Protective Coatings (eBook)

Mei Wen is a Research Associate at Axalta Coating Systems, located at the Coatings Technology Center in Wilmington, Delaware.  She has worked in the chemical industry for fifteen years, with her primary focus being directed toward organic coatings.  Since joining Axalta Coating Systems in 2013, she has worked on clearcoats for Automotive Coatings and leads an academic collaboration between Axalta and the Institute of Macromolecular Chemistry, Prague, Czech Republic on coatings film formation.  Prior to her current work, Dr. Wen worked at Arkema for ten years on acrylic, polyurethane, epoxy, marine antifoulant, mesoporous titanium oxide, and transparent conductive oxide coatings.   She served as a Director on the Board for the International Society of Coating Science and Technology (ISCST) from 2008 to 2012.  She was selected to attend the National Academy of Engineering’s U.S. Frontiers of Engineering Symposium in 2007.  In 2005 she received an R&D 100 award on Marine Antifoulant Coating binders with her colleagues and was an invited speaker at Gordon Research Conference for Coatings and Films. Prior to her time at Arkema, Dr. Wen also worked for Applied Materials on electroplating of copper. She has published 26 technical papers. She received her B.S. and M.S. degrees of Chemical Engineering from Tsinghua University in 1987 and 1995, respectively, and her Ph.D. degree of Chemical Engineering from University of Minnesota in 2001.Karel Dušek is at present Emeritus Professor of Institute of Macromolecular Chemistry (IMC), Academy of Sciences of the Czech Republic. He served for this institution since 1965 in various positions, since 1973 as Principal Scientist and Head of Department of Mechanical Properties and Polymer Networks; in the period 1975-1991 he headed the joint Department of Polymer Physics. He obtained his PhD degree from Institute of Physical Chemistry, Czechoslovak Academy of Sciences in 1958, and worked for SYNPO Research Establishment in Pardubice, CZ, until 1965. His educational and research activities included polymer physics and chemistry at Charles University in Prague, University of Pardubice, and visiting professorships at Technical University, Delft (The Netherlands), University of Essex (UK), University of Massachusetts in Amherst (USA), Kyoto Institute of Technology (Japan), University of Pau and INSA Lyon (France). Since 1997, he is Adjunct Professor of Bioengineering Department of University of Utah in Salt Lake City. In 1997, he was honored by the Doctor Honoris Causa degree by Wroclaw Technical University (Poland). Other honors and awards included State Prize of Czechoslovak Republic in 1988, Silver Medal of City of Paris in 1990, Heyrovský Medal for Merits in Chemical Sciences in 2000, P.J. Flory Polymer Research Award in 2004; he was awarded three times by Annual Prize of the Academy of Sciences. Prof. Dušek is Founding Member of Polymer Networks Group (1974), served as Chairman, Vice-Chairman, and Treasurer and organized three of the biennial meetings.  He is also Founding Member of Learned Society of the Czech Republic. He served as Editor in seven scientific journals. On European Union scene, Prof. Dušek served as Coordinator of Area of Excellence “Structure-Property Relationships” of Network of Excellence Nanostructured Multifunctional Polymer-Based Materials and Nanocomposites and as Coordinator of Czech representation in this Network. By January 2013, he published about 300 scientific papers with over 7700 citations and his H-index was 43.

