1

Polymer/inorganic nanocomposites:Polymer/inorganic nanocomposites:Opportunities for Opportunities for

food packaging applicationsfood packaging applications

Evangelos ManiasEvangelos ManiasPolymer Nanostructures Lab.Polymer Nanostructures Lab.

Materials Science & Engineering dept.Materials Science & Engineering dept.

Penn State UniversityPenn State University

University Park, PAUniversity Park, PA

manias@psu.edu

IFT Summit – Food PackagingBaltimore, May 2006

Ph.D. students:Ph.D. students:Ken StrawheckerMatt HeideckerTheresa FoleyZhiming WangVikram KuppaGreg HogsheadAlexei KisselevPonusa Songptiya

Financial Support:Financial Support:NIST NSFACS/PRF ONRAir Products UTC/IFC BAYER MatSciCoca-Cola Asahi-Kasei Arrow-BioMedSumitomo Chemicals Mitsubishi

Collaborators:Collaborators:M. Jimenez-Gasco (PSU)T.C. Chung (PSU)J. W. Gilman (NIST)

J. Genzer (NCSU)R. Krishnamoorti (UH)

R.A. Vaia (AFRL)

AcknowledgementsAcknowledgements

http://zeus.plmsc.psu.edu/

100 nm

Postdocs:Postdocs:Hiroyoshi NakajimaJin-Huh YoungS. ChowdhuryGeorge PolyzosLixin WuYang JiangM.Rackaitis

Fuel-Cells:Zijie LuHungoo ChoYungkyu Chang

OutlineOutline

Introduction”nanotechnology”, what is it and why do you care?one example: polymer/clay nanocomposites

Nanocomposite Opportunities in Packagingmechanical propertiespermeability (barrier properties)antifungal activity, flame retardancy, transparency

Concluding RemarksFuture Outlook: A personal Perspective

NanotechnologyNanotechnology

A Definition:When a material or system is reduced in size, at some characteristic size this material or system changes completely in nature. This characteristic size is dictated by the material in question, but is typically1-100 nm.

A couple of (not-so-good) examples:ants can raise small droplets of water as if they are solid objectsa semiconductor below a characteristic length ( λdB ) behaves like an insulator, and if a large voltage is applied it turns into a conductor

(tunneling diodes & quantum-effect transistors)

NanotechnologyNanotechnologywhat can we do with it?what can we do with it?

Problem:Make a device which can hold and transport a liquid, that:-is flexible but non-permeable to gases-can last 100 years, but if disposed can degrade completely in non-toxic products that are fully recyclable

-when torn or scratched it can fix itself on its own-can widen or shrink reversibly as flow-demands change

Solution:Take a bunch of polymers and “glue” them together with water (!!! ??)Examples:Veins and other biological structures in any animal(where the nm-structure is responsible for the properties)

Polymer/Inorganic NanocompositesPolymer/Inorganic Nanocomposites

PolymerizationAnnealing

above softening

temp

Immiscible Intercalated Exfoliated

“in situ” “melt mixing”

2

Structure of nanocompositesStructure of nanocomposites

100nm

Intercalated ExfoliatedCourtesy of

R. Vaia /AFRL

Property Enhancements due to nm FillersProperty Enhancements due to nm Fillers

Concurrent Property Changes (cf. the respective pure polymers):improved mechanical propertiesdramatically reduced gas permeabilityincreased thermal stabilityincreased fire resistance

AND Maintainprocessability (extrusion, molding)recyclability, optical clarityflexibility, light weight

Examples of “requests” in food-packaging applications:non-permeable (to gasses/liquids), but flexible and light-weightstiff, but thin and transparentstill cheap (!! in most cases, price determines commercialization)

Achieved with:extremely low filler content (typ. 1-5 wt%)simultaneous and non-trivial improvement in many properties

UBE Nylon 6 Toyota timing belt cover; engine manifold coverNylon 6 Film for packagingNylon 6/66, 12 Fuel system components

BAYER Plastics Nylon 6 Film for meat packaging Nylon 6 coating for paper board juice containerPC/ABS Flame retardant computer and monitor housings

Foster Corp. Nylon 12 nanocomposites used in catheter tubingGM Polyolefin TPO for step on Astro vans to replace talc filled material.

