Maurizio Galimberti is a Professor of Chemistry for Rubber and Composite Materials Technology at Milan Polytechnic, Milan, Italy, and a Visiting Professor at University of Insubria, Como, Italy. He is the former president and a current board member of the Italian Association of Macromolecules; has published over seventy scientific works in international books and journals; and is the author of more than forty patents.

PREFACE xvii

CONTRIBUTORS xxi

SECTION I CLAYS FOR NANOCOMPOSITES

1 CLAYS AND CLAY MINERALS 3

1.1 What’s in a Name / 3

1.2 Multiscale Organization of Clay Minerals / 6

1.2.1 Dispersion Versus Aggregation / 6

1.2.2 Delamination/Exfoliation Versus Stacking / 6

1.3 Intimate Organization of the Layer / 8

1.3.1 Cationic and Neutral Clay Minerals / 8

1.3.2 Anionic Clay Minerals (O) / 21

1.4 Most Relevant Physicochemical Properties of Clay Mineral / 22

1.4.1 Surface Area and Porosity / 22

1.4.2 Chemical Landscape of the Clay Surfaces / 24

1.4.3 Cation (and Anion) Exchange Capacity / 24

1.4.4 Intercalation and Confinement in the Interlayer Space / 27

1.4.5 Swelling / 30

1.4.6 Rheology / 31

1.5 Availability of Natural Clays and Synthetic Clay Minerals / 33

1.6 Clays and (Modified) Clay Minerals as Fillers / 35

Acknowledgment / 37

References / 37

2 ORGANOPHILIC CLAY MINERALS 45

2.1 Organophilicity/Lipophilicity and the Hydrophilic/Lipophilic Balance (HLB) / 45

2.2 From Clays to Organoclays in Polymer Technology / 47

2.3 Methods of Organoclay Synthesis / 49

2.3.1 Cation Exchange from Solutions / 49

2.3.2 Solid–State Intercalation / 58

2.3.3 Grafting from Solution / 59

2.3.4 Direct Synthesis of Grafted Organoclays / 62

2.3.5 Postsynthesis Modifications of Organoclays: The “PCH” / 64

2.3.6 An Overview of Commercial Organoclays / 64

2.3.7 One–Pot CPN Formation / 66

2.4 Other Types of Clay Modifications for Clay–Based Nanomaterials / 66

2.4.1 Organo–Pillared Clays / 66

2.4.2 Plasma–Treated Clays / 69

2.5 Fine–Tuning of Organoclays Properties / 69

2.5.1 Maximizing the Dispersion of the Filler: Effect

of Surfactant/CEC Ratio / 69

2.5.2 Improving Thermal Stability / 70

2.5.3 Chemical Treatments / 71

2.5.4 Physical Treatments (Freeze–Drying, Sonication, Microwave) / 71

2.6 Some Introductory Reflections on Organoclay Polymer Nanocomposites / 72

References / 75

3 INDUSTRIAL TREATMENTS AND MODIFICATION OF CLAY MINERALS 87

3.1 Bentonite: From Mine to Plant / 87

3.1.1 A Largely Diffused Clay / 87

3.1.2 Geological Occurrence / 89

3.1.3 Mining / 89

3.2 Processing of Bentonite / 90

3.2.1 Modification of Bentonite Properties / 90

3.2.2 Processing Technologies / 91

3.3 Purification of Clay / 93

3.3.1 Influence of Clay Concentration / 94

3.3.2 Influence of Swelling Time / 94

3.3.3 Influence of Temperature / 95

3.4 Reaction of Clay with Organic Substances / 97

3.5 Particle Size Modification / 99

References / 99

4 ALKYLAMMONIUM CHAINS ON LAYERED CLAY MINERAL SURFACES 101

4.1 Structure and Dynamics / 101

4.1.1 Packing Density and Self–Assembly / 102

4.1.2 Dynamics and Diffusion at the Clay–Surfactant Interface / 110

4.1.3 Utility of Molecular Simulation to Obtain Molecular–Level Insight / 111

4.2 Thermal Properties / 111

4.2.1 Reversible Melting Transitions of Alkyl Chains in the Interlayer / 111

