Surface tension oxyethylated alcohol solutions

FIGURE 17.5 Surface tension changes for solutions of lauryl alcohols with various degrees of oxyethylation as a function of their concentration. 

FIGURE 17.6 Changes in surface tension of 1 wt% oxyethylated alcohol solutions as a function of (a) oxyethylation degree and (b) length and nature of the alkyl chain. 

In the case of oxyethylated alcohol solutions, there is a pronounced increase in surface tension and wettability resulting from an increase in the length of the ethylene oxide chain and, to a lesser extent, from an increase in the length of the alkyl chain. The results obtained and the literature data present a relatively complex picture of the interactions in the surface phase. The most probable hypothesis is that a change in the arrangement of molecules takes place due to an increase in the length of the alkyl chain. The structures favored are those in which ethylene oxide mers do not stick to the surface. As a result, both the interaction of oxyethylated alcohol molecules with the surface and the amount of adsorbed compound decrease. 

The comparison of surface activity of individual alcohols was performed for their 1 wt% solutions for two reasons. First, at this concentration micelles formed both in the surface phase and in the bulk phase, and they appeared in relatively high concentrations. No changes in surface tension should be observed. Second, this is a predicted concentration of alcohols as additives in model lubricating substances. Changes in the surface tension of 1 wt% alcohol solutions as a function of the degree of oxyethylation and the nature of the alkyl chain are presented in fig. 17.6. 

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