Interfacial activity of narrow-range alcohol oxyethylates

Surface and interfacial tension isotherms for narrow-range distribution ALF OL 1214 alcohol oxyethylates were determined and compared with those obtain ed for broad-range alcohol oxyethylates. Various adsorption parameters were estimated. The effectiveness of surface tension reduction decreases when t he length of polyoxyethylene hydrophile increases. Micellization is observe d at log cmc ranging from -4.7 to -3.3. Effects of the length and distribut ion of the polyoxyethylene chain on cmc are very small. A minimum of A(min) /N-av(0.5) is obtained for N-av = 8, where A(min) and N-av denote the minim um interfacial area occupied by a statistical molecule at the saturated int erface and the average degree of oxyethylation, respectively. The interface becomes saturated at pC(20) = -5.61 +/- 0.35, where pC(20) denotes the log arithm 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 avera ge degree of oxyethylation equal to 8. Parameters are correlated with the a verage degree of oxyethylation and the oxyethylene chain distribution param eter according to empirical second-order polynomials. Small differences in adsorption abilities at the water/air interface are only observed for narro w- and broad-range distributed oxyethylates. The differences become importa nt for adsorption at the hexadecane/water interface. The lowest values of i nterfacial tension are obtained for narrow-range oxyethylates with N-av = 7 and 8. The Krefeld fabric detergency tests indicated that the best deterge ncy was observed for alcohol oxyethylates with N-av = 5-7. Narrow-range oxy ethylates exhibit somewhat better washing abilities than the broad-range pr oducts. No relationship between detergency of alcohol oxyethylates and thei r abilities to adsorb at the water/air and water/hydrocarbon interfaces is observed.