Micro and Nanostructured Epoxy / Rubber Blends

Epoxy resins are polymers which are extensively used as coating materials due to their outstanding mechanical properties and good handling characteristics. A disadvantage results from their high cross-link density: they are brittle and have very low resistance to crack growth and propagation. This necessitates the toughening of the epoxy matrix without impairing its good thermomechanical properties. The final properties of the polymer depend on their structure. The book focuses on the microstructural aspects in the modification of epoxy resins with low molecular weight liquid rubbers, one of the prime toughening agents commonly employed. The book follows thoroughly the reactions of elastomer-modified epoxy resins from their liquid stage to the network formation. It gives an in-depth view into the cure reaction, phase separation and the simultaneous development of the morphology. Chapters on ageing, failure analysis and life cycle analysis round out the book.

Table of Contents:
Preface XV List of Contributors XVII 1 Introduction 1 Raju Thomas, Christophe Sinturel, Sabu Thomas, and Elham Mostafa Sadek El Akiaby 1.1 Epoxy Resin – Introduction 1 1.2 Cure Reactions 1 1.3 Curing Agents 2 1.3.1 Catalytic Cure 3 1.3.2 Co-reactive Cure 3 1.4 Different Curing Methods 7 1.4.1 Thermal Curing 7 1.4.2 Microwave Curing 8 1.4.3 Radiation Curing 10 1.5 Curing of Epoxy Resins: Structure–Property Relationship 12 1.6 Toughening of Epoxy Resin 13 1.6.1 Different Toughening Agents 13 1.7 Rubber-Modified Epoxy Resin: Factors Influencing Toughening 16 1.7.1 Concentration Effects 16 1.7.2 Particle Size and Distribution of Rubber 16 1.7.3 Effect of Temperature 17 1.7.4 Effect of Rubber 17 1.7.5 Interfacial Adhesion 18 1.8 Toughening Mechanisms in Elastomer-Modified Epoxy Resins 18 1.8.1 Particle Deformation 18 1.8.2 Shear Yielding 19 1.8.3 Crazing 20 1.8.4 Simultaneous Shear Yielding and Crazing 21 1.8.5 Crack Pinning 22 1.8.6 Cavitation and Rumples 22 1.9 Quantitative Assessment of Toughening Mechanisms 23 1.10 Introduction of Chapters 24 References 25 2 Liquid Rubbers as Toughening Agents 31 Hanieh Kargarzadeh, Ishak Ahmad, and Ibrahim Abdullah 2.1 Introduction 31 2.2 Toughening of Thermoset Resins 31 2.3 Fracture Behavior of Rubber-Toughened Thermosets 32 2.4 Natural Rubbers 35 2.4.1 Preparation Method of LNR 36 2.5 Liquid-Toughening Rubber in Thermoset Resins 43 2.6 Concluding Remarks 49 References 50 3 Nanostructured Epoxy Composites 53 Yuan Meng and Xinghong Zhang 3.1 Introduction 53 3.2 Preparation Methods of the Nanostructured Epoxy Thermoset 54 3.3 Morphology of the Nanostructured Epoxy Thermoset 56 3.3.1 Parameters Controlling the Morphologies 56 3.4 Microphase Separation Mechanism 60 3.4.1 Self-Assembly Mechanism 61 3.4.2 Reaction-Induced Microphase Separation Mechanism 63 3.5 Mechanical and Thermal Properties 65 3.5.1 Fracture Toughness 65 3.5.2 Glass Transition Temperature 67 3.6 Conclusions and Outlooks 67 References 68 4 Manufacture of Epoxy Resin/Liquid Rubber Blends 73 Sahrim Bin Hj Ahmad, Mimi Azlina Abu Bakar, Ying Yi, and Qi Qin 4.1 Introduction 73 4.2 Comparison of Hardeners 74 4.3 Rubber-Toughened Epoxy Resins 77 4.4 Cure Reaction Analysis 79 4.5 Conclusions 79 References 80 5 Cure and Cure Kinetics of Epoxy-Rubber Systems 83 Humberto Vázquez-Torres 5.1 Introduction 83 5.2 Cure Analysis 83 5.3 Curing Kinetics 84 5.3.1 Kinetics Analysis 85 5.3.2 Autocatalytic Model 85 5.3.3 Activation Energies 86 5.4 Diffusion Factor 88 5.5 Differential Scanning Calorimetry 88 5.5.1 Dynamic DSC 89 5.5.2 Isothermal DSC 90 5.6 FTIR Spectroscopy 92 5.7 Dielectric Spectroscopy Thermal Method 94 5.8 Pressure–Volume–Temperature (PVT) Method 96 5.9 Dynamic Mechanical Analysis (DMA) and Rheological Methods 97 5.10 Conclusions 101 Acknowledgments 101 References 