Preface 5
Contents 7
Part I: Network Formation and Modeling 9
Chapter 1: Role of Distributions in Binders and Curatives and Their Effect on Network Evolution and Structure 10
Introduction 10
Distributions-Description and Transformation 11
Distributions in Coatings Binders 12
Distributions in Commercial Starting Components 13
Functionality Distribution in Polyisocyanates 13
Functionality and Molecular Weight Distributions in Telechelics 15
Distributions Generated by Side Reactions 15
Two-Stage Reactive Systems-Preparation of a Precursor in the First Stage and Its Cross-Linking in the Second Stage 16
Functional Copolymers 17
Hyperbranched Polymers 20
Off-Stoichiometric (Highly Branched) Copolyadducts 24
Systems with Distributions of Groups of Different Reactivities 28
Chain-Extended Systems 30
Multistage Network Formation Processes 34
Conclusions 36
Appendix 37
Definitions of Distributions and Their Transform Using the Formalism of Probability Generating Functions 37
Probability Generating Functions 37
Degree of Polymerization and Molecular Weight Distributions 39
Functionality Distributions 41
Distribution of Reaction States of Building Units in the Branching Process 41
References 42
Chapter 2: Heterogeneity in Crosslinked Polymer Networks: Molecular Dynamics Simulations 45
Introduction 45
Background 46
Model and Simulation Method 48
Heterogeneities in Network Polymers 51
Local-Scale Heterogeneities 53
Extended Heterogeneities 56
Swelling and Voids 60
Summary 67
References 69
Chapter 3: Rigidity Percolation Modeling of Modulus Development During Free-Radical Crosslinking Polymerization 72
Introduction 72
Network Load-Displacement Relationship 76
Modeling Method 80
Results and Discussion 85
Stress Distribution 86
Effect of Initiation Rate Constant 89
Effect of Primary Cyclization Rate Constant 92
Conclusions 93
References 94
Part II: Coating Film Formation and Properties 98
Chapter 4: Rheology Measurement for Automotive Coatings 99
Introduction 99
Viscosity in Simple Shear 100
Viscometers Used in Coatings Industry 102
Structures Causing Non-Newtonian Behavior 103
Viscometry Test Practices 104
Viscometry Applied to Paint Formulations 111
Dynamic Oscillatory Rheology 112
Nonlinear Dynamic Oscillatory Rheology 116
Summary/Outlook 116
References 117
Chapter 5: Magnetic Microrheology for Characterization of Viscosity in Coatings 118
Introduction 118
Magnetic Microrheometry for In Situ Characterization of Coating Viscosity 120
Magnetic Microrheometer Designed for Coatings 120
Coating Viscosity as a Function of Time and Position 123
Magnetic Microrheology of a Coating Used in Tissue Making 126
Experimental Methods 127
Magnetic Microrheometer Setup 127
Coating Formulations 128
Probe Particles 128
Imaging, Data Collection, and Analysis 131
Comparison with Traditional Rheology 132
Results and Discussion 132
Noncrosslinking PAE (NX PAE) Solutions 132
Plasticizer Concentration in NX PAE 134
Effect of Crosslinking Potential 136
Summary 137
References 138
Chapter 6: CryoSEM: Revealing Microstructure Development in Drying Coatings 140
Introduction 140
Scanning Electron Microscopy 141
Cryogenic Scanning Electron Microscopy (cryoSEM) 142
Vitrification 142
Cryo-fracture 145
Sublimation 146
Artifacts of CryoSEM Sample Preparation 147
Examples of CryoSEM Characterization in Coatings Research 149
Conclusions 153
References 154
Chapter 7: Film Formation Through Designed Diffusion Technology 156
Introduction 156
Model and Mechanism of Designed Diffusion Technology 158
Design and Synthesis of the Designed Diffusion Polymers 159
Physical and Analytical Results and Discussion 160
Acceleration of Hardness Development 160
VOC Reduction Without Compromising Film Formation 161
Coalescent (Texanol) Partitioning between Polymer A and Designed Diffusion Polymer DD 162
Percolation Threshold and Accelerated Diffusion or Permeation Pathways 164
