mvtr barrier of metallized pla films - aimcal3-6 1-3 bopp 150-180 0.5 – 0.8 nylon 2-3 15-25 •...

MVTR Barrier of Metallized PLA Films

Sigma Technologies Int’lA. Yializis PhD

Presented By: Steven Yializis

1

What Is PLAWhat Is PLAMVTR of Metallized PLA FilmsMVTR of Metallized PLA Films

PLA is a Natural Product Based on Plant Photosynthesisy

H2O + CO2 + Light CH2O + O2

C O SCH2O Sugar Fermentation Lactic Acid

PLAPLAPoly Lactic Acid

Lactic Acid(α-hydroxypropionic acid) Dimer Polymer

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What is PLAWhat is PLAMVTR of Metallized PLA FilmsMVTR of Metallized PLA Films

• PLA can be produced from many different sugars that are derived from i th t i l dvarious crops that include

– Corn, Rice, Wheat, Sugarcane, Beets, Potatoes

• In the US Corn is the most abundant and lowest cost source of sugar

• Corn is processed in a wet milling process where starch is separatedCorn is processed in a wet milling process where starch is separated from fats, fiber, proteins, etc.

• Starch is reacted with enzymes to produce Dextrose (sugar)• Starch is reacted with enzymes to produce Dextrose (sugar)

• Dextrose is fermented and purified to produce Lactic Acid

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PLA Polymer Films PLA Polymer Films MVTR of Metallized PLA FilmsMVTR of Metallized PLA Films

• Since PLA is an aliphatic polyester formed by condensation of an acid• Since PLA is an aliphatic polyester formed by condensation of an acid with an alcohol it should not be confused with PET which is known also as polyester

PLA PET

Th PLA l i h f d i t l fil i bi i ll• The PLA polymer resin when formed into a polymer film is biaxially oriented with the same MD and CMD stretch as PET, therefore a PET line can produce PLA with no efficiency loss

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Basic Properties of PLA FilmsMVTR of Metallized PLA FilmsMVTR of Metallized PLA Films

• Clear polymer filmsy• High modulus• Safe for Food Contact• Resists degradation by oils and fats• Resists degradation by oils and fats

Good: for Aroma and Non Polar Solvents• Barrier:

O COPoor: Moisture vapor, Oxygen and CO2

• Low Flammability – Low smoke generation (much lower than PET)• Resists UV degradation• Very Hydrophilic – good breathability – good printability• Biodegradable – Must first hydrolyze back to Lactic Acid• Effective hydrolysis requires 60+oC and 95%+RH

σ SEffective hydrolysis requires 60+ C and 95%+RH

Barrier Properties of PLA FilmsMVTR of Metallized PLA FilmsMVTR of Metallized PLA Films

POLYMER OTR (100sq.in) MVTR (100sq.in)

PLA 35-45 15-25

BOPET 3-6 1-3

BOPP 150-180 0.5 – 0.8

NYLON 2-3 15-25

• PLA films resemble Nylon6 when one looks at MVTR alone• Unlike Nylon Metallized Films result in a poor metallized barrier

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Unlike Nylon Metallized Films result in a poor metallized barrier

Metallized PLA MVTR BarrierMVTR of Metallized PLA FilmsMVTR of Metallized PLA Films

•• Eldridge Mount (Converting Magazine Sept 8 2008) Reported that Eldridge Mount (Converting Magazine Sept 8 2008) Reported that “the best metallized moisture barrier value I have seen being about “the best metallized moisture barrier value I have seen being about 3 gm/M^2/day 3 gm/M^2/day (0.2 gm/100in^2/day)”(0.2 gm/100in^2/day)”

C l l tC l l t h i l di t lli f PLA fil th i l di t lli f PLA fil t•• CelplastCelplast who is a leading metallizer of PLA films, reports:who is a leading metallizer of PLA films, reports:– For clear SiO2 – Ceramis coated PLA Films,

