4 rheological instruments e 20070214
TRANSCRIPT
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The world leader in serving science
Advanced SeminarRheology of Construction Materials
Rheological measuring systems
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Content
• Overview• Finger, Ford cup• Capillary viscometer• Falling ball viscometer• Rotational viscometer• Rotational rheometer• Selected accessories
• Temperature control units• Measuring geometries• Modules
• Extensional rheometer
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How can you measure viscosity ?
Feed back to other physical quantities, viscosity value relative or absolute.Rheometer: additional measurements of other (elastic) material characteristics
Krebs-Stormer-viscometerRotational viscometer / - rheometer
Compression viscometer
Torsion viscometer
(Mikro) Faling ball viscometerLaray-viscometer
ChangelFord cup(High pressure ) Capillary viscometer
Finger
Device
Force, DisplacementRotation sensor
Force, DisplacementCompression
DampingTorsion
TimeFalling weight
Time
Time (Pressure, Displacement)
Volum flow
Resistance (Force, Pressure)Biosensor
Measured quantityPrinciple
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Testing of Viscosity: Finger
... the cheapest viscometer
Advantages:+ cheap+ easy handling+ fast+ easy cleaning
Disadvantages:- relative- no reproducability- risky→ hazardous materials
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Ford-Cup
Disadvantages:- relative, type of cup and dye have to be
statede.g. DIN-cup Type A Dye Nr. 4
- no temperature control- wrong times for non-Newtonian fluids- not suitable for fluids with yield point
Method:Measurement of time ∆t (for a definedvolume), seconds as an index for theviscosity
Advantages:+ cheap+ easy handling /robust+ fast+ easy cleaning
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Method:The time is measured how long it takes for the fluid to pass two marks
Capillary viscometer (Gravity is the driving force)
Advantage:+ Relatively cheap+ Very precise for low and medium
viscosities+ Can be calibrated+ Absolute for Newtonian fluids
Disadvantage:- Long measuring time- High cleaning effort- Labor intensive (manual version)- relative values - for Non-Newtonian
fluids- Doesn't work for samples with a yield
stress- Limited operating temperature range
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Result:
ν - viscosity (kinematic) [ mm2 / s ] η = ν * ρ
C4 - Capillary constant,
depends on the used capillary and has to be determined by calibration
Boundary condition: L/D > 30 (L: length, D: diameter)
Application:Low viscous fluidse.g. oils
Capillary viscometer (Gravity is the driving force)
ν = C4 * ∆ t
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Method:The sample is pressed with a pistonthrough the capillary. Measurement of thepressure drop ∆p and the volume flow Q
High pressure capillary viscometer
Advantage:+ High shear rates+ Less friction heating because
alway new sample is feeded+ Calibration possible+ Absolute
Disadvantage:- High price- For test with rod capillary three test
are necessary for the Bagley-correction
- Not for low viscous materials- Cleaning
Calculations:
∆p = p1 - p2
τ = R/(2L) * ∆p
γ = 4/(π R3) * Q
η = π R4/8L * ∆p/ Q
Application: Polymers
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Method:Measuring the falling time of a ball bymeasuring marks in a tube with 10°inclination
HAAKE Falling Ball Viscometer Typ C Höppler (DIN 53015 / ISO 12058)
Advantages:+ High accuracy+ Temperature easy to control+ Absolute results for Newtonian
liquids+ Calibration+ Wide viscosity range+ Closed system
Disadvantages:- Long measuring time - Time consuming cleaning effort- Labour-intensive- Relative results for Non-Newtonian
liquids- Limited to transparent samples
without yield point- Sample density required
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Applications:- Low viscous fluids
e.g. oils- Evaporating fluids / solvents
e.g. toluene- Gases
HAAKE Falling Ball Viscometer Typ C Höppler (DIN 53015 / ISO 12058)
Result:
η - Viscosity (kinematic)
K - Calibration factor for the ball, Depends on the diameter of the ball and tube, has to be calibrated
η = K*(ρk - ρFl )*∆ t
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Rotational Viscometer / Rheometer (relative or absolute)
Method:Torque measurement at a given rotationalspeed (CR-Method)Deformation measurement (torque) at agiven torque (CS-Method)Differentiation: Searle-, Couette-type
