prejudices about polyamide for multilayer films
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Prejudices about
Polyamide in multilayer filmsTed Brink 17 June 2015
Page 2 Polyamide in multilayer film - PPS 2015
Contents
• polyamide structure
• processing
• polyamide in barrier applications
• conclusions
Page 3
Prejudices
Page 4 Polyamide in multilayer film - PPS 2015
Prejudices about polyamide
• moisture is difficult to control
• processing temperature is too high
• PA6 not suitable for blown film
• a PE-layer is required for good oxygen
barrier
Page 5
Structure
Page 6
The amide group
Page 7
Most common polyamides for extrusion
PA66
And PA6.66 copolyamide
PA6
Page 8 Polyamide in multilayer film - PPS 2015
Melting points of PA6.66, PA6 and PA66
PA6.66 PA6 PA66
190
220
255
melt
ing
po
int
[°C
]
Page 9 Polyamide in multilayer film - PPS 2015
Influence of PA6/PA66 ratio on the melting point
0 25 50 75 100150
175
200
225
250
275
PA66 [%]
melt
ing
po
int
[°C
]
100 % PA6
100 % PA66PA6.66(85/15 %)
Page 10 Polyamide in multilayer film - PPS 2015
Polyamide comparison
melting point
crys-tallinity
barrier clarity puncture resis-tance
price0
1
2
3
PA66PA6PA6.66lowest
highest
medium
relative comparison
Page 11 Polyamide in multilayer film - PPS 2015
Moisture absorption of PA6.66, PA6 and PA66
PA6.66 PA6 PA660
2
4
6
8
10
12
50 % RHin water
H2
O c
on
ten
t [%
m
/m] at 23 °C
Page 12 Polyamide in multilayer film - PPS 2015
Thermal properties of PA6
0
50
100
150
200
250
300
processing range
crystal growth
melting point
glass transition temperaturetem
pera
ture
[°C
]
Page 13 Polyamide in multilayer film - PPS 2015
Crystallization of polyamide
• at fast cooling rates: no crystallization
• at low cooling rates: large crystals
• presence of nucleant: small crystals
postcrystallization when Tg below ambient conditions
Page 14
Why use polyamide?
Page 15
Main reasons to use polyamide
O2
mechanical strength oxygen barrier
Page 16 Polyamide in multilayer film - PPS 2015
Oxygen versus moisture barrier
0.01 0.1 1 10 1000.01
0.1
1
10
100
1000
10000
water permeation at 23 °C and 85 % RH [g/m²•day]
oxyg
en
perm
eab
ilit
y
(ml•
cm
/m
²•d
ay•b
ar)
x1
00 LDPE
EVOH 32 %EVOH 38 %
EVOH 44 %
PA6
PVDC
BOPET
BOPP
film thickness 100 µmmeasured at 23 °C
Page 17 Polyamide in multilayer film - PPS 2015
O2 permeability of PA6 related to humidity and temperature
0 25 50 75 1000
25
50
75
100
5 °C
23 °C
40 °C
relative humidity [% RH]
oxyg
en
perm
eab
il-
ity (
ml•
cm
/m
2•d
ay•b
ar)
x1
00
Page 18 Polyamide in multilayer film - PPS 2015
Moisture sensitivity of PA6
Permeability:
• dry: 20 cm3/(m2dbar)
• at 85 % RH: 31 cm3/(m2dbar)
values for 50 µm film thickness
Page 19
Consequences for packaging
moisture insidepackaging
PEPA
PE = 100 µmPA = 20 µm
PA = outside
OTR = 16 ml/(m2day) OTR = 35 ml/(m2day)
moisture outsidepackaging
Page 20
Processing
Page 21
Moisture
Page 22
Temperature
Page 23
Double trouble?
Page 24 Polyamide in multilayer film - PPS 2015
Melt stability
• polyamide is a condensation polymer
• when dry → polymerization• when wet → hydrolysis
Page 25 Polyamide in multilayer film - PPS 2015
Melt stability
• reactivity depends on:- moisture content
- residence time
- temperature
- end groups
Page 26 Polyamide in multilayer film - PPS 2015
Extrusion of PA6 – dry (<0.02 % H2O)
residence time
mo
lecu
lar
weig
ht
PA6 = high viscous polymer
Page 27 Polyamide in multilayer film - PPS 2015
Extrusion of PA6 - wet (> 0.1 % H2O)
residence timemo
lecu
lar
weig
ht
PA6 = high viscous polymer
Page 28 Polyamide in multilayer film - PPS 2015
Influence processing temperature of dry PA6
lownormal
residence timemo
lecu
lar
weig
ht
PA6 = high viscous polymer
Page 29 Polyamide in multilayer film - PPS 2015
Moisture during film processing
Too much moisture results in:
• bubbles in the film
• bubble breaks
• hydrolitic degradation
• feeding problems
Page 30 Polyamide in multilayer film - PPS 2015
How to deal with moisture
• resin is supplied dry and ready-to-use
• avoid moisture absorption
• maximum allowable moisture content 0.1
%
Page 31
Bubble instability
Page 32 Polyamide in multilayer film - PPS 2015
Bubble instability during processing
Possible causes (PA-related):
• viscosity too low- wrong grade selection- too high temperature- too high moisture content
Page 33 Polyamide in multilayer film - PPS 2015
Process temperature
Polyamides have a sharp crystalline melting point
Recommendations:
• melt temperature:- PA6.66 ~ 225 °C- PA6 ~ 240 °C- PA66 ~ 270 °C
• apply a flat temperature or reversed temperature profile
• avoid adiabatic extrusion
Page 34 Polyamide in multilayer film - PPS 2015
Example temperature control for PA6
1 2 3 4 Tpol230
250
270
290set actual
barrel zone
tem
pera
ture
[°C
]
1 2 3 4230
250
270
290set actual
barrel zone
tem
pera
ture
[°C
]
flat temperature profile reversed temperature profile
Page 35 Polyamide in multilayer film - PPS 2015
Polyamide film properties
• films are hardly oriented• films are transparent• influence of moisture:
- when dry: high oxygen barrier high modulus
- when conditioned good oxygen barrier flexible postcrystallization possible
Page 36
Applications
Page 37 Polyamide in multilayer film - PPS 2015
Applications with polyamide - food
• meat• cheese• fish• milk• vegetables &
fruits• coffee
Page 38 Polyamide in multilayer film - PPS 2015
Applications with polyamide – non food
• agricultural• medical• industrial
Page 39 Polyamide in multilayer film - PPS 2015
Conclusions
• polyamide is a versatile polymer
• polyamide is easy to process
• polyamide has excellent mechanical
properties
• polyamide has good oxygen barrier
properties
Page 40
Email: ted.brink@extrusionist.com
Tel.: +31 651109899
Internet: www.extrusionist.com
Thank you foryour attention
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