Steric stabilization of emulsions pdf

Strong interactions between polymers and solvents organic solvent or water prevent the polymers from coming too closely into contact with one another. Table 1 summarizes the measured and calculated hydrodynamic dimensions of. Water ow emulsions stabilized with polyvinyl alcohol references. Steric stabilization in emulsion polymerization using. The various repulsive and attractive forces involved in these nanoscale disperse systems will be studied. There are three main methods of stabilizing colloids. Pharmaceuticals, such as anesthetics of ow emulsions, lipid emulsions, double and multiple emulsions paints, such as emulsions of alkyd resins and latex emulsions drycleaning formulations. Request pdf steric stabilization of pickering emulsions for the efficient synthesis of polymeric microcapsules it is commonly known that pickering emulsions are extremely stable against. It was demonstrated that polyglycerol polyricinoleate pgpr is superior to glycerol monooleate andor lecithin, but is incapable of stabilizing these fluid emulsions for sufficient storage periods. The droplets in an emulsion are referred to as the dispersed phase, while the surrounding liquid is referred to as the continuous phase. Preparation and characterization of oilinwater and water. Interaction between droplets containing adsorbed polymeric surfactant layers.

Steric stabilization in emulsion polymerization using oligomeric. The objective of this thesis was to study the steric stabilization of nbutylchloride drops in water with polyvinyl alcohol. Concept of stability, electrostatic stabilization of suspension dlvo, stability ratio and applications, steric stabilization of suspensions, factors affecting steric stabilization, flocculation slow and rapid, critical flocculation point, particle charging in nonpolar solvents. Steric stabilization of colloidal solutions by adsorption of flexible macromolecules. For example, highmolecularweight polymers can adsorb on the surface of the dispersed phase droplets and extend. With adsorbed or chemically attached polymeric molecules steric stabilization.

In aerated emulsions like ice cream and whipped cream, a partial destabilization of the fat globules is needed to obtain a satisfactory product. Electric double layer is the phenomenon playing a fundamental role in the mechanism of the electrostatic stabilization of colloids. Emulsion formation and stabilization by biomolecules. Each mechanism has its benefits for particular systems. In addition, each stabilization mechanism not only has its own advantages and limitations wax emulsions formulation and properties of wax emulsions for coatings and industrial applications by michelman. Although nonionic surfactants show improved stabilization characteristics in emulsion polymerization as well as superior shear and freeze thaw stability of the. Possible role of asphaltenes in the stabilization of waterin. Steric stabilization a pigment is said to be sterically stabilized when the surface of the solid particles are completely covered by polymers, making particletoparticle contact impossible.

Instead it will form gel lumps and fail to stabilize the emulsion. Waterwet particles tend to stabilize oilinwater emulsions, and oilwet particles stabilize waterinoil emulsions. Stabilization of soil using bitumenous emulsions presented by. The recycled styrenebutadiene steric stabilizer precursor was obtained as a thermomechanical devulcanized ground rubber tire in asphalt. Emulsion stabilization using polyelectrolytes wikipedia. In all cases, the aqueous emulsifier solution contained 1 wt%. Oct 25, 2014 stabilization of soil using bitumenous emulsions presented by.

It is commonly known that pickering emulsions are extremely stable against coalescence and are, therefore, potentially interesting for the synthesis of new materials, such as colloidosomes, microcapsules, composite particles, foams, and so on. Microcapsules are formed by heating the pickering emulsion above the glasstransition temperature of the particles. This structure changes the rheology of the filmforming oil to nonnewtonian, which prevents the film drainage at thickness less than about 50100 nm. Steric stabilization by nonionic surfactants nonionic surfactants. The research interest is preparation and characterization of oilinwater and waterinoil emulsions. A negatively charged particle attracts the positive counterions surrounding the particle. It can be used to optimize the formulations of suspensions and emulsions. Mar 09, 2004 the same mechanism of steric hindrance of coalescence was responsible for stabilization of emulsions by silica particles. In the present paper a steric stabilization model is developed for describing particle stabilization in emulsion polymerization systems in the presence of nonionic oligomeric surfactants. Stabilization of model beverage cloud emulsions using. Knowledge of the zeta potential can reduce the time needed to produce trial formulations.

