Polymeric Nanocomposites - Theory and Practice

352 Pages·2008·7.805 MB·352\352

by  Bhattacharya, Sati N., Kamal, Musa R., Gupta, Rahul K.

Sati N. Bhattacharya
Musa R. Kamal
Rahul K. Gupta
Polymeric
Nanocomposites
Theory and Practice
Carl Hanser Publishers, Munich • Hanser Gardner Publications, Cincinnati
The Authors:
Prof. Sati N. Bhattacharya, RMIT University, Rheology and Materials Processing Center, School of Civil, Environmental and
Chemical Engineering, Melbourne, VIC, Australia
Dr. Rahul K. Gupta, RMIT University, Rheology and Materials Processing Center, School of Civil, Environmental and
Chemical Engineering, Melbourne, VIC, Australia
Prof. Musa R. Kamal, McGill University, Department of Chemical Engineering, Montréal, Quebec, Canada
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Library of Congress Cataloging-in-Publication Data
Bhattacharya, Sati N.
Polymeric nanocomposites : theory and practice / Sati N. Bhattacharya, Musa
R. Kamal, Rahul K. Gupta.
p. cm.
Includes index.
ISBN 978-1-56990-374-2 (hardcover)
1. Nanostructured materials. 2. Polymeric composites. I. Kamal, Musa
R. (Musa Rasim), 1934- II. Gupta, Rahul K. III. Title.
TA418.9.N35B43 2007
620.1‘92--dc22
2007026090
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Preface
Nanostructured multi-phase polymers have generated great interest with promise to
produce a new generation of materials displaying enhanced physical,mechanical,thermal,
electrical,magnetic,andopticalproperties.Thekeytothesuccessofnanocompositeshinges
ontheabilitytoexploitthepotentialof nano-structuringinthefinalproduct.Therefore,it
isimportanttodeveloppracticalandeconomicalformulationsandprocessingmethodsfor
tailoringasustainablematerialconfigurationatthenanoscalelevel.Recently,muchprogress
has been made in meeting this challenge and in developing a wide range of commercial
processes, products, and devices as a result of the research efforts and advances by many
scientists,engineers,andtechnologists.Whilealargenumberof scientificpapersandsome
books on polymer nanocomposites have been published, there is a clear need to bring
together the scientific knowledge and the engineering developments relating to these
materials in terms of synthesis, characterisation, production, and application. This book
deals with clay-based polymer nanocomposites, which have been the subject of extensive
researchinthelastdecade.Besidesitslowcost,clayhasaplate-likegeometry,whichcould
impartexcellentproductpropertiesunderoptimumnanostructuringconditions.
Thebookprovidesanoverviewofthecompositionprocessingproductapplicationrelationships
inthefieldofpolymernanocomposites.Itdealswiththefundamentalprinciplesthatgovern
the synthesis and behavior of polymer/clay nanocomposites, such as thermodynamics,
kinetics,rheology,andmorphology.Otherchapterscoverpracticalaspects,suchasprocessing,
performance,and some commercial applications of polymer/clay nanocomposites in selected
industries,such as packaging,automotive,electronic,and telecommunications.It is hoped
that the book will serve as a reference and guide for those who work in various aspects of
the nanocomposite industry and technology or wish to learn about these promising new
materials.
Thepreparationof thisbookhasbeenpossibleduetotheactivesupportandhelpreceived
from many colleagues, research staff and graduate students. The authors would like to
express their sincere thanks to all these individuals for the direct and indirect efforts and
contributionstothepreparationofthisbook:Dr.S.Raha,Mr.M.Reddy,Mr.M.Pannirselvam
andMr.S.Bhattacharya,DrFCser,DrRPrasad,Dr.M.Al-Wohoush,Dr.L.IonescuVasii,
Dr.N.Borse,Dr.K.Kim,Dr.L.Feng,Mr.J.Uribe-Calderon,Ms.O.Tavichai,Mr.C.Lungu,
and Mr.N.Nassar.We also wish to express our appreciation to our respective universities,
RMIT and McGill,and the various granting agencies inAustralia and Canada for material
andmoralsupportthatmadeitpossibletoproducethisbook.
