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Some rheological properties of molten polytetrafluoroethylene
Author(s) -
Ajroldi G.,
Garbuglio C.,
Ragazzini M.
Publication year - 1970
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.1970.070140109
Subject(s) - viscoelasticity , rheology , creep , viscosity , materials science , activation energy , glass transition , thermodynamics , composite material , ultimate tensile strength , polytetrafluoroethylene , viscous flow , linear relationship , atmospheric temperature range , polymer chemistry , chemistry , polymer , mechanics , mathematics , statistics , physics
Measurements of melt viscosity on samples of polytetrafluoroethylene of different molecular weight were carried out at 360°C by means of tensile creep tests in the linear viscoelasticity range. The apparent activation energy for viscous flow in the range between 330° and 380°C was estimated to be 20 kcal/mole. A value of about 7,500 was also determined for the average molecular weight between entanglement points ( M e ), from the equilibrium compliance ( D e ). Melt viscosity data were compared with zero strength time ( ZST ) values and a linear correlation was found on a bilogarithmic scale. The dependence of ZST on the applied stress and temperature was also studied and the results are discussed on the basis of Bueche's theory on the creep at rupture above the glass transition temperature.