New Developments in Ionomer Technology for Film Applications

1
New Developments in Ionomer Technology for Film
Applications

• Barry Morris
• DuPont Packaging and Industrial Polymers

2
Acknowledgements

• Dave Walsh
• Karlheinz Hausmann
• John Chen
• David Londono
• Donna Visioli

3
Discussion Outline

• Ethylene Ionomer Introduction
• New Antistatic Ionomer
• Background
• Film Results
• New Highly Permeable Ionomers
• Novel ionomer technology
• Novel ionomer performance capabilities
• Morphological studies and modeling
• Conclusions

4
Ethylene Ionomer Introduction

• Partially neutralized ethylene co-polymers
  containing carboxylic acid
• E/AA or E/MAA
• neutralized with Na, Zn, etc.
• Thermally reversible network structure
• Crystals
• Ionic crosslinks
• Amorphous regions

5
Characteristic Ionomer MorphologyNetwork per
Ionic Domains and Crystallites
6
Ethylene Ionomer Performance Characteristics

• low seal initiation temperature
• broad hot tack strength
• High melt strength and formability
• oil and grease resistance/ seal around
  contamination
• high stiffness (for a sealant resin)
• outstanding toughness and puncture resistance
• optical clarity and high gloss
• high abrasion resistance
• excellent chemical resistance
• high resilience and cut resistance (golf balls)

7
Traditional Ionomer Design Parameters

• Acid copolymer base resin
• MI
• acid level
• acid type
• Termonomers (e.g. acrylate)
• Architecture (small extent)
• Neutralizing cation
• neutralization

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Antistats
9
Surface Resistance Spectrum
1016
Insulating
Polymers
1014
1012
Chemical Antistatic Compounds
1010
Dissipative
IDP Compounds
108
Surface Resistivity, W/sq.
106
104
Carbon powders and fibers based compounds
Conductive
102
10
Highly Conductive
EMI Compounds (carbon and metal fibers)
10-2
10-4
Metals
10-6
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Antistatic Ionomer

• Polyolefins are prone to static build-up
• Electrical insulator
• Do not readily pick up moisture
• Susceptible to dust accumulation, static
  discharge, etc.
• Methods used to reduce static build-up
• Antistatic additives
• Conductive fillers
• Antistatic coatings

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Current Types of Antistatic Additives

• Blooming
• Come to surface during processing
• 1 2 added
• Low cost
• Most do not work well at low RH
• Wear off with time
• May cause problems with delamination/adhesion
• Permanent
• Added at 10-30 levels
• Usually work at low RH
• Do not wear off
• Can cause processing and aesthetics problems
• May yellow upon aging

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Potassium Ionomers as Antistats

• Permanent type does not wear off
• Effective immediately (no blooming time)
• Compatible with polyolefins minimum change in
  optical properties
• Non-yellowing
• FDA compliant for direct food contact
• Effective at 30 RH and higher

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Blends with PE
Similar results were found for PP cast films
14
Blown film
15
Static Decay
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Highly Permeable Ionomers
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Novel Ionomers Through Fatty Acid Salt
Modification

• Mg Stearate used in the present study
• Novel performance capability for packaging
  applications
• Increased gas permeability
• Performance balance between breathability and
  stiffness
• Thermoplastic processibility
• Cast or blown film, Monolayer or multilayer coex
• Thermoformable

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Comparable modulus, much higher OTR
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Typical Heat Seal Strength Conventional
Ionomers vs. Novel Ionomers
Seal strength at 135 C,g/15 mm
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Higher modulus at comparable OTR
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Fundamental Study of Ionic Morphology

• SAXS analysis
• Liquid-like ionic domain modeling
• Thermal analysis (DSC)
• Primary and secondary ethylenic crystallites
• WAXS analysis
• Formation of small stearate crystals
• Proposed ionomer morphology changes
• Origin of performance enhancement

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SAXS Analysis of Novel Ionomers
Significant increase in the population of ionic
domains in MgSt modified ionomers
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SAXS Analysis For Morphology Study
Bimodal distribution in domain size and increase
in number density of domains
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DSC Analysis of Modified Ionomer
Ethylenic crystallinity reduced by MgSt
modification
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WAXS Analysis of Stearate Crystallinity Formation
Additional crystalline phase is developed by MgSt
modification
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ConclusionsOrigin of Performance Enhancement

• Ionic morphology refinement and enhancement
• Substantial increase in ionic domain population
• Suppressed ethylenic crystallinity
• Enhanced network structure leads to
• Higher gas permeability
• Stiffness decreased by reduction in primary
  crystallinity, increased by enhanced network
  structure
• Lower heat seal strength

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ConclusionsGraphical Representation of
Ionomer Morphology Changes
Fine secondary crystals are included in the
morphology
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Summary

• Ionomers have a unique combination of attributes
  for film applications
• New attributes continue to be developed
• The potassium cation creates antistatic
  functionality for blending with polyolefins
• Fatty acid salt modification creates new
  morphologies
• Breathabilty with stiffness

29
Thank You.
Questions?
Barry Morris DuPont Packaging Industrial
Polymers