SatiN.Bhattacharya
RahulK.Gupta
MusaR.Kamal
Table of Content
1 Introduction .......................................................... 1
1.1 PolymerNanocomposites ........................................... 1
1.2 CommercialPotential............................................... 2
1.3 BookStructure.................................................... 3
1.4 References ........................................................ 4
2 PreparationandSynthesis............................................... 5
2.1 PolymerNanocomposites ........................................... 5
2.1.1 Morphologyof Polymer-LayeredSilicateNanocomposites .......... 6
2.1.2 Structureof LayeredSilicates .................................. 7
2.1.3 OrganicallyModifiedClay..................................... 9
2.1.4 Formationof PolymerNanocomposites ......................... 10
2.1.5 Effectof CationExchangeCapacityonOrganoclay................ 11
2.1.6 Effectof OrganicCationStructureonOrganoclay................. 12
2.2 NanocompositesPreparationandSynthesis ............................ 12
2.2.1 SolutionDispersion.......................................... 13
2.2.2 In-SituPolymerization........................................ 15
2.2.3 MeltIntercalation............................................ 16
2.2.4 Effectof Mixing............................................. 20
2.3 PolymerMatrices:Thermoplastics,Thermosets,Elastomers,Natural,and
BiodegradablePolymers............................................. 22
2.3.1 Thermoplastics.............................................. 23
2.3.1.1 Polyethylene......................................... 23
2.3.1.2 Polypropylene ....................................... 23
2.3.1.3 Ethylene-VinylAcetate(EVA)Copolymers................ 24
2.3.1.4 Polyamides.......................................... 25
2.3.1.5 Poly(EthyleneTerephtalate)(PET) ...................... 25
2.3.1.6 Polystyrene.......................................... 26
2.3.2 Elastomers.................................................. 27
2.3.3 Thermosets................................................. 28
2.3.3.1 EpoxyNanocomposites................................ 28
2.3.3.2 Polyurethane ........................................ 28
2.3.4 NaturalandBiodegradablePolymers............................ 29
3 FundamentalIssuesinNanocompositeSynthesis........................... 35
3.1 Introduction ...................................................... 35
3.2 ThermodynamicsandInteractions.................................... 36
3.2.1 GeneralThermodynamicRelationships.......................... 36
X Inhalt
3.2.2 Multi-ComponentSystems .................................... 38
3.2.2.1 ChemicalPotential ................................... 38
3.2.2.2 PhaseEquilibriaandPhaseDiagrams.................... 38
3.2.3 SurfaceFreeEnergy.......................................... 43
3.2.4 Typesof InterfacialInteractions................................ 45
3.2.4.1 IntermolecularInteractionsVanDerWaalsForces ......... 45
3.2.4.2 DispersionForcesBetweenTwoMacroscopicBodies....... 47
3.2.4.3 LifshitzApproach .................................... 48
3.2.4.4 Polar(Acid-Base)Interactions.......................... 49
3.2.4.5 ApplicationstoNanocomposites........................ 50
3.3 Modelsof NanocompositesatEquilibrium............................. 53
3.3.1 Introduction................................................ 53
3.3.2 Mean-Field,Lattice-BasedModel............................... 55
3.3.3 Self-ConsistentFieldApproach(SFC)........................... 60
3.3.4 DensityFunctionalTheory(DFT).............................. 69
3.4 MixinginNanocompositeSynthesis .................................. 74
3.4.1 DistributiveMixing .......................................... 74
3.4.2 MixingQualityinNanocomposites............................. 76
3.5 Mechanicsof ParticleSeparationandAgglomerateDispersion............. 82
3.5.1 Separationof SphericalParticles................................ 83
3.5.2 Separationof Platelets........................................ 85
3.5.3 PeelingandLapShearingModels............................... 93
3.5.4 RuptureandErosion ......................................... 96
3.6 MechanismandKineticsof PolymerMeltIntercalation .................. 100
3.6.1 IntercalationMechanism...................................... 101
3.6.2 IntercalationKinetics......................................... 104
3.7 Crystallizationof PolymersinNanocomposites ......................... 109
3.7.1 Crystallizationof Polymers.................................... 109
3.7.2 CrystallineStructureandMorphology........................... 110
3.7.2.1 FoldedChainModel................................. 111
3.7.2.2 CrystallizationfromPolymerMelts...................... 111
3.7.3 CrystallizationKinetics ....................................... 113
3.7.3.1 IsothermalModels ................................... 114
