Rubber and Plastics Formulations for Food Contact

Dr. Mike Zumbrum, Maztech, Inc.

Dr. Roger Avakian, PolyOne Corp.

OutlineIntroduction: Polymer ParametersExample FormulationsImpact of AdditivesOptimizing FormulationsApplicationsConclusionsAcknowledgements

Polymer ParametersChemical CompositionMolecular Weight & DistributionStereochemistryTopologyMorphologyAdditives

© 2010 Thomas C. Ward

Important Energies to ConsiderIntermolecular Intramolecular

θ

φ

t

g+

g-

Chain Stiffness and Bond Rotation

Hydrogen Bonding in Polyamides© 2010 Thomas C. Ward

Microstructures of Chemical Composition

© 2010 Thomas C. Ward

Molecular Weight Distribution

http://openlearn.open.ac.uk/mod/resource/view.php?id=196637

Effects of Stereochemistry:Geometric Isomers of Polyisoprene

© 2010 Thomas C. Ward

Trans-Polyisoprene

© 2010 Thomas C. Ward

Additional Stereochemistry:Tacticity of Polymers

© 2010 Thomas C. Ward

Effect of Tacticity on Glass Transition Temperature (Tg) of Polyacrylates

© 2010 Thomas C. Ward

Topology of Polyethylene

HDPE

LDPE

LLDPE

© 2010 Thomas C. Ward

Thermoset Network Topology

© 2010 Thomas C. Ward

Morphology of Polymers

Tm Tg

© 2010 Thomas C. Ward

Spherulitic Morphology of PET

20 µ

Microphase Separated Morphology of Styrene Butadiene Block Copolymer

PR Lewis and C Price, Polymer, 13, 22 (1972)

Morphology of Impact Modified Nylon

IM1/Compatibilizer Only IM1

Smaller Impact Modifier Size Gives Better Impact in this System

Polymer ParametersChemical CompositionMolecular Weight & DistributionStereochemistryTopologyMorphologyAdditives

21CFR177.2600i. Elastomers—EPDM, Silicone, NRii. Vulcanization Materials

i. Vulcanizing Agents—Sulfurii. Accelerators/Retarders—TMTM, DiCUPiii. Activators—Stearic Acid

iii. Antioxidants—BHT, TNPP (21CFR178.2010)iv. Plasticizers—Dioctyl phthalatev. Fillers—ATH, TiO2, SiO2, carbon blackvi. Colorantsvii. Lubricantsviii. Emulsifiersix. Miscellaneous—blowing agents

OutlineIntroduction: Polymer ParametersExample FormulationsImpact of AdditivesOptimizing FormulationsApplicationsConclusionsAcknowledgements

Example Formulations

Thermosets:Platinum silicone EPDM

Thermoplastics:Styrenic block copolymer (TPE)PolypropylenePET

Platinum Silicone FormulationVinyl SiloxaneFumed SilicaHydride SiloxaneEthynyl CyclohexanolPlatinum Catalyst

70 %25 %5 %0.1 %15 ppm

Base PolymerReinforcementCrosslinkingInhibitorHydrosilylation

Vinyl Siloxane Hydride Siloxane

EPDM Formulation63 %31 %(15 %)0.6 %3 %0.9 %0.9 %0.3 %0.5 %

EPDMCarbon BlackOilStearic AcidZinc OxideSulfurTMTMMercapto BZAntioxidant

Base PolymerReinforcementExtenderCo-activatorActivator CurativeAcceleratorCo-acceleratorHeat Stabilizer

Could have 20 different ingredients

Thermoplastic Elastomer (TPE) Styrenic Block Copolymer

S-EB-SPolystyrenePolypropyleneMineral OilBHTAlphamethyl styrene

58 %22 %Optional16 %0.3 %3.4 %

Base PolymerReinforcementToughnessSoftnessStabilizerProcessing

Broad range of properties available depending upon composition

Composition called out in FCN from Kraton

Polypropylene FormulationPolypropylenePhosphiteBHTNucleant

99 %500 ppm1000 ppm0.5 %

Base PolymerProcessing stabilizerCo-stabilizerCrystallization

Thermoplastic formulations have fewer ingredients.

Materials sold as produced from resin manufacturer.

