Single screw

Thermal stability Screen size (mm) of screws (single/dual)... 

ET Screw, Single screw extrusion, blow molding, and injection molding, Barr, Robert, Inc. Ethacure, Liquid aromatic diamine epoxy, and urethane curatives, Albemarle Ethafoam, Polyethylene foam, Dow Plastics Ethanox, Hindered phenolic antioxidants, Albemarle... 

RoHer Compactor Feed Screw Des ns Twin feed screw. Single feed screw... 

If a linear mbber is used as a feedstock for the mass process (85), the mbber becomes insoluble in the mixture of monomers and SAN polymer which is formed in the reactors, and discrete mbber particles are formed. This is referred to as phase inversion since the continuous phase shifts from mbber to SAN. Grafting of some of the SAN onto the mbber particles occurs as in the emulsion process. Typically, the mass-produced mbber particles are larger (0.5 to 5 llm) than those of emulsion-based ABS (0.1 to 1 llm) and contain much larger internal occlusions of SAN polymer. The reaction recipe can include polymerization initiators, chain-transfer agents, and other additives. Diluents are sometimes used to reduce the viscosity of the monomer and polymer mixture to faciUtate processing at high conversion. The product from the reactor system is devolatilized to remove the unreacted monomers and is then pelletized. Equipment used for devolatilization includes single- and twin-screw extmders, and flash and thin film evaporators. Unreacted monomers are recovered for recycle to the reactors to improve the process yield. 

Continuous Solvent—Extrusion Process. A schematic for a typical continuous process, widely used for making solvent propellant for cannons, is shown in Figure 7. This continuous process produces ca 1100 metric tons of single-base propellant per month at the U.S. Army Ammunition Plant (Radford, Virginia). Continuous processes have also been developed for double- and triple-base propellants and for stick as well as granular geometries. A principal aspect of these processes has been the extensive use of single- and double-screw extmders instead of the presses used in the batch process. 

The entire continuous automatic process is computer controlled so that continuous performance information is available. Pressure reHef is permitted wherever possible to minimize the likelihood of a detonation. Continuous-screw extmsion processes may be employed for making nitrocellulose single-. 

The De Danske Sukkerfabriker (DDS) diffuser extractor (Fig. 6) is a relatively simple version of this family of machines, employing a double screw rotating in a vessel mounted at about 10° to the horizontal. The double screw is used to transport the soHds up the gradient of the sheU, while solvent flows down the gradient. Equipment using a single screw in a horizontal sheU for countercurrent extraction of soHds under pressure has been described (19). 

Screw presses consist of a single or double screw conveyor that has perforated walls. The soHds being conveyed are squeezed due to a gradual reduction in the pitch or diameter of the screw. Screw presses are used for dewatering of rough organic materials. 

Cranberry juice, too acidic to be consumed as a 100% juice drink, has been sold since 1929 as cranberry juice cocktail. Juice extraction usually involves pressing the juice from thawed cranberries in a tapered screw press, which affords a 60—64% juice yield. The juice is diluted with two volumes of water and sugar is added to raise the °Brix to 15 to produce a juice cocktail. Under the Federal Food, Dmg and Cosmetic Act, cranberry juice cocktail must contain not less than 25% single-strength cranberry juice with soluble soHds content of 14—16 °Brix, vitamin C content of 30—60 mg/177 mL (6 02), and... 

Fig. 13. Injection molding machine A, hydiaulic motoi foi turning the screw B, hydraulic cylinder and piston allowing the screw to reciprocate about three diameters C, hopper D, injection cylinder (a single-screw extmder) E, no22le F, fixed platen G, tie rods H, mold I, movable platen , hydraulic cylinder and piston used to move the movable platen and supply the force needed to keep the mold closed and K, machine base.

By contrast, the single-screw and double-hehcal screw compressors (Fig. 6) can operate at high or low pressure ratios. They can be appHed at pressure ratios below 2 1 and above 20 1 in a single stage. These compressors are suitable for use with higher pressure refrigerants such as CFC-12, HCFC-22, or ammonia. 

Fig. 6. (a) Single and (b) double-hehcal screw compressors (port areas shown as hatching). 

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