Advantages:+Wide range of viscosity,
temperature and shear rate+Applicable for Non-Newtonian
liquids and samples with yieldpoint
+Calibration (absolute measuringsystems)
Disadvantages:- Partially cleaning intensive
(cup and rotor)- Slightly limited accuracy
CR-Method CS-MethodMotor
Bearing of measuring shaft
Joint
Measuring and temperature cell
Torque-,Deformation-
sensor
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Method:Rotational viscometer with sensorgeometry (flow field can not be calculated) In most cases measuring cell withouttemperature control
Rotational Viscometer (relative)
Advantages:+ Easy handling+ Quick measurement+ Minimal cleaning effort+ Reasonable in price
Disadvantages:- Relative results for Non-
Newtonian liquids- Comparable results only using
same sensor and same measuringconditions (r.p.m., sensor)
- Faulty viscosity readings due to variation in temperature
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Method:Rotational rheometer with coaxial cylinders,Cone-Plate and Plate-Plate geometries witha calculable flow field
Rotational Rheometer (absolute)
Advantages:+ Absolute readings, calibration+ Modularity thanks different
temperature control units, measuring geometries and accessories
+ Minimal cleaning (P/C and P/P) + Small sample volume (P/C and
P/P)+ Computer controlled
measurement, i. e. user-independent, datadocumentation
Disadvantages:- Price- High cleaning effort (cylinder
measuring geometry)
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Overview about Temperature Control Units* * HAAKE RheoStress 600 and HAAKE MARS available.
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Overview about Measuring Geometries
Coaxial cylinder geometries:- acc. to DIN 53018- acc. to ISO 3219- Mooney/Ewart-system- Double gap acc. to DIN 54453
Plate/Plate- and Cone/Plate
Relative measuring geometries- Brookfield – spindles acc. to ISO 2555- Pin- and vane rotor- Krebs rotor- geometries with serrated surface- …
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Subjective impression of the sample
Low to medium viscosity
easy to clean
High viscous, pastes,
hard to clean
Large particles
sedimentation, separation
Coaxial cylinders
in various
dimensions
Cone/plate
(without particles)
Plate/plate
(with particles)
Special sensors
vane
or
helical groovedsensor
How to choose the measuring geometry
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Coaxial Cylinders
Couette – MethodRotor fix, measuring cup rotates (1888, Couette)+ No Taylor vortex+ Drive unit and torque sensor mechanical separated+ Structural disadvantages (temperature controller rotates)
Searle – MethodeRotor rotates, measuring cup fix (1912, Searle).Common method for commercially available rheometers . + Structural advantages- Taylor vortexes at high rotation speed and low viscosity
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Related to rotor surface
τi = 1 / ( 2π * L * Ri2 cL) * Md = A * Md
γi = 2 * Ra2 / (Ri
2 - Ra2) * 2π / 60 * n = Mk * n
Information and calculations for measuring geometries acc. to Searle method.
Coaxial Cylinders
Shear stressτ(r) = Md / ( 2π * L * r2 )
Shear rateγ(r) = 2 * Ri
2 * Ra2 / (Ri
2 - Ra2) / r2 * ω
Md – Torque [Nm]ω – Angular Velocity [1/s]
ω = ( 2π * n ) /60v(r) = ω * r
n – Rotation speed [1/min]δ – Ratio of radiie
δ =Ra / Ri
cL – Coefficient of resistance
A
Mk.
.
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Coaxial Cylinders acc. to DIN 53018
Application:Samples with medium viscosities+ High accuracy- Cleaning efforts- Not suitable for temperature ramps
(expansion of air bubble)- Sample volume- High inertia
L > 1,5 * Ri
δ = Ra / Ri < 1,10
LS= 3 * (Ra - Ri )cL = 1
LS
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Coaxiale Cylinders acc. to ISO 3219
Application: Samples with medium up to higher viscositiesStandard geometry+ Easy Filling+ Suitabe for temperature rampes- Cleaning efforts- Sample volume- Higher inertia
L > 3 * Ri L‘‘ = Ri
δ = Ra / Ri < 1,0847 α = 120° + 1°L‘ = Ri cL = 1,1
τi = 1 / ( 2π * L * Ri2 * cL ) * Md
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Coaxiale Cylinders acc. to DIN 54453
Application:Samples with low viscositiesMeasurements at higher shear rates+ Samples volume+ Temperature control- Cleaning effort- Higher inertia
L > 3 * R3
δ = R2 / R1 = R4 / R3 < 1,15
τi = 1 / ( 2π * L * (R22 + R3
2)) * Md
γi = 2 * δ2 / (δ2 - 1) * 2π / 60 * n.
