Formulation of Disperse Systems E-Book

Tharwat F. Tadros

• Herausgeber: Wiley-VCH
• Kategorie: Fachliteratur
• Sprache: Englisch

Seitenzahl: 847

Veröffentlichungsjahr: 2014

Beschreibung

This book presents comprehensively the science and technology behind the formulation of disperse systems like emulsions, suspensions, foams and others. Starting with a general introduction, the book covers a broad range of topics like the role of different classes of surfactants, stability of disperse systems, formulation of different dispersions, evaluation of formulations and many more. Many examples are included, too. Written by the experienced author and editor Tharwart Tadros, this book is indispensable for every scientist working in the field.

Leseprobe

Table of Contents

Cover

Related Titles

Title Page

Copyright

Preface

Chapter 1: General Introduction

1.1 Suspensions

1.2 Latexes

1.3 Emulsions

1.4 Suspoemulsions

1.5 Multiple Emulsions

1.6 Nanosuspensions

1.7 Nanoemulsions

1.8 Microemulsions

1.9 Pigment and Ink Dispersions

1.10 Foams

References

Chapter 2: Surfactants Used in Formulation of Dispersions

2.1 General Classification of Surface-Active Agents

References

Chapter 3: Physical Chemistry of Surfactant Solutions and the Process of Micellisation

3.1 Thermodynamics of Micellisation

3.2 Enthalpy and Entropy of Micellisation

References

Chapter 4: Dispersants and Polymeric Surfactants

4.1 Solution Properties of Polymeric Surfactants

4.2 General Classification of Polymeric Surfactants

4.3 Polyelectrolytes

References

Chapter 5: Adsorption of Surfactants at the Air/Liquid, Liquid/Liquid, and Solid/Liquid Interfaces

5.1 Introduction

5.2 Adsorption of Surfactants at the Air/Liquid (A/L) and Liquid/Liquid (L/L) Interfaces

5.3 The Gibbs Adsorption Isotherm

5.4 Equation of State Approach

5.5 The Langmuir, Szyszkowski, and Frumkin Equations

5.6 Interfacial Tension Measurements

5.7 Adsorption of Surfactants at the Solid/Liquid (S/L) Interface

References

Chapter 6: Adsorption of Polymeric Surfactants at the Solid/Liquid Interface

6.1 Theories of Polymer Adsorption

6.2 Experimental Techniques for Studying Polymeric Surfactant Adsorption

6.3 Determination of Segment Density Distribution ρ(z) and Adsorbed Layer Thickness δ

h

6.4 Examples of the Adsorption Isotherms of Nonionic Polymeric Surfactants

References

Chapter 7: Colloid Stability of Disperse Systems Containing Electrical Double Layers

7.1 Origin of Charge on Surfaces

7.2 Structure of the Electrical Double Layer

7.3 Stern–Grahame Model of the Double Layer

7.4 Distinction between Specific and Nonspecific Adsorbed Ions

7.5 Electrical Double Layer Repulsion

7.6 van der Waals Attraction

7.7 Total Energy of Interaction

7.8 Flocculation of Suspensions

7.9 Criteria for Stabilisation of Dispersions with Double Layer Interaction

References

Chapter 8: Stability of Disperse Systems Containing Adsorbed Nonionic Surfactants or Polymers: Steric Stabilisation

8.1 Introduction

8.2 Interaction between Particles Containing Adsorbed Nonionic and Polymeric Surfactant Layers (Steric Stabilisation)

8.3 Mixing Interaction

G

mix

8.4 Elastic Interaction

G

el

8.5 Total Energy of Interaction

8.6 Criteria for Effective Steric Stabilisation

8.7 Flocculation of Sterically Stabilised Dispersions

References

Chapter 9: Formulation of Solid/Liquid Dispersions (Suspensions)

9.1 Introduction

9.2 Preparation of Suspensions

9.3 Condensation Methods: Nucleation and Growth

9.4 Dispersion Methods

9.5 Bulk Properties of Suspensions

References

Chapter 10: Formulation of Liquid/Liquid Dispersions (Emulsions)

