Two amphiphilic polysaccharides derived from a nonionic bacterial polysaccharide of dextran (DexP(10) and DexP(15)) have been explored as emulsifiers for preparing highly concentrated oil-in-water emulsions in a semi-batch (two-step) process. A fixed amount of stabilizer (10 g/L of emulsion) was employed for preparing emulsions at dispersed-phase volumetric fractions ranging from 0.850 to 0.938. Their performances as stabilizers (interfacial tension, kinetics, droplet size distribution, rheological behavior and stability) were evaluated and compared with a group of four ABA non-ionic commercial stabilizers from Pluronic series (F68, F127, P105 and L64) and a low-molecular-weight surfactant (Tween 80). Our results demonstrate these AB(pi) graft amphiphilic polysaccharides can be promising stabilizers as efficient as commercial non-ionic polymeric stabilizers for preparing highly concentrated emulsions in spite of lower interfacial tensions, slower kinetics, or showing emulsions a larger droplet size and less monodispersity.

This work studied the adsorption at dodecane/water interface of amphiphilic polysaccharides derived from dextran (a nonionic bacterial polysaccharide) by random attachment of phenoxy groups along the chains (between 10 and 20 attached phenoxy groups per 100 glucose repeat units). The long-time kinetics of interfacial tension decrease was satisfactorily described assuming diffusion-limited adsorption of hydrophobic units (over 4h). Dilational rheology of dodecane/water interface was studied for the first time with that kind of amphiphilic polysaccharides and evidenced a significant elastic component. For all dextran derivatives, experimental results were conveniently described using Lucassen-van den Tempel model which assumed diffusion-limited of surface active species. The characteristic frequency increased with the number of attached phenoxy groups and its order of magnitude (10-3-10-2rad.s-1) was consistent with estimations based on the previous model. Experimental results were compared to those obtained with commercial stabilizers like Pluronics (L64, P105, F68 and F127) and Tween 80.

The present work illustrates the feasibility of performing Oil-in-Water (O/W) emulsions stabilized by different protein concentrates, as well as predicting the likelihood of emulsion destabilization over ageing time just after its preparation. To achieve this objective, four protein sources (rice, crayfish, potato and albumen) and four oil concentrations (450, 550, 650 and 750 g kg(-1)) were used. The emulsification process was monitored by the use of a mixer-type rheometer. This rheometer was a valuable tool for understanding and controlling the emulsification process through the measurement of the viscosity of the different systems during the emulsification stage.Results reveal the importance of controlling the emulsification process to optimize the properties of the final emulsion, which is highly influenced by the oil concentration. Then, emulsions were characterized by means of flow properties and droplet size distribution (DSD). Eventually, a relationship was found that relates the rheological properties and the microstructure of the final emulsions during and after emulsification stage. These measurements have been demonstrated to be useful in order to predict the stability of protein-based emulsions. (C) 2017 Elsevier Ltd. All rights reserved.

In the present work, concentrated Oil-in-Water (O/W) emulsions were stabilized using egg albumen protein isolate as the only emulsifier. A helicoidal geometry was used and compared with a conventional one to assure an optimal emulsion preparation with that unusual geometry in order to come up with the utility of this rheometer as a valuable tool for understanding and controlling the emulsification process. The results put forward the importance of controlling the emulsification process to optimize the properties of the final emulsion and demonstrating a good agreement between in situ and off-line measurements obtained in mixer-type and conventional rheometers, respectively. Flow properties of the different emulsion prepared were measured, showing an increase in the viscosity with the agitation speed (from 10 to 16 to 114-117 Pa s), protein concentration (from 30 to 40 to 106-125 Pa s) and oil concentration (from 15 to 20 to 130-180 Pa s). Furthermore, the droplet size distribution (DSD) was also measured obtaining the influence of the different parameters with the Sauter diameter (a decrease from 20 to 30 to 7-8 mu m, from 26 to 3 mu m and from 17 to 24 to 8-14 mu m was observed by increasing the agitation speed and the protein and oil concentration, respectively). The influence of the pH was also taken into account. Eventually, a relationship has been found that relates these properties to different composition (pH value, nature and concentration of proteins) or processing variables (agitation speed). (C) 2016 Elsevier Ltd. All rights reserved.