Will be integrated into other parts in near future.Unitika Nylon 6 automotive parts (Mitsubishi engine cover)

EVOH, Polylactic acid (various automotive uses) Wilson Sporting Tennis balls (nanoclay/butyl rubber coating from InMat) Honeywell Nylon 6 for food packagingUS Army MRE food tray (EVOH)Kablewerk Eupen EVA flame retardant cable coatingTNO polyurethane binding system for ceramic moldsMitsubishi Polypropylene nanocomposites for automotive partsTriton Systems Polyurethane bladder for athletic shoe

Polyolefin packaging films for food and pharmaceutical packagingNanocor MXD-6 Nylon for barrier food packaging

Courtesy ofR. Vaia /AFRLOctober 2002

Example Commercial VenturesExample Commercial VenturesPolymerPolymer--Clay NanocompositesClay Nanocomposites

starting particle: agglomerate

• several µm in size (5-20 µm)

• millions of individual plateletsmorelikely

The Challenge: Achieving MiscibilityThe Challenge: Achieving Miscibility

desired

Courtesy ofR. Vaia /AFRL

Achieving Miscibility thru “Chemistry”Achieving Miscibility thru “Chemistry”

In general : Polymers and Clays do not mix

thus, clays must be organically modified

“Rule of thumb” : favorable excess interactionsi.e. polymer-clay interactions better than

clay-surfactant interactions

Vaia & Giannelis, Macromolecules, 30, 7990 (1997)Balazs et al, Macromolecules, 31, 8370 (1998)

*** think blends rather than composites ***

CH2(CH2)16CH3

N +CH2(CH2)16CH3

CH3

CH3

CH2 CH

CH3N

PP alkyl-ammonium surfactant

Add favorable thermodynamics:

PP and alkyl-modified mmt: “Θ-conditions” i.e. dispersable at high T/γ extrusion

fully-exchanged C18-mmt

+ CF3-(CF2)5-(CH2)2-Si-Cl3

( f-mmt )

Route #2: Change o-mmt

low γ surfactant (fluoro-alkyl)CH2 CH2 CH2 CH

CH3

xCH3

CH2 CH2 CH2 CH

H2C

xCH3

OO OCH2 CH2 CH2 CH

CH2

xCH3

H2CCH2HO

X = 0.5% (!!!)

Route #1: Change PPPolar group addition on PP

E. Manias et al, Chem. Mater. 13, 3516 (2001)

The thermodynamic challengeThe thermodynamic challengeexample: Polypropyleneexample: Polypropylene

3

For naturally occurring fillers (e.g. montmorillonite)there coexist intercalated/exfoliated filler structures

TEM A: intercalated layersB: exfoliated/disordered

x=0.5% !!!

Polar groups added randomly across PPPolar groups added randomly across PP

CH2 CH CH2 CH

CH2

xCH3

H2CCH2HO

CH2 CH CH2 CH

CH3

xCH3

E. Manias et al, Chem. Mater. 13, 3516 (2001)

x=5%

Polar groups added as a block to PPPolar groups added as a block to PP

E. Manias et al, Chem. Mater. 13, 3516 (2001)

CH2 CH CH2 Cx

CH3

CH3

CO OCH3

y

Polar groups added as a block to PPPolar groups added as a block to PP

A single end-group(appropriately selected) can drive high miscibility

Z-M. Wang, H. Nakajima, E. Manias , and T.C. Chung Macromolecules 36, 8919 (2003)

500nm

H CH2 CH CH2 CH2 NH3

CH3n

Mechanical property changes (PP)Mechanical property changes (PP)

0 2 4 6 8 10600

800

1000

1200neat PP / C18H37 -MMT (conv. filler)neat PP / C18H37 & C8H4F13 -MMT

Mod

ulus

(MPa

)

inorganic concentration φ (wt %)

INSTRON; thin film ASTM protocol

0 2 4 6 8 100

200

400

600

800

1000

neat PP / C18

H37

-MMT (conv. filler)neat PP / C18H37 & C8H4F13 -MMT

Bre

ak s

trai

n (%

)

inorganic concentration φ (wt %)

