Extruder solids-conveying zone

The goal of this preliminary investigation was to gain more knowledge of the Interaction between solid polymer physical properties and their relation to extruder rate and energy dissipation characteristics In the solids conveying zone. The data presented here will focus on the effects of temperature and polymer type on solids... 

A more common situation, however, is that before there is any significant frictional heating, an axial position is reached where the barrel is heated to well above the melting point, forcing the creation of a him of melt. In either case, this marks the end of that portion of the process in the extruder called the solids conveying zone, where only solids are present and the only elementary step that occurs is handling of solids. 

Fig. 9.30 Graphical representation of the various components of the total power consumption in the solids conveying zone of screw extruders for H/Di, = 0.15 and a constant fs/fb ratio as a function of the angle (f> Pwb, which is the major component of the power, is the power dissipated into heat at the barrel plug interface Pws and Pwf are the power dissipated on the root of the screw and flights, respectively and Pwp is the power consumed for the pressurization of the plug. [Reprinted by permission from E. Broyer and Z. Tadmor, Solids Conveying in Screw Extruders, Part I. A Modified Isothermal Model, Polym. Eng. Sci., 12, 12-24 (1972).]...

Metal-to-solid polymer wear occurs in the solids conveying zone of the extruder. The introduction of the grooved barrel extruder has significantly increased the interest and concern about wear in this portion of the extruder. Grooved barrel sections substantially increase the shear and normal stresses between the polymer solid bed and the metal surfaces. As a result, grooved barrel sections are much more susceptible to wear than smooth barrels. The first systematic study of wear in the solids conveying section of extruders was made by Fritz [1 Ij. He used a diamond-shaped specimen that protruded into the screw channel. 

A.3 Scaleup of Solids Conveying Section. The optimum channel depth for the solids conveying zone of a single-screw extruder having a barrel diameter of 5.0 cm was found to be 0.6 cm. At 100 rpm the mass flow rate of nylon was found to be 10.45 g/s and P2/P = 100./s = 0.3 and = 0.5. Determine the screw rpm (N), the channel depth (//), and the mass flow rate (G) in scaling up to a single-screw extruder with Db = 11.4 cm. 

Under what conditions will the soUds-conveying rate through an extruder fall to zero What is the pressure rise across the solids conveying zone in this case ... 

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