Fundamentals of Latex Film Formation (eBook)

Preface 6
Contents 8
Symbols 14
Chapter 1 20
An Introduction to Latex and the Principles of Colloidal Stability 20
1.1 What is Latex? 20
1.2 Latex Synthesis and Uses 21
1.3 Historical Context and Economic Importance 27
1.4 Overview of the Film Formation Process 29
1.5 Environmental Legislation 34
1.6 Relevant Colloid Science 36
1.6.1 Interaction Potentials 36
1.6.1.1 Van der Waals Attraction 36
1.6.1.2 Electrostatic Repulsion Between Particles 37
1.6.1.3 DLVO Theory 38
1.6.1.4 Depletion Interactions 39
1.6.2 Fluid Motion 41
1.6.2.1 Diffusion 41
1.6.2.2 Low Shear Viscosity of Colloidal Dispersions 42
References 43
Chapter 2 46
Established and Emerging Techniques of Studying Latex Film Formation 46
2.1 Techniques to Study Latex in the Presence of Water (Wet and Damp Films) 47
2.1.1 Physical Probes of Drying 48
2.1.1.1 MFFT Bar 48
2.1.1.2 Film Scratching (Thin Film Analyser) 51
2.1.1.3 Gravimetry 51
2.1.1.4 Beam Bending (or Optical Cantilever) Technique 51
2.1.1.5 Ultrasonic Reflection 53
2.1.1.6 Electrical Conductivity 55
2.1.2 Specialist Electron Microscopies 55
2.1.2.1 Cryogenic Scanning Electron Microscopy 56
2.1.2.2 Environmental Scanning Electron Microscopy (ESEM) 56
2.1.2.3 Wet STEM 60
2.1.3 Scattering Techniques 61
2.1.3.1 Small Angle Neutron Scattering (SANS) and Small Angle X-Ray Scattering (SAXS) 61
2.1.3.2 Photo Correlation Spectroscopy, Diffusing Wave Spectroscopy, and Speckle Interferometry 63
2.1.3.3 Evanescent Dynamic Light Scattering 68
2.1.3.4 Ultramicroscopy and Confocal Microscopy 68
2.1.3.5 Optical Techniques: Transmission Spectrophotometry and Ellipsometry 69
2.1.4 Profiling Water and Particles with Spectroscopies 71
2.1.4.1 Confocal Raman Microscopy 71
2.1.4.2 IR Microscopy 72
2.1.4.3 NMR Profiling and Imaging 73
2.1.5 Probe Techniques for the Aqueous Environment 77
2.2 Techniques to Study Particle Packing and Deformation in Dry Films 80
2.2.1 Scanning Probe Microscopies 80
2.2.1.1 Contact Atomic Force Microscopy (AFM) 81
2.2.1.2 Intermittent Contact AFM and Phase Imaging 82
2.2.1.3 Electric Force Microscopy (EFM) and Scanning Electric Potential Microscopy (SEPM) 88
2.2.2 Scanning Near-Field Optical Microscopy (SNOM) and Shear Force Microscopy 89
2.2.3 Electron Microscopies 90
2.2.3.1 Transmission Electron Microscopy (TEM) 90
2.2.3.2 Scanning Electron Microscopy (SEM) 91
2.3 Techniques to Study Film Crosslinking 92
2.3.1 Ultrasonic Reflection and QCM 92
2.3.2 Spectroscopic Techniques 92
2.4 Techniques to Study Interdiffusion and Coalescence 93
2.4.1 Small Angle Neutron Scattering (SANS) 94
2.4.2 Fluorescence Resonance Energy Transfer (FRET) 95
2.4.2.1 Rate of Energy Transfer 95
2.4.2.2 Quantum Efficiency and Fraction of Mixing 97
2.4.3 Transmission Spectrophotometry 102
2.5 Concluding Remarks 102
References 102
Chapter 3 114
Drying of Latex Films 114
3.1 Humidity and Evaporation 114
3.1.1 Background 114
3.2 Evaporation Rate from Pure Water 115
3.3 Evaporation Rate from Latex Dispersions 117
3.4 Vertical Drying Profiles 118
3.4.1 Scaling Argument 120
3.4.2 Governing Equations 121
3.4.3 Experimental Studies 123
3.4.4 Consequence of Inhomogeneous Vertical Drying: Skin Formation 126
3.5 Horizontal Packing and Drying Fronts 126
3.5.1 Model for Horizontal Drying Fronts 129
3.5.2 Lapping Time and Open Time 130
3.6 Colloidal Stability 133
3.7 Film Cracking 135
3.7.1 Do the Cracks Follow the Drying Front or Propagate Quickly Over the Entire Film? 135
3.7.2 What Sets the Crack Spacing? 136
References 136
Chapter 4 140
Particle Deformation 140
4.1 Introduction 140
4.2 Driving Forces for Particle Deformation 141
4.2.1 Wet Sintering 142
4.2.2 Dry Sintering 142
4.2.3 Capillary Deformation 143
4.2.4 Capillary Rings 145
4.2.5 Sheetz Deformation 145
4.3 Particle Deformations 146
4.3.1 Hertz Theory – Elastic Spheres with an Applied Load 146
4.3.2 JKR Theory – Elastic Spheres with an Applied Load and Surface Tension 146
4.3.3 Frenkel Theory – Viscous Spheres with Surface Tension 147
4.3.4 Viscoelastic Particles 149
4.4 The Problem with Particle–Particle Approach 149
4.4.1 Routh and Russel Film Deformation Model 149