3.7.3.2 Non-IsothermalModels............................... 116
3.7.3.3 NucleationandGrowth:Lauritzen-HoffmanGrowth
Theory ............................................. 117
3.7.4 TheCrystallineStructureof PA-6............................... 119
3.7.5 PolymerCrystallizationinNanocomposites ...................... 120
3.7.5.1 GeneralConsiderations ............................... 120
3.7.5.2 CrystallizationKinetics................................ 121
3.7.6 MorphologicalEffects ........................................ 129
3.8 References ........................................................ 132
4 Rheologyof Nanocomposites............................................ 145
4.1 Rheologyof MultiphaseSystems...................................... 145
4.2 Rheologyof Polymer/ClayNanocomposites ............................ 146
Inhalt XI
4.3 RecentStudiesonRheology ......................................... 146
4.4 MeasurementTechniques............................................ 147
4.4.1 SteadyShearMeasurements ................................... 147
4.4.2 DynamicShearMeasurements ................................. 148
4.4.3 ExtensionalRheologyMeasurements............................ 150
4.4.3.1 Meissner-TypeRheometer ............................. 150
4.4.3.2 Drawingof MoltenMonofilamentAfterExtrusion......... 151
4.4.4 MeasuredParameters......................................... 153
4.5 SteadyShearRheology.............................................. 154
4.5.1 SteadyShearRheologyof Nanocomposites....................... 154
4.5.2 ShearThinningBehavior...................................... 155
4.5.3 NormalStressBehavior....................................... 156
4.6 DynamicRheology................................................. 157
4.6.1 DynamicRheologyof Nanocomposites.......................... 159
4.6.2 PercolationThreshold ........................................ 161
4.6.3 Time-TemperatureSuperposition............................... 166
4.6.4 Cox-MerzRule.............................................. 168
4.7 NonLinearViscoelasticProperties.................................... 168
4.8 ExtensionalRheology............................................... 170
4.8.1 Fundamentals............................................... 170
4.8.2 ExtensionalRheologyof Nanocomposites........................ 172
4.8.3 Drawingof MoltenMonofilamentafterExtrusion................. 173
4.9 RheologicalModelingof Nanocomposites.............................. 176
4.9.1 SteadyShearModels ......................................... 177
4.9.1.1 HerschelBerkeleyModel .............................. 177
4.9.1.2 Williamson-CarreauModel ............................ 179
4.9.1.3 MolecularDynamicsSimulation........................ 180
4.9.1.4 Coarse-GrainedComputerSimulation................... 182
4.9.2 ViscoelasticModels .......................................... 183
4.9.2.1 TheNetworkModel.................................. 183
4.9.2.2 ModelValidationTechnique............................ 188
4.9.2.3 TheFENEDumbbellModel ........................... 189
4.9.2.4 MolecularDynamicSimulation......................... 197
4.9.2.5 Bi-ModeFENEDumbbellModel ....................... 202
4.9.3 ExtensionalRheology......................................... 206
4.9.3.1 K-BKZModel ....................................... 208
4.9.3.2 ValidationTechnique ................................. 209
4.10 Summary......................................................... 212
5 Processingof Nanocomposites........................................... 233
5.1 Introduction ...................................................... 233
5.1 Extrusion......................................................... 234
5.1.1 Dispersionof Clay........................................... 235
5.1.2 Effectof ExtruderTypes ...................................... 240
5.1.3 Effectof ProcessingConditions ................................ 245
5.2 InjectionMolding.................................................. 245
XII Inhalt
5.2.1 StructuralHierarchy.......................................... 246
5.2.2 BarrierandMechanicalPropertiesforInjectionMoldedProducts.... 251
5.2.3 MicrocellularInjectionMolding................................ 252
5.3 BlowMolding..................................................... 255
5.3.1 BarrierPropertiesof BlowMoldedProducts ..................... 255
5.4 Foaming.......................................................... 257
5.5 RotationalMolding ................................................ 263
6 StructureandPropertiesCharacterization................................. 269
6.1 Introduction ...................................................... 269
6.2 ScatteringTechniques............................................... 270
6.2.1 X-rayScatteringFundamentals................................. 271
6.2.2 X-RayScatteringStudiesonPolymerNanocomposites............. 280
6.2.2.1 WAXSStudies ....................................... 280
