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Study of the variables affecting pressure drop and temperature rise in blow molding dies
Author(s) -
Kim H. T.,
Darby J. P.,
Wilson G. F.
Publication year - 1973
Publication title -
polymer engineering and science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.503
H-Index - 111
eISSN - 1548-2634
pISSN - 0032-3888
DOI - 10.1002/pen.760130509
Subject(s) - extrusion , materials science , pressure drop , mechanics , die (integrated circuit) , blow molding , drop (telecommunication) , work (physics) , composite material , thermodynamics , mechanical engineering , engineering , physics , mold , nanotechnology
The extrusion head systems for both pipe and blow molding were analyzed theoretically and relationships derived between pressure drop and temperature rise for various materials at different flow rates and die restrictions. Because of the complexity of the geometry involved, the die was segmented into several sections axially and momentum and energy equations for these sections were solved with the help of IBM 360. The floating boundary conditions were used in order to take into account the nature of the flow phenomenon involved. To complement and support this theoretical work, rigid polyvinyl chloride (PVC) bottle compounds were used to obtain extrusion data on a 3½ inch extruder with several different die sizes. A good agreement was found between the predicted versus experimental data. Results showed that temperature rise in the die systems in significant and that neglecting it would result in a gross error in the calculated pressure drop. Based on this work, a simplified version of the theoretical equation was developed to serve as an engineering tool in estimating pressure drop and stock temperature for a given material where extreme accuracy is not essential. Results of the engineering equation which contains several empirical constants correlate well with the data and support the theoretical effort.