As special with helicalgrowings againstsedimentation
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Cone/Plate measuring geometry acc. to ISO 3219
Application:Samples with medium up to high viscosities+ Shear rate within measuring gap is constant+ Easy cleaning+ Small sample volume+ Fast and accurate temperature control+ Low inertia- Correct gap setting necessary
R
Hα
τ = 3 / ( 2π * R3 ) * Md = A * Md
γ = 1 / tan α * ω ∼ 2π /(α * 60) * n = Mk*n
α < 4° Recommendation: α = 1°
.
"Truncation"
Truncation >3 x bigger particle size
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Plate/Plate measuring geometry acc. to DIN 53018
Application:Samples with medium up to high viscositiesWith particles+ Easy cleaning+ Variation of shear rate range due to variable
setting+ Small sample volume+ Low inertia+ As disposable geometries available+ Temperature ramps- Shear rate within gap not constant H
R
τ (R) = 2 / ( π * R3 ) * Md = A*Md
γ (R) = v / H = ω * R / H = 2π * R /(H * 60) * n
H << R
Mk
.
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1,0E-04
1,0E-02
1,0E+00
1,0E+02
1,0E+04
1,0E+06
1,0E+08
1,0E+10
1,E-03 1,E-02 1,E-01 1,E+00 1,E+01 1,E+02 1,E+03 1,E+04 1,E+05
Shear rate (1/s)
She
ar s
tress
(Pa)
1,E-04
1,E-02
1,E+00
1,E+02
1,E+04
1,E+06
1,E+08
1,E+10
Visc
osity
(mP
as)
Recommended measuring range
Cone 20 mm/1°
Cone 60 mm/1°
η = 10 Pa·s
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Double cone geometry
Application:Samples with low up to medium viscosities+ Evaporation blocked+ High accuracy+ Low sample volume+ Easy Cleaning- Sample temperature- Gap setting- Inertia higher than
standard cone /plate geometry
Double cone geometry as a quasi closed measuring cell.
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Disposable measuring geometries
Application: For measurements• on samples with curring behaviour• with high cleaning efforts
+ No cleaning necessary+ Higher measurement rate- Set-up measuring device- Lower Parallelism than standard
geometry
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Measuring geometries with serrated surface
Application: For samples with• Slippage effect• Hard surface
+ Improvement of contact betweensample and measuring geometry
- Quasi absolut geometry(reduced accuracy)
- Higher cleaning effort
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Relative measuring geometries
Application: Samples, which can not be measured witha standard geometry due to:
big particlessedimentation…
+ Easy handling+ Flexibiliy of design- Relative- Temperature control
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Measuring Cell for Construction Materials
Application: Rheological properties of fresh building materials
+ Easy and quick adaptation of the measurement geometry to new materials
+ Easily adaptable serration profile+ Vane sensors with various diameters + Prevention of slippage layer formation+ Measurement in both rotational and oscillatory
mode+ Large specimens possible + Robust detailing of equipment+ Optional temperature control
- Shear rate within gap not constant- Temperatur control
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Measuring Cell for Bitumen
Application: Determination of properties acc. to SHRP à Aging behaviourà Deformation behaviour
(Measurement of application behaviour at 135°C in rotational mode)
+ Easy sample trimming in plate / platemeasuring geometrie (8, 25mm)
+ Water temperature controlled+ Measurement in both rotational and oscillatory
mode- Temperature range 5 up to 95°C
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RheoScope Module
Combination of two analytical test methods:Correlation between rheological properties
und structur
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HAAKE MARS + RheoScope Module
Example:Polyethylene
Rheological Data
Images
Click: Video
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HAAKE CaBER 1 (Capillary Breakup Extensional Rheometer)
Sample
Laser-micrometer
• Extensional flows occur in many industrial processesand applications and influence these processes often to a great extent.
• As a consequence the knowledge of extensional properties is important.• Extensional properties can not be measured with rotational rheometers.
[Click Image to repeat animation.
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Questions?