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Unstable flow of molten polymers: A second site of melt fracture
Author(s) -
Tordella J. P.
Publication year - 1963
Publication title -
journal of applied polymer science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.575
H-Index - 166
eISSN - 1097-4628
pISSN - 0021-8995
DOI - 10.1002/app.1963.070070119
Subject(s) - hexafluoropropylene , tetrafluoroethylene , materials science , instability , capillary action , polymer , composite material , polyethylene , flow (mathematics) , melt flow index , viscometer , slip (aerodynamics) , flow birefringence , elastic instability , rheology , mechanics , copolymer , thermodynamics , viscosity , physics
Instability in melt flow initiates within capillaries for some samples of the two types of polymers linear polyethylene and copolymers of tetrafluoroethylene and hexafluoropropylene. This behavior contrasts with a previously described instability which initiated at capillary inlets. The instability initiating within capillaries results, initially, in fine‐scale surface roughness and, ultimately, in slip or plug flow. Instabilities initiating at both sites appear to result from elastic failure or melt fracture at critical elastic strains of about 5 units. Data supporting these conclusions were obtained from capillary flow and flow birefringence, and rotational viscometry.