This document discusses the fundamentals of rheology and how rheological tests can help with polymer processing and development. It describes different types of rheometers including capillary, rotational, and extensional rheometers. Capillary rheology provides information about how materials behave when melted and correlates flow parameters to mechanical properties. Capillary rheology can determine optimal processing parameters and investigate issues. The document also discusses how rheological properties relate to molecular weight and processing techniques like extrusion, injection molding, and blow molding that can be simulated using a capillary rheometer.

1. THE FUNDAMENTALS OF
RHEOLOGY

2. Rheological tests can be very helpful tools for polymer
processing and development. This presentation is
designed to be an informative introduction and guide to
rheological tests, and finding correlations between
equipment and processing techniques.

3. CAPILLARY RHEOLOGY
• Provides more information than melt
flow testing
• How does the material behave when
melted?
• What are the correlations between flow
parameters and mechanical properties?
• Polymers are non-Newtonian materials,
consequently their flow is not
proportional to the pressure applied
“the flow and shear properties of
materials up to high pressures”

4. WHY CAPILLARY
RHEOLOGY?
• Determine the optimal working
parameters for materials processing
(injection molding, blow molding,
extrusion, etc.)
• Investigate processing issues in a
faster and non-disruptive manner
• Find which materials will work best for
complex parts or long flow lengths
• Replicate manufacturing parameters
for design, troubleshooting, and
simulations

5. TYPES OF RHEOMETERS
Extensional CapillaryRotational
ROTATIONAL
RHEOMETERS
For viscoelastic properties
Rotary motion
Plate geometry: most common
for thermoplastic melts
EXTENSIONAL
RHEOMETERS
For elongational viscosity (high
viscosity materials)
Rotating drum
Extensional flows: very
sensitive to crystallinity &
polymer long-chain branching
CAPILLARY
RHEOMETERS
For viscous properties
Capillary action
Capillary flow: Flow through a narrow
space. Different piston speeds (shear
rates) applied. Viscosity changes
tracked relative to shear rates.

6. SHEAR FLOW
Flow between two parallel plates of area A
Moving with constant velocity V
θ
s
A
D
F

7. SHEAR FLOW
Flow between two parallel plates of area A
Moving with constant velocity V
Shear Rate
Shear Stress
Viscosity

8. POLYMER RHEOLOGICAL BEHAVIOR
WATER
POLYMERSP1
1
P2
1 2
P3
1 2 3
Pressure
Flow
WATER
POLYMERS
Polymer flow is not proportional to the applied pressure Flow curve

9. MECHANICAL & RHEOLOGICAL PROPERTIES
Vs. MOLECULAR WEIGHT
A polymer’s structure influences all its mechanical,
chemical, and rheological properties
MOLECULAR WEIGHT
LOW MEDIUM HIGH ULTRA-HIGH
Young’s
Modulus
Impact
Strength
Melt
Viscoscity

10. -2.000
-1.000
0.000
1.000
2.000
3.000
4.000
-2.00 -1.00 0.00 1.00 2.00 3.00 4.00 5.00
log(Viscosity)
log (shear rate)
Viscosity Vs. Shear Rate
M = 50000
M = 75000
M = 100000
RHEOLOGICAL PROPERTIES
Vs. MOLECULAR WEIGHT
-2.000
-1.000
0.000
1.000
2.000
3.000
4.000
-2.00 -1.00 0.00 1.00 2.00 3.00 4.00 5.00
log(viscosity)
log (shear rate)
Viscosity Vs. Shear rate
M = 75000 MWD broad
M = 75000 MWD narrow
Rheological curve at different MW
(monodisperse polymers)
Rheological curve at different MWD
(monodisperse and polydisperse polymer)
With the same average MW, polydisperse polymers can
be processed better than monodisperse polymers

11. High-molecular weight leads to:
1) Higher Strength: due to higher inter-chain forces, more
entanglements
2) Higher Impact Strength: due to lower degree of
crystallization at higher chain length, more
entanglements
3) Higher Chemical Resistance: due to higher inter-chain
forces
4) Reduction of the “fluidity” (inverse of viscosity) of the
polymer in the melted status: due to the presence of
more entanglements
MECHANICAL & RHEOLOGICAL PROPERTIES
Vs. MOLECULAR WEIGHT

12. POLYMERS & PROCESSES
MATERIAL
Polycarbonate
(PC)
Polyethylene
Terephthalate
(PET)
Polyvinyl chloride
(PVC)
Process • Injection molding • Blow molding • Extrusion
Application
(Examples)
• Spotlights • Plastic bottles • Electrical wires
Advantages
• Transparency
• High-optical clarity
• Acts as a barrier
• High impact
resistance
• Chemically resistant
• Recyclable
• Insulator
• Lightweight
• Durable
• Mechanical damage
resistance

13. CAPILLARY RHEOLOGY
• Many polymer processing
techniques can be simulated
using a capillary rheometer
• This allows users to experiment
with new parameters for
various polymer processing
equipment without having to
stop operation and waste a
batch of material
• Plastic extrusion, injection
molding, blow molding, film
blowing, co-extrusion...