6.2.2.2 SAXSStudies........................................ 285
6.2.3 SmallAngleLightScattering(SALS) ............................ 288
6.2.3.1 SALSTechniques..................................... 288
6.2.3.2 SALSStudiesonPolymerNanocomposites ............... 289
6.2.4 SmallAngleNeutronScattering(SANS)......................... 297
6.2.4.1 SANSTechniques .................................... 297
6.2.4.2 SANSStudiesonPolymerNanocomposites............... 297
6.3 MicroscopicTechniques............................................. 299
6.3.1 ElectronMicroscopy ......................................... 299
6.3.2 ElectronMicroscopyStudiesonPolymerNanocomposites.......... 299
6.3.2.1 SEMStudies......................................... 299
6.3.2.2 TEMStudies ........................................ 301
6.3.2.3 AFMStudies ........................................ 304
6.4 SpectroscopicTechniques ........................................... 307
6.4.1 FourierTransformInfra-Red(FTIR)Spectroscopy ................ 308
6.4.2 NuclearMagneticResonance(NMR)............................ 310
6.4.3 Ultraviolet(UV)Spectroscopy ................................. 312
6.5 Chromatography................................................... 313
6.6 Solid-StateCharacterization:MechanicalTesting........................ 315
6.6.1 MechanicalTesting........................................... 315
6.6.2 DynamicMechanicalAnalysis(DMA)........................... 317
6.7 ThermalCharacterization ........................................... 320
6.7.1 DifferentialScanningCalorimetry(DSC)........................ 320
6.7.2 ThermalGravimetricAnalysis(TGA) ........................... 325
6.7.3 HeatDistortionTemperature(HDT)............................ 329
6.7.4 ConeCalorimetry............................................ 331
7 Applicationof PolymerNanocomposites.................................. 339
7.1 Introduction ...................................................... 339
7.2 Thermoplastics.................................................... 341
Inhalt XIII
7.2.1 Polyethylene(PE)............................................ 342
7.2.2 Polypropylene(PP) .......................................... 344
7.2.2.1 AutomotiveApplications .............................. 347
7.2.2.2 BodyExterior........................................ 349
7.2.2.3 BodyInterior........................................ 350
7.2.3 Polyamides(PA)............................................. 351
7.2.4 Ethylene-VinylAcetate(EVA).................................. 355
7.2.5 PolyethyleneTerephthalate(PET)............................... 357
7.2.6 VersatileNanocarbons........................................ 358
7.3 Thermosets....................................................... 359
7.3.1 Polyurethanes(PU) .......................................... 360
7.3.2 Epoxies .................................................... 362
7.3.3 UnsaturatedPolyesters(UPE).................................. 364
7.3.4 Phenolics................................................... 364
7.4 BiodegradablePolymers............................................. 366
7.4.1 Polylactide(PLA)anditsNanocomposites....................... 367
7.4.2 Polycaprolactone(PCL)....................................... 368
7.4.3 Starch...................................................... 369
7.5 FinalComments................................................... 370
1 Introduction
Nanotechnology has created a key revolution in the 21st century exploiting the new
properties, phenomena and functionalities exhibited by matters when dealt at the level of
few nanometers as opposed to hundred nanometers and above. Nanoscale materials are
already recognized as unique because they produce qualitatively new behavior when
comparedwiththeirmacroscopiccounterparts.Itisunderstoodthatwhenthedomainsize
withinthematerialsbecomescomparablewiththephysicallengthscale,suchassegmentsof
a polymer macromolecule, the expected physical phenomena and the response to any
external disturbance do not follow the established principles. The scientific phenomena
occurringinnanoscalesystemscanonlybeexplainedbynewtheoreticalprinciplesandby
experimental techniques which are in the process of development. The challenge is to
manage the transition region where nanoscale phenomena are evolving from microscopic
andmacroscopicbulkproperties.Thelinkingofmolecularinteractiontonanostructuresto
bulkpropertiesisachallenge,bothscientificallyandtechnologically.Anotherchallengeisto
understand how deliberate tailoring at the nanoscale can produce novel and controlled
functionalitiesof thesematerials.
1.1 Polymer Nanocomposites
Nanocomposite technology is a newly developed field,in which nanofillers are added to a
polymer to reinforce and provide novel characteristics. Nanocomposite technology is
applicable to a wide range of polymers from thermoplastics and thermosets to elastomers.
