Rotation speed, extrusion

Type and level of binder (e.g., MCC, NaCMC) Rotational speed of extrusion head Temperature... 

Generally speaking, the appearance of the pipes and profiles was fairly good it was still noted that the extrudate appearance improves considerably, extrusion temperatures being the same, by operating with screw rotation speeds shifted toward high values. 

Reactive extruders and extrusion dies of different designs can be easily included in standard technological scheme of polymer production plants, such as those for polycaproamide synthesis, as shown in Fig. 4.39. In this case, a reactive material premixed in a tank 1 is fed into a static device 2 for prepolymerization, where part of the polymerization process takes place. Then the reactive mixture enters the extruder-reactor 3. The necessary temperature distribution is maintained along the extruder. Transfer of the reactive mass proceeds by a system of two coaxial screws mounted in series in a common barrel. Controlling the relative rotation speed of both screws provides the necessary residence time for the reactive mass in the extrader, so that the material reaching the outlet section of the die is a finished polymer. 

In extrusion problems, the rate of deformation is directly proportional to the rotational speed of the screw. Hence, a characteristic viscosity can be defined as... 

Fig. 10.12 Schematic representation of two melting mechanisms observed by Janssen (24) with PP processed in a double-flighted 47-mm counterrotating TSE operating at low rotational speeds, (a) Melting when the die pressure was set at the low value of 50 psi, where chamber-to-chamber leak pressure backflows are negligible, (b) Melting under the high die pressure of 2700 psi, which enables leak backflows, which result in chamber solid bed compaction and introduce the possibility of dissipative mix melting. [Reprinted by permission from L. P. B. M. Janssen, Twin Screw Extrusion, Elsevier Scientific, Amsterdam, 1978.]...

Different methods are used. An online ordinary common blown or cast film line uses a machine direction orienter (MDO) on the front end of biaxially oriented film heated chamber extrusion line. If only the machine direction is to be stretched, a series of precision controlled heated rolls can be used. Film is fed through a series of rolls where it is sequentially heated, drawn around rolls that increase in rotational speed providing the stretching action, annealed around larger diameter roll(s), and cooled on a final roll(s). 

Different types of downstream processing equipment are necessary for the hot-melt extrusion process. For extruded film preparations, chill rolls are used to cool down and control the film temperature before it is taken up by the roller. The thickness of the film can also be controlled by adjusting the rotating speed of the chill rolls. Control of the chill roll temperature... 

Profile extrusions are the most difficult to make because changes in take-up speed or screw rotational speed alone are not enough to compensate for deficient product dimensions. In the case of sheet and film, if the edges of the sheet are not at the target thickness, they can be trimmed off and sent back to the extruder... 

Figure 10.1. Schematic representation of the processing window for the extrusion process. The four curves identify limits to the process Une 1 indicates the maximum screw rotation speed, curve 2 represents the torque limitation of the drive system (region to the right and below of curve exceeds the allowable torque on the drive system), curve 3 represents the maximum temperature allowable to avoid the thermal degradation, and Une 4 shows the minimum screw rotational speed to provide the minimum throughput, acceptable by the process economics.

The ASR-pin tool optimal rotation speed was slower than fee fixed-pin tools due to the added heat contribution of both fee upper and lower shoulders. Excessively high rotation speeds result in extensive softening of the material outside fee pin-tool footprint, loss of extrusion die cavity, and improper flow pattern formation. The cylindrical fixed-pin tool required higher rotation speeds than fee ASR-pin tool to com-... 

Molten formulation also presents the advantage of preventing the use of solvents, which helps reduce the environmental impact, increase dispersion and reduce costs. The mixing and reactions can be performed by twin-screw extrusion, for example, with a rotation speed of 30 rpm and a temperature profile of 80, 85 and 90°C from the feed hopper to the screw. 

Sheets and films based on high-amylose starch (especially high-amylose cornstarch [66, 126]) normally exhibit greater mechanical performance [50] than those based on other starches. The extrusion of high-amylose starch, however, is more difficult than normal TPS because a higher die pressure is required due to the higher melt viscosity [127, 128], and unstable flow [37]. However, by increasing MC, the barrel and die temperature, the compression ratio of the screw and the screw rotation speed [37], these problems can be reduced or eliminated. 

A commercial biodegradable polymer, PLA reinforced with phosphate glass (PG) can be manufactured by the extrusion process followed by compression molding [40]. To limit polymer degradation, the mixture of PLA and PG was manufactured at 205 °C, with a screw rotation speed of 100 rpm and a dwelling... 

An interaction diagram, as given in Section II, can be convenient to study the various interactions in reactive extrusion. A numerical model for closely intermeshing twin screw extruders, based on this diagram gives good results, except for the influence of the rotational speed on the final conversion, which is probably due to a retardation of the onset of the reaction connected to heat transfer problems. 

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