10.1 Introduction

10.2 Industrial Applications of Emulsions

10.3 Physical Chemistry of Emulsion Systems

10.4 Adsorption of Surfactants at the Liquid/Liquid Interface

10.5 Selection of Emulsifiers

10.6 Creaming or Sedimentation of Emulsions

10.7 Flocculation of Emulsions

10.8 General Rules for Reducing (Eliminating) Flocculation

10.9 Ostwald Ripening

10.10 Emulsion Coalescence

10.11 Phase Inversion

References

Chapter 11: Formulation of Suspoemulsions (Mixtures of Suspensions and Emulsions)

11.1 Introduction

11.2 Suspoemulsions in Paints

11.3 Suspoemulsions in Agrochemicals

References

Chapter 12: Formulation of Multiple Emulsions

12.1 Introduction

12.2 Preparation of Multiple Emulsions

12.3 Types of Multiple Emulsions

12.4 Breakdown Processes of Multiple Emulsions

12.5 Factors Affecting Stability of Multiple Emulsions, and Criteria for Their Stabilisation

12.6 General Description of Polymeric Surfactants

12.7 Interaction between Oil or Water Droplets Containing an Adsorbed Polymeric Surfactant: Steric Stabilisation

12.8 Examples of Multiple Emulsions Using Polymeric Surfactants

12.9 Characterisation of Multiple Emulsions

12.10 Rheological Measurements

References

Chapter 13: Preparation of Nanosuspensions

13.1 Introduction

13.2 Nucleation and Growth, and Control of Particle Size Distribution

13.3 Preparation of Nanosuspensions by Bottom-Up Processes

13.4 Preparation of Nanosuspensions Using the Bottom-Down Process

References

Chapter 14: Formulation of Nanoemulsions

14.1 Introduction

14.2 Mechanism of Emulsification

14.3 Methods of Emulsification and the Role of Surfactants

14.4 Preparation of Nanoemulsions

14.5 Steric Stabilisation and the Role of the Adsorbed Layer Thickness

References

Chapter 15: Formulation of Microemulsions

15.1 Introduction

15.2 Thermodynamic Definition of Microemulsions

15.3 Mixed-Film and Solubilisation Theories of Microemulsions

15.4 Thermodynamic Theory of Microemulsion Formation

15.5 Characterisation of Microemulsions Using Scattering Techniques

15.6 Characterisation of Microemulsions Using Conductivity

15.7 NMR Measurements

15.8 Formulation of Microemulsions

References

Further Reading

Chapter 16: Formulation of Foams

16.1 Introduction

16.2 Foam Preparation

16.3 Foam Structure

16.4 Classification of Foam Stability

16.5 Drainage and Thinning of Foam Films

16.6 Theories of Foam Stability

16.7 Foam Inhibitors

16.8 Physical Properties of Foams

16.9 Experimental Techniques for Studying Foams

References

Chapter 17: Formulation of Latexes

17.1 Introduction

17.2 Emulsion Polymerisation

17.3 Polymeric Surfactants for Stabilisation of Preformed Latex Dispersions

17.4 Dispersion Polymerisation

References

Chapter 18: Formulation of Pigment and Ink Dispersions

18.1 Introduction

18.2 Powder Wetting

18.3 Breaking of Aggregates and Agglomerates (Deagglomeration)

18.4 Classification of Dispersants

References

Chapter 19: Methods of Evaluating Formulations after Dilution

19.1 Introduction

19.2 Assessment of the Structure of the Solid/Liquid Interface

19.3 Assessment of Sedimentation of Suspensions

19.4 Assessment of Flocculation and Ostwald Ripening (Crystal Growth)

19.5 Scattering Techniques

19.6 Measurement of Rate of Flocculation

19.7 Measurement of Incipient Flocculation

19.8 Measurement of Crystal Growth (Ostwald Ripening)

19.9 Bulk Properties of Suspensions: Equilibrium Sediment Volume (or Height) and Redispersion

References

Chapter 20: Evaluating Formulations without Dilution: Rheological Techniques

20.1 Introduction

20.2 Steady-State Measurements

20.3 Constant Stress (Creep) Measurements

20.4 Dynamic (Oscillatory) Measurements

References

Further Reading

Chapter 21: Assessment and Prediction of Creaming, Sedimentation, Flocculation, and Coalescence of Formulations

