Principles of Formulation

The bases for mathematical models are the fundamental physical and chemical laws, such as the laws of conservation of mass, energy, and momentum. To study dynamics we will use them in their general form with time derivatives 

The development of a model that incorporates the basic phenomena occurring in the process requires a lot of skill, ingenuity, and practice. It is an area where the creativity and iimovativeness of the engineer is a key element in the success of the proeess. 

The assumptions that are made should be carefully considered and listed. They impose limitations on the model that should always be kept in mind when evaluating its predieted results. 

MATHEMATICAL CONSISTENCY OF MODEL. Once all the equations of the mathematieal model have been written, it is usually a good idea, partieularly with 

Checking to see that the units of all terms in all equations are consistent is perhaps another trivial and obvious step, but one that is often forgotten. It is essential to be particularly careful of the time units of parameters in dynamic models. Any units can be used (seconds, minutes, hours, etc.), but they cannot be mixed. We will use minutes in most of our examples, but it should be remembered that many parameters are commonly on other time bases and need to be converted appropriately, e.g., overall heat transfer coefficients in Btu/h °F ft or velocity in m/s. Dynamic simulation results are frequently in error because the engineer has forgotten a factor of 60 somewhere in the equations. 

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V.G. Babak, M. J. Stebe, A review on highly concentrated emulsions Physicochemical principles of formulation, J. Disp. Sci. Technol. 23 (2002) 1-15. 

The general principles of formulation outlined earlier apply equally to compact and expandable plastisols for screen printing. Plastisols for compact products... 

Cationic Cure Epoxies. As with free radical uv chemistry, the same principles of formulation component selection apply to cationic cured uv epoxy adhesives. Although different monomers and oligomers are normally required for this type of chemistry, the main difference lies with the photoinitiator system. 

Chapter 7 describes paints, pigments, and industrial coatings. The major paint components, namely, pigments, binders, additives, and solvents are discussed in separate sections. These are followed by the principles of formulation, application techniques, durability, and testing of paints. 

Although new and iimovative formulations are urgently needed, work on extemporaneous formulations should not be disregarded, as this is stiU an activity of vital importance in many hospital pharmacies that collaborate with physicians in trials and who also work with orphan drugs. Hence the principles of formulation and manufacture espoused in this book are clearly relevant not only to those who work in industry but also to those who practice closer to the patient. 

Since the gravity force is proportional to R, then if R is reduced by a factor of 10, the gravity force is reduced by 1000. Below a certain droplet size (which also depends on the density difference between oil and water), the Brownian diffusion may exceed gravity and creaming or sedimentation is prevented. This is the principle of formulation of nanoemulsions (with size range 20-200 nm) that may show very little or no creaming or sedimentation. The same applies for microemulsions (size range 5-50 nm). 

The development of a mathematical model begins with an hypothesis that describes the system. The hypothesis is usually expressed as a set of differential equations that can be solved by a computer program. The computer implementation of the model provides not only a description of the system, but also predicts the response of the system to changing conditions. These predictions can be compared to real-world behavior. Since it will always be the case that the model is less complex than the real system, our comparisons will most often lead us to refine the model by increasing its complexity. The principles of formulating and testing mathematical models have been described by Berman (1963). 

The dynamic terms for heterogeneous systems will be exactly the same as for the homogeneous systems (refer to Chapters 2 and 3), but repeated for both phases. The reader should take this as an exercise by just repeating the same principles of formulating the dynamic terms for both mass and heat and for both lumped and distributed systems. For illustration, see the dynamic examples later in this chapter. 

Babak V and Stebe M. 2002. Highly concentrated emulsions Physicochemical principles of formulation. Journal of Dispersion Science and Technology 1—22. 

There are a number of excellent books on paint formulation and this chapter is not the place to go into detail on such a complex subject. The basic principles of formulating electrodeposition paints are the same as used in formulating any other paint, but the parameters such as pigment volume concentration tend to be somewhat different from those of dipping and spraying paints. 

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