Emulsifier Adsorption Research Articles

Quantification of emulsifier adsorption onto sugar crystals dispersed in vegetable oil and associated effects on flow behaviour

Emulsifiers play an essential role in the flow behaviour of confectionery products such as chocolate. This research associated emulsifier adsorption onto sugar crystals and its effects on the flow properties of model sugar-in-oil suspensions. A new method to quantify emulsifier adsorption onto sugar crystals dispersed in oil was developed by exploiting the relationship between oil–water interfacial tension and unadsorbed emulsifier in the continuous oil phase. The model system consisted of 30 wt% sugar-in-oil suspensions to which were added up to 1 wt% soy lecithin, ammonium phosphatides (AMP), citric acid esters of mono- and diglycerides (CITREM) or polyglycerol polyricinoleate (PGPR). The link between sugar crystal surface coverage, sedimentation, aggregation state and apparent viscosity was then investigated. The lecithin, AMP and CITREM showed the largest decrease in apparent viscosity when added to the suspension at 0.05 to 0.1 wt%, which corresponded to their critical micelle concentration. The largest decrease in sugar crystal aggregation and sedimentation was also evident at this emulsifier concentration. By contrast, addition of PGPR led to a continuous decrease in viscosity and aggregation in the sugar suspension as a function of concentration, with no evident optimal concentration observed. Key advantages of this new method are its simplicity and ability to quantify emulsifier concentration in dispersed systems irrespective of emulsifier identity.

Microstructure, rheology and freeze-thaw behavior of double (W1/O/W2) emulsions prepared with palm oil: Effect of Tween 80/sodium caseinate ratio

The objective was to study the effect of the variation of Tween 80/sodium caseinate ratio on the microstructure, rheology and freeze-thaw behavior of double (W1/O/W2) emulsions prepared with palm oil. Particularly, the impact of the composition of the outer interfacial film on partial coalescence and retention of inner water droplets was investigated. Partial coalescence was restrained in the emulsion prepared with sodium caseinate only, because aggregation of oil globules was prevented due to electrostatic and steric repulsions and a resistant interfacial film. The inclusion of Tween 80 produced competitive adsorption of emulsifiers, promoting partial coalescence and increasing the elastic and viscous modules of the system. A higher Tween 80 proportion led to lower retention of inner water droplets after cold storage, attributed to the formation of smaller oil globules and a thinner interfacial film. A cooling-heating-cooling cycle was applied by differential scanning calorimetry, showing that a higher oil globule aggregation degree led to higher retention of inner water droplets during freezing and higher release of inner water droplets during thawing. The findings expand the knowledge regarding the influence of the composition of the outer interfacial film on both partial coalescence and retention of inner water droplets in W1/O/W2 emulsions.

A microfluidic study of bubble formation and coalescence tuned by dynamic adsorption of SDS and proteins

During foaming, bubbles are formed at (sub)millisecond time scales, and emulsifier adsorption determines bubble formation and stabilisation against coalescence. Here we introduce a microfluidic device, in which bubbles are formed in two distinct pressure regimes at low versus high pressures, and emulsifier adsorption can be inferred from the easily-monitored dynamics of bubble formation and coalescence, as well as the bubble properties. We studied dynamic adsorption for various types and concentrations of emulsifiers, namely sodium dodecyl sulfate (SDS; 0.05–3% wt.) and various proteins (5% wt.) including whey protein isolate (WPI), β-lactoglobulin (β-lac), and bovine serum albumin (BSA). The results show that as SDS concentration increases up to 3% wt., the bubble formation time decreases in the low-pressure regime due to the enhanced adsorption of SDS, yet increases in the high-pressure regime due to the promoted ‘dripping-jetting’ transition; in both pressure regimes the neck thinning process slows down, leading to longer bubble growth time and thus larger bubble size. To suppress coalescence of bubbles formed at time scales down to 10 μs, SDS is the most efficient, followed by BSA, WPI, and finally, β-lac; this is ascribed to the dynamics of emulsifier adsorption, e.g., the resulting dynamic surface tension. To conclude, our microfluidic study highlights the dynamic effects in the presence of SDS and proteins during bubble formation, even at high concentrations. This means that to explain the properties of a freshly-formed foam product, it is crucial to understand (and thereafter manipulate) emulsifier adsorption at time scales relevant to bubble formation and coalescence.

Emulsifier adsorption kinetics influences drop deformation and breakup in turbulent emulsification.

