1 conferencia magistral - osswald

8/3/2019 1 Conferencia Magistral - Osswald

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Mixing

Distributive and Dispersive Mixing in Extrusion Processes

Polymer Engineering Center

University of Wisconsin-Madison

1

Tim A. Osswald


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Mixing

Rayleigh disturbances

Thread formation

Hole formation due tointerfacial instabilities

Pellet

Film ribbon formation

Distribution

Dispersion

Coalescence

Morphology withg

compatibilizer

Morphology withoutcompatibilizer

u

2


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Distributive Mixing

3


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Distributive Mixing

0

A0

A0A0

A(t)

(t)

4


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Distributive Mixing

= 0o

= 90o A(t)

A0= cosGrowth:

Orientation:

Deformation:

90o

90o

=

t

0

dt

5


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Distributive Mixing

Erwin/Ng (1980)6


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A

A0=

2

2

A

A0=

3

3

A

A0=

NN

A

A0=

A

A0 e

/2

Distributive Mixing

100

2,500

37,000

5E21

100

Erwin/Ng (1980)7


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Schematic diagram of a Kenics static mixer

Distributive Mixing

8


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Experimental progression of the

layering of colored resins in aKenics static mixer

Entrance

Exit

Distributive Mixing

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Schematic diagram of a co-kneater

Distributive Mixing

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Typical pin and slotted flight type

single screw extruder distributive

mixing sections.

Distributive Mixing

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Unwrapped channel contents of a pin barrel extruder.

Distributive Mixing

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Distributive Mixing

Boundary Element Model of Static Mixer

Gramann/Osswald (2000)13


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Distributive Mixing

Boundary Element Model of Static MixerPressure Distribution

Gramann/Osswald (2000)14


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Boundary Element Model of Static Mixer

Streamlines

Distributive Mixing

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f(t)

F

(t

)F(t) =

t

0

f(t)dt

0 t

t = 0

t = t

Residence Time Distribution


Cummulative



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Distributive MixingResidence Time Distribution

The Perfect Mixer

(1 C0)Q

C0Q

Q

Q QQ


17


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Various rhomboidal single screw extruder distributive mixing sections.

Distributive Mixing

Rios/Osswald (2000)18


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Distributive Mixing



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Distributive Mixing



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Dispersive mixing of a solid agglomerate

Dispersive MixingSolid agglomerates (Carbon black) into a polymer (Rubber)

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Dispersive Mixing

Felongation = 6r2

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Schematic diagram of an internal batch mixer

Fraction below 50nm

Dispersive Mixing

Manas/Tadmor (1980)23


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PA6 Thread

PS Matrix

Dispersive Mixing (Grace Diagram)Incompatible liquids (Polymer Blends)

Dispersive mixing of incompatible liquids

0 sec 1 sec 2 sec 3 sec 4 sec

Meijer24


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Ca 0

Ca < CacritCa = Cacrit

Ca =R

s

= SHEAR FLOW

25


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SHEAR FLOW

Cacrit

100

101

02

106

10310

0101

.......................

3.

8


drop

matrix

26


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Ca 0

Ca =R

s

=

Ca < CacritCa = Cacrit

ELONGATIONAL FLOW

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SHEAR FLOW

Cacrit

100

101

02

106

10310

0101

.......................

3.

8


drop

matrix

ELONGATIONAL FLOW

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Typical single screw extruder distributive mixing sections with dispersive capabilities

Dispersive Mixing

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Commonly used single screw extruder dispersive mixing section

Dispersive Mixing

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Twin screw extruders

Dispersive Mixing

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Dispersive Mixing (Blends)

Co-Rotating Twin screw extruder (Commonly used today)

32


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Dispersive Mixing (Blends)

Counter-Rotating Twin screw extruder (Not commonly used today)

33


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Schiffer/Osswald 200


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Krawinkel/Osswald 2


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Krawinkel/Osswald 2


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Distributive mixing governed by deformation

and orientation

Dispersive mixing governed by stresses

Elongational flows are preferred for both

distributive and dispersive mixing

Elongational flows lead to lower energy

consumption and consequently lower viscousheating

CONCLUSIONS

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