WVTR 7.75 gr/m2/24hrs - (0.5 grams/100 sq.in/24hrs) – For Al Metallized Films MVTR as low as 3.7gr/m2/24hrFor Al Metallized Films MVTR as low as 3.7gr/m2/24hr

(0.25 grams/100 sq.in/24hr)

• Sono-Tek Corp is reporting a coating of ultra-thin layer of clay nanoparticles to enhances PLA barrier properties

• A patent application by a major PLA film OEM is claiming metallized MVTR barrier of 1gr/m2/24hr using a polyolefin coating

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1gr/m2/24hr using a polyolefin coating

BASIC REQUIREMENTS FOR PRODUCING A HIGH METALLIZED FILM BARRIER

MVTR of Metallized PLA FilmsMVTR of Metallized PLA Films

SUBSTRATESUBSTRATE PROPERTIESPROPERTIESSUBSTRATE SUBSTRATE PROPERTIES PROPERTIES – Adequate Thermomechanical Stability

• To Allow Deposition of the Aluminum Layer with no MicrocrackingSubstrate Surface Should be Free of Contaminants– Substrate Surface Should be Free of Contaminants

• Low Molecular Weight Polymer – LMW, Additives • Loose Particles

– Surface Flatness: Apart of a Small number of IrregularitiesSurface Flatness: Apart of a Small number of Irregularities, Surface Microroughness Should be of the Same Order of Magnitude and the Barrier Layer Thickness

– Surface of Substrate Should Have Adequate Chemical Functionality to:

• Promote Adhesion Of Barrier Layer• Maximize Crystal Nucleation

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Can PLA Film Fulfill the Basic Requirements?


PLA SUBSTRATE PLA SUBSTRATE PROPERTIES PROPERTIES Adequate Thermomechanical StabilityYES – Adequate Thermomechanical Stability

• To Allow Deposition of the Aluminum Layer with no Microcracking

– Substrate Surface Should be Free of Contaminants

YES

YES? Substrate Surface Should be Free of Contaminants• Low Molecular Weight Polymer, Additives • Loose Particles

– Surface Flatness: Apart of a Small number of Irregularities,

YES?

YES p g ,Surface Microroughness Should be of the Same Order of Magnitude and the Barrier Layer Thickness

– Surface of Substrate Should Have Adequate Chemical F ti lit t

YESFunctionality to:

• Promote Adhesion Of Barrier Layer• Maximize Crystal Nucleation

Wh I th MVTR f M t lli d PLA S P ?

σ SWhy Is the MVTR of Metallized PLA So Poor?

Problem: Degradation of Al Layer in Contact with the PLA Polymer


LA Will C Al tAluminum Layer

LA Will Cause Al to Microcrack and Corrode

PLA FILMPLA FILM

HydrolyzedPartially Hydrolyzed PLA Polymer Prior to

Moisture During the MVTR Test

Hydrolyzed MonomericComponents Will cause Al to Microcrack

yMetallization Additional and PLA Polymer

σ SMicrocrack

Solution: Isolate the Al Metal Layer from the PLA Polymer


Aluminum Layer

PLA FILMUniform Thickness, Thermo echanically PLA FILM Thermo echanicallyStable Polymer Layer

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Polymer Coated PLAMVTR of Metallized PLA FilmsMVTR of Metallized PLA Films

•• Most PLA OEMs and converters have concluded the PLA filmMost PLA OEMs and converters have concluded the PLA filmMost PLA OEMs and converters have concluded the PLA film Most PLA OEMs and converters have concluded the PLA film must be coated in order to enhance the barrier properties of must be coated in order to enhance the barrier properties of metallized Aluminum metallized Aluminum

K P ti f l tiK P ti f l ti•• Key Properties of polymer coatingKey Properties of polymer coating– Must be thin enough not to disqualify PLA as a compostable and

renewable polymer film

– Uniform thickness to fully isolate the aluminum layer from the PLA

– Must Adhere to the PLA surface

– Thermomechanically stable

– High surface functionality to produce a good metallized layer

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Coating of PLA Film Inline with MetallizationCoating of PLA Film Inline with Metallization