4.4.1.1 Particle–Particle Deformation 150
4.4.1.2 Integration to Film Deformation 150
4.4.1.3 Assumption of a Viscoelastic Fluid 151
4.5 Deformation Maps 152
4.5.1 Wet Sintering 152
4.5.2 Capillary Deformation 152
4.5.3 Dry Sintering 152
4.5.4 Receding Water Front 152
4.5.5 Use of the Deformation Maps 153
4.6 Dimensional Argument 154
4.6.1 Wet Sintering 154
4.6.2 Capillary Deformation 154
4.6.3 Dry Sintering 155
4.6.4 Sheetz Deformation 155
4.7 Effect of Temperature 156
4.8 Effect of Particle Size 158
4.9 Experimental Evidence for Deformation Mechanisms 159
4.9.1 Inferring Deformation Mechanisms from Water Distributions 159
4.9.2 Determination of Deformation Mechanisms Using an MFFT Bar and Optical Techniques 162
4.9.3 Microscopy of Particle Deformation 162
4.9.4 Scattering Techniques 165
4.9.5 Detection of Skin Formation 165
References 165
Chapter 5 170
Molecular Diffusion Across Particle Boundaries 170
5.1 Essential Polymer Physics 172
5.1.1 Interface Width at Polymer-Polymer Interfaces 172
5.1.2 Polymer Reptation 173
5.2 Development of Mechanical Strength and Toughness 177
5.2.1 Dependence on the Density of Chains Crossing the Interface 181
5.2.2 Dependence on Interdiffusion Distance, . 181
5.3 Factors that Influence Diffusivity 183
5.3.1 Molecular Weight and Chain Branching 183
5.3.2 Temperature Dependence 184
5.3.3 Influence of Hard Particles 187
5.3.4 Latex Particle Size 191
5.3.5 Particle Structure and Hydrophilic Membranes 191
5.4 Faster Diffusion with Coalescing Aids 193
5.5 Simultaneous Crosslinking and Diffusion: Competing Effects 194
References 198
Chapter 6 203
Surfactant Distribution in Latex Films 203
6.1 Introduction 203
6.1.1 Where Can Surfactant Go in a Dried Film? 204
6.1.2 Effect of Non-Uniform Surfactant Distributions 206
6.1.2.1 Gloss and Appearance 206
6.1.2.2 Aesthetic Qualities and Dirt Pick-Up 207
6.1.2.3 Adhesion and Viscoelasticity 208
6.1.2.4 Barrier Properties and Water Whitening 208
6.1.2.5 Film Formation Process 209
6.1.3 Mechanisms of Surfactant Transport 209
6.2 Adsorption Isotherms 210
6.3 Modelling of Surfactant Distribution during the Drying Stage 212
6.4 Effect of Surfactant’s Vertical Distribution on Film Topography 217
6.5 Experimental Evidence for Surfactant Locations 219
6.5.1 Interfaces with Air and Substrates 219
6.5.2 Surfactant in the Bulk of the Film 220
6.5.3 Depth Profiling and Mapping 220
6.6 Reactive Surfactants 222
6.6.1 Reactive Surfactant Chemistry 223
6.6.2 Effect of Surfmers on Film Properties 223
6.7 Summary 225
References 225
Chapter 7 231
Nanocomposite Latex Films and Control of Their Properties1 231
7.1 Introduction 231
7.1.1 Properties of Nanocomposites 232
7.1.2 Applications of Colloidal Nanocomposites 234
7.2 Types of Hybrid Particles 235
7.2.1 Polymer-Polymer Hybrid Particles 235
7.2.2 Inorganic and Polymer Nanocomposite Particles 237
7.2.3 ‘Self-Assembly’ of Nanocomposite Particles by Precipitation or Flocculation of Pre-Formed Nanoparticles 241
7.3 Colloidal Particle Deposition and Assembly Methods 243
7.3.1 Deposition Methods 245
7.3.2 Vertical Deposition 247
7.3.3 Surface Pattern-Assisted Deposition 248
7.3.4 Long-Range Order from Self-Assembled Core-Shell Particles 250
7.4 Colloidal Nanocomposites from Particle Blends 251
7.4.1 Advantages of Particle Blends 251
7.4.2 Dispersion of Nanoparticles 251
7.4.3 Long-Range Order in Particle Blends 253
7.5 Three Lessons about the Properties of Waterborne Nanocomposite Films 256
7.5.1 Lesson One 256
7.5.1.1 Percolation of Spherical Particles 257
7.5.1.2 Percolation of Rod-Like Particles 258
7.5.1.3 Properties in Percolating Systems 259
7.5.1.4 Properties of Hybrid and Blend Systems 260
7.5.2 Lesson Two 262
7.5.3 Lesson Three 263
References 267
Chapter 8 278
Future Directions and Challenges 278
8.1 Film Formation from Anisotropic Particles 278
8.2 Assembly of Particles over Large Length Scales 280
8.3 Technique Development 282
8.4 Nanocomposite Structure and Property Correlations 282
8.5 Interdiffusion of Polymers in Multiphase Particles 284
8.6 Templating Film Topography 285
8.7 Resolving the Film Formation Dilemma 286
References 289
Index 317