Effects of the ethylene oxide distribution on nonionic surfactant properties

Abstract

AbstractDetergent‐range primary alcohols are readily converted into nonionic surfactants by reaction with ethylene oxide. Optimum performance properties for these surfactants generally are attained by varying the number of moles of ethylene oxide reacted with each mole of alcohol or by altering the structure of the primary alcohol. However, variations in the ethoxylate‐adduct distribution also affect surfactant properties in such a way that products with relatively narrow distributions possess features which are highly desirable in many household and industrial applications. For a given cloud point narrow‐range ethoxylates have lower molecular weights and therefore lower pour points than broad‐range surfactants. Because narrow‐range ethoxylates contain less unreacted alcohol and other water‐insoluble species, they are capable of forming aqueous solutions with much lower cloud points than their broad‐range counterparts. Aqueous solutions of narrow‐range products have lower viscosities, exhibit lower gel temperatures and remain fluid over a wider concentration range than solutions of broad‐range surfactans. While the foams obtained with narrow‐range surfactants in the Ross‐Miles test are higher initially, they are less stable than those produced by conventional nonionic surfactants. Draves wetting data show that narrow‐range products wet cotton substrates more efficiently than normal‐distribution materials. Narrow‐range ethoxylates exhibit higher aqueous surface tension and higher polyester adhesion tension values than their broad‐range counterparts. In addition, narrow‐range surfactants reduce the interfacial tension against paraffin oil more efficiently and more effectively than broad‐range products. These results, along with laboratory detergency data, suggest that the use of narrow‐range ethoxylates may lead to cleaning systems with improved performance and/or physical properties.