Extrusion processes twin-screw

Post-consumer PMMA plastics can be depolymerised back into their starting components. Degradative extrusion in twin-screw extruders can be used for this process. 10 refs. Translation of Kunststoffe, 87, No.2, Feb.1997, p.183-8... 

At times, low- or high-intensity blending alone can produce a suitable product for use by the fabricator. An example of this would be a polyvinyl chloride (PVC) blend used for several large-volume extrusion applications. More frequently, however, a compounding process is required to obtain the desired physical property. The five primary compounding processes used in the industry for controlling the above parameters are single-screw extrusion (SSE), twin-screw extrusion (TSE), continuous mixers, batch mixers, and kneaders. Table 18.1 summarizes key aspects of each process. 

Polystyrene foam sheet can be made by a variety of extrusion processes (single screw, twin screw) but is most commonly made using a tandem extrusion process as shown in Figure 11.6. This process uses two extruders in series, which effectively optimize the melting, mixing, and cooling unit operations. The diameters of the extruders currently used in this process are usually 115 mm for the primary extruder and 150 mm for the secondary extruder, with an output capability of 400 kg/h. 

For the tests of preparing dynamic vulcanizates in the continuous process of reactive extrusion a twin-screw mixer-extruder DSK 42/6D manufactured by Brabender was used. The vulcanizates were produced dynamically in the process of one-stage or two-stage extrusion process, setting the favorable operating parameters for the device, which had been determined based on multiple tests distribution of temperatures in each heating area... 

Extrusion. In general, extmsion is the process of forcing a polymer melt through a die (104,105). Typical extmsion appHcations include initial resin pelletization after manufacture and production of film, sheet, pipe, tubing, and insulated wire. The HDPE extmsion temperature is around 150°C, the pressure 40—50 MPa (5800—7250 psi). An extmsion production line usually consists of an extmder (mono- or twin-screw) with a die at the end, a cooling and shaping device, a pulling device (a roUer), and a cutter. 

Blends of polypropylene (PP) and liquid crystalline polymer (LCP) processed without melting the LCP were compared with conventional melt processed blends. In a first stage, PP was blended with 20 wt% of LCP in a twin-screw extruder with the take-up speed varied to achieve blends with different LCP fiber dimensions. In the second stage, these blends were processed both below and above the Tm of the LCP by extrusion and injection molding. 

Homopolymers and copolymers from amido-sulfonic acid or salt containing monomers can be prepared by reactive extrusion, preferably in a twin screw extruder [1660]. The process produces a solid polymer. Copolymers of acrylamide, N-vinyl-2-pyrrolidone, and sodium-2-acrylamido-2-methyl-propane sulfonate have been proposed to be active as fluid loss agents. Another component of the formulations is the sodium salt of naphthalene formaldehyde sulfonate [207]. The fluid loss additive is mixed with hydraulic cements in suitable amounts. 

Fig. 2.15. Reactors for producing these materials include batch, continuously vented, tray reactors, twin-screw extruders, and vented single-screw extruders. These production devices will not be covered in this text because they are of more interest to the manufacturing engineer than the extrusion process engineer.

Agur EE. Extruder scale-up in a corotating twin-screw extrusion compounding process. Adv Polym Technol 1986 6(2) 225-232. 

SAN can be modified, for example by grafting. For example, maleic anhydride (MA) can be grafted onto SAN. This process occurs preferably in a twin-screw extruder by reactive extrusion. An advantage of reactive extrusion is the absence of solvent as the reaction... 

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