MPR portugal 2007
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This 2007 presentation gives an overview on some aspects of the Cambridge Multipass Rheometer (MPR)

This 2007 presentation gives an overview on some aspects of the Cambridge Multipass Rheometer (MPR)

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  • 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%.

MPR portugal 2007 Presentation Transcript

  • 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 generalTemperature Pressure Flow Time Key features of MPRTemperature -10 to 210 CentigradePressure 1 to 200 barFlow 1 to 100000 reciprocal secondsTime ms to hoursEnclosed small volume
  • 4. Cambridge MPRs MPR3 MPR2 MPR4
  • 5. J Rheology 1995
  • 6. J Rheology 1995
  • 7. 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
  • 8. Ice cream matrix with foam inclusion 100000 10000 φ = 0.6Apparent 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)
  • 9. Ice cream matrix and foam inclusionVisualisation; Linkam CSS (Cambridge Shear System)
  • 10. Optical Flow birefringenceRudy Valette CEMEF SophiaAntipolis FranceDr David Hassell
  • 11. Multi-Pass Rheometer (MPR) top piston heating jacket pressure transducer slit die or capillary inserts bottom piston
  • 12. 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
  • 13. LLDPE Experiment and matching simulation
  • 14. Pressure drop vs Time MPR4 12 10 8Pressure 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
  • 15. Rheo-X-RAY Piston X-Ray 2D detector Sample Beryllium capillary Beam stop DetectorX-Ray positioning railsource
  • 16. The Cambridge Multipass Rheometer (MPR)Pressure variation mode Rheology flow mode Cross-slot flow mode
  • 17. Foaming Tri Tuladhar, Nitin NowjieTop piston Pressure Thermocouple transducer Thermal Capillary/ Optical window insulationBleed valve Heating circuit Bottom piston 5
  • 18. 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 3Bottom 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
  • 19. 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
  • 20. 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
  • 21. 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
  • 22. 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
  • 23. 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.
  • 24. 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
  • 25. Apparatus
  • 26. Centre Section 3 cm
  • 27. Typical Result-Dow PS680E-Piston velocity of 0.5mm/s (maximumextension rate =4.3/s).-Inlet slitwidth=1.5mm-Section depth=10mm- T=180°C.
  • 28. Pom-Pom Simulation Flowsolve8 modePom-PomConstitutiveEquation.
  • 29. Filament stretch
  • 30. DEP + 1 wt% PS +2.5 wt% PS + 5.0 wt% 1.2 mmt-ts = -20 ms -17 ms -17 ms -11 mst-ts = -1 ms 0 ms 0 ms 5 mst-ts = 1 ms 1 ms 2 ms 6 ms
  • 31. 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 mmFilament initially stretched to 1.5 mm on each side
  • 32. 1.2 mm