SCREWS AND BARRELS | PROCESSING
Getting to the core of compounding
Screw elements and barrels define the compounding process. Mark Holmes learns more about the latest designs and improvements in wear and corrosion resistance
Screw and barrel technology is advancing continually as extruder manufacturers design their machines to take on a wider variety of tasks, more efficiently and with easier changeovers of screw and barrel configurations. As the heart of the compounding system, screw and barrel wear and corrosion resistance is also essential and both extruder manufacturers and specialist providers of components and surface treatments are helping meet these challenges. According to CPM Extrusion Group, with
high-torque/high speed compounding extruders now increasingly the norm, compounders are finding the resulting higher melt temperatures and shear rates are degrading some of the more sensitive polymers and additives they work with. This is forcing them to sometimes operate at reduced screw speed and capacity to meet the specific compound property specifications. As a result, machine manufacturers are scrambling to create novel element designs that provide good dispersive mixing with lower shear input. CPM Extrusion has been deploying its High
Performance Element (HP) designs for applications where traditional Erdmenger kneading elements are limiting twin-screw extruder productivity. “The T3-Profile kneading elements, originally developed for the RingExtruder, have proven themselves in field trials at customers with significant reduction in shear-induced degradation and melt temperature,” says Adam Dreiblatt, Director of Process Technology. “With an asymmetric geometry that
www.compoundingworld.com
IMAGE: CPM EXTRUSION
enhances elongational mixing, the T3-Profile avoids the shear and pressure peaks associated with Erdmenger profile elements.” The company adds that one example illustrates the significant difference possible with elongational mixing used T3-Profile kneading elements at the same throughput and processing conditions as traditional kneading and mixing elements. Melt temperature, measured directly from the extruder screw tips, was reduced from 185°C to 130°C on a 58mm extruder. This allowed the material to be processed with an active ingredient without it breaking down and maintained the efficacy of the product. Further customer trials are planned to identify those applications where elongational mixing can improve productivity and/or product quality. “We are focusing on applications where machines cannot operate at high screw speed without degrading the properties of the material, such as ABS, TPU and POM,” says Dreiblatt. “Our HP elements enable high production rates without experiencing the shear and temperature peaks that tend to result in increased Yellow Index, for example. Our CXE series compounding extruders fitted with such elements can provide improved product quality and high capacity.”
� August 2020 | COMPOUNDING WORLD 57
Main image: Optimised screw profiles are even more important for today’s high torque/high speed
compounding equipment
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70
