Abstract
Extensional viscosity measurements are being made at increasingly high strain rates. The behaviour of semi-solid materials and molten polymers was generally studied at extensional strain rates well below one reciprocal second (1–4); some tests on polymer solutions were also carried out at low strain rates (5). These experiments showed that the Trouton ratio (extensional viscosity divided by shear viscosity) sometimes rose above the value 3 predicted by Newtonian theory. At higher rates of strain, for polymer solutions, the Trouton ratio rises rapidly and novel experimental methods are required (6). The orifice jet thrust technique of Metzner and Metzner (7) has been used independently by the present authors (8), confirming that the Trouton ratio for dilute polyacrylamide solutions is in excess of 103 for extensional strain rates of 103–104 sec−1. Precise knowledge of the flow pattern upstream of the orifice is essential for the accurate use of this method.
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Abbreviations
- C :
-
Constant defining extensional strain rate (see Appendix)
- d 11 :
-
Extensional strain rate in axial direction
- L :
-
Effective length of central jet, covering region of constant extensional strain rate
- R 0 :
-
Initial radius of central jet just outside orifice, corresponding to velocity R 0
- R 1 :
-
Final radius of central jet, corresponding to velocity V 1
- R x :
-
Radius of central jet at point distant x from tube exit
- R :
-
Radius of orifice in orifice jet thrust experiment
- t :
-
Time for which fluid has been subjected to extensional flow
- ΔT :
-
Reduction of thrust on central capillary following jet attachment
- V 0 :
-
Mean velocity of fluid in central jet before extensional flow commences
- V 1 :
-
Mean velocity of fluid in central jet at point distant “L” from tube exit
- V x :
-
Mean velocity of fluid in central jet at point distant “x” from tube exit
- V :
-
Mean velocity of fluid through orifice (in orifice jet thrust experiment)
- x :
-
Axial distance from central tube exit
- δ11 :
-
Axial stress in fluid
- (τ11)0 :
-
Initial axial stress in fluid in central jet
- (τ11) av :
-
Time-average axial stress in fluid in central jet
- μ E :
-
Extensional viscosity i.e. (τ11) av /d 11
- μ S :
-
Shear viscosity
References
Reiner, M., Deformation, Strain and Flow. Second Edition, p. 78 (New York 1960).
Ballman, R. L., Rheol. Acta 4, 137 (1965).
Cogswell, F. N., Plastics Polymers 109 (1968).
Stevenson, J. F., Amer. Inst. Ch. Eng. J. 18, 540 (1972).
Acierno, D., R. Greco, and G. Titemanlio, Elongational Flow of Dilute and Concentrated Polymer Solutions. Euromech 37 (Naples 1972).
Astarita, G., Ind. Eng. Chem. Fund. 7, 171 (1968).
Metzner, A. B. and A. P. Metzner, Rheol. Acta 9, 174 (1970).
Oliver, D. R. and R. Bragg, Chem. Eng. J. 5, 1 (1973).
Oliver, D. R. and W. C. Macsporran, Rheol. Acta 8, 176 (1969).
Oliver, D. R. and R. Bragg, Canad. J. Chem. Eng. 51, 287 (1973).
Oliver, D. R., Canad. J. Chem. Eng. 44, 100 (1966).
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© 1975 Springer-Verlag Berlin Heidelberg
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Oliver, D.R., Bragg, R. (1975). The triple jet: A new method for measurement of extensional viscosity. In: Vallet, G., Meskat, W. (eds) Rheological Theories · Measuring Techniques in Rheology Test Methods in Rheology · Fractures Rheological Properties of Materials · Rheo-Optics · Biorheology. Steinkopff, Heidelberg. https://doi.org/10.1007/978-3-662-41458-3_195
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DOI: https://doi.org/10.1007/978-3-662-41458-3_195
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