In this paper, the response of circular Couette flow of shear-thinning fluids between two infinitely long coaxial cylinders to weak disturbances is addressed. It is highlighted by transient growth analysis. Both power-law and Carreau models are used to describe the rheological behaviour of the fluid. The first part of the paper deals with the asymptotic long-time behaviour of three-dimensional infinitesimal perturbations. Using the normal-mode approach, an eigenvalue problem is derived and solved by means of the spectral collocation method. An extensive description and the classification of eigenspectra are presented. The influence of shear-thinning effects on the critical Reynolds numbers as well as on the critical azimuthal and axial wavenumbers is analysed. It is shown that with a reference viscosity defined with the characteristic scales $\hat{{\it\mu}}_{ref}=\hat{K}(\hat{R}_{1}\hat{{\it\Omega}}_{1}/\hat{d})^{(n-1)}$ for a power-law fluid and $\hat{{\it\mu}}_{ref}=\hat{{\it\mu}}_{0}$ for a Carreau fluid, the shear-thinning character is destabilizing for counter-rotating cylinders. Moreover, the axial wavenumber increases with $\mathit{Re}_{2}$ and with shear-thinning effects. The second part investigates the short-time behaviour of the disturbance using the non-modal approach. For the same inner and outer Reynolds numbers, the amplification of the kinetic energy perturbation becomes much more important with increasing shear-thinning effects. Two different mechanisms are used to explain the transient growth, depending on whether or not there is a stratification of the angular momentum. On the Rayleigh line and for Newtonian fluids, the optimal perturbation is in the form of azimuthal streaks, which transform into Taylor vortices through the anti-lift-up mechanism. In the other cases, the optimal perturbation is initially oriented against the base flow, then it tilts to align with the base flow at optimal time. The scaling laws for the optimal energy amplification proposed in the literature for Newtonian fluids are extended to shear-thinning fluids.

Rules of thumb that are used in the industry for polymer-flooding projects tend to limit the distance over which hydrolyzed polyacrylamide polymers can be transported in pipelines without undergoing significant degradation. However, in sensitive environments, such as offshore facilities where footprint minimization is required, centralization of the polymer-hydration process and long-distance transport may be desirable. More-reliable rules are required to design the pipe network and to estimate mechanical degradation of polymers during transport in turbulent conditions. In this work, we present evidence in the form of empirical large-scale pipeline experiments and theoretical development refuting the claim that polymer pipeline transport is limited by mechanical degradation. Our work concludes that mechanical degradation occurs at a critical velocity, which increases as a function of pipe diameter. Provided the critical velocity is not reached in a given pipe, there is no limit to the distance over which polymer solution can be transported. In addition, the drag reduction of viscous polymer solutions was measured as a function of pipe length, pipe diameter, fluid velocity, and polymer concentration. An envelope was defined to fix the minimum and maximum drag reductions expected for a given velocity in larger pipes. For pipes with diameters varying between 14 and 22 in. at a velocity greater than 1 m/s, the drag-reduction percentage is anticipated to be between 55 and 80%. A more-refined model was developed to predict drag reduction with less uncertainty. In conclusion, classical design rules applied for water transport (fluid velocity < 3 m/s) can be applied to the design of a polymer network. Therefore, for tertiary polymer projects, the existing water-injection network should be compatible with the mechanical requirements of polymer transportation. For secondary polymer projects, changing the rules of design by taking into account the high level of drag reduction should bring some economy to the pipe design and installation.

Nuclear decontamination is a key aspect of the decommissioning of facilities, can today be carried out using gelled reagents sprayed over contaminated surfaces (tens of square meters) and allows easy radionuclide retrieval. Wide ranges of formulations have been developed in our laboratory to treat several materials. The gels are formulated by adding colloidal silica particles to a reactive solution; they dry and form solid residues that are easily collected and directly conditioned. Dissemination hazards are reduced and no liquid effluent is generated or released. In order to adapt the process to the decontamination of small items, an original method involving a topping gel has been developed. A polysaccharide, carrageenan, is added to a conventional gel (silica particles + reactive solution) and by varying the temperature an abrupt sol-gel transition (around 45-50 degrees C) is observed. At high temperature, the low viscosity of the gel allows it to coat small parts easily, and simply removing them from the warm bath congeals the topping gel. Its decontaminating action takes place. The gel then dries and can be collected. A tradeoff has been found between the mineral mass fraction and the amount of carrageenan, and a formulation is proposed. Results on Co-60 contaminated black steel plates show that the decontamination factor is fully comparable to a conventional gel. Finally, drying kinetic measurements show that easily recoverable flakes are formed due to water evaporation. (C) 2014 Published by Elsevier B.V.

