barrier films

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

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

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.

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

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

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

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

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

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

10

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

11

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

12

Metal/foil laminationComposite building panelsComposite truck trailer panelsNail-collation tape

Metal Bonding Applications Metal Bonding Applications

13

Plastic pipeComposite multi-layer pipeXL-HDPE/Plexar/aluminumXL-HDPE/Plexar/EVOHUnder-floor heatingPotable water applications

Wire and cableAluminum/Plexar/LDPE Cable TV signal transmission


14

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)


15

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

16

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

17

(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

18

(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

19

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

20

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

21

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

22

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

23

Interfacial Interactions at Tie-Layer Adhesives/EVOH

Relationship to Performance:(II) FTIR Study

Main topics:

1. Detection of reaction

2. Correlation to performance

24

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

25

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

26

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

27

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.

28

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.

29

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

30

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

31

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

32

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.

33

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

34

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

35

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

36

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

37

Acknowledgments

The authors would like to thank Ms. Jennifer Nguyen, Mr. Michael Grubb and Mr. William Shumake for their significant contributions.

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