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MPR portugal 2007
- 1. “The Cambridge Multipass Rheometer” By Malcolm Mackley Department of Chemical Engineering University of Cambridge
- 2. The Cambridge MultiPass Rheometer (MPR) Pressure variation mode Rheology flow mode Cross-slot flow mode
- 3. Key issues for Processing in general Temperature Pressure Flow Time Key features of MPR Temperature -10 to 210 Centigrade Pressure 1 to 200 bar Flow 1 to 100000 reciprocal seconds Time ms to hours Enclosed small volume
- 4. Cambridge MPRs MPR3 MPR2 MPR4
- 8. Ice cream a complex composite material: Ice cream is a 3 phase material: diameter range -5°c –ice crystals 25µm to 40 µm 15% –air bubbles 20µm to 60 µm 50% –matrix 35% Conventional ice cream microstructure: Air cells Ice Crystals Matrix 100µm x300
- 9. Ice cream matrix with foam inclusion 100000 10000 φ = 0.6 Apparent viscosity (Pa.s) φ = 0.5 1000 φ = 0.4 φ = 0.0 100 10 1 Parallel Plates MPR-3 0 0.01 0.1 1 10 100 1000 10000 100000 Shear stress (Pa)
- 10. Ice cream matrix and foam inclusion Visualisation; Linkam CSS (Cambridge Shear System)
- 11. Optical Flow birefringence Rudy Valette CEMEF Sophia Antipolis France Dr David Hassell
- 12. Multi-Pass Rheometer (MPR) top piston heating jacket pressure transducer slit die or capillary inserts bottom piston
- 13. Case Study 1. Rudy Valette CMEF Pressure difference vs time Flow curve 10000 differential pressure 1000 time Predicted η * (Pa.s) RDS MPR2, L/D=2.5 MPR2, L/D=5 MPR2, L/D=20 MPR4, L/D=2.5 MPR4, L/D=4 MPR4, L/D=5 100 0.01 0.1 1 -1 10 100 1000 10000 shear rate (s ) FLOW
- 14. LLDPE Experiment and matching simulation
- 15. Pressure drop vs Time MPR4 12 10 8 Pressure drop (Bars) Experiment 6 Compressible Rolie Poly Compressible Carreau Incompressible Rolie Poly 4 2 0 0 0,5 1 1,5 2 2,5 3 3,5 4 Time (s) LLDPE differential pressure responses
- 16. Rheo-X-RAY Piston X-Ray 2D detector Sample Beryllium capillary Beam stop Detector X-Ray positioning rail source
- 18. The Cambridge Multipass Rheometer (MPR) Pressure variation mode Rheology flow mode Cross-slot flow mode
- 19. Foaming Tri Tuladhar, Nitin Nowjie Top piston Pressure Thermocouple transducer Thermal Capillary/ Optical window insulation Bleed valve Heating circuit Bottom piston 5
- 20. Growth profiles for different bubbles 5 Initial Final 4 41.94 – 149.89 – 6.83 PT – TT – XT 4.07 – 149.89 – 0.12 2 41.47 – 149.99 – 8.25 PB – TB – XB 4.44 – 150.01 – 1.38 450 1 400 3 Bottom barrel pressure (0.1 x bar) 350 Equivalent bubble radius (µ m) 300 250 200 Bubble 1 Bubble 2 150 Bubble 3 Bubble 4 Piston speed = 0.5 mm/s 100 Bubble 5 50 P-bot 0 0 500 1000 1500 2000 2500 Time (s) 12
- 21. Model matching with experimental data 400 Best fit conditions: 350 T = 150°C, Pf = 4.0 bar, Ro = 0.1 µm, co = 30wt%, η o= 1×105 Pa s, 300 Dw = 6×10-16 m2/s, ρ = 1500 kg/m3, σ = 0.05 N/m, KH = 1×10-8 Pa-1 Bubble radius ( µ m) 250 B u b b le 1 B u b b le 2 200 B u b b le 3 B u b b le 4 B u b b le 5 150 M o d e l - S o = 6 0 m ic ro n s , D w = 1E - 11 m 2 / s M o d e l - S o = 6 0 m ic ro n s , D w = 6 E - 16 m 2 / s 100 M o d e l - S o = 5 0 m ic ro n s , D w = 6 E - 16 m 2 / s 50 0 0.001 0.01 0.1 1 10 100 1000 10000 Time (s) 15
- 22. Starch melt rheology in the MPR 1.0E+05 Apparent viscosity (η app) of starch melt at 70 bar pressure Viscosity (Pa s) 1.0E+04 1.0E+03 1.0E+02 1.0E-01 1.0E+00 1.0E+01 shear rate (s-1) Capillary: 12mm diameter, 56mm length 30% moisture content potato starch T = 140oC 19
- 23. Viscoelastic behaviour of starch melt 1.0E+05 Initial pressure maintained at 70 bar 1.0E+04 G', G'', η * 1.0E+03 Storage modulus, G’ Loss modulus, G’’ Complex viscosity, η* 1.0E+02 1.0E-01 1.0E+00 1.0E+01 1.0E+02 Frequency (Hz) Capillary: 12mm diameter, 56mm length 25% moisture content potato starch T = 141.9oC 20
- 24. Cross Slot, Kris Coventry • The MPR action was modified for cross-slot flow • Pistons move out of phase and force polymer through a cross-slot geometry • New inserts were fabricated for cross-slot flow
- 25. Flow Pattern Cross-Slot flow • The aim is to generate a hyperbolic flow pattern as shown. • Near the walls the flow deviates from ideal. • Along the symmetry axes we have rotation free pure extensional flow.
- 26. Apparatus • Molten polymer is Servo-hydraullically driven through a driven piston central section by two servo- hydraulically driven pistons. Slave piston 1.5 mm 0.75 mm radius Slave piston • Air pressure is driven by air pressure driven by air pressure used to return it so 1.5 mm that multiple experiments can be carried out on the same Servo-hydraullically driven piston apparatus
- 27. Apparatus
- 28. Centre Section 3 cm
- 29. Typical Result -Dow PS680E -Piston velocity of 0.5 mm/s (maximum extension rate =4.3/s). -Inlet slit width=1.5mm -Section depth=10mm - T=180°C.
- 30. Pom-Pom Simulation Flowsolve 8 mode Pom-Pom Constitutive Equation.
- 31. Filament stretch
- 32. DEP + 1 wt% PS +2.5 wt% PS + 5.0 wt% 1.2 mm t-ts = -20 ms -17 ms -17 ms -11 ms t-ts = -1 ms 0 ms 0 ms 5 ms t-ts = 1 ms 1 ms 2 ms 6 ms
- 33. 5000 4500 Stretch velocity (mm/s) 4000 10 30 50 80 Mid filament diameter (µm) 100 130 150 180 3500 200 250 300 3000 2500 2000 Piston stop time, tstop = 150 ms 1500 1000 tstop = 50 ms 500 0 tstop = 30 ms 0 20 40 60 80 100 120 140 Time (ms) Piston diameter = 5 mm Filament initially stretched to 1.5 mm on each side
- 34. 1.2 mm
Notas del editor
- Exptl: No of bubbles = 150 Test surface area: 12 mm X 12 mm Therefore cell density: 150 bubbles/cm2 ~ 20,000 cells/cm3 From model: Sfinal ~ Rfinal Sfinal from expt: 0.5 mm Model SO = 0.15 mm; which is less than Sfinal_expt.. Void fraction: ~90%.