PET FormulationPolyethylene TerephthalatePhosphiteAnthranilic Acid derivative(Amorphous Nylon & cobalt catalyst) in masterbatchsAnthraquinone dyeBenzotriazole

99 %100 ppm200 ppm(3 %)

50 ppm1000 ppm

Base PolymerStabilizerScavengerOxygen scavenger

ColorantUV Absorber

Very low levels of additives today Depends upon application (ie. bottles)

OutlineIntroduction: Polymer ParametersExample FormulationsImpact of AdditivesOptimizing FormulationsApplicationsConclusionsAcknowledgements

Types of AdditivesStabilizers/Antioxidants (21CFR178.2010)Modifiers (plasticizers)Colorants

Organic (phthalocyanine, anthraquinone)Inorganic (TiO2, carbon black)

Mold Releases & Slip AgentsEuracamides, waxes, silicones

Flow AidsLow MW olefinsGlycerol monostearateVulcanized vegetable oil

Conductive materialsOthers

Why Use Stabilizers/Antioxidants?Protect Polymer During:

DryingProcessing—Extruding; moldingIn Use ExposureLong Term Exposure

Protect Against:Thermo-oxidative DegradationLong Term Heat/UV RadiationHarmful Effects of Gamma Radiation SterilizationGas Fading – reactions with NOx

Common StabilizersHindered phenolsPhosphites—TNPPThio-estersAluminum Trihydrate (ATH) Al2O3

.3H2O

BNX 1010

TNPP

Temperature Range for Stabilizers

HinderedAmines

HinderedPhenols

Thioesters

Phosphites

http://www.ampacet.com/usersimage/File/tutorials/Antioxidants.pdf

Modifiers(Typically Used at Levels >1 wt.% to ~40 wt. %)

PlasticizersDioctyl phthalate Mineral oil

Impact Modifiersrubbery materialcore shellfunctionalized EPDMHIPS—polybutadiene

Testing to Identify Extractables & Leachables

Test Conditions: Some Standard…Many CustomUsually 24 hrs at fixed temperature using:

Distilled Water5% Acetic Acid95% Ethanol or hexane to simulate Fatty Foods

Sometimes a “Synthetic Olive Oil” is Used

Analytical MethodsGravimetric Organic analysis: Chromatography—GC & LCElemental analysis: ICP & Ion Chromatography

Concerns about Leachables

Residual MonomersStyrene (Suspect Carcinogen) Bis-phenol A (Suspect Endocrine Disrupter)VCM (Vinyl Chloride Monomer) Carcinogen

ModifiersPlasticizers

Phthalates (Suspect Endocrine Disrupters)Mercaptothiazole (Suspect Carcinogen)

StabilizersTNPP tris(nonyl phenyl) phosphite (Endocrine Disrupter)

NanotechnologyExtractability of Inorganic ParticulatesCarbon Nanotubes

Fibrous Irritant like asbestos?

Do Nanomaterials penetrate cell walls?Can they be inhaled, or consumed internally from packaging End of LifeWhere do they go upon combustion, land burial, disposal at sea?

New Approaches

Naturally Occuring StabilizersVitamin EGlycerol Monostearates

Bound StabilizersInorganic Stabilizers

Non-migrating, e.g. nano Zn Oxide

NanoplateletsSynthetics: α-zirconium phosphate

OutlineIntroduction: Polymer ParametersExample FormulationsImpact of AdditivesOptimizing FormulationsApplicationsConclusionsAcknowledgements

Optimizing FormulationsStructure

Chemical Composition, MW, stereochemistryFillersCrosslinkersAdditives

ProcessShear/DispersionCoupling AgentsTemperature/time

PropertiesModulus, strength, fatigue life, compatibility

Properties

Structure Process

Extrusion and Compounding

16 mm Twin Screw Extruder Sigma Blade Dough Mixer

Example of a Optimized Mixture Design

COM-A COM-B COM-A COM-B

F.M.=a’ComA+b’ComB+c’*IM1Impact=a*ComA+b*ComB+c*IM1

Typical Response Surface Plot

X1 ( 1 . 0 0 )X2 ( 1 8 . 0 0 )

X2 ( 4 . 0 0 )

X3 ( 1 5 . 0 0 )

X3 ( 1 . 0 0 )

0 .0 0 0

0 .2 5 0

0 .5 0 0

0 .7 5 0

1 .0 0 0 D

esira

bility

X1 ( 1 5 . 0 0 )

OutlineIntroduction: Polymer ParametersExample FormulationsImpact of AdditivesOptimizing FormulationsApplicationsConclusionsAcknowledgements

Hygienic Envelope Gaskets

Hygienic EPDM Gaskets

BPE Standard Test Conditions

Dynamic Application: Effects of Fatigue on EPDM Diaphragm

FailedNew

Effects of Thermal & Chemical Cycling on Fluoropoymer Lined Hose

Severe Cracks

Smooth,Straight,New Liner

Failed HoseNew Hose

Conclusions

Start with the polymer parametersAdditives are often necessary—watch

for leachablesOptimize by understanding structure-property-process interrelationshipsUnderstand the application requirements

Acknowledgements

Tim Rugh – 3-A StandardRoger Avakian – PolyOne Corp.Tom Ward – VA TechBob Elbich – Exigo Manufacturing