Extrusion

1. Polyamide extrusion
Processing guidelines Ted Brink

2. Page  2

3. Moisture
Page  3

4. How to deal with moisture
Page  4
• reliable resin manufacturers supply nylon
dry and ready-to-use
• avoid moisture absorption
• use packaging size according to consumption
• shield hopper from atmosphere
• maximum allowable moisture content 0.1 %

5. Too high moisture
Page  5
• too high moisture content results in:
• bubbles/foaming of the melt
• holes in the film
• bubble collapses
• hydrolytic breakdown

6. Screws for polyamide extrusion
Page  6
General Purpose screws can be used, provided:
• the barrel is not grooved (unless .....)
• the heating capacity is sufficient
• the compression ratio is < 4.0
• the L/D ratio is > 24
• barrier screws suitable

7. Mixing or dispersing elements
Page  7
• mixing sections on standard 3-zone screws may be
needed
• dispersing antiblock agent
• pigments
• not needed for standard additives
• mixing elements:
• pineapple (distributive mixing)
• pin (distributive mixing)
• Maddock (dispersive mixing)

8. Screen pack
Function:
• build-up pressure
• filtration
Page  8

9. Extruder output PA6 extrusion
Page  9
800
600
400
200
0
30 60 90 120 150 180
output [kg/hr]
screw diameter [mm]
• single screw
• 3-zone
• Tcil 250 °C

10. Thermal properties of PA6
Page  10
300
250
200
150
100
50
0
processing range
melting point
crystal growth
glass transition temperature
temperature [°C]

11. Communicate with the machine
Page  11
• listen to what the machine is telling you
• watch energy demand of band heaters
– shows where energy is needed
– shows where no energy is needed
• avoid adiabatic extrusion
– the machine is in control, not you!
– Tpol will show large variations

12. Temperature settings
Page  12
• too low settings may result in too high polymer
temperature
• nylons with higher crystallinity require different
approach

13. Melt stability
Page  13
• polyamide is a condensation polymer
• consequence for extrusion:
• when dry: polymerization occurs
• when wet: depolymerization occurs
• reactivity depends on:
• moisture content
• residence time
• temperature
• end groups

14. Miscelleneous
General:
• die gap 1 – 1.2 mm
Blown film:
• BUR 1:1 – 1:3
• lay flat when film is stil warm to prevent wrinkles
Cast film:
Chill roll temperature:
• 20 – 40 °C for optimum thermoforming behavior
• 80 – 130 °C for optimum dimensional stability
• chill roll as close to the die to avoid neck-in
Page  14

15. Film post treatment
Page  15
• Corona treatment
• Plasma treatment
• Flame surface treatment
• Purpose of these treatments:
• increase surface energy so that inks “wet-out”
• improve adhesion during lamination
However, polyamide has intrinsically
good printing and lamination performance
and thus no real need for Corona treatment
untreated film
treated film

16. Polyamide film properties
Page  16
• films are (near to) isotropic
• films are transparent
• high puncture resistance

17. Influence of moisture on film properties
Page  17
• when dry:
• very high oxygen barrier
• high modulus
• when conditioned
• high oxygen barrier
• increased flexibility
• postcrystallization possible
• dimensional fluctuations

18. Coextrusion
Page  18
• polyamide mostly used in multilayer structures
• polyamide function:
• mechanical protection
• barrier properties
• tie resin required for adhesion to nonpolar polymers
like PE and PP
• coectruded polymers should rheologically match

19. Applications
Page  19
Food packaging
• cheese
• meat
• fish
Non food
• agricultural films
• medical films
• release films for smc

20. More information
Page  20
Contact
Ted Brink
Email: ted.brink@extrusionist.com
Internet: www.extrusionist.com
Tel.: +31 651109899