Maillefer extruder screw

The cold-feed extruder had shallow screw channels and a much longer length/diameter ratio. The original cold-feed extruder produced extrudates which had large temperature distributions and became distorted as they emerged from the die. The issue in cold-feed extrusion of rubber was to produce a thermally homogenized product in the extruder screw which would yield thermally uniform extrudate that does not distort. From the 1960s, there have been several improvements in cold-feed extruders. First, Maillefer [M6]... 

The inventor of the barrier flight extruder screw is Maillefer, a pioneer in the field of extrusion. He first appiied for a patent in Switzerland on December 31, 1959 [23], and later applied for patents in various other countries. Patents were granted, among other countries, in Germany [24] and in Engiand [25]. Maillefer filed a patent application in the U.S. on December 20,1960. However, Maillefer did not obtain a patent in the U. S. because of a particular provision in U. S. patent law. Geyer from Uniroyal filed a patent application for a barrier screw on Aprii 5, 1961, several months after Maillefer s filing date [26]. 

A comparison of a Maillefer type barrier screw with a conventional screw in Section 7.5.1, showed for the barrier screw, a reduced output rate when used with PP and an increased output rate when used with LDPE. Following the discovery that the metering zone of a Maillefer type screw was running only partially filled when extruding medium density polyethylene (MDPE), Qui and co-workers [25] evaluated a grooved feed zone to ensure the metering channel was filled. 

The early analysis of solids conveying in an extruder evolved through several simple models based on simple concepts such as the frictional forces between the polymer and the metal surfaces is credited to Decker [36] and Maillefer [37] and the concept of the differential torque at the screw and barrel surface was introduces by Simonds [38]. The rigor of the derivation was significantly improved by Darnell and Mol of DuPont and their analysis is most often cited as it gives a good description of the behavior observed. The model is based on the force and torque balance developed on the solid plug, which is assumed to completely fill the screw channel. The basic assumptions used for the derivation of the model are ... 

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