ISSN:
0021-8995
Keywords:
Chemistry
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
,
Physics
Notes:
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, η0, and steady-state compliance, Je0, 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 P0, the critical shear stress, τc, and the critical shear rate $\dot \gamma _c$ at which melt fracture begins to occur are subject to η0 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 M̄w, these quantities are governed by M̄w. Meanwhile, for such quantities as structural viscosity index N, end correction coefficient ν, and elastic pressure loss ratio P0/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 η0 and Je0 are respectively determined mainly by M̄w and the molecular weight distribution MWD, these quantities are governed by both M̄w and MWD. Physical meanings of η0·Je0 and η02 · Je0 are, respectively, mean relaxation time and a measure of stored energy in steady flow. The Barus effect has a positive correlation to Je0, ν, and P0/P. (The symbol ∝ employed here means positive correlation.)
Additional Material:
25 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/app.1972.070160202
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