• Sigma Has Been Working For Several Years to Develop P d E i t T h l i T F ti liProcess and Equipment Technologies To Functionalize Surfaces Without Solvents and Water

• IncentivesIncentives– Environmentally Friendly Processes – No Hazardous Waste– Low Energy Consumptiongy p– Small Real Estate Footprint

• Processes That Can Be Performed on Wed Substrates Without th U f S l t d W tthe Use of Solvent and Water– Vacuum Plasma Treatment– Atmospheric Plasma Treatment and Grafting

Vacuum Based Polymer Coatings

σ S– Vacuum Based Polymer Coatings

Polymer Multi Layer Coating TechnologyPolymer Multi Layer Coating Technology


•• Sigma has Developed an 100% Solids “Dry Coating” Process:Sigma has Developed an 100% Solids “Dry Coating” Process:•• Sigma has Developed an 100% Solids Dry Coating Process:Sigma has Developed an 100% Solids Dry Coating Process:– No Solvents which Require Recovery – No Hazardous Waste for Disposal– No Primers Surfactants and Adhesion Promoters – ReplacedNo Primers, Surfactants and Adhesion Promoters Replaced

by Inline Plasma Treatment

•• Monomers are Monomers are Deposited onto the Surface of a Substrate and Deposited onto the Surface of a Substrate and C d U iC d U i El t B C t iEl t B C t iare Cured Using are Cured Using an Electron Beam Curtainan Electron Beam Curtain

•• Submicron Thick Coatings Can be Used to Change the Submicron Thick Coatings Can be Used to Change the Chemical andChemical and ThermomechanicalThermomechanical Properties of Polymer FilmProperties of Polymer FilmChemical and Chemical and ThermomechanicalThermomechanical Properties of Polymer Film Properties of Polymer Film

•• Polymers Can be Deposited Polymers Can be Deposited IInline with the Metallization Process nline with the Metallization Process

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Polymer DepositionPolymer DepositionMVTR of Metallized PLA FilmsMVTR of Metallized PLA Films

σ SSOLID LIQUID GAS LIQUID

MONOMER DEPOSITIONMVTR of Metallized PLA FilmsMVTR of Metallized PLA Films

• Operating Pressure: 0.5torr and below

• 100nm Thick Layers are Adequate for most Applicationsy

• Deposition Speed: 200-1500+ft/min

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RADIATION CURING: UV or Electron BeamMVTR of Metallized PLA FilmsMVTR of Metallized PLA Films

•• EE--Beam Operating Beam Operating Pressure:Pressure:– 10 mtorr or lower

•• UV Operating Pressure:UV Operating Pressure:– Atmospheric Pressure or

V– Vacuum

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2.5m Wide Production Machine Designed for Acrylate Coating, Metallization and other Specialty Products


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Properties Of Different Properties Of Different Polymer Polymer CoatingsCoatings


•• Broad Range of Monomer Chemistry: Broad Range of Monomer Chemistry: – Free Radical Polymerizable AcrylatesFree Radical Polymerizable Acrylates – Cationically Polymerizable Materials

• Epoxies • Vinyl monomers

•• Clear and Transparent Films Clear and Transparent Films C ea a d a spa e t sC ea a d a spa e t s•• Thickness as low as 5Thickness as low as 5nmnm•• AntiAnti--StainStain•• AntiAnti--flammableflammable•• AntiAnti--bacterialbacterial•• Chemical Sensing Chemical Sensing -- Color ChangeColor Change•• Metal Chelating Metal Chelating •• ColorColor•• Heat Sealing Heat Sealing gg•• UV AbsorbingUV Absorbing•• IonicallyIonically ConductiveConductive•• Electrically DissipatingElectrically Dissipating•• ReleaseRelease

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Historic Best Barrier Data To date with Different Barrier Materials


