

Commercial software to predict the performance of composite modular co-rotating twin-screw extruders in industrial processing operations has been developed. This was first achieved by researchers at the University of Akron [109,110,126,129,135] and called Akro co twin screw. Subsequent developments of similar software were given by Potente et al. [125,128] at the University of Paderborn and by Vergnes et al. [136] at the Ecole de Mines. Typical computations by these programs are developed in Fig. 9.26. Pressure, temperature, fill factor, melting, and screw torque profiles are predicted as a function of process conditions. 

There have been many studies of applications of modular co-rotating twin-screw extruders. These investigations include devolatilization [137 to 140], polymerization [141 to 145], and modification of polymer by hydrolysis and grafting [ 146 to 149]. Some of these applications will be discussed in later sections. 

Cha and White [226] have made an exceptional study of grafting maleic anhydride onto polypropylene in both a batch reactor and a modular co-rotating twin-screw extruder. They propose the following kinetic scheme. First there is the decomposition of an initiator... 

Y. Wang, J. L. White, and W. Szydlowski, Flow in a Modular Intermeshing Co-rotating Twin Screw Extruder, Int. Polym. Process., 4, 262-269 (1989). 

Fig. 5.24. Modular machine concept of co-rotating twin screw extruders...

Figure 5.13 shows a schematic representation of the modular screw-element sequences, barrel sections, and overall assembly of an intermeshing co-rotating twin-screw extruder. 

Wang, Y., White, J.L., and Szydlowski, W. (1989) Flow in a modular intermeshing co-rotating twin screw extruder. Int. Polym. Proc., 4, 262-269. 

Generally, continuous mixers are superior to batch mixers. The compounds are more uniform have superior mechanical properties and much shorter residence times [135, 136]. The major continuous mixers used commercially in 2009 for compounding and blending are modular co-rotating self-wiping twin-screw extruders. 

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