Stabilization of droplets in nes by electrolytes is theoretically possible, but only if the fraction of the internal phase jislow. Coalescence stability of emulsions containing globular milk proteins slavka tcholakova a, nikolai d. In addition, the high interfacial tension values recorded during the micropipette experiments showed that cells stabilized emulsions without significantly changing the interfacial tension, consistent with the behavior of. This is because they form a substantial steric barrier between oil and water, inhibiting aggregation. One active area of current research is the stabilization of emulsions by conjugates and complexes of hydrocolloids with food proteins dickinson, 2008a. The total interaction free energy profile between the polyethylene particles shows that the efficiency of the steric stabilizer formation reaction can be improved significantly. Pva as stabilizer by varying the concentration of pva, the drop volume, and the interface age independently. Emulsification and stabilization mechanisms of ow emulsions in. Surfactants classification, features and applications.

Steric stabilization of pickering emulsions for the. Thus, i would like to talk about what is emulsion, what are the main characteristics of emulsions, what are the existing methods for preparations of emulsions and how to make simple emulsions. The adsorption of ps b ep provides steric stabilization to the pickering emulsion droplets, reduces aggregation significantly. The use of polymer and surfactants for the microencapsulation. Stabilization of oilwater emulsions by hydrophobic bacteria.

Steric stabilization steric stabilization is a mechanism that can explain the ability of certain additives to inhibit coagulation of suspensions. The low molecular weight butadiene and styrenebutadiene rubbers were. G, provided by the particular dispersing procedure at constant composition and pressure, can be expressed by. Steric stabilization arises from a physical barrier to contact and coalescence. Aggregation and rheological aspects eric dickinson, brent s. Zeta potential is a physical property which is exhibited by any particle in. In order to get an idea about the thermodynamics the change in the gibbs free energy of the system. Asphaltene hierarchical aggregation contributes to waterinoil wo emulsion stability by forming a network structure within thin oil film, separating approaching water droplets. Steric stabilization is simple, requiring just the addition of a suitable polymer. Rheology and stability of sterically stabilized emulsions. Aug 03, 20 29 emulsion stabilization steric stabilization abd karim alias, 20 30.

Significant aggregation is observed, if no ps b ep is used. The same mechanism of steric hindrance of coalescence was responsible for stabilization of emulsions by silica particles. The effectiveness of colloidal particles in stabilizing emulsions depends largely on the formation of a densely packed layer of solid particles film. However, for the efficient synthesis of such materials, one also has to consider the colloidal stability against aggregation, which is often neglected. Steric stabilization of pickering emulsions for the efficient synthesis of polymeric microcapsules. As the stability of wo emulsions appeared clea rly related to the presence of an interfacial network surrounding the water droplets 4043.

Multiple emulsions are complex polydispersed systems where both oil in water and water in. Bridging flocculation versus steric stabilization, macromolecules, 48. Size exclusion chromatography is used to prove and quantify the adsorption of psbep onto the pickering emulsion droplets. The use of polymer and surfactants for the microencapsulation and emulsion stabilization altynay a. Subsequently, psbep is added to the pickering emulsion to provide steric stabilization.

Spe distinguished lecturer series is funded principally through a grant of the. The mechanism of stabilization of emulsion droplets by the macromolecular surfactant is of the steric type while the stabilization by anionic surfactant is of the. Elastic steric stabilization of polyethyleneasphalt. Coalescence stability of emulsions containing globular. In many food situations, the kinetics of adsorption and the processes of interface stabilization are complicated by the fact that. Investigation of the interactions in emulsions stabilized by a.

Hydrocolloids as emulsifiers and emulsion stabilizers. Various stabilization methods electrostatic, steric, etc. Applications by michelman sponsored by michelman sep 2009. Colloid science three of the fundamental states of. Although nonionic surfactants show improved stabilization characteristics in emulsion polymerization as well as superior shear and freeze thaw stability of the final latex, their behaviour is generally not well understood. The formation of hp particles and their ability for shortterm and longterm stabilization of interfaces strongly depended on the hp concentration in stock solutions, as well as the solvent chemistry of both stock solutions and continuous phase media. Steric stabilization instead of using electrical charge, a repulsion potential can also be developed between dispersed particles by means of the adsorbed polymer coatings on the surface. Zeta potential is a physical property which is exhibited by any particle in suspension. Steric repulsion adsorbed polymers adsorbed polymers nonadsorbed polymers micelles.