4.2.2 Solvent Evaporation and Thermal Elimination of Alkyl Surfactants / 113

4.3 Layer Separation and Miscibility with Polymers / 115

4.3.1 Thermodynamics Model for Exfoliation in Polymer Matrices / 115

4.3.2 Cleavage Energy / 116

4.3.3 Surface Energy / 121

4.4 Mechanical Properties of Clay Minerals / 121

References / 123

5 CHEMISTRY OF RUBBER–ORGANOCLAY NANOCOMPOSITES 127

5.1 Introduction / 127

5.2 Organic Cation Decomposition in Salts, Organoclays and Polymer Nanocomposites / 128

5.2.1 Experimental Techniques / 128

5.2.2 Decomposition of Organoclays Versus Precursor Organic Cation Salts / 133

5.3 Mechanism of Thermal Decomposition of Organoclays / 135

5.4 Role of Organic Cations in Organoclays as Rubber Vulcanization Activators / 137

References / 141

SECTION II PREPARATION AND CHARACTERIZATION OF RUBBER–CLAY NANOCOMPOSITES

6 PROCESSING METHODS FOR THE PREPARATION OF RUBBER–CLAY NANOCOMPOSITES 147

6.1 Introduction / 147

6.2 Latex Compounding Method / 148

6.2.1 Mechanism / 148

6.2.2 Influencing Factors / 149

6.3 Melt Compounding / 157

6.3.1 Mechanism / 157

6.3.2 Influencing Factors / 160

6.4 Solution Intercalation and In Situ Polymerization Intercalation / 170

6.5 Summary and Prospect / 170

Acknowledgment / 171

References / 171

7 MORPHOLOGY OF RUBBER–CLAY NANOCOMPOSITES 181

7.1 Introduction / 181

7.1.1 Focus, Objective and Structure of Chapter 7 / 181

7.1.2 X–Ray Diffraction Analysis for the Investigation of RCN / 182

7.2 Background for the Review of RCN Morphology / 182

7.2.1 Cationic Clays Used for the Preparation of Rubber Nanocomposites / 182

7.2.2 Multiscale Organization of Layered Clays / 184

7.2.3 Clay Distribution and Dispersion / 184

7.2.4 Clay Modification: Intercalation of Low Molecular Mass Substances / 184

7.2.5 Types of Polymer–Clay Composites / 184

7.2.6 Specific Literature on RCN / 186

7.3 Rubber–Clay Nanocomposites with Pristine Clays / 186

7.3.1 Rubber Nanocomposites with Cationic Clays / 187

7.3.2 In a Nutshell / 187

7.3.3 Distribution and Dispersion of a Pristine Clay in a Rubber Matrix / 190

7.3.4 Organization of Aggregated Pristine Clays / 194

7.4 Rubber–Clay Nanocomposites with Clays Modified with Primary Alkenylamines / 197

7.4.1 In a Nutshell / 197

7.4.2 Composites with Montmorillonite and Bentonite / 198

7.4.3 Composites with Fluorohectorite Modified with a Primary Alkenylamine / 202

7.5 Rubber–Clay Nanocomposites with Clays Modified with an Ammonium Cation Having three Methyls and One Long–Chain Alkenyl Substituents / 206

7.5.1 In a Nutshell / 206

7.5.2 Composites with Montmorillonite and Bentonite / 207

7.6 Rubber–Clay Nanocomposites with Montmorillonite Modified with Two Substituents Larger Than Methyl / 212

7.6.1 In a Nutshell / 212

7.6.2 Hydrogenated Tallow and Benzyl Groups as Ammonium Cation Substituents / 213

7.6.3 Hydrogenated Tallow and Ethylhexyl Groups as Ammonium Cation Substituents / 213

7.6.4 Other Long– and Short–Chain Alkenyl Groups as Ammonium Cation Substituents / 215

7.7 Rubber Composites with Montmorillonite Modified with an Ammonium Cation Containing a Polar Group / 215

7.7.1 In a Nutshell / 217

7.7.2 Composites with Diene Rubbers / 217

7.8 Rubber Nanocomposites with Montmorillonite Modified with an Ammonium Cation Containing Two Long–Chain Alkenyl Substituents / 219

