Single-screw compounding

Wire and Gable. PVC has been used in wire and cable appHcations since World War II, when the U.S. Navy demanded lower combustibiUty materials in constmction. These products are manufactured by cross-head extmsion, usually from pellet compounds on single-screw extmders. Some line speeds are 1524 m (5000 ft) per minute (60 mph). The compounds are optimized for the requirements, including low temperature flexibiUty, high use temperature, especially low combustibiUty, weatherabiUty, and high resistance to cutthrough. 

Create a table listing two or more advantages and disadvantages of each of the following compounding systems batch mixers, continuous mixers, single screw extruders and twin screw extruders. 

Direct Compounding Using Single-Screw Extruders... 

Gale, M., Compounding with Single-Screw Extruders, Adv. Polym. TechnoL, 16, 251 (1997)... 

Black, T., Single-Screw Compounding, in Plastics Compounding Equipment and Processing, Todd, D.B. (Ed.), Hanser Publishers, Munich (1998)... 

Many compounding processes are configured with a twin-rotor mixer or twin-screw extruder to perform the compounding followed by a single-screw extruder to pressurize the material for pelletization. A typical process is shown in Fig. 13.8. In... 

Figure 13.8 Schematic for a compounding process with a single-screw pumping extruder...

Complex profiles require specialty manufacturing skills to build, maintain, and operate extrusion dies as well as cooling and sizing equipment to deliver the exact dimensions required. Cubed compound, where the PVC grains are already broken down, can be run faster on simple single-screw extruders on account of the typical low melt temperatures. 

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