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Extrusion operating temperatures

Polyethylene can be compounded on any of the standard types of mixing equipment used for visco-elastic materials. For laboratory purposes a two-roll mill is suitable operating temperatures varying from about 90°C to about 140°C according to the type of polymer. On the industrial scale, compounding is undertaken either in internal mixers, or more particularly, extrusion compounders. [Pg.232]

Note Values are typical for injection molding and most extrusion operations. Extrusion coating is done at higher temperatures (i.e., about 600 F for LDPE). [Pg.339]

All the hydraulic functions of the head, such as opening and closing, are controlled from a separate operator panel, located in the direct vicinity of the head itself. This panel also allows adjustments to the extrusion tool temperatures to be made, parallel to the downstream main control panel. [Pg.1018]

Characteristic temperatures are always given in terms of temperature differences. For example, the characteristic temperature of the melt of an amorphous polymer in an extrusion operation is AT 7), — 7, or the difference... [Pg.220]

The term dry extrusion, as opposed to wet extmsion, refers to the fact that this type of extruder does not require an external source of heat or steam (29). Dry extruders generate heat and pressure mechanically as a result of the frictional and shear forces produced within the extruder barrel. Provided that adequate operating temperatures are achieved (138°-150°C), this combination of heat and pressure is sufficient to substantially denature the important antinutritive factors in soybeans and render... [Pg.2953]

The heater bands have two more significant roles besides providing heat to melt the polymer. First, they supply the initial energy to heat up the hardware during start-up. An extrusion screw cannot be turned until the extruder is up to operating temperature. [Pg.45]

Steady state n. A condition of processes or parts of processes in which the state variables describing the process, e.g., temperature, pressure, compositions and velocities of streams, and amounts of materials residing in various process equipment, do not change with time. Most extrusion operations closely approximate the steady state except during startup and shutdown, whereas injection molding and sheet thermoforming are unsteady, intermittent processes. [Pg.925]

Band heaters are generally used on barrels of injection molding and extrusion equipment, dies, blow molding heads, and feed pipes. Mica-insulated band heaters are the most common type and can operate up to 371°C. Ceramic-insulated band heaters have thermal insulation to improve efficiency and conserve power, and they achieve operating temperatures of 815°C. Aluminum shoe-style band heaters... [Pg.253]

The small volume of the HS-SSE also results in short residence times. The mean residence time ranges from approx. 5 to 10 seconds. In conventional SSE the residence times are substantially longer typically between 50 to 100 seconds. Since HS-SSE can run at relatively low melt temperatures, the chance of degradation is actually less in these extruders. There is ample evidence in actual high-speed extrusion operations that the plastic is less susceptible to degradation in these operations. [Pg.25]


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