21.1 Assessment and Prediction of Creaming and Sedimentation

21.2 Assessment and Prediction of Flocculation Using Rheological Techniques

21.3 Assessment and Prediction of Emulsion Coalescence Using Rheological Techniques

References

Index

End User License Agreement

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Guide

Table of Contents

List of Illustrations

Figure 3.1

Figure 3.2

Figure 3.3

Figure 3.4

Figure 3.5

Figure 3.6

Figure 3.7

Figure 3.8

Figure 3.9

Figure 3.10

Figure 4.1

Figure 4.2

Figure 4.3

Figure 5.1

Figure 5.2

Figure 5.3

Figure 5.4

Figure 5.5

Figure 5.6

Figure 5.7

Figure 5.8

Figure 6.1

Figure 6.2

Figure 6.3

Figure 6.4

Figure 6.5

Figure 6.6

Figure 6.7

Figure 6.8

Figure 6.9

Figure 6.10

Figure 6.11

Figure 6.12

Figure 6.13

Figure 6.14

Figure 6.15

Figure 6.16

Figure 6.17

Figure 6.18

Figure 7.1

Figure 7.2

Figure 7.3

Figure 7.4

Figure 7.5

Figure 7.6

Figure 7.7

Figure 7.8

Figure 7.9

Figure 7.10

Figure 7.11

Figure 8.1

Figure 8.2

Figure 8.3

Figure 8.4

Figure 8.5

Figure 8.6

Figure 8.7

Figure 9.1

Figure 9.2

Figure 9.3

Figure 9.4

Figure 9.5

Figure 9.6

Figure 9.7

Figure 9.8

Figure 9.9

Figure 9.10

Figure 9.11

Figure 9.12

Figure 9.13

Figure 9.14

Figure 9.15

Figure 9.16

Figure 9.17

Figure 10.1

Figure 10.2

Figure 10.3

Figure 10.4

Figure 10.5

Figure 10.6

Figure 10.7

Figure 10.8

Figure 10.9

Figure 10.10

Figure 10.11

Figure 10.12

Figure 10.13

Figure 10.14

Figure 10.15

Figure 10.16

Figure 10.17

Figure 10.18

Figure 10.19

Figure 10.20

Figure 10.21

Figure 10.22

Figure 10.23

Figure 10.24

Figure 10.25

Figure 10.26

Figure 10.27

Figure 10.28

Figure 10.29

Figure 10.30

Figure 10.31

Figure 10.32

Figure 10.33

Figure 11.1

Figure 11.2

Figure 11.3

Figure 11.4

Figure 11.5

Figure 11.6

Figure 11.7

Figure 11.8

Figure 11.9

Figure 11.10

Figure 11.11

Figure 11.12

Figure 11.13

Figure 11.14

Figure 11.15

Figure 11.16

Figure 11.17

Figure 11.18

Figure 11.19

Figure 11.20

Figure 11.21

Figure 12.1

Figure 12.2

Figure 12.3

Figure 12.4

Figure 12.5

Figure 12.6

Figure 12.7

Figure 12.8

Figure 12.9

Figure 12.10

Figure 13.1

Figure 13.2

Figure 13.3

Figure 13.4

Figure 13.5

Figure 13.6

Figure 14.1

Figure 14.2

Figure 14.3

Figure 14.4

Figure 14.5

Figure 14.6

Figure 14.7

Figure 14.8

Figure 14.9

Figure 14.10

Figure 14.11

Figure 14.12

Figure 14.13

Figure 14.14

Figure 14.15

Figure 14.16

Figure 14.17

Figure 14.18

Figure 14.19

Figure 14.20

Figure 14.21

Figure 14.22

Figure 14.23

Figure 14.24

Figure 14.25

Figure 15.1

Figure 15.2

Figure 15.3

Figure 15.4

