Microsoft School Of Rheology Part 2 Capillary RH2000

User Manual: RH2000

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Part II: Capillary Rheometry

A method to predict flow properties

under processing conditions

Brno, 28-29th march 2012 – School of Rheology

Outline

• Range of Applications for Capillary Rheometry

• Introduction into capillary rheometry: Principle of Operation and

theoretical background

• Test results on LDPE: Complete Capillary Characterisation

• Advanced Test Types: pVT, Relaxation, Thermal Degradation etc.

Capillary Rheometry: Main Applications

Repeat from the previous session: Basic Terms

Repeat from the previous session: Basic Terms

Shear

Shear Force F

Force F

d, L

d, L

Displacement

Displacement u

u

a

ab

b

area

area A = a

A = a ·

·b

b

Height

Height = d

= d

Initial

Initial length

length = L

= L

A

F

dt

d

d

u

tan

=

=

=

τ

γ

γ

γ

&

Strain

Strain []

[]

Shear

Shear Stress [Pa]

Stress [Pa]

Shear

Shear Rate [1/s]

Rate [1/s]

Normal Force !

Normal Force !

Extensional

Extensional Stress [Pa]

Stress [Pa]

Extensional

Extensional Rate[1/s]

Rate[1/s]

Extension []

Extension []

L

= ln l

ε

dt

d

=l

ε

&L

1

A

Fnor

=

σ

Typical

Typical Shear

Shear Rate Ranges

Rate Ranges

10

10-

-1

1

10

10-

-3

3

Sagging

Sagging,

,

Levelling

Levelling

10

104

4

10

101

1

Extrusion,

Extrusion, Injection

Injection Moulding

Moulding

10

100

010

102

2

Mixing

Mixing, Blade

, Blade Coating

Coating,

, Brushing

Brushing

10

103

310

106

6

Roll

Roll Coating

Coating,

, Spraying

Spraying

s

s-

-1

1

Rotational

Rotational-

-Rheometer

Rheometer

High Pressure Capillary

High Pressure Capillary-

-Rheometer

Rheometer

Sample: Water up to high viscous

Sample: Water up to high viscous

Results: Shear

Results: Shear-

-Viscosity,

Viscosity, Elongational

Elongational-

-Viscosity, Wall Slip...

Viscosity, Wall Slip...

Sample: Water up to solids

Sample: Water up to solids

Results: Shear

Results: Shear-

-Viscosity, Yield

Viscosity, Yield Stesses

Stesses,

, Visco

Visco-

-Elasticity, Relaxation...

Elasticity, Relaxation...

Principle of Operation

Given quantity: piston speed ⇒wall shear rate

Measured quantity: pressure drop ⇒wall shear stress

Bore

L

Fully developed flow region

entry

P1

Pw

0

0L

Z

P

v

2R

Entrance pressure drop

Shear pressure drop

Shear pressure drop

Full pressure drop

=

+

⇒small ram extruder

Laminar Pipe Flow

Isothermal, stationary Flow of an incompressible fluid

3

app

Q

4

R

π

⋅

=γ

.

2

P

∆⋅

=τ R

⋅L

app

Newtonian

n =

d(log τ)

d(log γ)Non-Newtonian Index (Ostwald-de Waele)

-R R

0

v

-R 0R

Shear Rate

0

Volumen./s

∆Ρ

Newtonian

Non-

Newtonian

What are we doing to get flow curves?

measurement : ∆

∆

v

tt

Ramp in steps p

p

true

=γ

.

η

τtrue

3

app

Q

4

R

π

⋅

=γ

.

2

P

∆⋅

=τ R

⋅L

app

corrections

Correction: Entrance zone of a capillary die

Aim of the test: to separate entrance pressure and shear

pressure drop!

Pressure

transducer Capillary die

Convergent

Flow

Rosand Twin Bore Principle

Pfull

v

2R

Pfull= Pshear + Pentrance left: capillary right: orifice

v

Lpshear

pentrance pentrance

How do we get the Extensional Viscosity?

Cogswell`s Convergent Flow Model ⇒Extensional Viscosity

λ=9 (n+1)2(Ps)2

32 ηγ2

.

ε≈10-1 -10

3s-1

.

n =d(log τ)

d(log γ)

F. Cogswell, “Polymer Melt Rheology”, Woodhead Publishing Limited (1981)

Non-Newtonian Index (Ostwald-de Waele)

Pfull= Pshear + Pentrance

Zatloukal, Vlcek, Tzoganakis, Saha J. Non-Newtonian Fluid Mech. 107 (2002) 13–37

•Special Orifice Die according

to Uni Zlin Model enables characterisation

of very small extensional rates too.

Example LDPE

LDPE at 190°C

1,0E+01

1,0E+02

1,0E+03

1,0E+04

1,0E+05

1,0E-04 1,0E-02 1,0E+00 1,0E+02 1,0E+04 1,0E+06

Shear Rate / Extensional Rate (1/s)

Shear Viscosity / Extensional Viscosity (Pas)

Low Shear Test Zero Shear

Viscosity

Low Shear 2.0mm

Standard Shear 1mm

Standard Shear Melt Fracture

High Shear 0.5mm

Low Extension 2.0mm

Standard Extension 1mm

Standard Extension Melt

Rupture

High Extension 0.5mm

Extensional Rheology of LDPE

Blow Moulding

⇒Blow Moulding is mainly influenced by Extension!

Surface Instabilities LDPE

Cooling air

Surface shape

Surface Instabilities LDPE

How can the process be improved?