101 6 Theoretical Modeling of the Curing Process 105 Nicolas Boyard, Vincent Sobotka, and Didier Delaunay 6.1 Introduction 105 6.2 Modeling of the Curing Kinetics 106 6.2.1 Mechanistic Approach 107 6.2.2 Phenomenological Models Describing the Reaction 109 6.2.3 Rheological Models 118 6.2.4 Effect of Vitrification (Tg ) on the Reaction Rate 119 6.3 Applications of the Empirical Models 120 6.4 Conclusion 122 References 123 7 Phase-Separation Mechanism in Epoxy Resin/Rubber Blends 127 Vattikuti Lakshmana Rao and Bejoy Francis 7.1 Introduction 127 7.2 Thermodynamics of Phase Separation 128 7.2.1 Nucleation and Growth Mechanism 130 7.2.2 Spinodal Decomposition 130 7.3 Phase Separation in Uncured Epoxy Resin/Liquid Rubber Blends 131 7.4 Phase-Separation Mechanism in Cured Blends 133 7.5 Conclusion 144 References 144 8 Morphology Analysis by Microscopy Techniques and Light Scattering 147 Daohong Zhang, Junheng Zhang, and Aiqing Zhang 8.1 Introduction 147 8.2 Developments of Morphology Analysis in Rubber-Modified Epoxies 147 8.2.1 Optical Microscopy (OM) 148 8.2.2 Scanning Electron Microscopy (SEM) 150 8.2.3 Atomic Force Microscopy (AFM) 153 8.2.4 Transmission Electron Microscopy (TEM) 155 8.2.5 Small-Angle Light Scattering (SALS) 159 8.3 Different Types of Morphologies 160 8.3.1 Phase-Separation Morphology of Epoxy/Rubbers Blends 160 8.3.2 Morphology of Hybrids 161 8.3.3 Homogeneous Morphology 163 8.4 Morphology of Toughening and Reinforcing Effects 165 8.4.1 Conventional Additives 165 8.4.2 Hyperbranched Polymers 167 8.5 Conclusions 171 Acknowledgments 172 References 172 9 Pressure–Volume–Temperature (PVT) Analysis 179 Didier Delaunay, Nicolas Boyard, and Vincent Sobotka 9.1 Introduction 179 9.2 Generalities on the Behavior of the Polymers 180 9.3 Measurement Techniques 184 9.4 PvT Measures on Epoxies 187 References 190 10 Rheology of Rubber-Toughened Structural Epoxy Resin Systems 193 Richard A. Pethrick 10.1 Introduction 193 10.2 Epoxy Resin Chemistry 194 10.2.1 Basic Epoxy Chemical Reactions 195 10.2.2 Kinetics of Cure 196 10.2.3 Epoxy Reactivity 198 10.3 Modeling of the Cure Process 198 10.4 Rheological Implication of Differences in Reactivity 201 10.4.1 Modeling Rheological Behavior 202 10.4.2 Connection between Rheology and Cure 203 10.5 Rheological Studies of Cure 206 10.6 Toughened Epoxy Resins 209 10.6.1 Carboxy-Terminated Butadiene Acrylonitrile (CTBN) 210 10.6.2 Polyethersulfone (PES) 211 10.6.3 Nano Clay Toughening of Epoxy Resins 213 10.6.4 Toughening with Nano Carbon and Silica Nano Particles 213 10.6.5 Plasticization 213 10.7 Concluding Comments 214 Acknowledgments 214 References 214 11 Viscoelastic Measurements and Properties of Rubber-Modified Epoxies 219 Yingfeng Yu 11.1 Introduction 219 11.1.1 State Transitions from Liquid to Solid 220 11.1.2 Viscoelasticity of Cured Materials 222 11.2 Viscoelastic Behavior Below and Near Gel Point 224 11.2.1 Liquid-Rubber-Modified Epoxies 224 11.2.2 Core–Shell Rubber-Modified Epoxies 224 11.2.3 Ternary Systems with Fillers 228 11.3 Viscoelasticity of Cured Materials 228 11.3.1 Dynamic Mechanical Study 228 11.3.2 Dielectric Measurement 231 11.4 Other Remarks 233 11.5 Conclusion 234 References 234 12 Light, X-ray, and Neutron Scattering Techniques for Miscibility and Phase Behavior Studies in Polymer Blends 239 Chikkakuntappa Ranganathaiah 12.1 Introduction 239 12.2 Brief Theoretical Considerations of Scattering 240 12.3 Light Scattering Experiment 242 12.4 X-ray Scattering 251 12.5 Neutron Scattering 261 12.5.1 Small-Angle Neutron Scattering (SANS) 261 12.6 Conclusions and Future Outlook 267 Acknowledgments 267 References 267 13 Mechanical Properties 271 Shinu Koshy 13.1 Introduction 271 13.2 Morphology and Mechanical Properties of Rubber-Modified Epoxies 272 13.2.1 Influence of Rubber Concentration 273 13.2.2 Influence of