Mark C. Edwards ● Gammadot Rheology Testing & Consultancy Services ● www.gammadot.com Rheology - A Practical Approach To Quality Control A presentation to the Telford Polymer Association November 25th 2008
May 26, 2015
Mark C. Edwards ● Gammadot Rheology Testing & Consultancy Services ● www.gammadot.com
Rheology - A Practical Approach To Quality ControlA presentation to the Telford Polymer Association November 25th 2008
Why Rheology?The single most important parameter in the processing of a molten polymer is the viscosity function of the material – if it doesn't flow you can't process it! This parameter is highly sensitive to material structure. Rheological measurements can detect discrete changes in structure through flow behaviour, and can be fast & accurate methods of providing quality control for all aspects of the process.
Mark C. Edwards ● Gammadot Rheology Testing & Consultancy Services ● www.gammadot.com
Why Rheology?The single most important parameter in the processing of a molten polymer is the viscosity function of the material – if it doesn't flow you can't process it! This parameter is highly sensitive to material structure. Rheological measurements can detect discrete changes in structure through flow behaviour, and can be fast & accurate methods of providing quality control for all aspects of the process.
Mark C. Edwards ● Gammadot Rheology Testing & Consultancy Services ● www.gammadot.com
Discriminating batch to batch variance
Excellent in:
Why Rheology?The single most important parameter in the processing of a molten polymer is the viscosity function of the material – if it doesn't flow you can't process it! This parameter is highly sensitive to material structure. Rheological measurements can detect discrete changes in structure through flow behaviour, and can be fast & accurate methods of providing quality control for all aspects of the process.
Mark C. Edwards ● Gammadot Rheology Testing & Consultancy Services ● www.gammadot.com
Discriminating batch to batch variance
‘Mapping’ processing problems
Excellent in:
Why Rheology?The single most important parameter in the processing of a molten polymer is the viscosity function of the material – if it doesn't flow you can't process it! This parameter is highly sensitive to material structure. Rheological measurements can detect discrete changes in structure through flow behaviour, and can be fast & accurate methods of providing quality control for all aspects of the process.
Mark C. Edwards ● Gammadot Rheology Testing & Consultancy Services ● www.gammadot.com
Discriminating batch to batch variance
‘Mapping’ processing problems
Aiding failure analysis
Excellent in:
Mark C. Edwards ● Gammadot Rheology Testing & Consultancy Services ● www.gammadot.com
Which Rheometer?
Melt Flow Indexer (Rate)
Mark C. Edwards ● Gammadot Rheology Testing & Consultancy Services ● www.gammadot.com
Brookfield Viscometer
Mark C. Edwards ● Gammadot Rheology Testing & Consultancy Services ● www.gammadot.com
‘LV’ ‘RV’ ‘HB’ Low Viscosity Medium Viscosity High Viscosity
Capillary Extrusion Rheometer
Mark C. Edwards ● Gammadot Rheology Testing & Consultancy Services ● www.gammadot.com
Controlled Stress / Rate Rotational Rheometer
Mark C. Edwards ● Gammadot Rheology Testing & Consultancy Services ● www.gammadot.com
Which Rheometer??
Mark C. Edwards ● Gammadot Rheology Testing & Consultancy Services ● www.gammadot.com
Rule of thumb: if structure sensitive measurements are required such as batch variance, melt stability, degradation studies, etc, then a rotational rheometer in oscillation mode. Investigations required at process-relevant shear rates call for the capillary rheometer.
Oscillatory Rheometry
The oscillation technique involves applying a sinusoidal oscillating stress () wave to the sample and measuring the resulting strain wave ().
Mark C. Edwards ● Gammadot Rheology Testing & Consultancy Services ● www.gammadot.com
Oscillatory Rheometry
A purely elastic (Hookean solid) material will retain all of the deformation energy applied to it and will therefore have a phase difference (phase angle) of 0 degrees. Conversely, a purely viscous (Newtonian) fluid dissapates all of the applied energy and will have a phase angle of 90 degrees. Polymeric materials are Visco-elastic and as such their responses fall somewhere between these two extremes.