Effect of Coalescent Boiling Point 165
Ultimate Hardness of the Dominant Phase Polymer A as a Function of its Tg 166
Tg Effect of Designed Diffusion Polymer DD 167
Application Results and Discussion 168
Conclusions 170
References 171
Chapter 8: In Situ FTIR Study of Cure Kinetics of Coatings with Controlled Humidity 172
Background 172
Experimental 175
Materials 175
Sample Preparation 175
Humidity Control System 177
FTIR Kinetic Study 179
Results and Discussion 179
FTIR with Humidity Control 179
Bubbler DI Water Temperature Effect 179
Temperature Control and Condensation 180
Background Collection 181
Humidity Control 182
Kinetics of HDI Trimer Reacting with Water 182
Kinetics of HDI Trimer Reacting with Acrylic Polyol 187
Conclusions 193
References 194
Chapter 9: Shrinkage in UV-Curable Coatings 197
Introduction 197
Fundamentals and Applications of UV-Curable Coatings 197
Character and Influence of Shrinkage on UV-Curable Coatings 198
Measurement and Evaluations of Shrinkage in UV-Curable Coatings 200
Dilatometry Method 200
Pycnometer Method 201
Buoyancy Method 203
Bonded-Disk Method 204
Interferometer Method 205
Laser Displacement Method 206
Laser Scanning Method 207
Video-Imaging Device Method 208
Linometer and NIR Spectroscopy Combination Method 209
Photorheometry and NIR Spectroscopy Combination Method 209
Methods of Controlling the Shrinkage 210
The Condition of Photopolymerization 211
Addition of Inert Component 212
Adjusting the Structure of Monomers 212
The Density of Functional Groups 212
Structure Rigidity and Steric Hindrance 214
Ring-Opening Polymerization 214
Thiol-Containing System 216
Hybrid System 218
Solid-State Photopolymerization 219
Summary and Developing Prospects of Shrinkage Research in UV Curing 220
References 221
Chapter 10: Measurements of Stress Development in Latex Coatings 226
Introduction 226
Experimental 230
Stress Measurement 230
Minimum Film Formation Temperature 232
Latex 233
Results and Discussion 234
Effect of MFFT on Stress Development 234
Effect of Coalescing Aids on Film Stress Development 236
Conclusions 238
References 240
Chapter 11: Stress Development in Reactive Coatings 242
Introduction 242
Stress Measurement 245
Experimental 249
Synthesis of Acrylic Polyols 249
Molecular Weight 250
Coating Solutions 251
NCO Conversion 251
Glass Transition Temperature 252
Pendulum Hardness 252
Coating Stress 252
Results and Discussion 253
Effect of Monomer Type in Acrylic Polyols 253
Effect of Molecular Weight of Acrylic Polyol 257
Effect of Crosslink Density 257
Effect of Addition of Low-Tg Polyester 261
Effect of Solvent Addition 263
Effect of Baking During Film Formation 264
Conclusions 265
References 266
Part III: Coating Film Properties and Applications 269
Chapter 12: Swelling of Coating Films 270
Introduction 270
Degree of Swelling and Its Determination 271
Evolution of Network Structure 272
Theoretical Models of Equilibrium Swelling of Cross-Linked Polymers 274
Swelling of Networks of Gaussian Chains 275
Considering Finite Extensibility of Network Chains 277
Swelling of Adhering Coating Film 278
Effect of Constraints During Film Formation on Swelling of Detached Film 278
Effect of the Polymer-Solvent Interaction Parameter 280
Effect of Structural Parameters of the Network on Swelling and the Swell Test 282
The Swell Test as a Measure of Changes in Cross-Link Density or Solvent Quality 284
Correlations with Experiment 284
Pitfalls of the Swell Test 288
Conclusions 288
References 289
Chapter 13: Chemical Depth Profiling of a Multilayer Coating System Using Slab Microtomy and FTIR-ATR Analysis 291
Background 291
Experimental 293
Sample Preparation 293
Optical Microscope Imaging 293
Microtoming 294
FTIR-ATR 295
Indentation Hardness 295
Results and Discussion 296
Summary 308
References 309
Chapter 14: Characterization of Component Distributions in Acrylic Latex and Paint Films Containing an Alkali-Soluble Resin (A... 311
