Ethylene oxide groups

Number of ethylene oxide groups in esterified polyoxyethylene (POE). See Table 1. 

Polyurethane foams are formed by reaction with glycerol with poly(propylene oxide), sometimes capped with poly(ethylene oxide) groups with a reaction product of trimethylolpropane and propylene oxide or with other appropriate polyols. A typical reaction sequence is shown below, in which HO—R—OH represents the diol. If a triol is used, a cross-linked product is obtained. 

Ethoxylated fatty alcohols and alkylphenols were used. The products available on the market make up homologous series containing an average of between 3 and 100 ethylene-oxide groups. They thus have a wide HLB (hydrophilic/lipophilic balance) range. Besides, they are among the least expensive surfactants on the market. 

As an anionic surfactant, a synthetic alkylate-base sulfonate containing about 60 % active material (Synacto 476) was used. To make it compatible with the injection water considered (composition in Table I) containing 1500 ppm Ca++ and Mg++ ions, a nonionic cosurfactant was combined with it, i.e. an unsaturated ethoxylated fatty alcohol with 8 ethylene oxide groups (Genapol). Their main characteristics and properties are listed in Table II. 

Our goal is to develop a property-performance relationship for different types of demulsifiers. The important interfacial properties governing water-in-oil emulsion stability are shear viscosity, dynamic tension and dilational elasticity. We have studied the relative importance of these parameters in demulsification. In this paper, some of the results of our study are presented. In particular, we have found that to be effective, a demulsifier must lower the dynamic interfacial tension gradient and its ability to do so depends on the rate of unclustering of the ethylene oxide groups at the oil-water interface. 

Commercial mixtures of surfactants consist of several tens to hundreds of homologues oligomers and isomers. Their separation and quantification is complicated and a cumbersome task. Detection, identification and quantification of these compounds in aqueous solutions, even in the form of matrix-free standards, present the analyst with considerable problems. The low volatility and high polarity of some surfactants and their metabolites hamper the application of gas-chromatographic (GC) methods. GC is directly applicable only for surfactants with a low number of ethylene oxide groups and to some relatively volatile metabolic products, while the analysis of higher-molecular-mass oligomers is severely limited and requires adequate derivatisation. 

Ethylene Oxide Addition. Anionic and nonionic alkylaryl compounds containing amound of thylene oxide were used in this study. Addition of ethylene oxide groups is known to impart salt tolerance to the surfactant and therefore these compounds are of particular interest for micellar flooding purposes. 

Ethoxylated nonionic surfactants approximately obey a hnear mixing rule expressed as Eq. 1 when the characteristic property is the averaged number of ethylene oxide groups per molecules (EON) [35]. The goodness of the fit depends on the partitioning phenomena, which will be discussed later, in Sect. 4. 

A similar effect was noted in separate investigations by another group [108], Oil-in-water HIPEs, where the oil phase contained aromatic or halogenated liquids, were difficult or impossible to form, with nonionic surfactants. This was postulated to be as a result of interactions between the polar ethylene oxide groups of the surfactant and the aromatic or halogenated solvents, which are more polar than hydrocarbons. Water-in-oil systems also displayed this tendency [21] however, w/o HIPEs with m-xylene as the oil phase [13] could be produced with monolaurin as nonionic emulsifier, due to stronger intermolecu-lar interactions at the interface. 

The addition of salts to the aqueous phase of concentrated emulsions can have profound effects on their stabilities. Water-in-oil HIPEs are generally stabilised by salt addition [10,12,13,21,80,90,112] however, the nature of the salt used was found to be important [13]. Salts which decrease the cloud point of the corresponding nonionic surfactant aqueous solutions, i.e. which have a salting-out effect, were more active. The interactions of the surfactant molecules at the oil/water interface were increased due to dehydration of the hydrophilic ethylene oxide groups on addition of salt. This was verified experimentally [113] by an ESR method, which demonstrated that the surfactant molecules at the oil/water interface become more ordered if the salt concentration is increased. 

A major disadvantage of the HLB concept is that it makes no allowance for temperature effects. With increasing temperature, the hydration of lyophilic (particularly poly(ethylene oxide)) groups decreases and the emulsifying agent becomes less hydrophilic - i.e. its HLB decreases. 

Ether carboxylates are a very versatile class of surfactants, used in diverse applications from mild personal care formulations to lubricants and cutting fluids. They are interrupted soaps, with the addition of a number of ethylene oxide groups between the alkyl chain and the carboxylate group. The additional solubility imparted by the EO groups gives much greater resistance to hardness and reduced irritancy compared to soap. 

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