14. PLASTIC EXTRUSION
• Pellets are added into the feeder
• A constant temperature is maintained
• Screw is rotating continuously
• Polymer melts at a constant temperature
• Polymer is pushed through breaker plate into the die
Polymer
Granules
Feeder
Heaters
Polymer MeltExtrudate Die Screw/Barrel
Water
tank
Pull
Roller

15. Feeder
Heater
Polymer
Granules
Extrudate
Die
Screw/Barrel
Mold Cavity
Molded Part
PLASTIC INJECTION MOLDING (IM)
• Pellets are added into the feeder
• Screw is rotating (not continuously)
• Different temperature for different zones
• Screw moves along the barrel as a piston
• Polymer is injected into a mold
• The part is molded and ejected

16. Extrudate
drops
Extrudate fits to
the mold
Mold closes
& air blows
Air Hose
Residue is
trimmed
Cutter
PLASTIC BLOW MOLDING
• Extrusion or injection blow molding
• Molten material (parison) drops in the mold
• Mold is closed
• Air is blown through an air hose
• Molded part is ejected
Polymer Melt Extrudate
Mold
opens,
part
drops

17. PLASTIC FILM BLOWING
• Molten material is extruded through a circular die (usually vertically)
• Air is introduced in the center of the die
• “Bubble–like” expansion
• The tube of film passes through nip rolls
Extrudate
Air
Nip Rolls
Product

18. • Two or more materials fed into
co-extrusion dies
• Constant temperature is
maintained in the die
• Film is extruded
• Layer thickness controlled by
relative speeds and sizes of
extruders
Example Application: food packaging
PLASTIC CO-EXTRUSION
Adhesive Polymer Resin Polymer Resin
Co-Extrusion Dies
Rollers
Co-Extruded Tape
Winding
Feeder 1
Feeder 2

19. )(Log
)(Log-1 0 1 2 3 4 5
f (T, P, material)
INJECTION MOLDINGEXTRUSION
MELT FLOW
CAPILLARY
RHEOMETRY
ROTATIONAL RHEOMETRY
PROCESSING & FLOW CURVE OF POLYMERS

20. CAPILLARY RHEOMETERS
MEASURE LOAD
OR PRESSURE
SET DIE GEOMETRY
AND PISTON SPEED
Shear Rate=
Speed of Deformation
Viscosity =
Resistance to the Flow
Shear Stress
Pressure
Transducer
Motor-Driven
Piston
h
V

A
F






Capillary
Die (L/D)
Force (Load Cell)

21. RAW DATA:
Constant shear rate steps with
pressure reaching the equilibrium
after a transient stage
RHEOLOGICAL CURVES:
Viscosity (Pa· s) as a function of
shear rates (s-1)
Shear stress (Pa) vs shear rate
(s-1)
RHEOLOGICAL DATA

22. PP @ 230°C
Filled PP @ 230°C
RHEOLOGICAL DATA
Virgin PP:
Non–Newtonian
shear thinning behavior
η = 241 – 34 Pa·s
max P ≅ 8 MPa
Filled PP (50% wt flax):
Non–Newtonian
shear thinning behavior
η = 1061 – 81 Pa·s
max P ≅ 20 MPa

23. EXTRUSION/IM & THE CAPILLARY RHEOMETER
Polymer Granules
Feeding
Extrudate Die Barrel

24. CO-EXTRUSION & SQC ANALYSIS

25. Die Swell Accessory
EXTRUSION & SR DIE SWELL ACCESSORY
Extrudate Die
Swelling of the Polymer

26. EXTRUSION/IM & MELT FRACTURE
Unstable flow Polymer GranulesBarrel
Production Rate
Output
Smooth Shark
Skin
Spurt Fracture
Unstable flow
Direction
of flow
Increasing
Flow rate
Melt
Instability

27. IM MOLD FILLING & SR PVT ACCESSORY
Partial Filling Complete Filling
Simulations for Mold Filling Phase
PVT Test
Mold Cavity
Molded Part
Complete Mold Filling is Critical to the Process

28. IM MOLD FILLING& SR TC ACCESSORY
TC Test
Mold Cavity
Molded Part
Heat Conduction through the material is
critical to get a perfectly molded part

29. BLOW MOLDING/FILM BLOWING & SR STRETCHING UNIT
Polymer Melt Extrudate
Air Hose
Stretching

30. THANK YOU FOR YOUR TIME!