Barr energy transfer screws

In blown film trials comparing a barrier screw and an energy transfer screw, and VB energy transfer screw, the latter outperformed the others in the extrusion of LLDPE and LLDPE blends with regards to both output rate and melt temperature. The extruder screw was 88.9 mm diameter, with 30 1 L/D. 

Cross sections of screw channel samples from push-out trials showed significant improvements in both melting and mixing for the Stratablend mixing screw in comparison to the conventional screw with relatively small increases in melt temperature. A slightly higher screw speed was necessary for the Stratablend screw to match the output rate for the conventional screw, e.g., 80 rpm to match output at 74 rpm. 

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Figure 7.23 Energy transfer and VB energy transfer screws. (Reproduced with permission from J.A. Myers and R.A. Barr in Proceedings of the 60th SPE Annual Conference - ANTEC 2002, San Francisco, CA, USA, 2002, Paper No.251.

Two screws were designed with Energy Transfer (ET) sections from Robert Barr, Inc. [31], and the screws were labeled by Dow as ET-1 and ET-2. The original... 

Other mixing screws have been developed in the past to disrupt the solid bed and mix unmelted with melted material. The double wave screw shown in Fig. 8.80 breaks up the solid bed and mixes the material by forcing a cross-channel flow by the cyclic variation in channel depth. The principle of the double wave screw was used by Barr in his energy transfer (ET) screw [90]. The ET section is basically a double wave section with occasional undercuts in both flights to force a cross-channel mixing between the two channels. Modeling of the ET mixer is discussed in Section 12.4.3.2 see also Figs. 12.23 to 12.25. 

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