Twin screw co-rotating

Fig. 10.56 Different ZSK generations over a range of barrel diameters, (a) Values of OD/ID (b) values of the specific torque available. [Reprinted by permission from P. G. Andersen, The Wemer and Pfleiderer Twin Screw Co-rotating Extruder System, in Plastics Compounding, D. B. Todd, Ed., Hanser, Munich (1998) P. G. Andersen, private communication.]...

P. G. Andersen, The Wemer and Pfleiderer Twin Screw Co-rotating Extruder System, in Plastics Compounding, D. B. Todd, Ed., Hanser, Munich (1998). 

Figure 5.1 illustrates the functionality of the twin-screw co-rotating extruder. 

The twin-screw co-rotating extruder provides good compounding due to its unique features such as modular screw configuration, excellent mixing and independent feeding operation. 

Comparison of single-screw, co-rotating and counter-rotating twin-screw extruders... 

Several studies have been performed to evaluate the mixing capabilities of twin screw extruders. Noteworthy are two studies performed by Lim and White [12,13] that evaluated the morphology development in a 30.7 mm diameter screw co-rotating [28] and a 34 mm diameter screw counter-rotating [3] intermeshing twin screw extruder. In both studies they dry-mixed 75/25 blend of polyethylene and polyamide 6 pellets that were fed into the hopper at 15 kg/h. Small samples were taken along the axis of the extruder and evaluated using optical and electron microscopy. 

Extruderdesign l/D, single vs. twin screw, co vs. counter rotating... 

The continuous trials were performed on a twin shaft, co-rotating 31-liter kneader reactor that was equipped with a twin-screw discharge system. The rotation speed of the reactor shafts was higher than in the batch trials. Samples of the discharge from the twin-screw discharge system were tested for polymer conversion and the same process data was collected as in the batch trials. 

Report 116 Compounding in Co-rotating Twin-Screw Extruders, Y. Wang, Tunghai University. 

PC PC/15% MWNT masterbatch 2 wt.% 105 2-cm Melt mixing in intermeshing co-rotating twin screw extruder... 

White, J. L., Kim, E. K., Keum, ]. M., and Jung, H. C., Modeling Heat Transfer in Screw Extrusion with Special Application to Modular Self-Wiping Co-Rotating Twin-Screw Extrusion, Polym. Eng. Set, 41, 1448 (2001)... 

The industrial use of twin-screw extruders for this purpose revolves extensively, but not exclusively, around intermeshing co-rotating variants. Closely in-termeshing counter-rotating designs are widely used for profile extrusion of UPVC dry-blends since they permit close temperature control and exhibit a high conveying efficiency due to the positive displacement of material where the screws intermesh [150]. 

Fig. 26. Typical mixing elements for a co-rotating intermeshing twin-screw extruder...

Fig. 27. Progressive dispersion of calcium carbonate in polypropylene within a co-rotating intermeshing twin-screw extruder. Filler dispersion is expressed in terms of a mean volume diameter determined by image analysis...

A mixture consisting of powdered polypropylene (59.91 g) and the step 1 product (90 mg) were tumble-mixed in a glass container for 24 hours. Thereafter the mixture (4.5 g) was compounded at 239°C using a small co-rotating twin-screw extruder. The sample required 4 minutes at a screw speed of 40rpm to be prepared. The extruded material only had a slight haze content. 

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