Development of a new opposed-nozzle fixture for measuring the extensional properties of low viscosity liquids

Transcription

1 Development of a new opposed-nozzle fixture for measuring the extensional properties of low viscosity liquids May-August, 2009 MIT, Harvard University and University of Minnesota F. Le Goupil, J. Soulages, J. Hostettler, G. H. McKinley

2 Motivation RFX instrument by Rheometrics ARES-G2 Add-on G.G. Fuller et al., J. Rheol. 3: (987) Rheometer add-on to measure the apparent extensional viscosity of low-viscosity fluids at high deformation rates. P. Dontula et al., Can extensional viscosity be measured with opposed-nozzle devices?, Rheol. Acta 36: (997) 2

3 Working Equations Extension rate: Volumetric flow rate Nozzle to nozzle half distance Q Q Stress on nozzle: Nozzle radius Force acting on jet Measured torque L F F 2r Pivot arm length Apparent extensional viscosity: Inertia Correction: 2d Liquid density with P. Dontula et al., Rheol. Acta 36: (997) 3

4 Previous Work: ARES Operating Region Minimum flow rate based on syringe pump specifications 0 7 Operating Region as a.37 mm 0 6 Function of Nozzle 0.84 mm Diameter 0.5 mm ARES minimum resolvable torque (2x0-6 Nm) 3 x zero-shear viscosity (η 0 =0. Pas) ARES-G2 minimum resolvable torque (0.x0-6 Nm) 3 x zero-shear viscosity (η 0 =0.7 Pas) Maximum measurable viscosity based on the maximum pressure drop achievable with the syringe pump (8 bar): * Nozzle length ( 8 mm ) Maximum flow rate based on syringe pump specifications * assuming dε/dt [s - ] 4

5 ARES/ARES-G2 Residual Torques 5.0x x0-6 Residual Torque Torque [Nm] 3.0x x0-6 ARES minimum resolvable torque : 2x0-6 Nm.0x0-6 RFX minimum resolvable torque : 0.5x0-6 Nm Time [s] ARES-G2 minimum resolvable torque : 0.x0-6 Nm 5

6 System Definition Pivot Arm L Top view F nozzle ARES-G2 Torque reading : M > 0 y x z Q 4x0-5 Mode Expulsion (b=0) Suction (b=0) Sign of M measured + - Sign of a - + Sign of M inertia + + M [Nm] -4x0-5 Expulsion K I = 0.3 η 0 = 0.0 Pas ρ = 225 Kg.m -3 Suction -3x0 4 Eps [s - ] Eps [s - ] 3x0 4

7 Working Fluids : Zero-shear-rate Viscosity Two sets of fluids : Newtonian + PEO solutions with η Pas (high viscous set) Newtonian + PEO solutions with η 0 0. Pas (low viscous set) 0 0 T = 27 C T = 27 C 0 0 Pure glycerol (η 0 = 0.64 Pas) 0 0 PEO wt% in Glycerol/Water (50/50 wt%) (η 0 = 0.74Pas) η η 0 - Glycerol/Water (88/2 wt%) (η 0 = 0.0 Pas) 0 - PEO/Water (/99 wt%) (η 0 = 0.2Pas) [s - ] Newtonian Fluids [s - ] Non-Newtonian Fluids Shear thinning 7

8 Time-Temperature Superposition Newtonian Solutions Non-Newtonian Solutions 2 Pure glycerol (η 0 = 0.64 Pas) PEO wt% in Glycerol/Water (50/50 wt%) (η 0 = 0.74Pas) T 0 = 27 C η 0 (T)/η 0 (T 0 ) = = η 0 (T)/η 0 (T 0 ) -.0x x0-4 /T-/T 0 [K - ] -.0x x0-4 /T-/T 0 [K - ] Glycerol/Water (88/2 wt%) (η 0 = 0.0 Pas) 0 PEO/Water (/99 wt%) (η 0 = 0.2 Pas) η 0 (T)/η 0 (T 0 ) = 0 η 0 (T)/η 0 (T 0 ) = -2.0x x x0-4 /T-/T 0 [K - ] -.0x x0-4 /T-/T 0 [K - ] 8

