Adhesion to Foil – More Than Just a One-Sided Story
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Adhesion to Foil – More than Just a One-Sided Story
Günter Schubert Otto Plassmann
Session: Barrier Packaging - Paper 7698 Structure
• Introduction to aluminium foil surfaces • Storage of semi-finished laminates • Surface change during storage • Case studies in adhesion failure • Examination of foil/film interfaces using IR-ATR • Carbonyl Index –not only an issue of PE oxidation • ConclusionsPE
Adhesion to Foil – More than Just a One-Sided Story 2 Delaminations Occurring in Extrusion Coatings
Delamination
Aluminium foil LDPE Printed paper Pouch for a typical German barbecue spice mixture
Adhesion to Foil – More than Just a One-Sided Story 3 Structure of a Flat Pouch
Internal contact with packaged good
Flat pouch
PEcoex 30 µm Alufoil 9 µm
PEex 20 µm
Paper 60 g/m² (printed)PE
Pouch for a typical German barbecue spice mixture
Adhesion to Foil – More than Just a One-Sided Story 4 Coil Annealing
Oxygen can enter the coil
Core
Rolling oil can exit via the coil ends
Furnace Inside the coil Furnace tbegin
t1
t2
t3
Roling oil concentration tend
Adhesion to Foil –M Moreore than Just a One-Sided Story 5 Oxide Growth During Coil Annealing
Before annealing After annealing
Thin film of rolling oil Rolling oil residues
Top layer Oxide 1-8 nm 1-6 nm Top layer Barrier layer 1-2 nm 2-8 nm Barrier layer
Aluminium Metal/oxide Aluminium interface where oxide growth takes place If annealing time is too long, the oxide layers of adjacent surfaces can stick together - resulting in poor decoiling and the risk of web breaks
Adhesion to Foil – More than Just a One-Sided Story 6 Coiling Pressure Distribution in a Coil (Schematic)
Relative pressure Low
Core
High
Adhesion to Foil – More than Just a One-Sided Story 7 Wettability Profile Across a Foil Web Wettability High Moderate High (water) Relative Moderate High Moderate winding pressure
Adhesion to Foil – More than Just a One-Sided Story 8 Different Types of Chemical Bonding to Aluminium Foil
CH 2
CH 2 C = O O
HO - C Graft silane (CH2)6 O O C = O H Hydrogen bond Si - O - Soap O O OH OH O O Al -O -Al - O Al -O -Al - O -Al -Al -O -Al -O -Al Oxide Top layer O O Barrier layer Al -O -Al - O -Al Metal
Adhesion to Foil – More than Just a One-Sided Story 9 Practice of Storage of Single-Side Converted Aluminium Foil Contact between the blank side and the adjacent coated side can lead to a transfer of matter and adversely affect adhesion in the subsequent converting step
(e.g. a 50 g/m²-paper with 4 – 8% humidity contains 2 - 4 g/m² water)
Side A coated Side B blank
Adhesion to Foil – More than Just a One-Sided Story 10 Hydroxylation of an Oxide Layer on Aluminium Foil Exposed to Air
O R H
C O
O H C OH
R
H
O R O
H R
O
H C
O C H
OH O
H H
O
H H O O
H H H O H
AluminiumOxide oxidelayer layer
Aluminium foil
Adhesion to Foil – More than Just a One-Sided Story 11 Hydroxylation and Oxide Growth on an Al/PE Laminate Stored at Elevated Temperature with
0,40 *Al-Verbund, 16 825 311 Al-Seite, Polymer abgezogen, good, MW3, GG High 0,3Humidity8 *Al-Verbund, 16 825 312 Al-Seite, Polymer abgezogen, bad, MW3, GG 0,36 0,40 *Al-Verbund, 16 825 311 Al-Seite, Polymer abgezogen, good, MW3, GG 0,384 *A---l-VerbIR-ATRund, 16 825 312 Alof-Se ialuminiumte, Polymer abgezogen ,surface bad, MW3, GG of newly produced laminate 0,362 0.30 0,340 --- IR-ATR of aluminium surface after storage 0,20,328 0,26 0,24 Ext 0,22 inkt 0.20ion 0,2 0 0,18 ν(O-H) ∼ 3300 cm-1 ν(A-O) ∼ 950 cm-1 0,16 0,14 0,12 Absorbance 0.10 0,10 0,08 0,06 0,04 0,02 0.00 0,00 4000 3000 22000000 1500 1000 500 4000 3000 2000We ll enz a h len (c m- 15001) 1000 500 Wave number [cm-1]
Adhesion to Foil – More than Just a One-Sided Story 12 Changes Occurring in Oxide Layer on Aluminium Foil Exposed to Air
H
H R
C O O H O OH
H R
O
H
O
O
O C
OH
H H
R H C R
R
O H
H H C H H C O
H O H O O O O O Hydroxylated top layer AluminiumOxide oxidelayer layer
Aluminium foil
Adhesion to Foil – More than Just a One-Sided Story 13 Bonding to an Oxide Layer on Aluminium Foil Exposed to Air
O CH2 Polymer chain of coating CH2 C CH2
R
O CH
H 2 CH H O 2 R
CH H H 2 CH2 C R CH R O H O OH
H H C H H C C O H
O O O O O O O O H Hydroxylated top layer AluminiumOxide oxidelayer layer
Aluminium foil