Turbulent drop breakup is of large importance for applications such as food and pharmaceutical processing, as well as of substantial fundamental scientific interest. Emulsification typically takes place in the presence of surface-active emulsifiers (natural occurring and/or added). Under equilibrium conditions, these lower the interfacial tension, enabling deformation and breakup. However, turbulent deformation is fast in relation to emulsifier kinetics. Little is known about the details of how the emulsifier influences drop deformation under turbulent conditions. During the last years, significant insight in the mechanism of turbulent drop breakup has been reached using numerical experiments. However, these studies typically use a highly simplistic description of how the interface responds to turbulent stress. This study investigates how the limited exchange rate of emulsifier between the bulk and the interface influences the deformation process in turbulent drop breakup for application-relevant emulsifiers and concentrations, in the context of state-of-the-art single drop breakup simulations. In conclusion, if the Weber number is high or the emulsifier is supplied at a concentration giving an adsorption time less than 1/10th of the drop breakup time, deformation proceeds as if the emulsifier adsorbed infinitely fast. Otherwise, the limited emulsifier kinetics delays breakup and can alter the breakup mechanism.

Microfluidics as a tool to assess and induce emulsion destabilization.

Microfluidic technology enables judicious control of the process parameters on a small length scale, which in turn allows speeding up the destabilization of emulsion droplets interface in microfluidic devices. In this light, microfluidic channels can be used as an efficient tool to assess emulsion stability and to observe the behavior of the droplets immediately after their formation, enabling to determine whether or not they are prone to re-coalescence. Observation of the droplets after emulsifier adsorption also allows the investigation of emulsion stability over time. Both evaluations would contribute to determine emulsion stability aiming at specific applications in food and pharmaceutical industries. Furthermore, emulsion coalescence can also be performed under extremely controlled conditions within the microfluidic devices in order to explore emulsion droplets as micro-reactors (for regulated biological and chemical assays). Such microfluidic procedures can be performed either in confined environments or under dynamic flow conditions. Under confined environments, droplets are observed in fixed positions simulating different environmental conditions. On the other hand, with the scrutiny of emulsions under dynamic flow processes, it is possible to determine the behavior of the droplets when subjected to shear forces, comparable to those experienced in conventional emulsification techniques or even in pumping operations. Given the above, this paper reviews different microfluidic techniques (such as changing channel geometry or wettability) hitherto used to destabilize emulsions, mainly focusing on the specificities of each study, whether the droplets are destabilized in confined or dynamic flow processes. Thereby, by going deeper into this review, readers will be able to identify different strategies for emulsion destabilization (in order to understand stabilizing mechanisms or even to apply these droplets as micro-reactors), as this paper shows the particularities of the most recent studies and elucidates the current state-of-the-art of this microfluidic-related application.

Exploration of molecular dynamics for the adsorption of anionic emulsifier on the main chemical composition surface of aggregate

In this study, we conducted molecular simulation and conductivity experiments to systematically explore the adsorption of five anionic emulsifiers on the main chemical composition surface of the aggregate (calcium carbonate: CaCO3, silica: SiO2), which have the same hydrophobic group and different hydrophilic groups. Simulation results and experimental conclusions indicated that the adsorption of the five anionic emulsifiers on the SiO2 surface was stronger than that on the CaCO3 surface. The order of adsorption of the hydrophilic group of the anionic emulsifier on the CaCO3 surface was: benzene sulfonate group (▪) > sulphate group (-OSO3-) > sulfonate group (-SO3-) > diphenyl ether disulfonate group (▪), and that on the SiO2 surface is ▪>-OSO3->-SO3-. These sequences show that the structure of the hydrophilic group of the anionic emulsifier and the degree of branching have an influence on the adsorption of the emulsifier on the CaCO3 and SiO2 surThe adsorption of five anionic emulsifiers on the SiO2 surface is better than faces. The adsorption of anionic emulsifiers on the SiO2 surface is enhanced whereas that on the CaCO3 surface declines with the increase in number of phenyl functional groups. Additionally, the same adsorption characteristics are observed when the branching degree of the hydrophilic group increases. The experimental results fully verified the accuracy of the simulation conclusions. The binding ability of the hydrophilic group of anionic emulsifiers and metal cations is strengthened with an increase in the oxidation of metal cations. Therefore, to avoid early demulsification of emulsified asphalt, it is necessary to prevent the solution from containing a large amount of strong oxidising metal cations under high-mineralization construction conditions. Molecular level micro-information provided by molecular dynamics (MD) can provide guidance for the demulsification of emulsified asphalt and the structural design of the hydrophilic group of the emulsifier.

