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Relationship in polypropylene melt between its linear viscoelasticity and its steady capillary flow properties
Author(s) -
Fujiyama Mitsuyoshi,
Awaya Hiroshi
Publication year - 1972
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.1972.070160202
Subject(s) - viscoelasticity , materials science , capillary action , thermodynamics , melt flow index , viscosity , elasticity (physics) , shear flow , shear rate , steady state (chemistry) , mechanics , chemistry , composite material , polymer , physics , copolymer
It is the object of the present study to obtain clear knowledge of the relations in the polypropylene melt between its linear viscoelasticity and its nonlinear steady capillary flow, paying particular attention to the elastic properties in its capillary flow. By representing the linear viscoelasticity numerically with zero‐shear viscosity, η 0 , and steady‐state compliance, J e 0, evaluation has been made of the properties concerning the elasticity of polymer melt in the capillary flow, such as non‐Newtonianity, the entrance pressure loss, the end correction, the Barus effect, and the melt fracture. The steady flow viscosity η, the entrance pressure loss P 0 , the critical shear stress, τ c , and the critical shear rate $\dot \gamma _c$ at which melt fracture begins to occur are subject to η 0 as follows:$$ \log \eta {\rm }\prop {\rm }\log {\rm }\eta _0 ,{\rm }\log P_0 {\rm }\prop {\rm log }\eta _{\rm 0} ,{\rm }\tau _c {\rm }\prop - \log \eta _{\rm 0} ,{\rm }\log \dot \gamma _c {\rm }\prop - \log {\rm }\eta _{\rm 0} . $$ From the well‐known relationship between η and the weight‐average molecular weight M̄ w , these quantities are governed by M̄ w . Meanwhile, for such quantities as structural viscosity index N , end correction coefficient ν, and elastic pressure loss ratio P 0 / P , following correlations hold:$$ N{\rm }\prop {\rm log}\left( {\eta _0 \cdot J_{e^0 } } \right),{\rm }\log v{\rm }\prop {\rm }\log \left( {\eta _{0^2 } \cdot J_{e^0 } } \right),{{{\rm }P_0 } \mathord{\left/ {\vphantom {{{\rm }P_0 } P}} \right. \kern-\nulldelimiterspace} P}{\rm }\prop {\rm log }\left( {\eta _{0^2 } \cdot J_{e^0 } } \right). $$ As η 0 and J e 0are respectively determined mainly by M̄ w and the molecular weight distribution MWD, these quantities are governed by both M̄ w and MWD. Physical meanings of η 0 · J e 0and η 0 2 · J e 0are, respectively, mean relaxation time and a measure of stored energy in steady flow. The Barus effect has a positive correlation to J e 0, ν, and P 0 / P . (The symbol ∝ employed here means positive correlation.)