Adhesion to Foil – More than Just a One-Sided Story 14 Coiling and Storage of Aluminium Foil Converted on One Side - Transfer of Matter from the Adjacent Surface
Clay-coated paper
Extruded PE Aluminium foil
Adhesion to Foil – More than Just a One-Sided Story 15 Transfer of Ester Wax Species in a Coil from a Coated Paper to an Aluminium Surface 0.20 0,20 *Al-Verbund, Schlechtmuster "Bad, 2.5 Monate", Rand, MW3, GG *Al-Verbund, Gutmuster "48h", Rand, MW3, GG 0.18 0,18
0,16 0.16 Surface plaque after 0.14 0,14 a storage time of 10 -1 0.12 0,12 weeks ν(Al-O) 950 cm Ext inkt 0,10 0.10ion Newly produced 0.08 0,08 laminate, aged for Absorbance 0.06 0,06 3d/40°C in a stack 0.04 0,04 0.02 0,02 0.00 0,00 4000 3000 202000 1500 1000 500 4000 3000 2000We lle nz ah l en (c m 1500-1) 1000 500 Wave number [cm-1] Processing aid on foil surface leads to poor ink adhesion
Adhesion to Foil – More than Just a One-Sided Story 16 Coiling and Storage of Aluminium Foil Converted on One Side – an Adhesion Issue
Extrusion coating
Aluminium foil
Printing pattern
Adhesion to Foil – More than Just a One-Sided Story 17 Printing-Pattern-Related Adhesion of an Extrusion Coating on Aluminium Foil Areas of good adhesion
Areas of poor adhesion O Adhesion to Foil – More than Just a One-Sided Story 18 Different Peel Patterns of the PE Coating
Area with the best adhesion Stick-slip pattern ⊥ Peel direction MD + peel direction
Area with the poorest adhesion No peel pattern O Adhesion to Foil – More than Just a One-Sided Story 19 Examination of Peel Interfaces between Coating and Foil Using IR-ATR
Pressure stamp
Delaminated interface (on coating or foil)
Diamond crystal
ZnSe crystal
IR spectrometer
Adhesion to Foil – M Moreore than Just a One-Sided Story 20 IR-ATR Spectra of Outer Coating Surface and Peel Interfaces
0.30 0,034 0,032 *Polymer, Zone good, glänzende Seite, MW3, ATR *Polymer, Zone good, matte Seite, MW3, ATR 0,030 *Polymer, Zone bad, glänzende Seite, MW3, ATR 0,028 *Polymer, Zone bad, matte Seite, MW3, ATR 0,026 0,024 Ester species present in cases of 0,022 0.20 poor adhesion ( (C=O) 1739 cm-1) 0,020 ν Ext in 0,0kt 18 ion 0,016 Acid compounds 0,014 ν(C=O) 1719 cm-1
Absorbance 0,012 0.10 0,010 0,008 0,006 0,004 0,002 0,000 0.00 1800 1750 1700 1650 1800 1750 W e ll enz ahl1700en (cm-1 ) 1650 Wave number [cm-1] O Adhesion to Foil – More than Just a One-Sided Story 21 Preparation of Interfaces in Aluminium/ Polyethylene Laminates for IR-ATR
Aluminium foil dissolved in dilute acid
Coating (single or coex) Side A
Aluminium foil Side B
LDPE-lamination layer Information depth of IR-ATR Cardboard or paper ~ 2 - 4 µm
Adhesion to Foil – More than Just a One-Sided Story 22 Polyethylene Surface at the Frontier of Acid Attack on Aluminium
Aluminium, not yet dissolved
PE-coating surface for examination
Frontier of acid attack
Adhesion to Foil – More than Just a One-Sided Story 23 Oxidation Index Dependent on the Surface Preparation Method
0,065 *Al-Verbund, LD MFR4, Poly/Al-Seite, HCl, 2cm, GG *Al-Verbund, LD MFR4, Poly/Al-Seite, HCl, 19cm, GG 0,060 *Al-Verbund, LD MFR4, Poly/Al-Seite, HCl, 37.5cm, GG 0.60 *Al-Verbund, LD MFR4, Poly/Al-Seite, HCl, 56cm, GG *Al-Verbund, LD MFR4, Poly/Al-Seite, HCl, 73cm, GG 0,055 *Al-Verbund, LD MFR4, Poly/Al-Seite, Polymer abgezogen, 2cm, GG -1 *Al-Verbund, LD MFR4, Poly/Al-Seite, Polymer abgezogen, 19cm, GG ν(C=O) 1719 cm 0,050 *Al-Verbund, LD MFR4, Poly/Al-Seite, Polymer abgezogen, 37.5cm, GG 0.50 *Al-Verbund, LD MFR4, Poly/Al-Seite, Polymer abgezogen, 56cm, GG 0,045 *Al-Verbund, LD MFR4, Poly/Al-Seite, Polymer abgezogen, 73cm, GG
0,040
(scale) Al foil dissolved Ext 0.40in 0,kt035 in acid ion 0,030
0,025 0.30 PE peeled off - 0,020 lower intensity! Absorbance 0,015
0.20 0,010
0,005
-0,000 0.00 1800 1750 1700 1650 1600 1550 1800 1750 1700 W e ll enz ah1650len (cm-1) 1600 1550 Wave number [cm-1]
Adhesion to Foil – More than Just a One-Sided Story 24 Preparation of Interfaces in Aluminium/ Polyethylene Laminates by Peeling Functional groups close to the surface Better adhesion leads to elongation of the coating and lower concentration of C=O-groups Extrusion coating close to the surface Aluminium foil Functional groups close to the surface
Oxide layer Peel direction ∼ 180° + coating residues Extrusion coating Aluminium foil
Adhesion to Foil – More than Just a One-Sided Story 25 Does the Oxidation Index Correlate with Adhesion Performance?