Effect of Bile Salts on the Interfacial Dilational Rheology of Lecithin in the Lipid Digestion Process.

The effects of bile salts on the emulsifier adsorption layer play a crucial role in lipid digestion. The current study selected sodium cholate (NaCh) and lecithin as model compounds for bile salts and food emulsifiers, respectively. The interface dilational rheological and emulsification properties of NaCh and lecithin were carried out. The results showed that the NaCh molecules could quickly diffuse from the bulk to interface, which broke the tightly-arranged interfacial layer of lecithin and enhanced the viscoelasticity of interfacial film. As a result, the interfacial adsorption layer, which was originally dominated by the slow relaxation processes within the interface, was transformed into one controlled by the fast molecular diffusion exchange. This accelerated the exchange of materials between the bulk and interface, thereby creating suitable conditions for the interfacial adsorption of lipases, which promoted the digestion process. These results provided a mechanism for the promotion of lipid digestion by bile salts from the perspective of interfacial viscoelasticity and relaxation processes. A deeper understanding of the interfacial behavior of bile salts with emulsifiers would provide a basis for the rational design of interfacial layer for modulating lipid digestion.

The Importance of Interfacial Tension in Emulsification: Connecting Scaling Relations Used in Large Scale Preparation with Microfluidic Measurement Methods

This paper starts with short descriptions of emulsion preparation methods used at large and smaller scales. We give scaling relations as they are generally used, and focus on the central role that interfacial tension plays in these relations. The actual values of the interfacial tension are far from certain given the dynamic behavior of surface-active components, and the lack of measurement methods that can be applied to conditions as they occur during large-scale preparation. Microfluidic techniques are expected to be very instrumental in closing this gap. Reduction of interfacial tension resulting from emulsifier adsorption at the oil-water interface is a complex process that consists of various steps. We discuss them here, and present methods used to probe them. Specifically, methods based on microfluidic tools are of great interest to study short droplet formation times, and also coalescence behavior of droplets. We present the newest insights in this field, which are expected to bring interfacial tension observations to a level that is of direct relevance for the large-scale preparation of emulsions, and that of other multi-phase products.

MODELLING NANO-TECHNOLOGICAL PROCESSES OF OIL EMULSIONS FORMATION AND DESTRUCTION

It is shown that oil preparation process is related to nanotechnologies, since they are carried out at the Nano-dimensional level consisting in the charge interaction of mono and polyvalent ions being present in interacting environments of oil and reservoir (intermediate) water. Taking into account specific features (Nano-phenomena) of oil emulsion formation and destruction, a mathematical model for thermochemical oil dehydration process is proposed. As it is known, the main processes of formation and destruction of AC at the interfacial section (oil-water) occur at the molecular level, and molecular-surface phenomena (Nano-phenomena) are dominant in the process of oil preparation. First of all, this is the charge interaction of nano-dimensional particles, manifested in the form of physicochemical adsorption of natural emulsifiers on the surface of EWD, wetting the armoring casings of the latter (with corresponding demulsifier interaction), ion-exchange formation of a double electric layer (DEL) on surfaces of EWD and mechanical impurities (solid particles of clay, quartz, limestone, dolomite, iron sulfide, etc.). Consequently, the modeling of these processes is an urgent task, and the article is dedicated to above-mentioned problem.

Effect of emulsifier-fat interactions and interfacial competitive adsorption of emulsifiers with proteins on fat crystallization and stability of whipped-frozen emulsions

Fat crystals and adsorbed interfacial layer are very important in controlling the stability of partly crystalline fat globules. In this study, the effects of competitive adsorption of emulsifiers, including glyceryl monooleate (GMO) and sucrose ester (SE) with milk proteins and emulsifier-fat (anhydrous milk fat, AMF; coconut oil, CO) interactions on the fat crystallization behavior and stability of whipped-frozen emulsions were investigated. Parameters such as zeta potential, surface protein coverage, rheological property, fat crystallization behavior, overrun, melting rate and microstructure of ice cream were determined. The results indicated both GMO and SE affected the crystallization behavior, changing the crystal growth, morphology and stiffness. Different mechanism was involved in fat partial coalescence in emulsion systems with different fat-emulsifier interactions. The promotion of partial coalescence in whipped-frozen emulsions with increasing concentration of GMO was mainly related to fat crystallization behavior combined with increased fat crystal growth dimension and protrusion length at the fat globule surface, since protein surface coverage was not affected by GMO concentration. However, in the case of emulsions with SE, enhancement of partial coalescence was mainly related to decreased protein surface coverage combined with less resistance of interfacial membranes to penetration by small fat crystals. Ice cream based on CO were distinguished by higher overruns and lower melting rates compared to ice cream based on AMF with the same levels of emulsifiers, especially strong fat crystal network in the presence of GMO accounts for the increased air bubble stability. These findings provides a theoretical basis for aerated food processing.

