The world leader in serving science Common sources of errors in viscosity measurements Seminar Basics on Rheology
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The world leader in serving science The world leader in serving science
Common sources of errors in viscosity
measurements
Seminar
Basics on Rheology
2
Overview
Reasons for measuring errors
- Instrument related
- Handling related
- Sample related
3
Source of trouble
Handling Sample Instrument
Reasons
Torque measurement
r.p.m. measurement
Geometry factors (A, M)
Geometry
Choice of sensor
Test definition
Sample history
Sample loading
Gap setting
Temperature control
Zero point
Friction heat
Particles, trapped air
Solvent loss
Chemical reaction
Swelling / shrinking
Slipping
Elasticity
Taylor vorticis
Sedimentation
4
Error sources DIN 53018
Viscosity = Geometry * Md/n
• Geometry +/- 0.5 % ABS
- Tolerance of the dimensions (diameter, radius, length, angle)
- Tolerance of positioning (excentricity, inclination, distances)
• Revolutions n +/- 0.5% ABS
- the speed is very accurately recorded with digital encoders (+/-1bit)
- speed is very constant and accurate with stepper motors
- tachometer generators are less accurate
-Torque M+/- 1% FSD or +/-0.5 % ABS
- +/- 1% for traditional instruments and +/- 0.5% for modern rheometer
- Full Scale Deflection leads to greater tolerance range
5
Mess-Unsicherheit der Viskosität
400,0
420,0
440,0
460,0
480,0
500,0
520,0
540,0
560,0
1,E-01 1,E+00 1,E+01 1,E+02 1,E+03 1,E+04
Shear rate (1/s)
Vis
co
sit
y (
mP
as)
RS300 C35 /2 RV1 C35 /2
Soll- V isosity 500 mPa s +/ - 5% Error
ThermoHaake
RS 300 with C35/2 RV 1 with C35/2
Measuring uncertainty („error trumpet“)
6
Air bearing friction
Air bearing friction
is proportional to:
• rotational speed
• viscosity of air
Remedy: friction correction
Air
Rotating
bearing shaft Measuring
gap
Thin liquids and low shear
7
Position-dependent torque
The torque value is dependent on:
• excentricity of the rotating shaft
• tolerance of the bearing housing
Remedy: Micro Stress Control
Thin liquids und Low Shear
8
Torsion of the shaft
If samples are very rigid and a
high torque is applied there is a
torsion shaft to be observed
Remedy: compensation of the
torsion
Torque
Shaft
9
Inertia correction
0 50 100 150 200 250 300 350 400 450 500
Á [1/s]
0
5
10
15
20
25
‚ [Pa]
HAAKE RheoWin Pro 2.6
Flow curve
Without inertia correction
With inertia correction
I_on_2‚ = f (Á)
I_off_2m‚ = f (Á)
10
Source of trouble
Handling Sample Instrument
Reasons
Torque measurement
r.p.m. measurement
Geometry factors (A, M)
Geometry
Selected geometry
Test definition
Sample history
Sample loading
Gap setting
Temperature control
Zero point
Friction heating
Particles, trapped air
Solvent loss
Chemical reaction
Swelling / shrinking
Slipping
Elasticity
Taylor vorticis
Sedimentation
11
Type - factor [-]
- factor [Pa/Nm]
Min. Viscosity [mPas]
Max. Viscosity [mPas]