BARRIER STACK MVTR (gr/m2/24hr)at 37C

Polycarbonate/Acrylate/ ITO/ 0 04 ± 0 04Acrylate 0.04 ± 0.04

PET/Acrylate/SiO2/Acrylate 0.03 ± 0.002y y

PET/Acrylate/Al/Acrylate 0.004± 0.005

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PLA Barrier StructureMVTR of Metallized PLA FilmsMVTR of Metallized PLA Films

•• Given the lowGiven the low--end packaging application of metallized PLA films and issues relating end packaging application of metallized PLA films and issues relating to added thickness of non compostable and renewable polymer materials, a thin to added thickness of non compostable and renewable polymer materials, a thin p p y ,p p y ,acrylate undercoat with thickness of 0.1acrylate undercoat with thickness of 0.1--0.2 mm is a realistic target (instead of 0.2 mm is a realistic target (instead of Acrylate/Al/Acrylate)Acrylate/Al/Acrylate)

•• First Series of Experiments: (Aluminum OD=2.7)First Series of Experiments: (Aluminum OD=2.7)PLA/Al– PLA/Al

– PLA/Plasma/Al– PLA/Acrylate - PET/Acrylate (witness sample) – PLA/Plasma/Acrylate - PET/Plasma/Acrylate (witness sample) y y ( p )– Perform adhesion tests

•• Control metallization trials show that Al bonds well to PLA films, although reaction Control metallization trials show that Al bonds well to PLA films, although reaction with the hydrolyzed PLA surface causes Al to perhaps microwith the hydrolyzed PLA surface causes Al to perhaps micro--crack and corrode crack and corrode M A l t f l ti f il d t dh t PLA dl f th l l f lM A l t f l ti f il d t dh t PLA dl f th l l f l•• Many Acrylate formulations failed to adhere to PLA, regardless of the level of plasma Many Acrylate formulations failed to adhere to PLA, regardless of the level of plasma treatmenttreatment

•• It appears that the hydrolyzed surface of the PLA has too high a quantity of low It appears that the hydrolyzed surface of the PLA has too high a quantity of low molecular weight species to allow it to bond with the molecular weight species to allow it to bond with the acylateacylate coatings, unless the coatings, unless the

σ Sacrylate is made to react with the PLA surface acrylate is made to react with the PLA surface

MVTR of PLA Coated with Acrylate Polymer Layers of Different Chemistry


ACRYLATE CHEMISTRY

BARRIER STACKDEPOSITED ON PLA

MVTR -37C (gr/m2/24hr)

COMMENTSCHEMISTRY DEPOSITED ON PLA (gr/m2/24hr)

± 0.002

A Plasma/AlPlasma/Acrylate/Plasma/Al

2.200.25

AdhesionNo Adhesiony

B Plasma/Acrylate/Plasma/Al 0.50 No Adhesion

Plasma/Al 2 20 AdhesionC Plasma/AlPlasma/Acrylate/Plasma/Al

2.200.33

AdhesionNo Adhesion

DPlasma/Al

Plasma/Acrylate/Plasma/Al2.200.39

AdhesionNo Adhesiony

E* Plasma/AlPlasma/Acrylate/Plasma/Al

2.000.15

AdhesionGood Adhesion

σ S* Designed to React with the PLA Polymer

ConclusionsMVTR of Metallized PLA FilmsMVTR of Metallized PLA Films

• Metallized Al adheres well to PLA films but has relatively poor moisture vapor barrier propertiesvapor barrier properties

• Many Acrylate polymer chemistries have poor adhesion to PLA regardless of level of plasma treatment, degree of cross linking and polymer thickness

• All acrylate polymer coatings improve the moisture vapor barrier of the metallized films by about an order of magnitude, even if some coatings have poor adhesion to the PLA film

• The barrier results suggest that key properties for an effective polymer coating include, uniform thickness, high surface energy and adequate thermomechanical properties to allow it to be metallized without damage

• This work was conducted in a narrow web development machine, higher barrier is expected in a production machine

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mvtr barrier of metallized pla films - aimcal3-6 1-3 bopp 150-180 0.5 – 0.8 nylon 2-3 15-25 •...

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