Introduction 311
Experimental 313
Materials 313
Latex Film Analyses 314
Water Contact Angle 314
Atomic Force Microscopy (AFM) 314
Confocal Raman Microscopy (CRM) 314
Paint Film Analyses 315
Paint Formulation and Film Preparation 315
Results and Discussion 316
WaterContact Angle on Acrylic Polymer and ASR/AL Blends 316
Film Morphology and ASR Distribution 317
ASR Distribution in Latex Films 318
ASR Distribution in Paint Films 321
Surfactant Enrichment on Paint 1 Film 324
Conclusions 327
References 327
Chapter 15: Advances in NanoScratch Testing of Automotive Clearcoats 330
Introduction 330
Experimental Methodology 332
Materials 332
Test Procedure 333
Scratch Test Conditions 335
Scratching Coefficient of Friction 335
Scratch Morphology 336
Optical Microscope 336
Atomic Force Microscopy 336
Results and Discussion 336
Indenter Characterization 337
Determination of Fracture Threshold 339
Measurement of Plastic Resistance 339
Measurement of Scratch Recovery 340
Scratch Visibility 343
Statistical Comparison Between Materials 346
Conclusion 351
Appendix MATLAB and Kornucopia ML Analysis of Scratch Data 352
References 356
Chapter 16: Scratch and Mar Resistance of Automotive Coatings 357
Introduction 357
Experimental 359
Scratch and Mar Resistance Test Methods 359
Crockmeter-2mum 360
Crockmeter-9mum 361
Amtec Kistler Car Wash 361
Nano Scratch 361
Results and Discussion 363
Effect of Crosslink Density on Scratch and Mar Resistance 363
Chain Elasticity vs. Scratch and Mar Resistance 364
Aging and Weathering Effect on Scratch and Mar Resistance 366
Nanotechnology 368
Conclusions 371
References 372
Chapter 17: Appearance of Automotive Coatings 373
Introduction 373
Experimental 376
Results and Discussion 377
Film Formation: Low- vs. High-Bake Coatings 377
Flow and Leveling 379
Substrate Telegraphing 385
Gradients of Drying and Curing 388
Multi-Layer Compatibility 390
Consolidated Systems 394
Conclusions 397
References 397
Chapter 18: Craters and Other Coatings Defects: Mechanisms and Analysis 399
Introduction 399
Surface Tension-Driven Defects 399
Craters 400
General 400
Surface Flow 401
Crater Formation Time 403
Crater Size and Contaminant Volume 404
Causes of Craters 404
Crater Prevention 405
Wetting and Dewetting 406
Picture Framing (Fat Edges) 407
Telegraphing 408
Convection Flow Defects 409
Wrinkling 411
Volatile-Related Defects 412
Popping 413
Gassing 415
Air Entrapment 417
Defects Related to Flow or Lack of It 418
Sagging 418
Poor Leveling and Orange Peel 418
Conclusions 419
References 420
Chapter 19: Degradation of Polymer Coatings in Service: How Properties Deteriorate Due to Stochastic Damage 422
Introduction 422
Background 423
Opportunities for Degradation 423
Statistics of Random Events 425
Intrinsic Defects in Crosslinked Networks 426
Degradation Kinetics of Physical Properties 427
Gloss 429
Toughness 432
Other Degradation Kinetics 435
Nonsimultaneous Degradation 438
Summary 441
References 443
Chapter 20: Long-Term Mechanical Durability of Coatings 446
Introduction 446
Fracture Mechanics 447
Crack Initiation 447
Crack Propagation 449
Stresses in Organic Coatings 450
Long-Term Resistance to Cracking in Coatings 452
Evolution of Cracking Patterns 455
Conclusions 456
References 457
Chapter 21: Automotive Paint Application 459
Introduction 459
The Evolution of Automotive Coating Application from 1980 to Today 460
Typical Automotive Coating Sequence 463
Conversion Coating 463
Electrocoat 464
Primer, Basecoat, and Clearcoat 464
Practical Application 465
Uniform Film 465
Predicting Deposited Film Thickness from Application Parameters 471
Flow Rate Calculation Example 472
Transfer Efficiency Example Calculation 475
Wet Film Nonvolatiles 476
Atomization 477
Pneumatic Atomization 478
Rotary Atomization 482
Electrostatic Deposition by Rotary Atomizer 488
Summary 489
References 489
Index 491