7.8.1 In a Nutshell / 220

7.8.2 Composites with Two Talloyl Groups as Ammonium Cation Substituents / 220

7.9 Proposed Mechanisms for the Formation of Rubber–Clay Nanocomposites / 228

7.9.1 Two Mechanisms for the Formation of an Exfoliated Clay / 228

7.9.2 Two Mechanisms for the Formation of an Intercalated Organoclay / 228

7.9.3 Intercalation of Polymer Chains in the Interlayer Space / 229

7.9.4 Intercalation of Low Molecular Mass Substances in the Interlayer Space / 230

Abbreviations / 232

Acknowledgment / 233

References / 233

8 RHEOLOGY OF RUBBER–CLAY NANOCOMPOSITES 241

8.1 Introduction / 241

8.2 Rheological Behavior of Rubber–Clay Nanocomposites / 242

8.2.1 Natural Rubber (NR), Epoxidized Natural Rubber (ENR) and Polyisoprene Rubber (IR)–Clay Nanocomposites / 243

8.2.2 Styrene–Butadiene Rubber (SBR)–Clay Nanocomposites / 246

8.2.3 Polybutadiene Rubber (BR)–Clay Nanocomposites / 247

8.2.4 Acrylonitrile Butadiene Rubber (NBR)–Clay Nanocomposites / 250

8.2.5 Ethylene Propylene Rubber–Clay Nanocomposites / 253

8.2.6 Fluoroelastomer–Clay Nanocomposites / 254

8.2.7 Poly(isobutylene–co–para–methylstyrene) (BIMS) Rubber–Clay Nanocomposites / 257

8.2.8 Poly(ethylene–co–vinylacetate) (EVA) Rubber–Clay Nanocomposites / 257

8.2.9 Polyepichlorohydrin Rubber–Clay Nanocomposites / 259

8.2.10 Thermoplastic Polyurethane (TPU)–Clay Nanocomposites / 261

8.2.11 Styrene–Ethylene–Butylene–Styrene (SEBS) Block Copolymer–Clay Nanocomposites / 262

8.3 General Remarks on Rheology of Rubber–Clay Nanocomposites / 263

8.4 Overview of Rheological Theories of Polymer–Clay Nanocomposites / 269

8.5 Conclusion and Outlook / 270

References / 271

9 VULCANIZATION CHARACTERISTICS AND CURING KINETIC OF RUBBER–ORGANOCLAY NANOCOMPOSITES 275

9.1 Introduction / 275

9.2 Vulcanization Reaction / 276

9.3 Rubber Cross–Linking Systems / 278

9.3.1 Sulfur Vulcanization / 278

9.3.2 Peroxide Vulcanization / 282

9.4 The Role of Organoclay on Vulcanization Reaction / 283

9.4.1 Influence of Organoclay Structural Characteristics on Rubber Vulcanization / 288

9.5 Vulcanization Kinetics of Rubber–Organoclay Nanocomposites / 290

9.6 Conclusions / 297

References / 298

10 MECHANICAL AND FRACTURE MECHANICS PROPERTIES OF RUBBER COMPOSITIONS WITH REINFORCING COMPONENTS 305

10.1 Introduction / 305

10.2 Testing of Viscoelastic and Mechanical Properties of Reinforced Elastomeric Materials / 307

10.2.1 Dynamic–Mechanical Analysis / 307

10.2.2 Tensile Testing / 310

10.2.3 Assessment of Toughness Behavior under Impact–Like Loading Conditions / 313

10.2.4 Hardness Testing / 315

10.2.5 Special Methods / 316

10.3 Characterization of the Fracture Behavior of Elastomers / 319

10.3.1 Fracture Mechanics Concepts / 319

10.3.2 Experimental Methods / 321

10.4 Mechanism of Reinforcement in Rubber–Clay Composites / 328

10.5 Theories and Modeling of Reinforcement / 333

Acknowledgment / 336

References / 336

11 PERMEABILITY OF RUBBER COMPOSITIONS CONTAINING CLAY 343

11.1 Introduction / 343

11.1.1 Butyl Rubbers as Nanocomposite Base Elastomers / 343

11.1.2 Measurement of Tire Innerliner Compound Permeability / 345

11.1.3 Further Improvement in Tire Permeability / 346