9 CaBER Measurements 0. wt%peo in Water (η 0 = 0.2 Pas) 0. wt%peo in Glycerol/Water (50/50 wt%) (η 0 = 0.74 Pas) R/R R/R E-3 Minimum resolvable diameter ratio E-3 Minimum resolvable diameter ratio E time [s] E time [s] Based on Oldroyd-B model, the onset of extensional-thickening occurs for Extensional-thickening expected when For wt%peo in Water For wt%peo in Glycerol/water (50/50 wt%) 9

10 ARES-G2 Measurements with Newtonian Fluids Expulsion mode, Nozzle diameter = 0.84 mm, T = 27 C 0 Even for Newtonian solutions, 0 0 Pure glycerol =.92 Pa s probably due to dynamic pressure and shear in the nozzles 0 - Glycerol/Water (88/2 wt%) = 0.30 Pa s Inertia correction* 0-2 Operating Enveloppe ARES Operating Enveloppe ARES-G dε/dt [s - ] * The increase in the apparent extensional viscosity due to liquid inertia is more visible at higher extension rates 0

11 Tests with Smaller Nozzle Diameter Glycerol/Water (88/2 wt%) (η 0 = 0.0 Pas) T = 27 C The data at higher extension rates confirm the increase in the apparent extensional viscosity due to inertia 0.2 ARES-G2 (nozzle diameter=0.84mm) expulsion = 0.3 Pas ARES (nozzle diameter=0.5mm) expulsion ARES (nozzle diameter=0.5mm) suction Onset of ARES-G2 (nozzle diameter=0.84mm) suction Cavitation dε/dt [s - ] Cavitation issues must be solved to observe the effect of inertia for the suction mode

12 ARES-G2 Measurements with Non-Newtonian Fluids Expulsion mode, Nozzle diameter = 0.84 mm, T = 27 C PEO wt% in (Glycerol/Water) (50/50 wt%) The onset of extensional thickening based on the CABER relaxation time is not experimentally observed, probably due to the fact that the strain experienced by a fluid element is not sufficient : = 2.22 Pa s PEO/Water (/99 wt%) = 0.35 Pa s Enveloppe ARES-G2 Enveloppe ARES dε/dt [s - ] Inertia correction* * for For this low constant strain, the strain hardening phenomenon is expected to be small. However, it could be possible to observe it by going to higher extension rates. 2

13 Suction mode with Non-Newtonian Fluids Expulsion mode ( ) and suction mode ( ), Nozzle diameter = 0.84 mm, T = 27 C 00 Onset of extensional thickening Onset of Cavitation Significant discrepancy between the two modes 0 = 2.22 Pa s PEO wt% in (Glycerol/Water) (50/50 wt%) Extensional thickening is observed in suction mode (stretching) but not in expulsion (compression) 0. PEO/Water (/99 wt%) = 0.35 Pa s Expulsion Suction Onset of extensional thickening dε/dt [s - ] Onset of Cavitation Cavitation starts at lower extension rates for more viscous solutions 3

14 Suction mode : Comparison Newtonian/Non-Newtonian Suction mode, Nozzle diameter = 0.84 mm, T = 27 C 0 Onset of extensional thickening Onset of Cavitation PEO/Water (/99 wt%) Extensional thickening is observed in suction mode for the non- Newtonian solution but not for the Newtonian counterpart = 0.35 Pa s = 0.30 Pa s Glycerol/Water Onset of (88/2 wt%) Cavitation dε/dt [s - ] Cavitation starts at lower extension rates for the non-newtonian solution, which is more viscous 4