Mark C. Edwards ● Gammadot Rheology Testing & Consultancy Services ● www.gammadot.com
Hookean Solid Response Newtonian Fluid Response Visco-Elastic Response
Phase Angle = 0 Phase Angle = 90 Phase Angle = 0<>90
Oscillatory Rheometry
Measurements are normally made isothermally at constant strain amplitude, across a range of frequencies. A wealth of information relating to structural responses can be gained in oscillation mode.
Mark C. Edwards ● Gammadot Rheology Testing & Consultancy Services ● www.gammadot.com
100.0
1000.0
10000.0
100000.0
Frequency (Hz)
Com
plex
Vis
cosi
ty (
Pa.
s)
Mo
dulu
s (P
a)
G'G"
h*
Narrow MwD
Broad MwD
High Mw Low Mw
Modulus Cross Over Point
Oscillatory Rheometry
Relationship of G’ / G” cross-over point to average molecular weight for HDPE.
Mark C. Edwards ● Gammadot Rheology Testing & Consultancy Services ● www.gammadot.com
HDPE Molecular Weight Average Vs Modulus Cross Over Frequency
1000
10000
100000
1000000
0.1 1 10 100 1000 10000Frequency (Hz)
Mol
ecul
ar W
eigh
t (M
w)
Mw 120k
Mw 98k
Mw 145k
Mw 90k
Mw 60k
Mw 75k
Mw 340k
Mw 40k
Mw 8k
Oscillatory Rheometry
Extremely accurate, reproducible results – calibrated instruments should give comparable data.
Mark C. Edwards ● Gammadot Rheology Testing & Consultancy Services ● www.gammadot.com
Reologica Viscotech Controlled Stress Rheometer DataControl PP @ 220°C, 5 millistrain
10
100
1000
10000
0.01 0.10 1.00 10.00 100.00
Frequency (Hz)
Co
mp
lex
Vis
cosi
ty (
Pa.
s)
Nov.04 (StressTech)
Jun.08 (ViscoTech)
Oct.08 (ViscoTech)
Oscillatory Rheometry
Simple ‘Go / No Go’ quality control programme set up for an automotive component manufacturer suffering from batch variance of incoming materials.
Mark C. Edwards ● Gammadot Rheology Testing & Consultancy Services ● www.gammadot.com
Reologica ViscoTech Controlled Stress RheometerTemperature: 220°C, Strain: 5 millistrain
100.0
1000.0
10000.0
0.01 0.10 1.00 10.00 100.00
Frequency (Hz)
Co
mp
lex
Vis
cosi
ty (
Pa
.s)
Short Shot
Oscillatory Rheometry
Invaluable in most failure analysis projects – oscillatory rheometry can usually give first indications of failure cause or at least point the investigation in the right direction.
Mark C. Edwards ● Gammadot Rheology Testing & Consultancy Services ● www.gammadot.com
Reologica ViscoTech Controlled Stress Rheometer DataTemperature: 255°C, Strain: 2 millistrain
0.01
0.1
1
10
100
0.1 1 10
Frequency (Hz)
Co
mp
lex
Vis
cosi
ty (
Pa.
s)
PBT Virgin Granules
0 Hrs Drying
1 Hrs Drying
2 Hrs Drying
3 Hrs Drying
'Good' Component
Failed Component
‘Good’ Component
‘Failed’ Component
Oscillatory Rheometry
Individual test programs can be run as a ‘macro’ to give tailored test profiles.
Mark C. Edwards ● Gammadot Rheology Testing & Consultancy Services ● www.gammadot.com
Reologica ViscoTech Controlled Stress Rheometer DataExotherm Tracker Programme. Frequency: 1Hz, Strain: 5 millistrain
1.0
10.0
100.0
1000.0
10000.0
100000.0
1000000.0
10000000.0
100000000.0
0.001 0.01 0.1 1 10 100
Time (Hours)
Sto
rag
e M
od
ulu
s (P
a)
Blue Curve: Thermal Ramp (20°C to 130°C @ 20°C/min Heating)Red Curve: 1 hour 130°C Isothermal (simulate adiabatic heating)Green Curve: 18 Hr Thermal Ramp (130°C to 20°C @ -0.102°C/min cooling)
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For further information on rheological theory & measurement techniques check out the relevant sections on our website:
Mark C. Edwards ● Gammadot Rheology Testing & Consultancy Services ● www.gammadot.com