11.2 Nanocomposites / 346

11.3 Preparation of Elastomer Nanocomposites / 352

11.4 Temperature and Compound Permeability / 352

11.5 Vulcanization of Nanocomposite Compounds and Permeability / 356

11.6 Thermodynamics and BIMSM Montmorillonite Nanocomposites / 358

11.7 Nanocomposites and Tire Performance / 362

11.8 Summary / 364

References / 364

SECTION III COMPOUNDS WITH RUBBER–CLAY NANOCOMPOSITES

12 RUBBER–CLAY NANOCOMPOSITES BASED ON APOLAR DIENE RUBBER 369

12.1 Introduction / 369

12.2 Preparation Methods / 371

12.2.1 Latex / 371

12.2.2 Solution / 373

12.2.3 Melt Blending / 374

12.3 Cure Characteristics / 377

12.4 Clay Dispersion / 379

12.4.1 Detection / 380

12.4.2 Characterization / 383

12.5 Properties / 387

12.5.1 Mechanical (Dynamic–Mechanical) / 387

12.5.2 Friction/Wear/Abrasion / 392

12.5.3 Barrier / 393

12.5.4 Fire Resistance / 396

12.5.5 Others / 397

12.6 Applications and Future Trends / 398

Acknowledgment / 399

References / 399

13 RUBBER–CLAY NANOCOMPOSITES BASED ON NITRILE

RUBBER 409

13.1 Introduction / 409

13.2 Preparation Methods and Clay

Dispersion / 410

13.2.1 Solution / 410

13.2.2 Latex / 411

13.2.3 Melt Blending / 412

13.3 Cure Characteristics / 414

13.4 Properties / 416

13.4.1 Mechanical (Dynamic–Mechanical) / 416

13.4.2 Friction/Wear / 421

13.4.3 Barrier / 423

13.4.4 Fire Resistance / 424

13.4.5 Others / 425

13.5 Outlook / 425

Acknowledgment / 426

References / 426

xii CONTENTS

FOR SCREEN VIEWING IN DART ONLY

14 RUBBER–CLAY NANOCOMPOSITES BASED ON BUTYL AND

HALOBUTYL RUBBERS 431

14.1 Introduction / 431

14.1.1 Butyl Rubber: Key Properties

and Applications / 431

14.1.2 Butyl Rubber–Clay Nanocomposites / 433

14.2 Types of Clays Useful in Butyl Rubber–Clay

Nanocomposites / 435

14.2.1 Montmorillonite Clays / 435

14.2.2 Hydrotalcite Clays / 435

14.2.3 High Aspect Ratio Talc Fillers / 436

14.2.4 Other Clays / 437

14.3 Compatibilizer Systems for Butyl Rubber–Clay

Nanocomposites / 438

14.3.1 Surfactants and Swelling Agents / 439

14.3.2 Butyl Rubber Ionomers / 439

14.3.3 Maleic Anhydride–Grafted Polymers / 443

14.3.4 Low Molecular Weight Polymers and Resins / 444

14.4 Methods of Preparation of Butyl Rubber–Clay Nanocomposites / 444

14.4.1 Melt Method / 445

14.4.2 Solution Method / 445

14.4.3 Latex Method / 447

14.4.4 In Situ Polymerization / 448

14.5 Properties and Applications of Butyl Rubber–Clay Nanocomposites / 449

14.5.1 Air Barrier Properties / 449

14.5.2 Reinforcement Properties / 452

14.5.3 Vulcanization Properties / 454

14.5.4 Adhesion Properties / 456

14.5.5 Other Properties / 457

14.6 Conclusions / 457

References / 458

15 RUBBER–CLAY NANOCOMPOSITES BASED ON OLEFINIC RUBBERS (EPM, EPDM) 465

15.1 Introduction / 465

15.2 Types of Clay Minerals Useful in EPM–, EPDM–Clay Nanocomposites / 466

15.3 Compatibilizer Systems for Olefinic Rubber–Clay Nanocomposites / 467

15.4 Preparation of EPDM–Clay Nanocomposites by an In Situ Intercalation Method / 469

15.5 Characteristics of EPDM–Clay Nanocomposites / 473

15.5.1 Gas Barrier Properties of EPDM–Clay Nanocomposites / 473

15.5.2 Rheological Properties of EPDM–Clay Nanocomposites / 474