DG41 72.67 3701 0.5 1.0 10+4
Z40DIN 12.29 6029 5 1.0 10+5
Z20DIN 12.29 48230 50 1.0 10+6
DC60/1 57.3 6796 1 1.0 10+4
C35/2 28.65 89090 100 1.0 10+6
PP60 30 23850 2 1.0 10+5
PP20 10 636600 500 1.0 10+8
Z43DIN/E 12.29 4746 10 1.0 10+5
HS25 440.5 88090 1 1.0 10+2
Consideration of
- Measuring range
- Sample properties
Handling – Selection of measuring geometry
12
Measuring range
in comparison with RS1&PP20+ RS1&PP60
PP20 PP60
RS1 RS1
PP20 PP60
636600 A 23580 A
10 M 30 M
Gp (1/s) Gp (1/s)
Eta (mPas) Eta (mPas)
Tau (Pa) Tau (Pa)
ThermoHaake Rheometer Measuring Range
1,0E-04
1,0E-02
1,0E+00
1,0E+02
1,0E+04
1,0E+06
1,0E+08
1,0E+10
1,0E+12
1,E-04 1,E-03 1,E-02 1,E-01 1,E+00 1,E+01 1,E+02 1,E+03 1,E+04
Shear rate (1/s)
Sh
ea
r st
ress
(P
a)
1,E-04
1,E-02
1,E+00
1,E+02
1,E+04
1,E+06
1,E+08
1,E+10
1,E+12
Vis
co
sity
(m
Pa
s)
RS1
PP20
RS1
PP60
Handling – Selection of measuring geometry
13
Cone & Plate Gap Error / Platte-Kegel
Abstandsfehler
0,0%
0,5%
1,0%
1,5%
2,0%
2,5%
3,0%
3,5%
4,0%
4,5%
0 5 10 15 20 25
Gap error / Abstandsfehler (microns)
Vis
co
sit
y E
rro
r / V
isk
os
itä
tsfe
hle
r (%
)
A Winkel 1,0° Radius 30,0mm
B Winkel 2,0° Radius 30,0mm
C Winkel 4,0° Radius 30,0mm
4 °
1 °
2 °
Cone
angle
Handling – Gap Setting and Error
14
Reduced effective Radius / Einschnürungsfehler
0,0%
5,0%
10,0%
15,0%
20,0%
25,0%
30,0%
35,0%
40,0%
0 0,5 1 1,5 2
Reduced effective radius / Einschnürung (mm)
Vis
co
sit
y e
rro
r / V
isk
os
itä
tsfe
hle
r (%
)
A Winkel 1,0° Radius 10,0mm
B Winkel 2,0° Radius 17,5mm
C Winkel 4,0° Radius 30,0mm
60 mm
35 mm
20 mm
Handling – Sample Loading and Error
15
Handling – Lost of gap filling
0 50 100 150 200 250 300 350 400 450 500 0
10
20
30
40
50
60
70
80
0.1
1.0
10.0
[Pas]
Flow- and Viscosity curve
CR-Modus
[Pa]
[1/s] .
16
Measurements on viscoelastic materials:
measuring geometry plate / plate 35mm with different gaps (0.3 …. 1.0 mm)
Handling – Lost of gap filling
17
Friction heating
0 100 200 300 400 500 600 700 800 900 1000
Á [1/s]
0
500
1000
1500
2000
2500
3000
‚ [Pa]
2.5
3.0
3.5
4.0
4.5
ƒ [Pas
]
19.9
20.0
20.1
20.2
20.3
20.4
20.5
20.6
T [°C]
HAAKE RheoWin Pro 2.6
Flow and viscosty curve
ViscosityShear stress
Temperature
Fr-heat1‚ = f (Á)ƒ = f (Á)T = f (Á)
18
Source of trouble
Handling Sample Instrument
Reasons
Torque measurement
r.p.m. measurement
Geometrya factors (A,M)
Geometry
Selected geometry
Test definition
Sample history
Sample loading
Gap setting
Temperature control
Zero point
Friction heating
Particles, trapped air
Solvent loss
Chemical reaction
Swelling / shrinking
Slipping
Elasticity
Taylor vorticis
Sedimentation
19
Slippage CS/CR-Measurement
Shear Rate
Shear
Str
ess
20
1 10 100 1000 0
0.0005
0.0010
0.0015
0.0020
0.0025
0.0030
0.0035
0.0040
0.0045
0.0050
0.0055
Taylor1
= f ( )
[Pa·s
]
[1/s] .
.
Taylor vortex
21
Loss of solvent
22
Thank you for your attention
Any questions ?
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