Figure 15.5

Figure 15.6

Figure 15.7

Figure 15.8

Figure 15.9

Figure 15.10

Figure 15.11

Figure 15.12

Figure 15.13

Figure 15.14

Figure 16.1

Figure 16.2

Figure 16.3

Figure 16.4

Figure 17.1

Figure 17.2

Figure 17.3

Figure 17.4

Figure 17.5

Figure 17.6

Figure 17.7

Figure 17.8

Figure 17.9

Figure 17.10

Figure 18.1

Figure 18.2

Figure 18.3

Figure 18.4

Figure 18.5

Figure 18.6

Figure 18.7

Figure 18.8

Figure 18.9

Figure 18.10

Figure 18.11

Figure 18.12

Figure 18.13

Figure 18.14

Figure 18.15

Figure 18.16

Figure 18.17

Figure 18.18

Figure 18.19

Figure 19.1

Figure 19.2

Figure 19.3

Figure 19.4

Figure 19.5

Figure 19.6

Figure 19.7

Figure 19.8

Figure 20.1

Figure 20.2

Figure 20.3

Figure 20.4

Figure 20.5

Figure 20.6

Figure 20.7

Figure 20.8

Figure 20.9

Figure 20.10

Figure 20.11

Figure 20.12

Figure 20.13

Figure 20.14

Figure 21.1

Figure 21.2

Figure 21.3

Figure 21.4

Figure 21.5

Figure 21.6

Figure 21.7

Figure 21.8

Figure 21.9

Figure 21.10

Figure 21.11

Figure 21.12

Figure 21.13

Figure 21.14

Figure 21.15

Figure 21.16

Figure 21.17

Figure 21.18

List of Tables

Table 3.1

Table 3.2

Table 3.3

Table 3.4

Table 7.1

Table 7.2

Table 7.3

Table 7.4

Table 10.1

Table 10.2

Table 10.3

Table 10.4

Table 11.1

Table 14.1

Table 14.2

Table 14.3

Table 14.4

Table 14.5

Table 17.1

Table 17.2

Table 17.3

Table 17.4

Table 18.1

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Tharwat F. Tadros

Formulation of Disperse Systems

Science and Technology

The Author

Prof. Dr. Tharwat F. Tadros

89 Nash Grove Lane

RG40 4HE Wokingham, Berkshire

United Kingdom

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Preface

Several disperse systems can be identified, including solid/liquid (suspensions), liquid/liquid (emulsions) and their mixtures (suspoemulsions), gas/liquid (foams), nanodispersions (with particle sizes in the range 20–200 nm), microemulsions, dispersions of pigments and inks, and latexes. These disperse systems exist in many industrial applications such as paints, paper coatings, dyestuffs, printing inks, agrochemicals and pharmaceuticals. The formulation of these complex multiphase systems is still an art, and in most cases they are produced by industrial chemists using simple trial-and-error techniques. Apart from being time-consuming, this approach does not provide a rational understanding on how a system is arrived at. In addition, whenever a problem arises – such as instability and separation of the formulation on storage – the formulation chemist may struggle to find a solution for the resulting instability.

