Download - Barrier Films
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Determining the Most Effective Tie-Layer in Response to New Material Developments
Barrier Film ConferenceBrussels, Belgium
Dr. Maged Botros and Dr. Jean Merrick-MackFebruary 22, 2006
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2Main Topics
Background Exploring requirements and applications enabled
by new adhesives
Correlation of performance to interactions at tie-layer/substrate interface
New developments in high-performance tie-layers Summary and conclusions
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3PLEXAR products are tie-layer adhesives manufactured in the United States by Equistar Chemicals, a Lyondell company. They are maleic anhydride modified polyolefins for high-performance packaging.
Functionalized polymers are used to bond dissimilar materials in coextruded, coated or laminated structures.
Market introduction in 1976 First tie-resin in North America Equistar is one of the largest suppliers.
Key applications: High-barrier food packaging Metal bonding
PlexarPlexar TieTie--Layer Resins Layer Resins BackgroundBackground
Plexar is a registered trademark of Equistar Chemicals, a Lyondell company.
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Tie-Layer Adhesives
Product / Base Resin Selection
Plexar Adhesives Used in Food and Non-Food Applications
Plexars used in food contact applications are subject to Specific Migration Limits (SML) under European Directive 2002/72/EC - Food Contact Plastics and Amendments. Not all Plexar grades are suitable for all food applications. Please consult Lyondell Product Safety for additional details
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5LLDPE-Based Tie-Layer Adhesives
LLDPE-based adhesives are the resin of choice for a majority of EVOH/PA applications. These grades provide cost-effectiveness, high adhesion, good processability, and clarity.
Applications: Flexible packaging for meat and cheese Liquid packaging for wine, soups, sauces and
condiments Lidstock for sealing to rigid containers PE blow molding adhesive for EVOH PE sheet for thermoformed containers
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6EVA- and LDPE-Based Tie-Layer AdhesivesApplications: Films with high Clarity Flexible meat and cheese packaging Thermoformed trays
Products: Medium VA content adhesive for flexible packaging High VA content adhesive for flexible packaging and
thermoformed containers with adhesion to PE, EVOH, PA, ionomer, PS and PET
LDPE-based tie-layer resinsCommonly used in flexible packagingExhibit excellent melt strength, clarity and taste/odor
characteristics.Primarily used in coextrusion coating and bubble wrap
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7Polypropylene-Based Tie-Layer Adhesives
PP-based products provide high adhesion to EVOH and PA, good processability, stiffness, and stress crack resistance for flexible and rigid coextrusion.
PP-based Plexar product line is designed to offer a variety of adhesion levels depending upon end use.
Applications: Flexible packaging Thermoformed sheets Blow molded bottles
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8HDPE-Based Tie-Layer Adhesives
HDPE-based adhesives are designed for improved moisture vapor barrier in flexible packaging, high stiffness for rigid packaging, low taste and odor, and high adhesion for mostly PA barrier structures.
Applications: Cereal/cracker box liners Meat/cheese packaging Blow molded liquid packaging
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9 Blown/cast film: Meat and cheese packaging Liquid packaging Boil in bag Dry food packaging Bubble films
Extrusion coating: Paperboard cartons Snack packaging Ovenable board
Blow molding: Bottles Fuel tanks
Other applications: Metal/foil laminations Plastic pipe Wire and cable Sheet/thermoforming Tubes
TieTie--Layer Coextrusion ApplicationsLayer Coextrusion Applications
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Coextrusion Coating
Plexar products for coextrusion coating are designed for easy extrudability, high melt strength, and excellent adhesion to polyamide (PA), ethylene vinyl alcohol (EVOH), cellulose and foils.
Applications: Liquid packaging Flexible packaging Truck panels
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Laminating Resins
Laminating resins are designed for high adhesion to steel, aluminum, EVOH, PA and PE.
