Basic Training March/April 2003
Basis Extrusion of Polyamides / Nylons
Albert Flepp
FPA/ 01.02/ Extrusion-e
Seite 1
The main Differences between
Injection Moulding and Extrusion (1/2)
Property
Injection Moulding
Extrusion
Process
Discontinuous
Continuous (except EBM)
Shear rate
High
Low
Moisture influence (Nylon) High
Very high
Material viscosity
Low
Middle - very high
EMS-Material grades and
Polymer Types
• GF-reinforced
• Non reinforced
• Semi crystalline and
• Semi crystalline
amorphous
• PA 12, PA 6, Grivory G 16/
• Grivory GV/HT, PA 6, PA 66,
G 21, CoPA 612, PBt
Grilamid TR, PA 12
FPA/ 01.02/ Extrusion-e
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The main Differences between
Injection Moulding and Extrusion (2/2)
Property
Injection Moulding
Extrusion
Typical applications with • Functional automotive-, elec- • Automotive media conveyEMS-Polyamides
tronics- and I&O-parts
ing tubes
• Barrier packaging- and
technical films
• Barrier juice bottles and agrochemical containers
• Sheathing (OF, cables, etc.)
• Automotive air-ducts
Forming
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Tool
Die / Calibrator
Process follows viscosity
Viscosity [Pa • s]
Process
Very high - Extrusion Blow
Moulding (EBM)
EMS-Extrusion
Polymers
Typical Material
PA 6 / PA 12
Grilon R 50 HNZ
(Grilamid L 25 ANZ)
30 / 275°C, 21.6 kg
- Blown-film
PA 6
Grilamid L25 W40 X, 30 / 275°C, 5 kg
Grilon R 47 HW,
Grilpet B 24 HNZ
8 / 275°C, 5 kg
Grilon F 50
Medium
- Coating / Sheathing
AL-pipes
- Cast-film
PA12 / PA 6
PA 6
CoPA 612
Grilamid L 20
Grilon F 40
Grilon CR 8
Low
- Sheathing e.g. cables,
optical fibres etc.
- Sheathing automotive
hand brake cable
PA12,
PBT
PA 66
Grilamid L 16
Grilpet B 24
(Grilon T 300 NZ
only EMS PA 66
extr. grade)
High
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- Tube extrusion,
PA12, PA 6, PBT
Corrugated tube extrusion
MVR/Measurement
conditions [cm³/10 min]
120 / 275°C, 5 kg
50 / 230°C, 2.16 kg
Melt Volume Rate (MVR)
Mesurement principle
kg
(e.g. 5 Kg)
Z
Start
Melt
e. g.
Grilamid L 25 W 40 X
End
Heating
(e.g. 275°C
Die
Barrel
Ø D
Z = distance in 10 minutes
FPA/ 01.02/ Extrusion-e
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Volume [cm³] = ø D ² x ¶ / 4 x Z
Process follows viscosity
High Viscosity = low Melt Volume Rate (MVR)
According to the MVR a rough estimate of the
viscosity (low, medium, high) is possible within
the same Polymer group (e.g. PA6). The testing
conditions (temp & force) have to be identical.
FPA/ 01.02/ Extrusion-e
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Viscosity Grilamid L 25 W 40 X
10000
Viscosity [Pas]
230°
250°
270°
1000
100
10
7
100
300
1000
Shear rate [1/s]
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3000
10000
Fusing Process
Bulk Density, PA 12 0.6 - 0.7 kg/dm³
Breaker Plate
Screen
Pack
Heat + Friction
Melt
Torpedo
Melt + Sold Material
Metering Zone
Compression
Solid Material
Feeding Zone
Water tempered
Feed bush
Temperatures settings
210°C
200°C
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200°C
50 - 80°C
Typical Outputs with Grilamid and Grilon
Output 300
[kg/h]
200
Example: Extruder D 60
Grilamid L 25 W 40 X
Tube 8 x 1 mm
100
80
Extrusion Speed 60 m/min
60
40
Ô
20
0
0
30
60
90
screw diameter [mm]
FPA/ 01.02/ Extrusion-e
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Output 80 kg/h
High Driving Power Necessary for Processing
Nylons
P [kW]
300
high-viscosity PA
medium-viscosity PA
200
100
60
30
15
10
5
0
0
30
60
Screw ø D [mm]
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90
120
Proven Feeding Bush for Nylon
Filler Shaft
Cylinder
Groove
Conveying
Direction
Sealing Flansh
Feeding-Bush
Isolation
2D
Detail Cross Section (Feeding Bush):
≤ 0.5 mm
Smooth or slight grooved e.g.
„Saw-Tooth-Shaped“
Water tempered 50 - 80°C
5 mm
8 mm
Feeding - Bush
Oil tempered ~ 125°C Õ high heat temperature
and gently start-up necessary.
