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Investigations on the extrusion of rigid PVC on twin screw extruders
Author(s) -
Lutterbeck J.,
Menges G.,
Potente H.
Publication year - 1980
Publication title -
journal of vinyl technology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.295
H-Index - 35
eISSN - 1548-0585
pISSN - 0193-7197
DOI - 10.1002/vnl.730020309
Subject(s) - extrusion , materials science , axial symmetry , homogeneity (statistics) , shearing (physics) , barrel (horology) , mechanics , residence time distribution , rheology , thermal , plastics extrusion , mechanical engineering , rotational speed , composite material , flow (mathematics) , thermodynamics , structural engineering , engineering , computer science , physics , machine learning
The processing of rigid‐PVC is mainly performed on twin screw extruders. For a thermal sensitive material, such as rigid PVC, this implies certain advantages. They consist primarily in the fact that intermeshing counter‐rotating twin screw extruders are axially closed pump systems, whereas single screw and co‐rotating twin screw extruders represent axially open mixing systems, conveying by means of friction forces. This fundamental difference leads to totally different flow rate and shearing force distributions of the axial flow, which in turn affects the residence time distribution and the thermal dynamics of the process. Investigations have been carried out to determine the influence of screw speed, die resistances, barrel wall temperatures and different compounds on the melt temperature and its homogeneity. It could be shown that the melt temperature can be essentially influenced by heating the barrel wall and the screw. This even applies to the most diverging degrees of mechanical power consumption resulting from different compounds. The homogeneity of the melt temperature thus depends on the relationship between the barrel wall temperature and the melt temperature within the respective heating zone. The possibility is shown to establish a model theory based on energetic and rheological similarities, which can be employed in the construction of machines of different diameters. For this purpose the geometrical and operational data of an optimal operating machine serve as a basis.