Two decades ago,researchers from Toyota Central Research and Development produced a
new group of polymer-clay complexes or composites, which was aptly called polymer-
layered silicate nanocomposites or polymer nanocomposites. Today, there is a variety of
nanofillersusedinnanocomposites.Costandavailabilitycontinuetochangeasthefieldis
relativelynewandseveralof thesefillersarestillbeingdeveloped.Themostcommontypes
of fillers are natural clays (mined, refined and treated), synthetic clays, nanostructured
silicas, nanoceramics, nanocalcium carbonates and nanotubes (carbon based). The
properties conferred by the nanoparticles to the polymer matrix are remarkable. The
property enhancements have allowed these materials to commercially compete with
traditionalmaterials.[Collister(2001)]listssomeof thepropertyimprovementsas:
Efficientreinforcementwithminimallossinductilityandimpactstrength,
Thermalendurance,
Flameretardance,
Improvedliquidandgasbarrierproperties,
Improvedabrasionresistance,
Reducedshrinkageandresidualloss,and
Alteredelectrical,electronicandopticalproperties.
2 1 Introduction [Referencesonpage4]
Layeredsilicates(clay)dispersedasreinforcementinanengineeringpolymermatrixisone
of the most important forms of polymer nanocomposites. Amongst all the potential
nanocompositesprecursors,thosebasedonclayandlayeredsilicatehavebeenmorewidely
studied, probably because the starting clay materials are easily available and because their
intercalation chemistry has been studied for a long time [Van Olphen (1977)]. The
commercialuseofintercalatedclayforindustrialapplicationgoesbackmanydecades.Early
applicationreportedduringthe1930s –tothe1950sforintercalatedclaywaspapercoating
(hydrophilic application) and lubricants, grease and oil based mud (hydrophobic
application). First use of polymer/clay composites using onium compounds to intercalate
montmorillonite clay MMT was reported in 1950 [Carter et al.(1950)].Polymerization of
vinylmonomerinthepresenceofintercalatedMMTwaslaterreported[Blumslein(1961)].
The manufacture of LDPE/clay hybrid (1:1) was reported in a patent by Nahin and
Bucklund in 1963 [Nahin and Backlund (1963)]. Fujiwara and Sakamoto filed a patent
application for ammonium salt intercalated clays for hydrophobic matrices in 1976
[Fujiwara and Sakamoto (1976)]. Organo-clay was added to the monomer before
polymerization of PA. The first patent by the Toyota group for in situ polymerization of
styreneandothervinylmonomersinthepresenceofclaywasobtainedin1984.ThefirstUS
patentforPA6/claynanocomposites,whereclaywasusedinsmallquantities,wasobtained
in1989[Usukietal.(1989)].
Few nanocomposites have been produced commercially, but their potential applications
havefuelledfrenzyintheresearcharena[ZerdaandLesser(2001)].Forexample,intheUS,
research funding for the National Nanotechnology Initiative in 2003 alone exceeded US
$600Million.
1.2 Commercial Potential
ThefirstcommercialnanocompositeproductwasbasedontheToyotaprocessofin-reactor
processing of caprolactum and montmorillonite to produce a polyamide 6-clay product.
This producthasbeen commercially available for severalyears.Generalmotorusesalarge
amount of polyolefin-based clay nanocomposites for some of its vehicle parts. Mitsubishi
Gas Chemical Company [Sherman (2004)] offers nylon-6 based nanocomposites with
highlyimprovedgasbarrierpropertiescomparedtounfillednylon-6,ethylene-vinylalcohol
(EVOH)andpolypropylene(PP).
Althoughthepotentialforthecommercialapplicationofnanocompositesisenormous,the
actual application has been occurring at a very slow pace. In many instances, the
performanceofthedevelopednanocompositesdidnotmeettheexpectations,e.g.,notvery
significant increase in their useful properties or drop in mechanical or optical properties.
Whileithasbeenshownthatthemodulusorstiffnessofthermoplasticscanbeincreasedby
adding very small amounts of clay, in many cases it comes with the disadvantage of
decreasing strength.Addition of clay to polymers,such as nylon-6 and EVA,increases the
gas barrier properties but their optical properties may be compromised. Performance not
yet meeting expectations may not be due to any inherent flaws in the concept of
nanocompositetechnology.Itisratherduetothefactthatthedevelopmentsinthisnewarea