Effects of Branched Hydrophobic Tails in Fatty Alcohol Ethoxylates on Interfacial Properties in Relation to Detergency

Abstract

The detergency of nonionic fatty alcohol ethoxylates having branched hydrophobic tails was investigated in comparison with that of corresponding linear surfactants. The various interfacial properties of aqueous surfactant solutions, such as CMC, surface tension above CMC, solubilization capacity, contact angles of surfactant solution on solid soils, and wetting time, were measured to correlate with detergency. The surface tension of linear surfactant aqueous solutions was lower below CMC, but higher above CMC than that of the branched surfactant. The solubilization capacity of linear surfactant is higher than that of branched surfactant due to lower CMC and compact packing of surfactant molecules in micelles. But the contact angle between surfactant solution and solid soil was smaller for branched surfactant, which resulted in shorter wetting time due to stronger penetrating power. The better detergency was obtained with linear surfactant for liquid soil due to higher solubilization capacity, but branched surfactants removed solid soils more efficiently than linear surfactant due to stronger penetrating power. The results of this study could guide in formulating the detergents depending upon the kinds of soils to be removed by detergency.