Interfacial activity of narrow‐range alcohol oxyethylates

Abstract

AbstractSurface and interfacial tension isotherms for narrow‐range distribution ALFOL 1214 alcohol oxyethylates were determined and compared with those obtained for broad‐range alcohol oxyethylates. Various adsorption parameters were estimated. The effectiveness of surface tension reduction decreases when the length of polyoxyethylene hydrophile increases. Micellization is observed at log cmc ranging from −4.7 to −3.3. Effects of the length and distribution of the polyoxyethylene chain on cmc are very small. A minimum of Amin/Nav0.5 is obtained for Nav=8, where Amin and Nav denote the minimum interfacial area occupied by a statistical molecule at the saturated interface and the average degree of oxyethylation, respectively. The interface becomes saturated at pC20=−5.61±0.35, where pC20 denotes the logarithm of concentration required to obtain the surface pressure equal to 20 mNm−1. The highest and lowest values of the surface excess at saturation and the free energy of adsorption, respectively, are obtained for an average degree of oxyethylation equal to 8. Parameters are correlated with the average degree of oxyethylation and the oxyethylene chain distribution parameter according to empirical second‐order polynomials. Small differences in adsorption abilities at the water/air interface are only observed for narrow‐ and broad‐range distributed oxyethylates. The differences become important for adsorption at the hexadecane/water interface. The lowest values of interfacial tension are obtained for narrow‐range oxyethylates with Nav=7 and 8. The Krefeld fabric detergency tests indicated that the best detergency was observed for alcohol oxyethylates with Nav=5–7. Narrow‐range oxyethylates exhibit somewhat better washing abilities than the broad‐range products. No relationship between detergency of alcohol oxyethylates and their abilities to adsorb at the water/air and water/hydrocarbon interfaces is observed.