Interfacial competitive adsorption of different amphipathicity emulsifiers and milk protein affect fat crystallization, physical properties, and morphology of frozen aerated emulsion

This study investigated interfacial competitive adsorption of different emulsifiers, including lipophilic [sucrose stearate 370 (S370); mono- and di-acylglycerols (MDG)] and hydrophilic [sucrose stearate 1670 (S1670) and Tween 20 (TW20)] emulsifiers with milk proteins and its influence on fat coalescence behavior in frozen aerated emulsions (10% w/w fat). Lipophilic emulsifiers accelerated fat crystallization, promoting interface heterogeneous nucleation and partial coalescence of fat droplets. In contrast, hydrophilic emulsifiers favored large fat crystal formation with a reduced rate and capacity of fat crystal protrusion. The combination of surfactants (0.5% w/w) with milk proteins (5% w/w) produced concerted effects on the stability of emulsions. The lipophilic surfactant-protein mixture also enabled strong aeration activity (overrun) and a short melting starting time. Moreover, a remarkable array of bee wax-like network was observed in such lipophilic emulsifier-stabilized frozen whipped emulsions with a similar effect seen between S370 and MDG. However, for whipped emulsions produced with hydrophilic emulsifiers, especially with TW20, fewer and irregularly-shaped air bubbles were notable, contrary to the round, slightly arching shape with glossy surface in frozen whipped emulsions with lipophilic emulsifiers. Overall, lipophilic emulsifiers were superior to hydrophilic emulsifiers in producing the well-textured frozen aerated emulsions.

Mesoscale modeling of emulsification in rotor-stator devices: Part II: A model framework integrating emulsifier adsorption

Precise and rational control of droplet size distribution (DSD) is important in emulsification for target-oriented product design. To develop a complete DSD model, crossing the two mesoscales of two different levels is of great significance, viz., the emulsifier adsorption at interfacial level (Mesoscale 1) and the droplet breakage and coalescence in turbulence in rotor-stator device level (Mesoscale 2). While the first mesoscale can be simulated by coarse-grained molecular dynamic (CGMD), the second has been investigated in computational fluid dynamics and population balance model (CFD-PBM) simulation through the Energy-Minimization Multi-Scale (EMMS) approach in Part I. We then developed a model framework in Part II, coupling CGMD and CFD-PBM simulation through surfactant transport equations in bulk phase and at interface, with source terms taking account of emulsifier adsorption parameters. The parameters including maximal adsorption amount, diffusion coefficient and adsorption/desorption kinetic constants are acquired from CGMD. The coalescence efficiency is then corrected by the interfacial area fraction not occupied by surfactant and fed into the coalescence kernel functions in PBM. Compared to traditional CFD-PBM simulation, the coupled model can greatly improve the simulation of DSD, Sauter mean diameter, median diameter and span for high dispersed phase amount (DPA), and correctly reflect the influence of DPA, surfactant concentration and rotational speed of rotor-stator (RS) devices. While the simulation cases validate and demonstrate the advantage of this new model framework, it is also promising to incorporate different types of surfactant in future.

Coalescence of protein-stabilised emulsions studied with microfluidics

Emulsion droplet formation occurs in milliseconds to seconds when emulsifier adsorption is often not yet completed, therewith allowing coalescence to take place. Because of these short time-scales, it is difficult to quantify adsorption and coalescence during processing. A microfluidic device can be used to measure coalescence shortly after droplet formation in laminar flow, and this device was used to assess coalescence of oil-in-water emulsions stabilised with dairy proteins (β-lactoglobulin, whey protein isolate, and oxidised whey protein isolate). Different microfluidic designs were used to vary the protein adsorption time prior to droplet collision.Coalescence stability depended on protein concentration (0.0002–0.02 wt %) and adsorption time (11–173 ms): emulsion droplets were stable at low protein concentrations (as low as 0.005 wt % β-lactoglobulin), as long as the time allocated for protein adsorption was sufficient (in this case 31 ms). Protein type was also important for coalescence stability: emulsions stabilised with whey protein isolate were less stable than those with β-lactoglobulin, and coalescence stability further decreased upon protein oxidation. Regarding the effect of pH (3.0–8.0), coalescence stability was lowest around the protein's isoelectric point.With the coalescence channel we demonstrated the importance of adsorption time and interface composition for coalescence stability at low protein concentrations. Coalescence can be measured at small time-scales and in high detail since coalescence measurements are decoupled from droplet formation. The microfluidic coalescence channel can be used as an analytical tool to gain better understanding of fluid interface stabilisation during emulsification, and to develop emulsion formulations ab initio.