Physical gels have been studied as an advantageous alternative to traditional decontamination techniques, which most often rely on the use of surfactant solutions. Such physical gels consist of colloidal particles suspended in a decontaminating solution. They can be sprayed over the surfaces to be treated, where they dry and form solid disposable residues. In order to improve their efficiency, the formulation of gels containing superabsorbents (such as sodium polyacrylate) has recently been suggested. But the mechanism accounting for the observed efficiency increase has not yet been investigated. These additives have a large swelling potential in aqueous media and the amount of adsorbed water depends on the presence of salts in the medium. We anticipated that specific ion effects on the swelling behavior of superabsorbent polymers were the driving force of efficiency enhancement and confirmed this assumption by rheology and in situ tests. (C) 2014 Elsevier B.V. All rights reserved.

When a caustic soda solution is slowly added up to a cationic oil-in-water emulsion, prepared with dodecylamine as surfactant, the chemical equilibrium is altered. As a consequence, a progressive viscosity diminution is observed until complete emulsion destabilization. Original cationic emulsions are stable thanks to the droplet electrical double layer formed by the ionized surfactant adsorption on the liquid interface at very low pH values. However, the alkali addition changes the chemical equilibrium in different ways, such as reducing the hydronium ion concentration, allowing for dodecylamine deionization and increasing the ionic species concentration. These changes and the fact that the emulsion's droplet size and distribution remain constant (noticed by granulometric measurements) during the process, let us assuming that viscosity decreases as a consequence of the overall positive layer charge diminution. However, emulsion destabilization can be explained in terms of some formulation parameters such like SAD or HLD. Our system evolves from a very negative to a positive HLD value passing through the optimal formulation when destabilization is observed. An interfacial formulation analysis is presented and a hypothetically extrapolation to asphalt emulsions is briefly analyzed. (C) 2014 Elsevier B.V. All rights reserved.

This study focuses on the mechanisms of bitumen emulsification and on the impact of the formulation, when emulsification is carried out in the area of high internal phase ratio (0.9). Kinetics of emulsification were determined using systemic rheology coupled with optical microscopy observations. Microscopic observations revealed a catastrophic phase inversion with formation of abnormal multiple emulsions, occurring very quickly after contacting the bitumen with the aqueous phase containing the surfactant. The direct emulsion thus obtained is then refined during a subsequent agitation step. The viscosity follow-up during the emulsification highlights four steps in the kinetic of catastrophic phase inversion, which have been related to morphological characteristics of the dispersions observed by optical microscopy. (C) 2014 Elsevier B.V. All rights reserved.

Abstract Rules of thumb that are used in the industry for polymer flooding projects, tend to limit the distance over which HPAM polymers can be transported in pipelines without undergoing significant degradation. However, in sensitive environments such as offshore facilities where footprint minimization is required, centralization of the polymer hydration process and longdistance transport may be desirable. More reliable rules are required to design the pipe network and to estimate mechanical degradation of polymers during transport in turbulent conditions. In this work, we present evidence in the form of both empirical, large-scale pipeline experiments as well as theoretical development refuting the claim that polymer pipeline transport is limited by mechanical degradation. Our work concludes that mechanical degradation occurs at a critical velocity which increases as a function of pipe diameter. Provided the critical velocity is not reached in a given pipe, there is no limit to the distance over which polymer solution can be transported. In addition, the drag reduction of viscous polymer solutions was measured as a function of pipe length, pipe diameter, fluid velocity and polymer concentration. An envelope was defined to fix the minimum and maximum drag reductions expected for a given velocity on larger pipes. For pipes with diameter varying between 14″ and 22″ at a velocity higher than 1 m/s, the drag reduction percentage is anticipated to be between 45 and 80%. A more refined model was developed to predict drag reduction with less uncertainty. In conclusion, classical design rules applied for water transport (fluid velocity <3m/s) can be applied to the design of a polymer network. Therefor, for tertiary polymer projects, the existing water injection network should be compatible with the mechanical requirements of polymer transportation.

