Dispersion of powders in liquids and stabilization of suspensions

• Main Author: Tadros, Tharwat F
• Format: eBook Book
• Language: English
• Published: Weinheim Wiley-VCH 2012; John Wiley & Sons, Incorporated
• Edition: 1
• Subjects: Colloids; Pigments; Powders; Suspensions (Chemistry)

Teaching the fundamental knowledge required for successful dispersion of powders in a liquid, this book covers a host of topics -- from recent advances to industrial applications. In 15 chapters it supports formulation chemists in preparing a suspension in a more rational way, by applying the princi...

Table of Contents:

• 8.5 Examples for Suspension Stabilization Using Polymeric Surfactants -- 8.6 Polymeric Surfactants for Stabilization of Preformed Latex Dispersions -- References -- 9: Properties of Concentrated Suspensions -- 9.1 Interparticle Interactions and Their Combination -- 9.1.1 Hard-Sphere Interaction -- 9.1.2 "Soft" or Electrostatic Interaction: Figure 9.1b -- 9.1.3 Steric Interaction: Figure 9.1c -- 9.1.4 van der Waals Attraction: Figure 9.1d -- 9.1.5 Combination of Interaction Forces -- 9.2 Definition of "Dilute," "Concentrated," and "Solid" Suspensions -- 9.3 States of Suspension on Standing -- References -- 10: Sedimentation of Suspensions and Prevention of Formation of Dilatant Sediments -- 10.1 Sedimentation Rate of Suspensions -- 10.2 Prevention of Sedimentation and Formation of Dilatant Sediments -- 10.2.1 Balance of the Density of the Disperse Phase and Medium -- 10.2.2 Reduction of the Particle Size -- 10.2.3 Use of High Molecular Weight Thickeners -- 10.2.4 Use of "Inert" Fine Particles -- 10.2.5 Use of Mixtures of Polymers and Finely Divided Particulate Solids -- 10.2.6 Controlled Flocculation ("Self-Structured" Systems) -- 10.2.7 Depletion Flocculation -- 10.2.8 Use of Liquid Crystalline Phases -- References -- 11: Characterization of Suspensions and Assessment of Their Stability -- 11.1 Introduction -- 11.2 Assessment of the Structure of the Solid/Liquid Interface -- 11.2.1 Double-Layer Investigation -- 11.2.1.1 Analytical Determination of Surface Charge -- 11.2.1.2 Electrokinetic and Zeta Potential Measurements -- 11.2.2 Measurement of Surfactant and Polymer Adsorption -- 11.3 Assessment of Sedimentation of Suspensions -- 11.4 Assessment of Flocculation and Ostwald Ripening (Crystal Growth) -- 11.4.1 Optical Microscopy -- 11.4.1.1 Sample Preparation for Optical Microscopy -- 11.4.1.2 Particle Size Measurements Using Optical Microscopy
• Intro -- Dispersion of Powders in Liquids and Stabilization of Suspensions -- Contents -- Preface -- 1: General Introduction -- 1.1 Fundamental Knowledge Required for Successful Dispersion of Powders into Liquids -- 1.1.1 Wetting of Powder into Liquid -- 1.1.2 Breaking of Aggregates and Agglomerates into Individual Units -- 1.1.3 Wet Milling or Comminution -- 1.1.4 Stabilization of the Resulting Dispersion -- 1.1.5 Prevention of Ostwald Ripening (Crystal Growth) -- 1.1.6 Prevention of Sedimentation and Formation of Compact Sediments (Clays) -- 1.2 Particle Dimensions in Suspensions -- 1.3 Concentration Range of Suspensions -- 1.4 Outline of the Book -- References -- 2: Fundamentals of Wetting and Spreading -- 2.1 Introduction -- 2.2 The Concept of the Contact Angle -- 2.2.1 The Contact Angle -- 2.2.2 Wetting Line - Three-Phase