This book has been written to set the fundamental basis of the formulation of the various types of disperse systems. It starts (Chapter 1) with a general introduction of the different types of disperse systems, while Chapter 2 provides a brief description of the various surfactant classes used in the formulations. Chapter 3 describes the physical chemistry of surfactant solutions, with emphasis placed on the process of micellisation, while the various dispersants and polymers used for stabilisation of disperse systems, and the criteria required for an effective dispersant are summarised in Chapter 4. Chapter 5 describes the adsorption of surfactants at the air/liquid, liquid/liquid, and solid/liquid interfaces, with details given of the adsorption process and its effect on the surface, interfacial, and solid/liquid tensions. In Chapter 6, an account is provided of the adsorption of polymeric surfactants at the solid/liquid interface, with emphasis on the general behaviour of polymer adsorption and its irreversibility. Chapter 7 describes the colloid stability of disperse systems containing electrical double layers, and the combination of electrostatic repulsion with van der Waals attraction is used to describe the theory of colloid stability. Chapter 8 describes the stability of disperse systems containing adsorbed nonionic surfactants or polymers referred to as steric stabilisation, while Chapter 9 describes the formulation of solid/liquid dispersions (suspensions). The preparation of suspensions by condensation (nucleation and growth) and dispersion methods are also described, with the stabilisation of suspensions using electrostatic and/or steric repulsion being described in terms of the various interaction forces. Chapter 10 deals with the formulation of liquid/liquid dispersions (emulsions). Here, the various methods that can be applied for selection of emulsifiers are described, and this is followed by an analysis of the stability/instability of emulsions, namely creaming or sedimentation, flocculation, Ostwald ripening, coalescence, and phase inversion. Chapter 11 describes the formulation of suspoemulsions (mixtures of suspensions and emulsions), and the application of suspoemulsions in agrochemicals, cosmetics and paints is briefly described. Chapter 12 deals with formulation of multiple emulsions: water-in-oil-in-water (W/O/W) and oil-in-water-in-oil (O/W/O) systems. The structure of multiple emulsions and their breakdown processes are described, and this is followed by a section on the preparation of multiple emulsions using a two-stage process. Chapter 13 describes the methods of preparation of nanosuspensions, and details of the application of nanosuspensions in cosmetics and drug delivery are given. The preparation of nanosuspensions, using top-up (starting from molecular units) and bottom-down (by comminution of larger particles) processes is also described. Chapter 14 deals with the formulation of nanoemulsions and the factors relating to their transparency; the advantages of nanoemulsions in personal products and healthcare products are also summarised. Chapter 15 deals with the formulation of microemulsions and the surfactant composition, with definition being provided of microemulsions and the origin of their thermodynamic stability. Theories of the stability of microemulsions are also outlined. Chapter 16 deals with the formulation of foams, starting with the factors responsible for foam formation, and the stability/instability of foams and the role of surfactants are described. Chapter 17 describes the formulation of latexes and methods of their preparation by emulsion and dispersion polymerisation, while Chapter 18 deals with the formulation of pigments and inks, and provides details of the various pigment types and their general properties. The colloid stability of pigment dispersions in terms of electrostatic, steric and electrosteric forces is also described. Chapter 19 describes the methods for evaluating formulations after dilution, starting with optical microscopy and particle size distribution using image analysis, phase contrast, differential interference contrast and polarising microscopy. This is followed by the various scattering methods, including time average light scattering, turbidity, light diffraction, dynamic light scattering and back-scattering techniques. Chapter 20 describes the methods used for the evaluation of formulations without dilution, namely rheological techniques; steady-state shear stress-shear rate measurements and the flow curves are also described, as are constant stress (creep) measurements and measurement of the residual (zero shear) viscosity. This is followed by investigations of stress relaxation after the sudden application of strain, and the dynamic (oscillatory) methods and evaluation of the elastic and viscous components are described. Finally, Chapter 21 deals with the methods that can be applied for the assessment and prediction of creaming or sedimentation, flocculation and coalescence. In addition, accelerated tests for the evaluation of stability using temperature changes and centrifugation, and their limitations, are described. The rheological methods that can be applied for the prediction of creaming or sedimentation, flocculation and coalescence are also described.

This book will be valuable for industrial scientists engaged in the formulation of disperse systems, and should provide them with a more rational approach of how to formulate a product. In addition, it should enable the formulation scientist to better understand the fundamental basis of the factors responsible for producing a stable formulation with an acceptable shelf life. The book should also be very useful for teaching the subject of formulation at academic institutions.

November 2013

Tharwat Tadros

1General Introduction

Several classes of formulations of disperse systems are encountered in the chemical industry, including suspensions, emulsions, suspoemulsions (mixtures of suspensions and emulsions), nanoemulsions, multiple emulsions, microemulsions, latexes, pigment formulations, and ceramics. For the rational preparation of these multiphase systems it is necessary to understand the interaction forces that occur between the particles or droplets. Control of the long-term physical stability of these formulations requires the application of various surfactants and dispersants. It is also necessary to assess and predict the stability of these systems, and this requires the application of various physical techniques.

A brief description of the various formulation types is provided in the following sections.

1.1 Suspensions

These are by far the most commonly used systems for the formulation of insoluble solids. The solid can be hydrophobic, such as most organic materials that are used in pharmaceuticals, agrochemicals, and paints; the solid can also be hydrophilic, such as silica and clays. With some pigments and inks the particles need to be very small – that is, in the nanosize range – and these are referred to as . Latexes may also be considered as suspensions, particularly if the particles are solid-like at ambient temperatures. With many of the latexes that are used in paints the particles are liquid-like at below and ambient temperature, but when applied to a surface these liquid-like particles coalesce to form a uniform film. The system may then be considered as an emulsion.