For the first time, the in situ follow-up of the viscosity evolution with reaction time during the synthesis of isocyanate-terminated urethane prepolymers has been done. For that, the systemic rheology has been applied with the purpose of mimic the unit operations of adhesive processing, particularly the mixing and chemical reaction. Several behaviors were revealed with the methodology applied. For all the synthesis prepared at 100°C, we observed that the viscosity evolution tended toward a plateau, i.e., the viscosity reached constant values. However, for all the synthesis made at 60°C, the viscosity plateau was not at all observed and the viscosity remarkably increased during the studied reaction time. The viscosity decreased with an increase of: (a) molecular weight of the PPG or PPG blends, and (b) NCO/OH ratio. We also found that the latent pre-reaction time increased and the PPG's reactivity decreased when the molecular weight of PPG was increased. Moreover, at low NCO/OH ratio, the viscosity quickly increased when the amount of PPG-400 related to the PPG-2000 was high. Surprisingly, this behavior was not observed at high NCO/OH ratio.

Aqueous slurries made of silica or alumina particles may behave like sols or like gels depending on the particle concentration, but also the pH or the ion force of the medium. The present study aimed at investigating the different sol-gel transitions observed in systems between a diluted state and concentrated formulations. For this purpose zeta potential and G', G '' measurements, reflecting elastic and viscous behaviors, were selected as the tools of choice to get insights into the mechanisms accounting for the sol-gel transition. We discuss about the relevancy of these simple measurements and affirm that they are sufficient to explain the evolutions in an alumina based system. Indeed, particles can adopt a "repulsive" organization at low salt concentration values (i.e. high surface potential values) or form an attractive percolating network, when the ion strength reaches a critical level. Moreover, the addition of NaOH can lead to very complex moduli variations as both the electrostatic shielding and the pH change; yet, these variations are easily predictable using our reasoning. (C) 2013 Elsevier B.V. All rights reserved.

Percolation thresholds of multiwalled carbon nanotube/polystyrene (MWCNT/PS) nanocomposites (NC) were determined by rheology and electrical conductivity. The percolation threshold found by electrical conductivity was 0.5% carbon nanotubes (CNT) and that by mechanical spectroscopy and relaxation measurements was 0.9% CNT. These results together with those reported in the literature show several types of percolation thresholds, depending on the average filler–filler (CNT and/or aggregates) distance in a polymer matrix. A distance close to polymer gyration radius corresponds to a “soft” rheological threshold (PC rheosoft). Close contacts between fillers giving rise to a conductive path corresponds to an electrical threshold (PC elec). At high filler concentration, fillers form a network, corresponding to a “rigid” rheological threshold (PC rheorigid). These thresholds depend on the filler content and follow the order: PC elecsoft < PC elec < PC rheorigid. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers

The use of asphalt emulsions for road fabrication is rapidly gaining in importance mainly due to energy savings, less environmental impact, and better properties of the final product. However, the formulation of these emulsions still requires a better understanding, particularly concerning their breaking phenomena. When a cationic model emulsion is contacted with a solid having a negative-charged surface, physicochemical driving forces result in the emulsion destabilization. As a consequence, a viscosity reduction of the remaining emulsion is observed, as well as the emulsion breakup through a heteroflocculation mechanism provided the solid surface is large enough. Emulsion systems at equilibrium, containing cetylpyridinium chloride (CPC), paraffin oil, and Fontainebleau's sandstone powder and having different droplet sizes, are studied. The results show that the dispersed oil fraction decreases after each addition of sandstone aliquots, and this depends on the concentration of CPC in the continuous phase of the emulsion. As the droplet size and distribution remain constant during the process, it is assumed that the emulsion heteroflocculation is the result of direct oil droplets adhesion on the sand surface, followed by their coalescence around the sand particles.

The universality of the model proposed by Princen and Kiss is analyzed in the case of highly concentrated water-in-oil emulsions containing dispersed-phase volume fractions (phi) ranging from 0.89 to 0.97. Although Princen and Kiss equation has been rigorously established for a two-dimensional system and involves no adjustable parameter, the model for a tridimensional system, which is an extrapolation of the 2D model, requires the introduction of a phenomenological linear function E(phi) to account for experimental deviations. As mentioned by Princen and Kiss themselves, there is no satisfactory theoretical derivation of E(phi). Indeed, in this paper we point out that the linear dependence in phi of E(phi) is a consequence of the particular set of experimental data exploited by Princen and Kiss. Another choice of experimental data could have led to propose other mathematical functions since at very high volume fraction, sortie experimental data found in the literature show a more rapid increase of the storage modulus G' with phi than predicted by Princen land Kiss equation, which tends to underestimate the values of G'. Finally, for the studied highly concentrated emulsions, the dispersed-phase volume fraction dependence of storage modulus is discussed.