0 2 4 6 8 1010

15

20

25

30

35

neat PP / C18H37-MMT (conv. filler)neat PP / C18H37 & C8H4F13 -MMTYi

eld

Stre

ss (M

Pa)

inorganic concentration φ (wt %)

“General” changes:tensile modulus 60% increase (small changes in yield stress)(small changes in break strain)

Other Thermomechanical PropertiesOther Thermomechanical Properties

0 2 4 6 8 10

110

120

130

140

150

160

PP/ f-mmt (melt) PP/ f-mmt (extr) PP/ 2C18M (extr)

HD

T (o C

)

φ (wt %)E. Manias et al, Chem. Mater. 13, 3516 (2001)

PP heat deflection temperature

Similar trends for:

apparent Tgscratch resistancesurface moduluscompressive G’

generally across polymers

Maintaining the filler dispersionMaintaining the filler dispersion

2 4 6 8 10

15 min

10 min5 min2 min0 min

diffr

acte

d in

tens

ity

2 Θ (degrees)

In absence of favorable thermodynamics (e.g. PP/2C18M)

Experiment:1. trap exfoliated

structure(e.g. solvent casting,

high γ/T extrusion)

2.“process” and follow evolutionof structure

(e.g. compressionmolding @180oC )

4

Maintaining the filler dispersionMaintaining the filler dispersion

2 4 6 8 10

(b)

30 min

10 min

2 min

0 min

2 Θ (degrees)

diffr

acte

d in

tens

ity

(a)

8 min

5 min2 min0 min

With favorable thermodynamics

(a) PP/f-mmt

intercalated/exfoliated

structure recovered

(b) PP-MA0.5% /2C18M

trapped exfoliated

structure maintained

(as per: PVA, PUU, PU, etc)

E. Manias et al, Chem. Mater. 13, 3516 (2001)

Example: Structural Automotive PartsExample: Structural Automotive Parts

Bob Ottaviani, GM R&D Manager, steppinginto a van with a TPO nanocomposite step assist

parts in Astro, Safari Van (below, 2002), various parts in 6 more models (2005)TPO/clay nanocomposites: GM/Basell/Southern Clay Products/Blackhawk

Partners in DevelopmentMark Bennett, Blackhawk;Alan Taub, GM; Bill Windscheif, BasellBob Briell, Southern Clay Products

A better example: Medical DeviceA better example: Medical Device

Catheter tubing with improved modulus

nylon-12nanocomposite unfilled

nylon-12

Foster Corporation

A crossA cross--section of a simple packaging section of a simple packaging

paper (label printing)clear plastic (reverse-printing)

polymer adhesiveBarrier layer (gases, light, … e.g. PET, aluminum foil, …)

cheap polymer (e.g. PE)Mechanical PropertiesFDA approved for food contact

Can we replace this multi-layer with a much simpler structure?

Requirements:- cheap (!!!)- mechanical properties (stiff and high-temperature)- low or selective permeability to gases/ light/ water- FDA approved for direct food contact

Tensile Modulus

(MPa)

Tensile Strength (MPa)

Elongation at break

(%) unfilled

(0% Clay)

306 (±15)

24 (±1)

324 (±11) unfilled-TS*

(0% Clay)

329 (± 5)

24 (±1)

291 (± 5)

3% Clay 587 (± 9) 23 (±1) 325 (±11) 6% Clay 825 (±17) 24 (±1) 396 (± 6)

met

hod

A

9% Clay 1120 (±25) 23 (±1) 295 (±23)

3% Clay 581 (±32) 22 (±1) 316 (±17) 6% Clay 842 (±33) 25 (±1) 400 (± 1)

met

hod

B

9% Clay 1106 (±66) 22 (±1) 294 (±13)

Mechanical property changes (PE)Mechanical property changes (PE) Barrier propertiesBarrier properties

0.0

0.2

0.4

0.6

0.8

1.0

0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4

Volume Fraction Silicate

Rel

ativ

e Pe

rmea

bilit

y

Nanocomposite(PCL Nanocomposites)

Conventionally filled systems

AB

Messersmith & Giannelis (1995)

5

PermeabilityPermeability--Structure RelationStructure Relation

R. Xu, E. Manias, A.J. Snyder & J. Runt Macromolecules, 34, 337-339 (2001)

Origins:path tortuosity

General Trend:nylons (6,66,12) PP PE PET PDMS PU PUU PS PVA...