Line (Solid/Liquid/Vapor) -- 2.2.3 Thermodynamic Treatment - Young's Equation -- 2.3 Adhesion Tension -- 2.4 Work of Adhesion Wa -- 2.5 Work of Cohesion -- 2.6 Calculation of Surface Tension and Contact Angle -- 2.6.1 Good and Girifalco Approach -- 2.6.2 Fowkes Treatment -- 2.7 The Spreading of Liquids on Surfaces -- 2.7.1 The Spreading Coefficient S -- 2.8 Contact Angle Hysteresis -- 2.8.1 Reasons for Hysteresis -- 2.8.2 Wenzel's Equation -- References -- 3: The Critical Surface Tension of Wetting and the Role of Surfactants in Powder Wetting -- 3.1 The Critical Surface Tension of Wetting -- 3.2 Theoretical Basis of the Critical Surface Tension -- 3.3 Effect of Surfactant Adsorption -- 3.4 Dynamic Processes of Adsorption and Wetting -- 3.4.1 General Theory of Adsorption Kinetics -- 3.4.2 Adsorption Kinetics from Micellar Solutions -- 3.4.3 Experimental Techniques for Studying Adsorption Kinetics -- 3.4.3.1 The Drop Volume Technique -- 3.4.3.2 Maximum Bubble Pressure Technique -- 3.5 Wetting of Powders by Liquids
• 12.4.1 Analysis of Oscillatory Response for a Viscoelastic System
• 11.4.2 Electron Microscopy -- 11.4.2.1 Transmission Electron Microscopy (TEM) -- 11.4.2.2 Scanning Electron Microscopy (SEM) -- 11.4.3 Confocal Laser Scanning Microscopy (CLSM) -- 11.4.4 Scanning Probe Microscopy (SPM) -- 11.4.5 Scanning Tunneling Microscopy (STM) -- 11.4.6 Atomic Force Microscopy (AFM) -- 11.5 Scattering Techniques -- 11.5.1 Light Scattering Techniques -- 11.5.1.1 Time-Average Light Scattering -- 11.5.2 Turbidity Measurements -- 11.5.3 Light Diffraction Techniques -- 11.5.4 Dynamic Light Scattering - Photon Correlation Spectroscopy (PCS) -- 11.5.5 Backscattering Techniques -- 11.6 Measurement of Rate of Flocculation -- 11.7 Measurement of Incipient Flocculation -- 11.8 Measurement of Crystal Growth (Ostwald Ripening) -- 11.9 Bulk Properties of Suspensions: Equilibrium Sediment Volume (or Height) and Redispersion -- References -- 12: Rheological Techniques for Assessment of Stability of Suspensions -- 12.1 Introduction -- 12.1.1 Steady-State Shear Stress σ-Shear Rate γ Measurements -- 12.1.2 Constant Stress (Creep) Measurements -- 12.1.3 Dynamic (Oscillatory) Measurements -- 12.2 Steady-State Measurements -- 12.2.1 Rheological Models for Analysis of Flow Curves -- 12.2.1.1 Newtonian Systems -- 12.2.1.2 Bingham Plastic Systems -- 12.2.1.3 Pseudoplastic (Shear Thinning) System -- 12.2.1.4 Dilatant (Shear Thickening) System -- 12.2.1.5 Herschel-Bulkley General Model -- 12.2.2 The Casson Model -- 12.2.3 The Cross Equation -- 12.2.4 Time Effects during Flow Thixotropy and Negative (or anti-) Thixotropy -- 12.3 Constant Stress (Creep) Measurements -- 12.3.1 Analysis of Creep Curves -- 12.3.1.1 Viscous Fluid -- 12.3.1.2 Elastic Solid -- 12.3.2 Viscoelastic Response -- 12.3.2.1 Viscoelastic Liquid -- 12.3.2.2 Viscoelastic Solid -- 12.3.3 Creep Procedure -- 12.4 Dynamic (Oscillatory) Measurements
