Jean-Louis Salager

A correlation for phase behavior of nonionic surfactants

Abstract In previous studies, the systematics of variation of phase behavior of oil/water/surfactant systems have been detailed for anionic surfactants. The present study details the behavior of such systems with nonionic surfactants, including the variables: temperature, alcohol type and concentration, added electrolyte, ethylene oxide number of the surfactant, alkane molecular weight for the oil phase, and the hydrophobic molecular weight for the surfactant.

Solubilization of polar oils with extended surfactants

Starting with previous results showing that the solubilization of oil and water in a microemulsion can be improved by the introduction of an additive, i.e. a so-called lipophilic linker, a new surfactant type that mimics the additive effect is tested. The so-called extended surfactant has a poly-propylene oxide chain inserted in between the conventional alkyl and ether sulfate groups. These surfactants exhibit a critical micelle concentration and a cloud point that changes with the number of propylene oxide groups per molecule (ranging from 6 to 14). They show three-phase behavior at optimum formulation, with hexadecane, ethyl oleate, and, as reported for the first time, with triglyceride oils, such as soya oil. Outstanding values of the optimum solubilization parameter are reached (in the 10–30 ml g−1 range).

SORFACTANT-OIL-WATER SYSTEMS NEAR THE AFFINITY INVERSION Part III: THE TWO KINDS OF EMULSION INVERSION

ABSTRACT The inversion locus is represented on a generalized mixed bidimensional scan (formulation-WOR), where the formulation variable may be the salinity, oil ACN, alcohol type or concentration, surfactant parameter such as EON, or temperature At near unity water/oil ratio the inversion locus (Phase Inversion Formulation: PIF) approximately matches the optimum formulation for minimum tension and phase behavior. In this region the inversion depends essentially upon physico-chemical factors. At extreme water/oil ratios, the inversion locus depends essentially upon the volumetric proportions of the phases, i.e., a physical factor A general classification of emulsion type is proposed according to the optimum formulation and phase inversion lines The alterations of the inversion locus with surfactant type, oil viscosity and conditions of emulsification, are discussed.

Interfacial Tension and Phase Behavior of Surfactant Systems

Perturbations of system parameters are shown to affect the surfactant partitioning between oil and water through changes in the relative standard chemical potentials of the surfactant in the 2 phases. For the systems investigated, low interfacial tensions are associated with near-unity values of the partition coefficient. The conditions necessary for optimum low tension and phase behavior at high surfactant concentrations are identical to those required for a tension minimum at low surfactant concentrations, where solibilization effects may not be visible. The effects of alcohol and other system parameters on surfactant chemical potential and hence on interfacial tension are noted. (18 refs.)

SURFACTANT-OIL-WATER SYSTEMS NEAR THE AFFINITY INVERSION PART I: RELATIONSHIP BETWEEN EQUILIBRIUM PHASE BEHAVIOR AND EMULSION TYPE AND STABILITY

ABSTRACT A systematic relationship was found between the equilibrium phase behavior of a surfactant-alcohol-oil-water system and the type and stability of the corresponding emulsion. Formulations are scanned through the three phase transition by changing (one at the time) brine salinity, oil EACN, surfactant nature and alcohol concentration. Whatever the scanning variable, it is found that the electrical conductivity exhibits a large change near the optimum formulation, indicating the inversion of the continuous phase of the dispersed system. On the other hand, the emulsion stability is found to undergo a deep minimum for formulations corresponding to the three phase behavior at equilibrium. The large but relatively smooth variation of the conductivity gives some hints on the possible continuity structure of the MOW triphasic emulsions.

Emulsion instability in the three-phase behavior region of surfactant-alcohoi-oil-brine systems

Abstract The stability of the emulsion is estimated from a dual criterion, i.e., from both oil and water phases settling. The two criteria overlap and swap their respective meaning (coalescence vs clearing) in the three-phase zone. Three-phase emulsion breaking is interpreted with the help of a simple model. The removal of one of the phases prior to emulsification produces an emulsion as unstable as the triphasic ones. The middle phase appears to behave as a trap which hinders the surfactant from stabilizing a macroemulsion.

A new method to estimate the stability of short-life foams☆

Abstract In classical foam stability studies, foam height variation is monitored versus time. The decay pattern depends, however, upon the foam structure at the start of the decay; in many instances this structure changes significantly during the first few minutes, and it is difficult to select a proper “zero time” of decay. We have found that the decay behavior is very well defined when the original state of the foam is taken as the equilibrium state of the classical Bikermans experiment, i.e. when the foam formation by bubbling (at the bottom of the column) exactly compensates the foam collapse (at the top). It is found that under such starting conditions, short life foam decay exhibits a linear variation in the foam column height with the logarithm of the elapsed time. A dimensionless H vs. log t plot exhibits the same features for different systems; thus, both a characteristic height and a characteristic time can be extracted from the experimental data, the latter being readily related to the foam stability. These parameters are used to quantify the effect of additives on the decay of several foam systems containing nonionic and anionic surfactants.

Partitioning of ethoxylated alkylphenol surfactants in microemulsion-oil-water systems☆

Ethoxylated alkyl phenol oligomer partitioning between the microemulsion-water-oil (heptane) phases of a Winsor III system is determined by high performance liquid chromatography for systems containing octyl, nonyl, decyl, dodecyl and dinonyl phenol species. The partition coefficient between the water and oil phases obeys a simple law depending upon the alkyl chain length and the number of ethylene oxide groups per oligomer molecule. The results allow estimation of the energy of transfer of an ethylene oxide group and of a methylene group from oil to water.

Physicochemical parameters influencing the emulsion drop size

The stirring-mixing energy is the most obvious factor in the drop size reduction process, but it is not necessarily the most important one. Both the physicochemical formulation and the composition variables are shown to play a determinant role, at constant stirring condition.The generalized formulation versus water/oil ratio diagram allows to map emulsion properties such as emulsion type, stability and viscosity. It is used to discuss the combined effect of the formulation and composition upon the emulsion drop size, through their influences on the interfacial tension, and the emulsion viscosity and stability.

Practical Surfactant Mixing Rules Based on the Attainment of Microemulsion–Oil–Water Three-Phase Behavior Systems

Surfactant mixture are generally used to fine-tune formulations to an exact property value, such aschanging its hydrophilicity. To do so a precise characterization method has to be used. The presentedtechnique consists of the attainment of a microemulsion–oil–water Winsor III three-phasebehavior in a reference system. It allows one to classify surfactants in a hydrophilicity scalewith an accuracy equivalent to one tenth of HLB unit. The characterization method is applied in differentways, including simple and double scans, to an unknown surfactant and to mixtures of two base surfactants.It is also used to test the ideality of the mixing rule expression, which is equivalent to a linearvariation of the characteristic parameter versus the mixture composition. Conditions for linearity of themixing rule are discussed. The selective partitioning of different species results in non-linear mixingrules, whose detection is discussed according to the aspect of the three-phase region in different diagrams.Typical mixing rules for pH sensitive systems containing fatty acids and fatty amines are shown. Anionic–nonionicmixtures are found to exhibit a slight deviation from ideality. The special case of antagonistic anionic–cationicmixture is shown to be easily linearized by introducing a virtual, catanionic species.