‘Tortuous Path’

Macromolecules 2001, 34, 9189

effective α alignment

PermeabilityPermeability--Structure RelationStructure Relation

PUU Blood Sacs in Artificial Heart: PUU Blood Sacs in Artificial Heart: Barrier ProblemBarrier Problem

Relatively high permeability of gases and water vapor through the membraneLeads to:

Accumulation of water in device; requires extractionLoss of gas pressure → non-optimum pump performance; requires injection of air back into the system

Particular problem if patient is to be self-sufficient

Artificial Heart ProjectArtificial Heart ProjectPSU PSU HerseyHersey MedicalMedicalA.J. Snyder , J.P. Runt & E. ManiasA.J. Snyder , J.P. Runt & E. Manias

0

0.005

0.01

0.015

0.02

0.025

0.03

0 200 400 600 800 1000 1200 1400

Extension (%)

PUU

0.3%

0.8%

2%

3.8%

5.9%vol% silicate

Microtensile die (ASTM D1708-93)

PUU Nanocomposites:PUU Nanocomposites:Mechanical properties retainedMechanical properties retained

R. Xu, E. Manias, A.J. Snyder & J. Runt Macromolecules, 34, 337-339 (2001)

Still Highly Rubbery !!Still Highly Rubbery !!

Wilson high performance tennis ballsWilson high performance tennis balls

inner core (barrier)butyl-rubber + clay

http://www.wilsonsports.com.au/tennis/doublecore.html

A crossA cross--section of another packaging section of another packaging

Barrier layers (e.g. nylon+ O2 scavenger vs. nylon+clay; 5 layers vs. 3 layers; …)

traditional polymer (e.g. PET-copolymer)Mechanical PropertiesFDA approved for food contact

Improving barrier propertiesby multi-layered structures…

e.g. plastic beer bottles (compare USA vs. Asia)

[ref. next presentation by Brody]

6

Antifungal “functionality”Antifungal “functionality”

Maria JimenezMaria Jimenez--Gasco Gasco Plant Pathology Dept, PSUPlant Pathology Dept, PSU

0 2days 4days

Increased O2

barrier effecton Fusariumgrowth

first study for proof of concept

Courtesy ofM. Jimenez-Gasco

Antifungal Antifungal “functionalityfunctionalityfirst study for proof of concept

Maria JimenezMaria Jimenez--Gasco Gasco Plant Pathology Dept, PSUPlant Pathology Dept, PSU

Organo-clayeffecton Fusariumgrowth

Average Diameter of Growth vs. TimeStart Date: 4/19/06

0

1

2

3

4

5

6

7

8

9

10

0 24 46 75 98 123Time (hours)

Dia

met

er o

f Gro

wth

(cm

)

Control A

Control B

Cellophane A

Cellophane B

PE film APE film B

PE film L5 A

PE film L5 B

PE film LL3 A

PE film LL3 B

Courtesy ofM. Jimenez-Gasco

Optical clarity + UV ‘blocking’Optical clarity + UV ‘blocking’

10-3

10-2

10-1

1 200 400 600 800 1000wavelength λ [nm]

10 wt%

6 wt%

PVA

trans

mitt

ance

[ I

TR /

I O ]

K. Strawhecker & E. ManiasChem. Mater. 12, 2943 (2000)

200 400 600 800 10001E-5

1E-4

1E-3

0.01

0.1

1

zoom (x 1000)

visible range

trans

mitt

ance

neat PP-MA 3% hybrid 9% hybrid 20% hybrid (!!!)

wavelength (λ)

600 800 1000

0.1

1

Poly(propylene) / montmorillonite hybrid

E. Manias et al, Chem. Mater. 13, 3516 (2001)

Optical clarity + UV ‘blocking’Optical clarity + UV ‘blocking’

Flame retardancyFlame retardancy

0

200

400

600

800

1000

1200

1400

1600

0 120 240 360 480 600

PP intercalated (2 % silicate) PP pure (PP-g-MA, 0.4 % MA)PP intercalated (4 % silicate)

Hea

t Rel

ease

Rat

e (k

W/m

2 )

Time (seconds)

Flux = 35 kW/m2

Cone calorimeter studies(at NIST)