Dehnviskosität - Vergleichskurven zwischen Homopolymer PE und Polymerblend PE-PP

1,0E+02

1,0E+03

1,0E+04

1,0E+05

1,0E-04 1,0E-02 1,0E+00 1,0E+02 1,0E+04 1,0E+06

Extensional Rate (1/s)

Extensional Viscosity (Pas)

Sample 2

Sample 2

Sample 2

Sample 2

Sample 1

Another Example: Co-Extrusion

High

acceleration

Low

acceleration

Similar instabilites

LDPE in Co-Extrusion Die

Instabilities

Instabilities caused

caused by

by Extensional

Extensional Flow

Flow Behaviour

Behaviour of LDPE

of LDPE

Zatloukal et. al. Journal of Applied Polymer Science, 98 (2005) 153

Further Examples: Dispersions

⇒Capillary Rheometry can predict Die Blocking

Scherviskositätskurven bei 40°C

1.0E-02

1.0E-01

1.0E+00

1.0E+01

1.0E+02

1.0E+03

1.0E+04

1.0E-03 1.0E-02 1.0E-01 1.0E+00 1.0E+01 1.0E+02 1.0E+03 1.0E+04 1.0E+05 1.0E+06

Scherrate (1/s)

Scherviskositätskurven (Pas)

Probe 1 Kapillar Test 1

Probe 1 Kapillar Test 2

Probe 2 Kapillar Test 1

Probe 3 Kapillar Test 1

Probe 1 Rotation Test 1

Probe 1 Rotation Test 2

Probe 2 Rotation Test 1

Probe 2 Rotation Test 2

Probe 3 Rotation Test 1

Probe 3 Rotation Test 2

Düsenverstopfung durch

Agglomeration bei Probe 3

Kapillarrheometer

Rosand RH10

Rotationsrheometer

Bohlin Gemini

Rotational:

Bohlin Gemini, Peltier Option,

Cone Plate CP 4°/40

Capillary:

Rosand RH10-D, capillary die

0.4mm diameter / 32mm length,

pressure sensors 500psi,

Rabinowitsch corrected

2. Newtonsches

Plateau Probe 1

(ca. 96 mPas)

2. Newtonsches

Plateau Probe 2

(ca. 170 mPas)

Besseres Standvermögen

Bessere Verarbeitbarkeit

⇒Shear Thickening effect depends on the particle volume fraction

Example: Dispersion Adhesive for Spray Coating

⇒

⇒Rotational and Capillary

Rotational and Capillary Rheometry

Rheometry cover approx 13 decades in shear

cover approx 13 decades in shear

Wide Shear Rate Range

Further Applications: Wall Slip

Wall Slip Velocity of chromium catalyzed HDPE at 190°C

Wall slip velocity increases

dramatically at just above

0.1 MPa.

Wandgleitgeschwindigkeit bei 190°C

-0,1

0

0,1

0,2

0,3

0,4

0,5

0,6

0,7

0,8

0,9

0 50 100 150 200 250 300 350 400

Shear Stress (kPa)

Wall Slip Velocity (m/s)

Wall Slip according to Mooney

Model

Critical Stress

critical stress 120 kPa

Vmax Vmax

Vw= 0

Vw= 0

No wall slip Wall slip

Equilibrium Pressure: Homogeneity

Pressure drop is important

⇒For polymer blens, filled polymers, suspensions, emulsions, composites etc.

homogeneous inhomogeneous

Thermal degradation / Curing

⇒Gives max process time

v

t

Prinzip:

Thermischer Abbau at 260°C

0

1

2

3

4

5

6

0 1000 2000 3000 4000 5000 6000

real time (sec)

Pressure (MPa)

0

10

20

30

40

50

60

70

Pressure Drop

Shear Rate

Extruded Volume

Shear Rate (/s) / Extruded Volume (cm3)

Stick-Slip

Flow Instabilities

⇒What is the max processing pressure / Shear Rate?

Melt fracture

v

t

Linear Ramp

Melt Fracture

Unstable flow, poor product

quality.

1,000s-1 0.1

1

10

100

0 50 100 150 200 250 300

Time

Pressure (Mpa)

POPC

10000

100000

1000000

1 10 100

Shear Rate (1/s)

Shear Stress (Pa)

?

Relaxation LDPE

What happens after processing

⇒inner stresses can lead to surface crack (automotive industry)

v

t

Prinzip:

Relaxation 190°C LDPE

0

5

10

15

20

25

0 50 100 150 200 250 300 350 400

Real Time (sec)

Pressure Drop (MPa)

0

2000

4000

6000

8000

10000

12000

Online Pressure Drop

Shear Rate

Thermal Equilibrium Time

Relaxation Time

λ= 26.75 sec

( Mono-exp. Decay)

Compressibility

PV-Isotherm

PVT: • Mainly needed for flow simulation

pV Isotherme bei 190°C

0

50

100

150

200

250

0 2 4 6 8 10121416

dV/V0 (%)

Pressure (MPa)

PV-Isotherm

dV/V = 1/K·p

Rheometer Types

Benchtop RH2000 and Floor Standing RH7/10

Example: Test Run at RH7

Conclusion

The complete flow behaviour under

processing conditions

Rosand Double Capillary System with Orifice Die:

• direct measurement of the entrance pressure drop - no extrapolation

needed

• calculation of extensional viscosity according Cogswell method

• flow curve up to very high shear end extensional rates

• ability to detect wall slip by Mooney‘s method

• correlation with structural changes during processing

• additional Options for detection of elastic behaviour (Die-Swell)

Thank you for your attention.