Rotational twins

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

Type Single screw Low speed type High speed type Counter-rotating twin screw... 

Most of the compounds were extrusion compounded in a conical, partially intermeshing, counter rotating twin screw extruder (Haake Reomix TW-lOO). The extruder speed was set at 50 rpm and the barrel temperature profile was set to produce a melt temperature of 260°C at the die. Samples were injection molded in a 31.8 MT Battenfeld press with a 59 cc shot size. Where noted, samples were compounded in a 60 cc Brabender internal mixer and compression molded. 

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)... 

In general, twinning of the modulated structures is present. Figure 11 shows a [001] 90° rotation twin in the 2212 sample. On the left part (A), the modulation is in the plane of view and on the right (B), it is along the viewing direction. No misfit dislocations are observed at the twin plane. 

Figure 11 [001J 90° rotation twin in 2212. Modulation variant is in the plane of view (A) and along the viewing direction (B). A gradual decrease in the modulation towards the twin plane is seen. 

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. 

Fig. 2. Internieshing co-rotating twin-sciew extruder A, motor B, gear box C, feed port D, clam shell barrel E, vent port F, screw shafts G, conveying screws H, kneading paddles I, barrel valve and J, bHster rings. Courtesy of APV Chemical Machinery Inc.

Potente H, Bastian M, Bergemann K, Senge M, Scheel G, Winkelmann T (2001) Morphology of polymer blends in the melting section of co-rotating twin screw extruders. Polym Eng Sci 41 222-231... 

There seems to be considerable disagreement about co-versus counter-rotating twin screw extruders between different groups in the polymer processing industry and academic community. 

Figure 3.36 Number and weight average of polyamide 6 domain sizes along the screws for a counter-rotating twin screw extruder.

A. C. Y. Wong, F. Zhu, and T. Liu, Qualitative Study on Intermeshing Co-rotating Twin Screw Extrusion Using Novel Visual Technique, Plast. Rubber Comps. Proc. Appl., 26, 271 (1997). 

L. Zhu and X. Geng, Visual Research of Melting Mechanism of Polymer Pellets in Intermeshing Co-rotating Twin-screw Extrusion, SPE ANTEC Tech. Papers, 55, 3684 (1997). 

H. Potente and U. Melish, Theoretical and Experimental Investigations of the Melting of Pellets in Co-rotating Twin-screw Extruders, Int. Polym. Proc., 11, 101 (1996). 

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). 

B. Vergnes, G. Souveton, M. L. Delacour, and A. Ainser, Experimental and Theoretical Study of Polymer Melting in a Co-rotating Twin Screw Extruder, Int. Polym. Process., 16, 351-362 (2001). 

H. Jung and J. L. White, Investigations of melting Phenomena in Modular Co-rotating Twin... 

Fig. 10.69 Locations of the thermocouple and pressure transducers used by Ishikawa et al. (113). Numerical velocity, pressure, and temperature field at cross-sections A-A, B-B, and C-C. [Reprinted by permission from T. Ishikawa, S. I. Kihara, and K. Funatsu, 3-D Numerical Simulations of Nonisothermal Flow in Co-Rotating Twin Screw Extruders, Polym. Eng. Set, 40, 357 (2000).]...

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