In explaining the function of an extruder screw, that part of the instrument was divided, as usual, into 3 different sections:
a. The feed or solid-conveying section
b. The compr.ession or melting section
c. The metering section
The feed section which was placed right under the hopper picked up and conveyed the powdery or granular solid plastics to the adjoining section. It was commonly believed that the material confined in the helical channel of the screw moved "en bloc" under the frictional influence of the screw and of the walls of the barrel. Therefore, this material might as well be theoretically considered as a solid plug which filled the screw channel. On a similar basic assumption, from which W.H. Darnel and E.A.J. Mol had derived their equations, but which, in our case, was marked off by a concept of a screw channel as a modification of a confined vessel, (difference in pressure concept of the material), we, too, obtained some equations. However, our first experimental study of conveyillg of solid (plastics and standard sand) fed in a split-type extruder at room temperature showed deviations from the results obtained by means of the above theoretical equations, as some layers of materials confined in the screw channel did not move as a solid plug, and had inside sliding zones. Consequently, our empirical formulae have been rewritten as Equations (1), (18) and (14).
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