Applications: Building panels Truck trailer panels Wire and cable coatings
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Metal/foil laminationComposite building panelsComposite truck trailer panelsNail-collation tape
Metal Bonding Applications Metal Bonding Applications
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Plastic pipeComposite multi-layer pipeXL-HDPE/Plexar/aluminumXL-HDPE/Plexar/EVOHUnder-floor heatingPotable water applications
Wire and cableAluminum/Plexar/LDPE Cable TV signal transmission
Metal Bonding Applications Metal Bonding Applications
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External protective pipe coatings
Anti-corrosion coatingLarge diameter metal pipesGas and crude oil (on- and offshore)Coating: three-layer coated pipe Pipe/epoxy/tie-layer (PE or PP)/HDPE + black (LLD, LDPE and PP)
Metal Bonding Applications Metal Bonding Applications
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Coextruded sheet/thermoformed containers
Examples/applications:
HDPE/tie/EVOH/tie/HDPEPolystyrene/tie/EVOH/tie/PESingle-portion containers
Coextruded tubes
LDPE/tie/EVOH/tie/LDPE
Application:Highly-flavored toothpaste, specialty creams and lotions
Sheet/Thermoforming and Tube ApplicationsSheet/Thermoforming and Tube Applications
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Correlation of Performance to Interactions at Tie-Layer/Substrate Interface
Adhesion performance in flexible and rigid application Interfacial interactions at tie-layer adhesives/EVOH Relationship to performance
9 Performance of new developments9 Applications: Film, blow molding, sheet and
thermoforming
Techniques applied:
Rheological investigation FTIR spectroscopy
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(A) Film Applications: Adhesion at Tie-Layer/EVOH Interface for PP-Based Tie-Layers
1.72.3
1.82.8
3
6.2
1.31.9 1.8
2.5
012
34567
8
A
d
h
e
s
i
o
n
(
N
/
1
5
m
m
)
PP Tie-1 PP Tie-2 PP Tie-3 PP Ref-1 PP Ref-2
Adhesive
Day 0 Day 1
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(B) Blow Molding Application: Adhesion at Tie-Layer/EVOH Interface for PP-Based Tie-Layers
24 23
7
0
5
10
15
20
25
30
A
d
h
e
s
i
o
n
(
N
/
1
5
m
m
)
PP Tie-2 PP Tie-3 PP Ref-1
Adhesive
Day 1
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Interfacial Interactions at Tie-Layer Adhesives/EVOH
Relationship to Performance: (I) Rheological Study
Parameters studied:
1. Complex viscosity
2. Storage modulus, G
3. Loss modulus, G
4. G, G relationship
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1.E+03
1.E+04
1.E+05
1.E+06
0.01 0.1 1 10 100 1000
Frequency (radians/second)
E
t
a
*
,
P
o
i
s
e
Tie-1
Tie-2
Tie-3
Ref-1
Ref-2
PP
Complex Viscosity Versus Frequency for PP-Based Tie-Layer Blends With EVOH
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1.00E+02
1.00E+03
1.00E+04
1.00E+05
1.00E+06
1.00E-02 1.00E-01 1.00E+00 1.00E+01 1.00E+02 1.00E+03
Frequency, rad/s
G
'
PPRef-2 Ref-1Tie-3'Tie-2'Tie-1'
G Versus Frequency for PP-Based Tie-Layer Blends With EVOH
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1.00E+02
1.00E+03
1.00E+04
1.00E+05
1.00E+06
1.00E-02 1.00E-01 1.00E+00 1.00E+01 1.00E+02 1.00E+03
Frequency, rad/s
G
"
,
G
'
PP / G" PP / G'
Ref-1/G" Ref-1 / G'
Tie-3/G" Tie-3 / G'
G and G Versus Frequency for PP-Based Tie-Layer Blends With EVOH
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Interfacial Interactions at Tie-Layer Adhesives/EVOH
Relationship to Performance:(II) FTIR Study
Main topics:
1. Detection of reaction
2. Correlation to performance
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Tie - 1Tie - 2
Tie - 3
Ref - 1Ref - 2
PP
0.550.600.650.700.750.800.850.900.951.001.051.101.151.201.251.30
A
b
s
o
r
b
a
n
c
e
1650 1700 1750 1800 1850 Wavenumbers (cm-1)
1740 cm-1Ester Band
Acid Band
FTIR Spectra For PP Tie and PP Blends With EVOH
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Correlation Between Adhesion and Ester Formation in PP Tie/EVOH Structures
0
0.005
0.01
0.015
0.02
0.025
0.03
0.035
0.04
0.045
0.05
Tie-1 Tie-2 Tie-3 Ref-1 Ref-2 PP
Adhesive
N
o
r
m
a
l
i
z
e
d
E
s
t
e
r
B
a
n
d
0
0.2
0.4
0.6
0.8
1
1.2
A
d
h
e
s
i
o
n
(
L
b
s
.