Initial Cure Temperature 276 13.2.3 Influence of Curing Agent 278 13.2.4 Influence of Acrylonitrile Content 279 13.2.5 Influence of Strain Rate 280 13.2.6 Kerner Equation 281 13.3 Fracture Toughness 281 13.3.1 Effect of Concentration on Fracture Toughness 282 13.3.2 Effect of Strain Rate on Fracture Toughness 284 13.3.3 Effect of Curing Agent on Fracture Toughness 285 13.4 Conclusion 285 References 286 14 Thermal Properties 289 Vincent Sobotka, Didier Delaunay, Nicolas Boyard, Sabu Thomas, and Poornima Vijayan P. 14.1 Specific Heat 289 14.2 Thermal Conductivity 292 14.2.1 Main Methods of Characterization 292 14.2.2 Classical Model to Describe Thermal Conductivity as a Function of Temperature and Degree of Cure 296 14.3 Thermogravimetric Analysis of Rubber/Epoxy Systems 297 14.4 Kinetic Study from TGA 300 References 301 15 Dielectric Properties of Elastomeric Modified Epoxies 305 Yerrapragada Venkata Lakshmi Ravi Kumar, Swayampakula Kalyani, and Nidamarthy Vasantha Kumar Dutt 15.1 Introduction 305 15.2 Dielectric Study in Rubber/Epoxy Systems 306 15.2.1 Dielectric Constant () 306 15.2.2 Volume Resistivity (VR) 308 15.2.3 Conductivity () 310 15.2.4 Combined Studies on Dielectric Constant, Volume Resistivity, and Conductivity 311 15.3 Summary 312 References 312 16 Spectroscopy Analysis of Micro/Nanostructured Epoxy/Rubber Blends 315 Xiaojiang Wang and Mark D. Soucek 16.1 Introduction 315 16.2 Fourier Transform Infrared (FTIR) and Raman Spectroscopy 316 16.2.1 DGEBA Epoxy/Rubber Blends 316 16.2.2 Other Epoxy/Rubber Blends 320 16.2.3 FTIR Image and Raman Spectroscopy 322 16.3 Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) 323 16.3.1 Acid-Terminated Rubber/DGEBA Epoxy Blends 323 16.3.2 Hydroxyl-Terminated Rubber/DGEBA Epoxy Blends 326 16.3.3 Neutral Rubber/DGEBA Epoxy Blends 329 16.3.4 Other Type Epoxy/Rubber Blends 331 16.4 Other Spectroscopy 333 16.5 Summary 333 Abbreviations 334 References 334 17 Applications 339 17.1 Applications of Toughened Epoxy Resins 339 Richard A. Pethrick 17.1.1 Introduction 339 17.1.2 Aerospace Adhesive Applications 339 17.1.3 Rubber-Modified Resins 340 17.1.4 Composites 341 17.1.5 Epoxy Resin Modification 342 17.1.6 Thermoplastic Modification 343 17.1.7 Nanoparticle Modification 343 17.1.8 Other Areas of Application 343 17.2 Thermoset-Based Materials for Optical Applications Containing Azobenzene Choromophores 344 Luciana M. Sáiz, Antonela B. Orofino, María José Galante, and Patricia A. Oyanguren 17.2.1 Introduction 344 17.2.2 Synthesis and Optical Properties of Cross-linked Azo Polymers 345 17.2.3 Photoaddressable Networks Containing Alkyl Compounds 354 17.2.4 Conclusions 358 References 360 18 Comparison of Epoxy/Rubber Blends with Other Toughening Strategies: Thermoplastic and Hyperbranched Modifiers 363 Gianluca Cicala 18.1 Epoxy/Thermoplastic Blends: Development and Properties 363 18.2 Epoxy/Hyperbranched Polymer Blends: Development and Properties 375 18.3 Novel Toughening Approaches for Liquid Molding Technologies 378 18.4 Rubbers as Tougheners: Comparison with Thermoplastics and Hyperbranched Modifiers 383 18.5 Conclusions 387 References 388 19 Reliability Testing 391 Marius Bâzu and Titu Bãjenescu 19.1 Introduction 391 19.2 Reliability Tests Used in Micro/Nanotechnologies 392 19.3 Behavior in Real Applications and Aging Studies of Epoxy/Rubber Blends 394 19.3.1 Epoxy/Rubber Blends Used in Packaging of Active Electronic Components 394 19.3.2 Epoxy Matrix Used in Nanocomposites 399 19.4 Conclusions 402 References 402 20 Failure Analysis 405 Marius Bâzu and Titu Bãjenescu 20.1 Introduction 405 20.2 Methods for Failure Analysis of Epoxy/Rubber Blends 405 20.3 Typical Failure Modes and Failure Mechanisms of Epoxy/Rubber Blends Used in Micro and Nanotechnologies 405 20.3.1 Mechanical Damages 409 20.3.2 Ion Contamination 414 20.4 Self Healing 