Fabrication of oil-in-water nanoemulsions by dual-channel microfluidization using natural emulsifiers: Saponins, phospholipids, proteins, and polysaccharides

Nanoemulsions are utilized within the food, pharmaceutical, and personal care industries because of their unique physicochemical properties and functional attributes: high optical clarity; prolonged stability; and, enhanced bioavailability. For many applications, it is desirable to utilize natural ingredients to formulate nanoemulsions so as to create “label-friendly” products. In this study, we compared the effectiveness of a number of natural emulsifiers at fabricating corn oil-in-water nanoemulsions using dual-channel microfluidization. These emulsifiers were either amphiphilic biopolymers (whey protein and gum arabic) or biosurfactants (quillaja saponin and soy lecithin). Differences in the surface activities of these emulsifiers were characterized using interfacial tension measurements. The influence of emulsifier type, concentration, and homogenization pressure on the efficiency of nanoemulsion formation was examined. The long-term stability of the fabricated nanoemulsions was also monitored during storage at ambient temperature. For all of the natural emulsifiers, nanoemulsions could be produced by dual-channel microfluidization, with the mean particle diameter decreasing with increasing emulsifier concentration and homogenization pressure. Whey protein isolate and quillaja saponin were more effective at forming nanoemulsions containing fine droplets than gum arabic and soy lecithin, with a lower amount of emulsifier required and smaller droplets being produced. This effect was attributed to faster emulsifier adsorption and a greater reduction in interfacial tension leading to more efficient droplet disruption within the homogenizer for saponins and whey proteins. This study highlights the potential of dual-channel microfluidization for efficiently producing label-friendly nanoemulsions from natural emulsifiers.

Food-grade Pickering emulsions stabilised with solid lipid particles.

Aqueous dispersions of tripalmitin particles (with a minimum size of 130 nm) were produced, via a hot sonication method, with and without the addition of food-grade emulsifiers. Depending on their relative size and chemistry, the emulsifiers altered the properties of the fat particles (e.g. crystal form, dispersion state and surface properties) by two proposed mechanisms. Firstly, emulsifiers modify the rate and/or extent of polymorphic transitions, resulting in the formation of fat crystals with a range of polarities. Secondly, the adsorption of emulsifiers at the particle interface modifies crystal surface properties. Such emulsifier-modified fat particles were then used to stabilise emulsions. As the behaviour of these particles was predisposed by the kind of emulsifier employed for their manufacture, the resulting particles showed different preferences to which of the emulsion phases (oil or water) became the continuous one. The polarity of the fat particles decreased as follows: Whey Protein Isolate > Soy Lecithin > Soy Lecithin + Tween 20 > Tween 20 > Polyglycerol Polyricinoleate > no emulsifier. Consequently, particles stabilised with WPI formed oil-in-water emulsions (O/W); particles stabilised solely with lecithin produced a highly unstable W/O emulsion; and particles stabilised with a mixture of lecithin and Tween 20 gave a stable W/O emulsion with drop size up to 30 μm. Coalescence stable, oil-continuous emulsions (W/O) with drop sizes between 5 and 15 μm were produced when the tripalmitin particles were stabilised with solely with Tween 20, solely with polyglycerol polyricinoleate, or with no emulsifier at all. It is proposed that the stability of the latter three emulsions was additionally enhanced by sintering of fat particles at the oil-water interface, providing a mechanical barrier against coalescence.

Convective mass transport dominates surfactant adsorption in a microfluidic Y-junction.

