MPR portugal 2007
34
“The Cambridge Multipass Rheometer” By Malcolm Mackley Department of Chemical Engineering University of Cambridge
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This 2007 presentation gives an overview on some aspects of the Cambridge Multipass Rheometer (MPR)
Transcript of MPR portugal 2007
“The Cambridge Multipass Rheometer”
By
Malcolm MackleyDepartment of Chemical Engineering University of Cambridge
The Cambridge MultiPass Rheometer (MPR)
Pressure variation mode Rheology flow modeCross-slot flow mode
Key issues for Processing in general Temperature Pressure Flow Time
Key features of MPR
Temperature -10 to 210 CentigradePressure 1 to 200 bar Flow 1 to 100000 reciprocal secondsTime ms to hoursEnclosed small volume
Cambridge MPRs
MPR2
MPR4
MPR3
J Rheology 1995
J Rheology 1995
Conventional ice cream microstructure:
100m x300
Ice Crystals
Matrix
Air cells
Ice creama complex composite material:
Ice cream is a 3 phase material: diameter range -5°c
–ice crystals 25m to 40 m 15%–air bubbles 20m to 60 m 50%–matrix 35%
= 0.6 = 0.5
= 0.4
= 0.0
0
1
10
100
1000
10000
100000
0.01 0.1 1 10 100 1000 10000 100000
Shear stress (Pa)
Ap
par
ent
visc
osi
ty (
Pa.
s)
Parallel Plates MPR-3
= 0.6 = 0.5
= 0.4
= 0.0
0
1
10
100
1000
10000
100000
0.01 0.1 1 10 100 1000 10000 100000
Shear stress (Pa)
Ap
par
ent
visc
osi
ty (
Pa.
s)
Parallel Plates MPR-3
Ice cream matrix with foam inclusion
Ice cream matrix and foam inclusion
Visualisation; Linkam CSS (Cambridge Shear System)
Optical Flow birefringence
Rudy Valette CEMEF Sophia Antipolis
France
Dr David Hassell
Multi-Pass Rheometer (MPR)top piston
heating jacket
pressure transducer
slit die orcapillary inserts
bottom piston
time
diff
ere
nti
al p
ressu
re
FLOW
100
1000
10000
0.01 0.1 1 10 100 1000 10000shear rate (s-1)
*
(Pa.
s) PredictedRDSMPR2, L/D=2.5MPR2, L/D=5MPR2, L/D=20MPR4, L/D=2.5MPR4, L/D=4MPR4, L/D=5
Pressure difference vs time Flow curve
Case Study 1. Rudy Valette CMEF
LLDPE Experiment and matching simulation
Pressure drop vs TimeMPR4
0
2
4
6
8
10
12
0 0,5 1 1,5 2 2,5 3 3,5 4
Time (s)
Pre
ssu
re d
rop
(B
ars)
Experiment
Compressible Rolie Poly
Compressible Carreau
Incompressible Rolie Poly
LLDPE differential pressure responses
Rheo-X-RAY
X-Ray source
X-Ray 2D detector
Sample
Piston
Beam stop
Beryllium capillary
Detector positioning rail
The Cambridge Multipass Rheometer (MPR)
Pressure variation mode Rheology flow mode Cross-slot flow mode
Foaming Tri Tuladhar, Nitin Nowjie
Thermocouple
Capillary/ Optical window
Heating circuit
Bottom piston
Top piston
Pressure transducer
Thermal insulation
Bleed valve
5
Growth profiles for different bubbles
12
1
2
3
4
5
Initial FinalPT – TT – XT
PB – TB – XB
41.94 – 149.89 – 6.83
41.47 – 149.99 – 8.254.07 – 149.89 – 0.12
4.44 – 150.01 – 1.38
Piston speed = 0.5 mm/s
0
50
100
150
200
250
300
350
400
450
0 500 1000 1500 2000 2500
Time (s)
Bo
tto
m b
arr
el p
res
su
re (
0.1
x b
ar)
Eq
uiv
ale
nt
bu
bb
le r
ad
ius
(m
)
Bubble 1
Bubble 2
Bubble 3
Bubble 4
Bubble 5
P-bot
0
50
100
150
200
250
300
350
400
0.001 0.01 0.1 1 10 100 1000 10000
Time (s)
Bu
bb
le r
adiu
s (
m)
Bubble 1
Bubble 2
Bubble 3
Bubble 4
Bubble 5
Model - So = 60microns, Dw = 1E-11 m2/s
Model - So = 60microns, Dw = 6E-16 m2/s
Model - So = 50microns, Dw = 6E-16 m2/s
Model matching with experimental data
15
Best fit conditions:
T = 150°C, Pf = 4.0 bar, Ro = 0.1 m,
co = 30wt%, o= 1105 Pa s,
Dw = 610-16 m2/s, = 1500 kg/m3,
= 0.05 N/m, KH = 110-8 Pa-1
1.0E+02
1.0E+03
1.0E+04
1.0E+05
1.0E-01 1.0E+00 1.0E+01
shear rate (s-1)
Vis
cosi
ty (
Pa
s)
19
Capillary: 12mm diameter, 56mm length
30% moisture content potato starch
T = 140oC
Apparent viscosity (app) of starch melt at 70 bar pressure
Starch melt rheology in the MPR
1.0E+02
1.0E+03
1.0E+04
1.0E+05
1.0E-01 1.0E+00 1.0E+01 1.0E+02
Frequency (Hz)
G',
G'',
*
20
Capillary: 12mm diameter, 56mm length
25% moisture content potato starch
T = 141.9oC
Viscoelastic behaviour of starch melt
Storage modulus, G’Loss modulus, G’’Complex viscosity, *
Initial pressure maintained at 70 bar
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
Flow PatternCross-Slot flow
• The aim is to generatea hyperbolic flowpattern as shown.
• Near the walls the flowdeviates from ideal.
• Along the symmetry axeswe have rotation free pure extensional flow.
Apparatus
• Molten polymer is driven through a central section by two servo-hydraulically driven pistons.
• Air pressure is used to return it so that multiple experiments can be carried out on the same apparatus Servo-hydraullically
driven piston
Servo-hydraullically driven piston
Slave piston driven by air pressure
Slave piston driven by air pressure
1.5 mm
1.5 mm0.75 mm radius
Apparatus
Centre Section
3 cm
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.
Pom-Pom SimulationFlowsolve
8 mode Pom-Pom Constitutive Equation.
Filament stretch
DEP + 1 wt% PS +2.5 wt% PS + 5.0 wt%
t-ts = -20 ms -17 ms -17 ms -11 ms1.2 mm
t-ts = -1 ms 0 ms 0 ms 5 ms
t-ts = 1 ms 1 ms 2 ms 6 ms
Piston diameter = 5 mm
Filament initially stretched to 1.5 mm on each side
0
500
1000
1500
2000
2500
3000
3500
4000
4500
5000
0 20 40 60 80 100 120 140
Time (ms)
Mid
fila
men
t di
amet
er (
µm
) 10 30 50 80
100 130 150 180
200 250 300
Stretch velocity (mm/s)
Piston stop time,tstop = 150 ms
tstop = 50 ms
tstop = 30 ms
1.2 mm1.2 mm