/
I
n
)
EsterAdhesion
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New Developments in High-Performance Tie-Layers
I. High-clarity barrier films Multi-layer film transparency Challenges New developments
II. High-performance tie-layer development for polystyrene (PS)/high-impact polystyrene (HIPS) applications Performance Advantages of new development
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Global Trend: Increasing Demand for High-Clarity Barrier Films
Consumer preference for retail display packages with excellent optics Films with poor clarity detract from a
quality image.
Intense competition in film-converting industry for distinguishing benefits Clarity is a must-have feature.
Low-clarity films are at a disadvantage.
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Transparency Loss in Barrier Coextrusions
Measurement: narrow angle scattering (NAS)
Phenomena:
Coextruded barrier films with low optical transparency due to apparent instability at tie-barrier interface- Ground glass, graininess, orange peel appearance
Cause:
An uneven interface between tie layer and barrier layer, possibly caused by covalent bonding, that amplifies interfacial stresses that lead to nanometer scale distortions.
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Adhesion Versus Clarity in Standard Multi-layer Films With EVOH Barrier
0
1
2
3
4
5
6
2MI LLDPE Adh-A Adh-B
Adhesive
A
d
h
e
s
i
o
n
(
N
/
1
5
m
m
)
0
5
10
15
20
25
30
35
40
45
50
N
A
S
Adhesion
NAS Clarity
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Performance of New Tie-Layer Developments in Multilayer Films With EVOH Barrier
7.9
2118.4
28
42
27
05
101520
25303540
45
Standard-A Tie-Clarity1 Tie-Clarity-2
5X Adh (N/15 mm) NAS
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Key Attributes of New Developments
LLDPE-based tie-layer: 1.1 MI, 0.92 density
Specifically designed for EVOH blown film coextrusions when excellent optics and transparency are required9 Good viscosity and shear stress matched of most blown film EVOH grades9 Optimized anhydride content for adhesion and transparency9 Unique structure and graft architecture 9 Ability to absorb and dissipate interfacial stresses
High quality and unique benefits Low gel levels High melt strength, thermal stability, and good processability -- similar to
unmodified LLDPE
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Summary of High-Clarity Development
The effect of adhesion on multi-layer film clarity was investigated.
It was concluded that the higher the adhesion, the lower the clarity.
New adhesives maintain high clarity and high adhesion at the same time.
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Product characteristics
LLDPE-based tie-layer adhesive
Melt index = 3.30 g/10 min (D 1238)
Density = 0.9335 g/cc (D 1505)
Vicat softening point = 88.3C (D 1525)
High-Performance Tie-Layer Development for PS/HIPS Applications
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Plexar Tie-layer Performance
600 Micron Coex Sheet: PS+HIPS/PX/EVOH/PX/PS+HIPS
16.2
7.58.3
1.9
02468
1012141618
Adhesion (N/2.54 cm)
Inner OuterTie-Layer
PlexarReference
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Technical Summary for PS/HIPS Applications
Obtained excellent results with new Plexar tie-layer development
Doubled performance compared to reference Main advantages:
1. Excellent processability in sheet and thermoforming applications
2. Improved adhesion3. Low odor4. Good cutability (no stringing)5. High-temperature applications
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Summary and Conclusions Plexar tie-layer adhesives produced by Equistar is the first maleic
anhydride tie-layer adhesive developed in North America. Discussed requirements and applications are enabled by new
adhesives. Investigated interactions between tie-layer adhesives and EVOH: Direct relationship between adhesion and observed ester/acid
formation suggests a reaction between maleic anhydride groups in the tie layer and OH groups in EVOH.
The techniques employed in this investigation were used as tools in developing high-performance Plexar tie-layer adhesives that are targeted for specific applications. New tie-layer developments for high-performance applications: High-clarity, multi-layer film application High-performance tie-layer development for PS/HIPS applications
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Acknowledgments
The authors would like to thank Ms. Jennifer Nguyen, Mr. Michael Grubb and Mr. William Shumake for their significant contributions.