Surfactant adsorption during emulsification can be quantified by measuring the acting interfacial tension using a Y-junction microfluidic device. To obtain insight into the surfactant transport mechanism to the interface, the effect of shear force on the acting interfacial tension was assessed by systematically varying the continuous phase viscosity and velocity. Varying the continuous phase viscosity did not affect the acting interfacial tension, indicating that surfactant adsorption during Y-junction emulsification is not diffusion-limited. The acting interfacial tension was inversely dependent on the continuous phase velocity, which indicates that surfactant adsorption is governed by convective mass transfer resulting from the continuous phase velocity. The acting interfacial tension can be measured in the sub-millisecond time scale and under convective transport conditions using the Y-junction. These conditions are relevant to industrial emulsification and cannot be assessed by conventional tensiometry techniques (e.g., drop tensiometers) where surfactant adsorption is mostly driven by diffusion. We believe, therefore, that this method can be used to understand emulsifier adsorption during industrial emulsification, which can, in turn, be used to rationally design emulsion formulations and processes.

Framboidal ABC triblock copolymer vesicles: a new class of efficient Pickering emulsifier.

Pickering emulsions offer important advantages over conventional surfactant-stabilized emulsions, including enhanced long-term stability, more reproducible formulations and reduced foaming problems. The recent development of polymerization-induced self-assembly (PISA) offers considerable scope for the design of a wide range of block copolymer nanoparticles with tunable surface wettability that may serve as bespoke Pickering emulsifiers. In the present study, we exploit PISA to design a series of model framboidal ABC triblock copolymer vesicles with exquisite control over surface roughness. Transmission electron microscopy (TEM) and small-angle X-ray scattering (SAXS) were utilized to characterize these nanoparticles, which were subsequently used to stabilize n-dodecane emulsion droplets in water. The adsorption efficiency, Aeff, of the nanoparticles at the n-dodecane/water interface was determined as a function of increasing vesicle surface roughness using a turbidimetry assay. A strong correlation between surface roughness and Aeff was observed, with Aeff increasing from 36% up to 94%. This is a significant improvement in Pickering emulsifier efficiency compared to that reported previously for similar vesicles with smooth surfaces. In summary, nanoparticles with appreciable surface roughness are much more effective Pickering emulsifiers and this parameter can be readily fine-tuned using a highly efficient PISA formulation.

Chemical reactivity of mineral aggregates in aqueous solution: relationship with bitumen emulsion breaking

This paper reports a study on chemical reactivity of gneiss, diorite and limestone aggregates in aqueous solution. The originality of this study is that it extended to very short times (less than 1440 min). Rise in pH tests was implemented and dissolution kinetics was analysed. The results showed that calcium was the major element released by the aggregates. It has also been found that dissolution had an influence on the final morphology of aggregates. Polyamine emulsifier adsorption onto aggregates has been assessed using electrophoresis. Finally, the rise in pH and electrophoretic tests were compared to the breaking test traditionally performed to characterise bitumen emulsions. It was found that breaking values were controlled by both the surface area and the surface charge of the particles. Results may be correlated to polyamine adsorption on aggregates. Adsorption seemed to be efficient for gneiss and diorite: at pH 2, their charge turned from slightly negative to highly positive. At this pH value, limestone particles were dissolved and polyamine adsorption must be less efficient than with gneiss and diorite, for which the emulsion breaking was facilitated by the high attraction of particles for the emulsifier, due to their negative surface charge.

A high-pressure homogenization emulsification model—Improved emulsifier transport and hydrodynamic coupling

The high-pressure homogenizer emulsification modelling framework by Håkansson et al. (2009a, Chemical Engineering Science 64, 2915–2925; 2009b. Food Hydrocolloids 23, 1177–1183), is further developed in this study. The model, including the simultaneous fragmentation of drops, coalescence of drops and kinetic adsorption of macromolecular emulsifiers, is improved with regard to two points. First, the transport of adsorbed emulsifier between drops of different sizes due to the fragmentation and coalescence of drops, is included using bivariate population balances. Second, the coupling of hydrodynamics to the emulsification model is improved using information from recent hydrodynamic investigations. The proposed framework is exemplified using a set of physically reasonable kernels and a production scale high-pressure homogenizer geometry, showing realistic emulsification results.

Role of Surfactants in Emulsion Polymerization Polymers by design

The determination of an emulsifier�s adsorption properties under conditions similar to those occurring during emulsion polymerization can provide important information to aid in the selection of the most appropriate surfactant for a given system. Results show that the latex particle size is dependent on the strength of emulsifier adsorption (DEads) at the particle/aqueous phase interface and is a function of the polymer polarity. Use of reactive surfactants can improve latex characteristics by reducing the desorption and migration of surfactant to film interfaces and minimize film water sensitivity. The fraction of bound surfactant can be maximized by using relatively low emulsifier concentrations and higher initiator concentrations.