*Al-Verbund, Probe 1, OK-gelb, links, Polymerseite, MW3, GG *Al-Verbund, Probe 1, OK-gelb, mitte, Polymerseite, MW3, GG 0,060 IR-ATR of PE-coatings 0.60 *Al-Verbund, Probe 1, OK-gelb, rechts, Polymerseite, MW3, GG *Al-Verbund, Probe 2, OK-gelb, rechts, Polymerseite, MW3, GG *Al-Verbund, Probe 2, OK-gelb, mitte, Polymerseite, MW3, GG 0,055 *Al-Verbund, Probe 2, OK-gelb, links, Polymerseite, MW3, GG *Al-Verbund, Probe 3, OK-rot, rechts, Polymerseite, MW3, GG -1 *Al-Verbund, Probe 3, OK-rot, mitte, Polymerseite, MW3, GG ν(C=O) 1718 cm 0,050 0.50 *Al-Verbund, Probe 3, OK-rot, rechts, Polymerseite, MW3, GG *Al-Verbund, Probe 4, BAD-rot, links, Polymerseite, MW3, GG *Al-Verbund, Probe 4, BAD-rot, mitte, Polymerseite, MW3, GG 0,045
(scale) *Al-Verbund, Probe 4, BAD-rot, rechts, Polymerseite, MW3, GG Ext Adhesion Al/PE in 0,0kt 40 0.40ion
0,035 Good
0.30 0,030 Absorbance 0,025 Poor
0.20 0,020 Good 0,015 1800 1780 1760 1740 1720 1700 1680 1660 1640 1620 1800 1760 1720Wellenzah l e n (c m -1 ) 1680 1640 Wave number [cm-1]
Adhesion to Foil – More than Just a One-Sided Story 26 Melt Creep Behaviour of Extrusion Coatings (LDPE MI 4)
Measurement set-up
Cone-plate geometry 190 °C 300 s / 100 Pa 600 s / 0 Pa
Observation of creep deformation and elastic back deformation
Molten extrusion-coated film
Adhesion to Foil – More than Just a One-Sided Story 27 Melt Creep Behaviour of Differently Oxidised Extrusion Coatings (LDPE MI 4) Materials
• Granules MI 4 • Good (coating) [1] Bad (coating) γ • stress [Pa] Deformation Shear
5 10 15 20 Time [min]
Adhesion to Foil – More than Just a One-Sided Story 28 Delamination of a Flat Pouch
0.20 0,20 *Al-Verbund, India, Al-Seite, MW3, Diamant *Al-Verbund, India, Al-Seite, MW3, EtOH, Diamant Ölsäure, Firma: Merck, 2001, Diamant 0.18 0,18 Oleic acid ν(C=O) 1710 cm-1 0.16 0,16 1710 cm-1 ν(C=O) oleic acid 0.14 0,14 ν(Al-O) 0.12 0,12
0.10 0,10 Extinktion Al-surface 1710 cm-1 ν(C=O) 0.08 0,08 Absorbance νbefore(C-H) and after washing
0.06 0,06
0.04 0,04
0.02 0,02
4000 3000 20002000 1000 4000 3000 2000Wellenzahlen (cm-1) 1000 Wave number [cm-1]
Adhesion to Foil – More than Just a One-Sided Story 29 Conclusions
• Aluminium foil surface ensures good wetting and robust adhesion, safely stored in a coil • Exposed aluminium surfaces in semi-finished laminates can undergo changes when in contact with adjacent surfaces of other coiled materials • Matter transfer during storage can be assessed/predicted by means of laboratory tests • IR-ATR is a valuable tool for identifying superficial plaques or adhesion-related interfacial changes • Packaged goods can have adverse and unpredictable effects on adhesion • Adhesion chemistry of polyethylenes is more than the Carbonyl Index
Adhesion to Foil – More than Just a One-Sided Story 30 NOTICE COMPLAINT DEPARTMENT
200 MILES
Adhesion to Foil – More than Just a One-Sided Story 31 Thank you for lending me your ear
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