15.5.3 Stability of EPDM–Clay Nanocomposites / 475

15.5.4 Swelling Properties of EPDM–Clay Nanocomposites / 475

15.5.5 Mechanical Properties of EPDM–Clay Nanocomposites / 476

15.6 Preparation and Characteristics of EPM–Clay Nanocomposites / 479

15.6.1 Tensile Properties of EPM–CNs / 480

15.6.2 Temperature Dependence of Dynamic Storage Moduli of EPM–CNs / 481

15.6.3 Creep Properties of EPM–CNs / 482

15.6.4 Swelling Properties of EPM–CNs / 483

15.7 Conclusions / 486

References / 486

16 RUBBER–CLAY NANOCOMPOSITES BASED ON THERMOPLASTIC ELASTOMERS 489

16.1 Introduction / 489

16.2 Selection of Materials / 491

16.2.1 Polymer Resin / 491

16.2.2 Nanoparticles / 493

16.3 Experimental / 493

16.3.1 Processing of Thermoplastic Elastomer Nanocomposites / 493

16.3.2 Morphological Characterization / 494

16.3.3 Thermal Properties Characterization / 495

16.3.4 Flammability Properties Characterization / 495

16.3.5 Thermophysical Properties Characterization / 496

16.4 Numerical / 497

16.4.1 Modeling of Decomposition Kinetics / 497

16.5 Discussion of Results / 501

16.5.1 Nanoparticle Dispersion / 501

16.5.2 Thermal Properties / 503

16.5.3 Flammability Properties / 507

16.5.4 Microstructures of Posttest Specimens / 511

16.5.5 Thermophysical Properties / 512

16.5.6 Kinetic Parameters / 513

16.6 Summary and Conclusions / 516

16.7 Nomenclature / 517

Acknowledgments / 518

References / 518

SECTION IV APPLICATIONS OF RUBBER–CLAY NANOCOMPOSITES

17 AUTOMOTIVE APPLICATIONS OF RUBBER–CLAY NANOCOMPOSITES 525

17.1 Introduction / 525

17.2 Automotive Application of Rubber / 526

17.2.1 Automotive Hose / 527

17.2.2 Automotive Seals / 528

17.2.3 Automotive Belts / 529

17.2.4 Automotive Tubing / 529

17.2.5 Door Seal and Window Channels / 529

17.2.6 Diaphragms and Rubber Boots / 529

17.2.7 Tire, Tube and Flap / 529

17.2.8 Other Miscellaneous Rubber Parts / 531

17.3 Prime Requirement of Different Elastomeric Auto Components from Application Point of View / 531

17.4 Elastomeric Nanocomposites and Rubber Industry / 531

17.5 Superiority of Clay/Clay Mineral in Comparison to Other Nanofillers / 534

17.6 Organo–Modified Clay/Clay Minerals / 534

17.7 Scope of Application of Elastomeric Nanocomposites in Automotive Industry / 534

17.7.1 Lighter Weight and Balanced Mechanical Property / 535

17.7.2 Barrier Property or Air Retention Property / 538

17.7.3 Aging and Ozone Resistance / 539

17.7.4 Solvent Resistance / 541

17.7.5 Better Processability / 542

17.7.6 Elastomeric Polyurethane–Organoclay Nanocomposites / 544

17.7.7 Use of Organoclay Nanocomposites in Tire / 545

17.8 Disadvantages of Use of Organoclay Elastomeric Nanocomposites in Automotive Industry / 548

17.9 Conclusion / 549

Acknowledgment / 550

References / 550

18 NONAUTOMOTIVE APPLICATIONS OF RUBBER–CLAY NANOCOMPOSITES 557

18.1 Water–Based Nanocomposites / 557

18.1.1 Barrier Properties / 557

18.1.2 Comparison with Thermally Processed Elastomers / 566

18.2 Applications / 566

18.2.1 Sports Balls and Other Pneumatic Applications / 566

18.2.2 Breakthrough Time Applications / 571

References / 573

INDEX 575

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