1 Gilman, J. W.; Morgan, A. B.; Harris, R.; Giannelis, E. P.; Manias; E. Wuthenow, M. Chemistry of Materials 12, 1866 (2000)

Higher extend of intercalation seems to promote flame retardancy 1

Universal Enhancement:PS nylon-6 PEPP PI various epoxies

Origins:

formation of surface-char+ barrier (O2, fumes)+ thermal isolation

Char StructureChar Structure

nanocomposite structure char structure

Gilman, J. W.; Morgan, A. B.; Harris, R.; Giannelis, E. P.; Manias; E. Wuthenow, M. Chemistry of Materials 12, 1866 (2000)

7

Durability comparison of a 5wt% nanocomposite and pure nylon-6: 10min of oxygen plasma exposure [concentration ~1018 ions/liter] &

SEM of nylon-6/5wt% clay nanocomposite after exposure to simulated solid-rocket

motor exhaust & & R.A. Vaia et al ,Air Force Research Lab, 2001

nylon 6nanocomposite

purenylon 6

Formation of Surface CharFormation of Surface CharEffect of filler dispersionEffect of filler dispersion

Flux = 35 kW/m 2

0

200

400

600

800

1000

1200

1400

1600

0 40 80 120 160 200 240 280

PS purePS immiscible (3 % NaMMT)

PS intercalated/delaminated (3 % 2C18-MMT) extruded at 170 oC

PS intercalated (3 % C14-FH) extruded at 170 oC

Hea

t Rel

ease

Rat

e (k

W/m

2 )

Time (seconds)Gilman, J. W.; et al Chemistry of Materials 12, 1866 (2000)

Nanoscale Dispersion

is important

and necessary !!

NonNon--halogen, low flammability cableshalogen, low flammability cables

ATH basedcompound

Nanocomposite

Additionof organo-clay

Additionof organo-clay

Improvementson fire performanceand smoke density

Improvementson fire performanceand smoke density

Char formation of a cable with nanocomposite

Courtesy ofJ.W. Gilman/NIST

Concluding RemarksConcluding Remarks

Nanotechnology is not nanobots or Star-Trek gadgets !!It can be as simple as a polymer nanocomposite that you may already “use” (e.g. in food packaging, in your car bumper).

Applications drive a progress in materials science, incl. real-life applications of nanotechnology.For example, cost reduction in food packaging or substantial extension of shelf-life, can be achieved by non traditional approaches (all the simple solutions have been implemented a long time ago!).

Polymer/Inorganic nanocomposites are a viable technology for “new” materials for near-future food-packaging applications.Especially for flexible and transparent barrier films (wraps, etc). However, they are not the solution to all problems (!)

Future Outlook: A Personal Perspective Future Outlook: A Personal Perspective

Beyond Dispersion Control of Hierarchy of Structurese.g. alignment, house of cards, control at the µm scale, preferential dispersion in one phase or at the interphase

what can be done tomorrow…

Design and Incorporate Multiple Desired Functionalities.Move beyond barrier + stiffness, cf. anti-microbial, antibiotic, antifouling, biodegradable, selectively manipulate biological moieties, incorporate responses to environmental or chemical changes (not just sensors, but ‘smart’ stimuli-responses)…

Bioinspired Nanostructured Polymers and Composites.Here the opportunities are almost limitless… Look at nature’s examples of packaging, skins, structures with specific processes, and imagine if we could make synthetic equivalents

what can be in the near future…

what can be in the not-so-near future…

Future Outlook: A Personal Perspective Future Outlook: A Personal Perspective

8

AcknowledgementsAcknowledgements

PE, PP/clay: H. Nakajima, L. Wu, J.Y. Huh, G. Polyzos

f-PP synthesis: Z. Wang, T.C. Chung*

PUU/clay: R. Xu, J.P. Runt*, A.J. Snyder

PVA/clay: K. Strawhecker

PC,PET/clay: M. Heidecker

Fungal growth: M. Jimenez-Gasco*, P. Songptiya, N. Khetarpal&

Flammability: J.W. Gilman* (NIST), C.A. Wilkie* (Marq.U)

Acknowledge: R.A. Vaia* (AFRL)

*co-PI / collaborator & under-graduate student