• 6.1.7 Alkyl Phenol Ethoxylates -- 6.1.8 Fatty Acid Ethoxylates -- 6.1.9 Sorbitan Esters and Their Ethoxylated Derivatives (Spans and Tweens) -- 6.1.10 Ethoxylated Fats and Oils -- 6.1.11 Amine Ethoxylates -- 6.1.12 Polymeric Surfactants -- 6.1.13 Polyelectrolytes -- 6.1.14 Adsorption of Surfactants at the Solid-Liquid Interface -- 6.1.15 Adsorption of Ionic Surfactants on Hydrophobic Surfaces -- 6.1.16 Adsorption of Ionic Surfactants on Polar Surfaces -- 6.1.17 Adsorption of Nonionic Surfactants -- 6.1.18 Theoretical Treatment of Surfactant Adsorption -- 6.1.19 Examples of Typical Adsorption Isotherms of Model Nonionic Surfactants on Hydrophobic Solids -- References -- 7: Adsorption and Conformation of Polymeric Surfactants at the Solid-Liquid Interface -- 7.1 Theories of Polymer Adsorption -- 7.2 Experimental Techniques for Studying Polymeric Surfactant Adsorption -- 7.3 Measurement of the Adsorption Isotherm -- 7.4 Measurement of the Fraction of Segments p -- 7.5 Determination of the Segment Density Distribution ρ(z) and Adsorbed Layer Thickness δh -- 7.6 Examples of the Adsorption Isotherms of Nonionic Polymeric Surfactants -- 7.7 Adsorbed Layer Thickness Results -- 7.8 Kinetics of Polymer Adsorption -- References -- 8: Stabilization and Destabilization of Suspensions Using Polymeric Surfactants and the Theory of Steric Stabilization -- 8.1 Introduction -- 8.2 Interaction between Particles Containing Adsorbed Polymeric Surfactant Layers (Steric Stabilization) -- 8.2.1 Mixing Interaction Gmix -- 8.2.2 Elastic Interaction Gel -- 8.2.3 Total Energy of Interaction -- 8.2.4 Criteria for Effective Steric Stabilization -- 8.3 Flocculation of Sterically Stabilized Dispersions -- 8.3.1 Weak Flocculation -- 8.3.2 Incipient Flocculation -- 8.3.3 Depletion Flocculation -- 8.4 Bridging Flocculation by Polymers and Polyelectrolytes
• 3.5.1 Rate of Penetration of Liquids: The Rideal-Washburn Equation -- 3.5.2 Measurement of Contact Angles of Liquids and Surfactant Solutions on Powders -- 3.5.3 Assessment of Wettability of Powders -- 3.5.3.1 Sinking Time, Submersion, or Immersion Test -- 3.5.3.2 List of Wetting Agents for Hydrophobic Solids in Water -- References -- 4: Structure of the Solid-Liquid Interface and Electrostatic Stabilization -- 4.1 Structure of the Solid-Liquid Interface -- 4.1.1 Origin of Charge on Surfaces -- 4.1.1.1 Surface Ions -- 4.1.1.2 Isomorphic Substitution -- 4.2 Structure of the Electrical Double Layer -- 4.2.1 Diffuse Double Layer (Gouy and Chapman) -- 4.2.2 Stern-Grahame Model of the Double Layer -- 4.3 Distinction between Specific and Nonspecific Adsorbed Ions -- 4.4 Electrical Double-Layer Repulsion -- 4.5 van der Waals Attraction -- 4.6 Total Energy of Interaction -- 4.6.1 Deryaguin-Landau-Verwey-Overbeek Theory -- 4.7 Flocculation of Suspensions -- 4.8 Criteria for Stabilization of Dispersions with Double-Layer Interaction -- References -- 5: Electrokinetic Phenomena and Zeta Potential -- 5.1 Stern-Grahame Model of the Double Layer -- 5.2 Calculation of Zeta Potential from Particle Mobility -- 5.2.1 von Smoluchowski (Classical) Treatment -- 5.2.2 The Huckel Equation -- 5.2.3 Henry's Treatment -- 5.3 Measurement of Electrophoretic Mobility and Zeta Potential -- 5.3.1 Ultramicroscopic Technique (Microelectrophoresis) -- 5.3.2 Laser Velocimetry Technique -- 5.4 Electroacoustic Methods -- References -- 6: General Classification of Dispersing Agents and Adsorption of Surfactants at the Solid/Liquid Interface -- 6.1 Classification of Dispersing Agents -- 6.1.1 Surfactants -- 6.1.2 Anionic Surfactants -- 6.1.3 Cationic Surfactants -- 6.1.4 Amphoteric (Zwitterionic) Surfactants -- 6.1.5 Nonionic Surfactants -- 6.1.6 Alcohol Ethoxylates