Volume 47, Issue 3

Reverse phase HPLC (High Performance Liquid Chromatography) was used to analyze the length distribution of polyoxyethylene (POE) chains in commercial surfactants that can be used as melt additives for hydrophilic polypropylene surface modification. Ten nonionic surfactants including ethoxylated alcohols, nonyl phenols and amines, PEG esters, and mono glycerides were investigated. HPLC methods described herein are capable of analyzing ethoxylated nonionic surfactants and offer the advantage of separating the components in surfactants according to both the hydrophobe and hydrophile chain length. Moreover, the method is rapid and gradient elution allows for good baseline separation of the several components in the additives.

This investigation considers branched alkyl alcohol propoxylated sulfate surfactants as candidates for chemcial enhanced oil recovery (EOR) applications. Results show that these anionic surfactants may be preferred candidates for EOR as they can be effective at creating low interfacial tension (IFT) at dilute concentrations, without requiring an alkaline agent or cosurfactant. In addition, some of the formulations exhibit a low IFT at high salinity, and hence may be suitable for use in more saline reservoirs. Adsorption tests onto kaolinite clay indicate that the loss of these surfactants can be comparable to or greater than other types of anionic surfactants. Surfactant performance was evaluated in oil recovery core flood tests. Selected formulations recovered 35–50% waterflood residual oil even with dilute 0.2 wt% surfactant concentrations from Berea sandstone cores.

The micellization behavior of three cationic gemini surfactants, C 16 H 33 N + (CH 3 ) 2 (CH 2 ) S N + (CH 3 ) 2 C 16 H 33 , 2Br − (s = 4, 6, 10) have been studied in the presence of 1% (w/v) and 5% (w/v) polyethylene glycol-600 (PEG-600) by conductivity measurements at 300–320 K. From the conductivity data the critical micelle concentration, the degree of counterion ionization (α) and the thermodynamics of micellization ΔG o m , ΔH o m , ΔS o m , of the gemini surfactants have been determined. The micellar parameters show a significant dependence on the spacer length and as well as amount of polymer.

In this study we used electrical conductivity, dynamic viscosity, dynamic light scattering, and small angle X-ray scattering for the characterization of the water + propylene glycol/sucrose laurate/ethoxylated mono-di-glyceride/peppermint oil microemulsion systems. The maximum water solubilization in the peppermint oil was found to be dependent on the surfactants mixing ratio (w/w). A Static percolation threshold was determined. The activation energy of conductive flow depends on the surfactants mixing ratio. The hydrodynamic diameter of the diluted microemulsions decreases with the increase in temperature. The periodicity d of the microemulsions increases with the increase in the aqueous phase content. The correlation length ξ increases and decreases with the increase in the aqueous phase content indicating the onset of structural transitions.

Surfactants as organic compounds are widely used in the processes of textile finishing and care with regard to different variations and specific hydrophilic/hydrophobic character. Specific behaviour of these compounds is partly based on the adsorption process. In this study the adsorption and desorption of ionic surfactants have been studied upon the influence of fibre composition and surfactant ionogenity as well as variation of hydrophobic chain length and hydrophilic group in the molecule. Textile fibres were characterized through electrokinetic potential, sorption characteristics and swelling capacity expressed by moisture regain and water retention value (WRV). Different types of cationic and anionic surfactants were adsorbed on cotton, wool, polyester and polypropylene fibres at 20°C during 60 minutes. The quantity of adsorbed surfactants on textile fibres was determined by potentiometric titration. The textile fibres were centrifuged afterwards and the amount of surfactants was determined in the centrifugate, respectively. Drying followed at 60°C. The desorption of surfactants was performed at 20°C during 30 minutes. The results showed a correlation between amount of adsorbed, desorbed and residual surfactants and swelling capacity expressed through WRV.

Structural peculiarities of the rod-like micelles in lyotropic liquid crystalline nematic-calamitic and hexagonal mesophases have been investigated. The lengths, the parameters of anisometricity, the form factors and the volumes of these micelles have been determined. The method of the electrical conductivity anisotropy in the orientational shear flow has been used. The rod-like micelles of nematic-calamitic and hexagonal mesophases were considered as the prolonged ellipsoids.

Ultrasonic measurements were made on terbium laurate and myristate in 60/40 benzene-methanol mixture (v/v), to determine the critical micellar concentration (CMC), ultrasonic velocity and other acoustic parameters. The results confirm that there is a significant interaction between the soap and solvent molecules. The critical micellar concentration and thermodynamic parameters for dissociation and micellization process for terbium laurate and myristate in a mixture of 60/40 benzene-methanol (v/v) at different temperature were evaluated from conductivity measurements. The results showed that these soaps behave as weak electrolytes in dilute solutions.

Nonionic surfactants do not produce ions in aqueous solution. As a consequence, they are compatible with other types of surfactants and are excellent candidates to enter complex mixtures, as found in many commercial products. Nonionic surfactants are found today in a large variety of domestic and industrial products, such as powdered or liquid formulations. This review paper describes the history, properties, types and uses of nonionic surfactants.