Constant temperatures = constant output
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Deep grooved
(PE-design)
The Typical Extruder for Processing Nylons
1
2
3
4
5
Drive unit (high driving power)
Feed section / Feeding Bush (water cooled)
Cooling vents
Feed hopper
Heater vents 3.5 W/cm²
(setting temp. up to 320°C)
Head
PI
PI
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= Melt pressure indicator
Screw:
3 - Zone screw L/D 24 or 25
Compression ratio 2.5 - 3 : 1
Material: Nitrided steel
dD3
D
d1
h1
h3
Proven screw dimensions for processing
Polyamide
Metering Zone
L/D
20
24 or 25
28
Compression Zone
L
L3
L2
8 -10
8 -10
9 -12
4-7
4-7
4-7
Compression ratio
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L1
L2
L3
V2
Feeding Zone
L1
4 -7
8 - 11
9 - 11
Tread depth ratio
Barrier-Screw (Basic Diagram)
Sold Material Channel
Principal Flight
Barrier Flight
Barrier
Screw
Standard
Screw
Melt and Solid Materia
in same Chanel
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Separation melt and
solid material
Proven Heads for the Extrusion of Nylon-Articles
(1/2)
Head-Type
Typical use
Spider-head (Centre fed- •Mono tubes
die)
•Mono corrugated hoses
Characteristics
•Simple design
•Long parallel zone (high
pressure drop)
•Risk of weld lines
Spiral mandrel-head
•No weld lines
•Multilayer (coextrusion)
•Expensive
tubes, corrugated hoses and
•Good layer distribution
blown-film
•Short parallel zone
Pan cake-die
•Multilayer tubes and blownfilm
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•Compact design
•Each layer/material
separately heatable
Proven Heads for the Extrusion of Nylon-Articles
(2/2)
Head-Type
Typical use
Cable-coating-die
•Sheathing (cable, OF, metal
•1 weld line
pipe, etc.)
Flat-film-die (Coat
hanger-die)
•Cast-film
Accumulator head
•Extrusion Blow Moulding
(technical parts)
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Characteristics
•Discontinuous process
•Combination of spiral
mandrel and spider-head
Proven Heads for the Extrusion
of Nylon Articles
Spider Head (Center-Fed-Die)
Torpedo
Screw
Screen
pack
Pin
Die
Catering screw
Braker
plate
Pin holder
Spiral Mandrel Head
Flat Film Die (Coat Hanger Die)
Melt
Distribution
Principle
Lower Part
Top
Part
Wire
Restricted Flow Zone
Coathanger manifold
Cable Coating Die
Coated cable
Spiral
Mandrel
Die
FPA/ 01.02/ Extrusion-e
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Wire
Pinole Feeding Point
Troubleshooting Tips (1/2)
Problem
Possible Cause
Corrective Action
Melt foams, contains air
bubbles
•Material is wet
Drying 70°C in dehumidifying
dryer 8 - 18 hours
•Temperature hopper zone
not constant
•Temperature hopper zone
too low
•Granule size not equal
•Not equal feeding
í Regulation hopper zone
temperature
í Increase temperature hopper
zone
í Change material
í Use 0.05 - 0.1 % lubricant
(Mg-Sterat recommended)
Melt pressure/amperage
not constant
Necessary driving power
too high
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•Deep grooved feeding bush í Tempering feed bush up to
125°C (with oil)
(PE design)
•Barrel setting temperature í Increase barrel setting
temperature
too low
Troubleshooting Tips (2/2)
Problem
Possible Cause
Corrective Action
Extrudate has weld lines
(Dornhalter)
•Head temperature too low
í Increase head setting
temperature
•Melt temperature too low
í Increase barrel setting
temperature
í Use of screen pack in front of
breaker plate
(90/900/90 mesh/cm²)
Poor meld
homogenisation
FPA/ 01.02/ Extrusion-e
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•Shear in the extruder too
low
Moisture absorption
Grilon (PA 6), Grilamid (PA 12)
at 23°C/50% RH
Water content [%]
0.25
Grilon (PA 6)
0.2
Grilamid (PA 12)
0.15
Upper
limit
0.1
0.05
0
0
2
4
6
Time [h]
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8
10
12
Moisture absorption
Grilon (PA 6), Grilamid (PA 12)
At 23°C/50% RH
Water content [%]
3.5
3
2.5
Grilon (PA 6)
2
Grilamid (PA 12)
1.5
1
0.5
0
0
2
4
6
Time [days]
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8
10
12
Convection Drying / Dehumidifying System
1
2
3
4
5
6
7
8
9
10
12
=
=
=
=
=
=
=
=
=
=
=
Ventilator
Filter
Control Value
Hopper
Absorption Molecular Filter
Heating
Temperature Control
Thermometer Gauge
Outlet
Feeding Hopper
Ventilator
Dew point ≤ 25°C, Temperature 70°C
Drying time 8 - 18 hs (depending on the water content)
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Pellet Oven
(Basic Principle)
a, b, c
= Sheet Guide for Air
d
= Fresh Air Inlet
e
= Ventilator
f
= Exhaust Air
g
= Heating
Not dried hot air
Summer: 20°C/80% R.H.
Dew point + 15.5°C = 13.5 g water/m3 air
Autumn or Spring: 15°C/70% R.H.
Dew point + 9°C = 9.15 g water/m3 air
Winter: 0°C/70% R.H.
Dew point -4°C = 3.46 g water/m3 air
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