Emulsion stability basic concepts

Although the aim of the book is to provide an introduction to the field, it does so in a very applications-oriented manner. Thus, the focus of the book is practical rather than theoretical. In a systematic progression, beginning with the fundamental principles of petroleum emulsions, the reader is soon introduced to characterization techniques and fiow properties, and finally to industrial practice. Chapters 1-4 present the fundamental concepts and properties involved in emulsions within the context of their occurrence in the petroleum industry. Chapter 1 sets out the basic foundation for all subsequent chapters. Selected areas of special importance are then expanded in Chapter 2 on emulsion stability. Chapter 3 on characterization techniques, and Chapter 4 on rheological properties. All of these use petroleum emulsion examples for illustration, and in most cases cover the latest useful techniques available. 

I summarize briefly below the basic concepts of this approach, which is derived from that developed by Beerbower and Hill [31] for the stability of classical nonionic emulsions, which is referred to as the cohesive energy ratio (CER) concept. The treatment lies in a perfect chemical match between the partial solubility parameters of oil ( ) and surfactant lipophilic tail 6]) and of water and hydrophilic head. Under these conditions, one obtains for the optimum HLB (hydrophile-lipophile balance) of the surfactant the relation... 

Understanding the adsorption and conformation of polymeric surfactants at interfaces is key to understanding how these molecules act as stabilizers for suspensions and emulsions. Most basic theories on polymer adsorption and conformation have been developed for the solid/liquid interface (9). The same concepts may be applied for the liquid/liquid interface, with some modifications whereby some part of the molecule may reside within the oil phase, rather than simply staying at the interface. Such modifications do not alter the basic concepts, particularly when one deals with the stabilization by these molecules. 

This chapter describes the basic principles involved in the development of disperse systems. Emphasis is laid on systems that are of particular pharmaceutical interest, namely, suspensions, emulsions, and colloids. Theoretical concepts, preparation techniques, and methods used to characterize and stabilize disperse systems are presented. The term particle is used in its broadest sense, including gases, liquids, solids, molecules, and aggregates. The reader may find it useful to read this chapter in conjuction with Chapters 8, 12, and 14, since they include some of the most important applications of disperse systems as pharmaceutical dosage forms [1]. 

For nonionic surfactants, an optimization of the process was achieved by using a similar approach to the so-called Cohesive Energy Ratio (CER) concept developed by Beerbower and Hill for the stability of classical emulsions (H). Its basic assumption is that the partial solubility parameters of oil and emulsifier lipophilic tail and of water and hydrophilic head are perfectly matched. Thus, the Vinsor cohesive energy ratio Ro, which determines the nature and the stability of an emulsion, is directly related to the emulsifier HliB (hydrophile-lipophile balance) by... 

In the emulsion field, we often meet less scientific concepts, e.g. that of creaminess . Emulsions is a field between science and art. We will start this chapter with some basic definitions and look at some more applications. Then, we will present the most important property of emulsions, the stability, the factors that affect it, and how we can manipulate (influence) the stability of emulsions. We will discuss destabilization mechanisms of emulsions and use the HLB factor (as introduced in Chapter 5) as a quantitative design tool in emulsion science. 

This chapter first reviews general theoretical concepts and then proceeds to discuss relevant experimental results. It is assumed that readers are already reasonably familiar with basic rheological principles and techniques as set out in various texts. "Any review of this sort, of course, has some inevitable bias in coverage. In this instance it is towards the rheology of milk protein-stabilized emulsions—a topic of particular interest to the author. 

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