Stability instability

Storage stability Instability occurs with high temperatures or severe shock, particularly when involving containers of greater than 30 gal capacity unstable liquid. Liquid chloropicrin will attack some forms of plastics, rubber, and coatings. 

Now we can readily deduce the stability/instability conditions from Figure 6. For < J the attraction is too weak to overcome the particle entropy loss and the dispersion is stable. 

P. Glendinning. Stability, instability and chaos an introduction to the theory of nonlinear differential equations. Cambridge University Press, 1994. 

The role of surfactants in stabilization/destabilization of foam (air/liquid dispersions) is similar to that for emulsions. This is due to the fact that foam stability/instability is determined by the surface forces operative in liquid films between air bubbles. In many industrial applications, it is essential to stabilize foams against collapse, e.g., with many food products, foam in beer, fire-fighting foam, and polyurethane foams that are used for furniture and insulation. In other applications, it is essential to have an effective way of breaking the foam, e.g., in distillation... 

Density Functional Theory External (Stability/Instability)... 

Clearly, since the FF indices of the two subsystems are closely related to the structure of the condensed hardness tensor n (l 12), these stability/instability regions can also be identified in terms of the ff and f% subsystem FF indices defining the orientation of the associated FF vector in the populational space of the two subsystems [25]. 

The effects of the concentration of the dispersed phase, emulsifier type and concentration on the inversion of water-in-oil emulsions have been described above. However, since in this chapter, it is proposed to examine the effects of a multi-ingredient system on emulsion stability, each of the following factors must be considered emulsion formation, stability, instability, effects of shear and effects of ingredients (Becher, 1977). 

Figure 71. Morphological stability/ instability of the interfaces in a corrosion experiment.265...

Evaluation of the stability/instability of suspensions without any dilution (which can cause significant changes in the stracture of the system) requires carefully designed techniques that should cause as little disturbance to the structure. The most powerful techniques that can be applied in any industrial laboratory are rheological measurements [1-7]. These provide accurate information on the state of the system, such as sedimentation and flocculation, and may also be applied to predict the long-term physical stability of the suspension. The various rheological techniques that can be applied and the measurement procedures are listed below. 

Glendining, R, Stability, Instability and Chaos An Introduction to the Theory of Nonlinear Differential Equations, Cambridge, UK Cambridge University Press, 1994. 

In the analysis of autonomous non-gradient systems the methods of gradient system theory have proved useful. The notions such as a stationary (critical) point, degenerate stationary point, structural stability (instability), morsification, phase portrait can be directly transferred to autonomous systems. A qualitative description of dynamical autonomous systems is constructed analogously with the description of gradient systems. 

The above simple analysis highlights an important issue in process dynamics the influence of positive and negative feedback on system s stability. Instability can occur in recycle systems due to positive feedback when the gain is larger than unity. We may give as example the recycle of energy developed by an exothermal reaction in an adiabatic PFR for feed preheating. Instability may occur because of the exponential increase in reaction rate with the temperature when this cannot be properly controlled (Bildea Dimian, 1998). Another example is the recycle of impurities in a plant with recycles, whose inventory cannot be kept at equilibrium by the separation system (Dimian et al., 2000). 

Clarke and Vincent in these studies established the phase diagrams for the free polystyrene-microgel-ethyl benzene systems, two of which are displayed in Fig. 16.2a and b. In all cases, only the stability/instability boun ry is shown. These lines correspond to the locus of the critical volume fraction of free polymer required to induce flocculation (vj ) as a function of the volume fraction of the microgel particles (< 3). 

This diagram is able to explain some puzzling observations disclosed by Cowell and Vincent (1982). They report clear differences between the stability behaviour of latex dispersions depending upon whether the particles are naked or pre-coated by terminally anchored chains. The addition of free polymer to the sterically stabilized particles resulted in the transition sequence stability- instability stability. This is precisely what would be predicted from Fig. 17.20 if bridging flocculation is absent (as it must be if the free polymer and stabilizing moieties are identical in chemical composition). 

Stability (instability) of an emulsion is caused by the coupling of coalescence and flocculation. Meanwhile, for emulsifiers (or demulsifiers) the elaboration of their influence on the elementary act of coalescence only is mainly... 

Interfaeial rheology should be used with care as a predictive tool for emulsion stability/instability. Graham et al. (162) showed that there was reduction in interfaeial shear viscosity of Forties crude oil/water interface with demulsifier added in methanol. Cairns et al. (177) revealed for... 

To describe mathematically the process of thin liquid film instability the shape of the corrugated film surfaces is presented as a superposition of Fourier-Bessel modes, proportional to Jo(kr/R), for all possible values of the dimensionless wave number k (Jo is the zeroth order Bessel function). The mode, which has the greatest amplitude at the moment of film breakage, and which causes the breakage itself, is called the critical mode, and its wave number is denoted by cr- The stability-instability transition for this critical mode happens at an earlier stage of the film evolution, when the film thickness is equal to Atr - the so-called transitional thickness, h r > her (Ivanov 1980). The theory provides a... 

Surface forces are well known and are important in colloid science. They determine the stability and behavior of colloidal suspensions and emulsions [2]. In the case of emulsions/suspen-sions, their properties and behavior (stability, instability, rheology, interactions, and so oti) are governed by surface forces acting between colloidal particles or droplets [2]. The corresponding theory is widely referred to as DLVO flieory [1] according to the names of four scientists who substantially contributed to the area Deijaguin, Landau, Vervey, and Overbeek. 

Finally, other issues like the qualitative behaviour of solutions (stability, instability and asymptotic stability), can be analysed using this approach. Moreover, in all the examples studied, solutions exhibited weak stability, which in terms of the electrochemical problem means that experimental errors in the initial surface concentrations tend to remain limited as the reaction proceeds to completion. Nevertheless, these experimental errors never tend to vanish, and this fact is a consequence of having a null eigenvalue. As observed earlier, all these facts can be proved combining mathematical theorems with chemical laws, so they can be easily generalised to other unimolecular reactions mechanisms. 

---