15 Comparison with RFX Data : Newtonian Solutions Glycerol/water (88/2 wt%) (η 0 = 0.0 Pas) Pure Glycerol (η 0 = 0.64 Pas) 00 T = 27 C T = 27 C 00 = 0.30 Pas 0 ARES Expulsion ARES Suction RFX Expulsion RFX Suction dε/dt [s - ] 0. =.92 Pas ARES Expulsion RFX Expulsion RFX Suction ARES Suction dε/dt [s - ] Good agreement with RFX data 5

16 Comparison with RFX Data : Non-Newtonian Solutions wt%peo in Water (η 0 = 0.2 Pas) wt%peo in Glycerol/water (50/50 wt%) (η 0 = 0.74 Pas) T = 27 C T = 27 C 00 0 ARES Expulsion ARES Suction = 0.35 Pas RFX Expulsion RFX Suction dε/dt [s - ] 0. = 2.22 Pas ARES Expulsion ARES Suction RFX Expulsion RFX Suction dε/dt [s - ] Suction mode : increase of : extensional-thickening confirmed by the RFX data Expulsion mode : increase of at higher rates : extensional-thickening? 6

17 Tests with New Tubing Glycerol/Water (88/2 wt%) (η 0 = 0.09 Pas) T = 24 C Expulsion K I = 0.7 At lower extension rates : = 0.28 Pa s dε/dt [s - ] K I = 0.2 Suction Expulsion mode : the increase of at higher extension rate is well captured with an inertia correction coefficient K I = 0.7 Suction mode : cavitation issues are solved and also increases but with a smaller coefficient K I = 0.2 7

18 Tests with New Tubing wt% PEO in Water (η 0 = 0.2 Pas) T = 24 C = 0.45 Pa s Expulsion new tubing Suction new tubing Expulsion old tubing Suction old tubing dε/dt [s - ] Suction K I = 0.7 Expulsion The decay of at lower extension rates has not been completely eliminated : there probably still exists a shear contribution Expulsion mode : the increase of is well captured with an inertia correction coefficient of K I = 0.70, which is in agreement with that of the Newtonian fluid counterpart Suction mode : the extensional-thickening and cavitation are still observed 8

19 Inertia Correction : K I measured (K Im ) with one single nozzle According to Dontula s notations : Expulsion/Suction in immersion with one single nozzle at 24 C Expulsion K Im 2.2 Suction K Im 0.2 M inertia [Nm] 7.0x x x x x x0-4.0x Water (0.84mm) K Im =2.3 Gly/H2O (88/2 wt%) (0.84mm) K Im = x x Q [m 3 s - ] Water (0.5mm) K Im =2.2 M Inertia [Nm] 6.0x x x x x0-5.0x0-5 Water (0.84mm) K Im = x x0-6 9 Q [m 3 s - ] Gly/H2O (88/2) (0.84mm) K Im =0.3 Water (0.5mm) K Im =0.

20 Inertia Correction : Comparison of K I and K Im Glycerol/water (88/2 wt%) (η 0 = 0.09 Pas) K Im = 2.2 K I = 0.7 T = 24 C Expulsion Another contribution decreasing the apparent extensional viscosity during the inertia measurement? K Im = 0.2 with 0.4 K I = 0.2 Suction mode : 0.3 = 0.28 Pa s Suction Expulsion mode : Wall effect? dε/dt [s - ] 20

21 Conclusions Good agreement with RFX results for the Newtonian and viscoelastic solutions Extensional-thickening observed only in suction mode As good as original RFX At lower extension rate : Cavitation issues in suction mode solved by using shorter tubing Flexibility of the fixture that can be mounted on ARES-G2 or ARES Better than original RFX Inertia calibration: different correction coefficients in suction and expulsion Measured inertia coefficients and sign different from those proposed by Dontula Expulsion : Suction : 2

22 Acknowledgments Dr. Johannes Soulages Prof. Gareth H. McKinley, MIT Jürg Hostettler, ETH Zürich Russell Ulbrich, TA Instruments Aadil Elmoumni, TA Instruments Sujit S. Datta, Harvard University Prof. David Weitz, Harvard Univeristy David Gilles, University of Minnesota Prof. Christopher W. Macosko, University of Minnesota 22