Emulsions stabilization for topical application scitechnol. Colloidal particles gain negative electric charge when negatively charged ions of the dispersion medium are adsorbed on the particles surface. Surfactants classification, features and applications surfactants classification, features and applications. It also provides a steric stabilization mechanism to the system. Longterm stabilization of foams and emulsions with in. Possible role of asphaltenes in the stabilization of water. The fundamental aspects of elastic stabilization of polyethyleneasphalt emulsions are discussed. Polyelectrolytes of a high molecular weight are the most effective at stabilization. Each particle is surrounded by an envelope of solvated polymer molecules and, when approaching, two particles overlap and penetrate these polymer envelopes. Several statistical thermodynamic theories of steric stabilization have been proposed since the early experiments by zsigmondy 3. For any landbased structure, the foundation is very important and has to be strong to support the entire structure. Emulsions containing 3% polyethylene were stabilized against coalescence in an asphalt medium by low molecular weight virgin polybutadiene and recycled styrenebutadiene stabilizers.

The results presented in this study confirm previous knowledge and stress the need for both hydrophobic emulsifiers and submicronial fat particles to stabilize waterinvegetable oil emulsions. Steric stabilization of colloidal solutions by adsorption. According to fischers theory, if the dissolved polymer sheaths surrounding two sterically stabilized particles were to inter penetrate, the chemical potential of the sol. Asphaltenes do not have welldefined hydrophilic heads and hydrophobic tails and, thus, do not have amphiphilic character. Steric stabilization is generally found in the systems. Marinova, antifoam effects of solid particles, oil drops and oil. Grigoriev 4 and reinhard miller 5 1 industrial engineering department, kazakh national research technical. Formation of liposomestabilized allaqueous emulsions. With free polymer in the dispersio n medium depletion stabilization. Pdf emulsion types, stability mechanisms and rheology. Applications by michelman sponsored by michelman sep. With an electrical double layer electrostatic or charge stabilization. It is also an aid in predicting longterm stability.

Velev, department of chemical and biomolecular engineering, north carolina state university, raleigh, north carolina 27695, department of chemistry, university of hull, hull, hu6 7rx, united kingdom. Morphology and applications emulsions are dispersions of one immiscible liquid into another in the form of droplets. Polymeric stabilization of colloids involves polymeric molecules added to the dispersion medium in order to prevent the aggregation of the colloidal particles. Factors affecting stability of an emulsion and ways to alleviate them. The importance of proteins to provide steric stabilization of food emulsions is discussed. The preparation of emulsions requires energy to disperse the organic phase solvent or solution. Therefore, they are not similar to surfactants and cannot stabilize emulsions the way classic emulsifiers do. The preparation of emulsions requires energy to disperse the organic phase solvent or solution in water.

Steric stabilization is simple, requiring just the addition of a. The model takes into account the effect of unequal particle sizes on the steric interaction potential and the resulting enhanced heterocoagulation. Allen procter department of food science, university of leeds, leeds ls2 9jt, uk. These additives include certain waterloving polymers and surfactants with waterloving chains. Steric stabilization is a generic term that embraces all aspects of the stabilization of colloidal particles by nonionic macromolecules. Bioreactor droplets from liposomestabilized allaqueous. However, if the polyelectrolyte is too heavy it will not dissolve in the solution. Some degree of particle interaction is necessary for effective stabilization. Steric stabilization of pickering emulsions for the efficient synthesis of polymeric microcapsules joris w. Mar 30, 2007 the importance of proteins to provide steric stabilization of food emulsions is discussed. Steric stabilization in emulsion polymerization using oligomeric nonionic surfactants.

Steric stabilization of pickering emulsions for the efficient. Salari, jeroen van heck, and bert klumperman department of polymer chemistry, eindhoven university of technology, p. The stabilization of droplet found in the emulsion interface is achieved through the addition of emulsifier which acts increasing the electrostatic repulsion between droplets, steric hindrance and by decreasing the phase interfacial tension. Preparation and characterization of oilinwater and waterin. Longterm stabilization of foams and emulsions with insitu formed microparticles from hydrophobic cellulose hartmut a. Longterm stabilization of foams and emulsions with insitu. As the stability of wo emulsions appeared clea rly related to the presence of an interfacial network surrounding the water droplets 4043, many rheological studies of waterasphalted.