416 20.5 Conclusions 417 References 418 21 Life Cycle Assessment (LCA) of Epoxy-Based Materials 421 Jyotishkumar Parameswaranpillai and Dhanya Vijayan 21.1 Introduction to Life Cycle Assessment (LCA) 421 21.2 Significance of Life Cycle Assessment (LCA) 422 21.2.1 Goal and Scope Definition 422 21.2.2 Life Cycle Inventory Analysis 423 21.2.3 Life Cycle Impact Assessment 423 21.2.4 Life Cycle Result Interpretation 424 21.3 Life Cycle Analysis of Epoxy Systems 424 21.3.1 Life Cycle Analysis of Epoxy Resins Produced Based on Propylene and Glycerin 424 21.3.2 Life Cycle Analysis of Epoxy Resin Containing Carbon Nanotubes 426 21.3.3 Life Cycle Assessment of Wind Turbine Blade Materials 426 21.3.4 Life Cycle Assessment in Automotive Application 428 21.3.5 Life Cycle Assessment in Aerospace Application 429 21.3.6 Life Cycle Assessment of a Novel Hybrid Glass-Hemp/Thermoset Composite 429 21.3.7 Natural Fiber-Reinforced Epoxy Composites 430 21.4 Conclusion 430 References 431 Index 433

About the Author :
Sabu Thomas is a Professor and Director of Polymer Science and Engineering at the School of Chemical Sciences, as well as the Director of Centre for Nanoscience and Nanotechnology, Mahatma Gandhi University, Kerala, India. He received his Ph.D. in 1987 in Polymer Engineering from the Indian Institute of Technology (IIT), Kharagpur, India. He is a Fellow of the Royal Society of Chemistry. Prof. Thomas has (co-)authored more than 600 research papers in international peer-reviewed journals in the area of polymer composites, nanocomposites, membrane separation, polymer blends and alloys, polymeric sca olds for tissue engineering and polymer recycling. Prof. Thomas has been involved in a number of books (35 books), both as author and editor. He has been ranked no. 5 in India with regard to the number of publications (listed in the panel of most productive scientists in the country). He received the coveted Sukumar Maithy Award for the best polymer researcher in the country for the year 2008. The h index of Prof. Thomas is 67 and he has more than 17,000 citations. Prof. Thomas has 4 patents to his credit. Recently he has been awarded CRSI and MRSI awards. Prof. Thomas has supervised 64 PhD theses and has delivered more than 200 invited /plenary and key note talks over 30 countries. Christophe Sinturel received his Masters degree in Organic Chemistry in 1994 and his Ph.D. in Polymer Science in 1998 from the University Blaise Pascal of Clermont-Ferrand (France). He spent one year at the University of Brighton (UK) in 1999 as Postdoctoral Research Associate before being appointed as an associate professor the same year at the University of Orléans (France). He accepted a full-professor position at the University of Orléans in 2010. Christophe is currently conducting research in Orléans at the Centre de Recherche sur la Matière Divisée, a joint research institute of the Centre National de la Recherche Scienti que (CNRS) and the University of Orléans. His current research interests concern polymer blends, nanostructured polymers, polymer nano-composites and block polymers. He has published 40 publications in various international journals and books, 2 patents and participated in several international conferences. Raju Thomas is Vice Chancellor of Middle East University FZE, Ras Al Khaimah, UAE. He received his Ph.D. under the supervision of Prof. abu Thomas, Director of International and Interuniversity Centre for Nanoscience and Nanotechnology, Mahatma Gandhi University, Kottayam, Kerala, India. His research works are re ected in his six published research articles in international journals and few articles which are under review status. Also many articles are published in popular journals. He has a wide teaching experience in Chemistry for more than 32 years in Graduate and Postgraduate levels.