Note that these HLB values show greater affinity towards an oil phase relative to an aqueous phase
Hello,
You need to know two things:
First, your "real" HLB will be:
HLB = mass fraction of HLB1 x value of HLB1 + mass fraction of HLB2 x value of HLB2.
Second, you might have competition for the interface between the two surfactant. Indeed, if there is too much surfactant (surfactant 1 + surfactant 2), they will fight to find themselves at the interface, because none of them will "like" to be anywhere else. This would lead to a non optimum emulsion and might even create destabilization.
This is, for example, the case between casein and whey protein when in an oil in water emulsion.
Since the HLB values favour, solubility of surfactant in oil, it will best for water in oil emulsion. Mixture of the two can be used with no issues if are non ionic in nature..
Hello,
You need to know two things:
First, your "real" HLB will be:
HLB = mass fraction of HLB1 x value of HLB1 + mass fraction of HLB2 x value of HLB2.
Second, you might have competition for the interface between the two surfactant. Indeed, if there is too much surfactant (surfactant 1 + surfactant 2), they will fight to find themselves at the interface, because none of them will "like" to be anywhere else. This would lead to a non optimum emulsion and might even create destabilization.
This is, for example, the case between casein and whey protein when in an oil in water emulsion.
Hi et Bon Soir, Important, as Emma pointed out, is to calculate the HLB from the fractions of the two surfactants with different HLB-values. For each specific combination of water- and oil phases, there's an optimal HLB-value, that provides maximal stability of the emulsion. Generally, emulsions become more stable, using a combination of more than one surfactants. If you will face physical instabilities, like creaming and coalescence, you'd better increase the viscosity and/or increase the repulsion between the water droplets. That latter you can do by avoiding electrolytes, by adding an ionic surfactant or , if the droplets are < 1 µm, by adding a polymer providing steric stabilization. In "lucky" cases, you could end up with a thermodynamically stable, transparent, one-phase microemulsion. This requires relatively high amounts of surfactant and a that the surfactant mixture has equal solubility in both phases. Recently, I was lucky enough to prepare on of these magic liquids, sufficiently innovative for taking a patent of its composition. / With Best Wishes & Meilleurs Saluts from/de Johan at On Target Chemistry, Uppsala, Sweden.
There should not be any problem in using two surfactants of similar HLB. More often than not, a combination of surfactants is beneficial for emulsion stability. However, it is important to check their compatibility and optimum ratio of usage by studying interfacial tension properties of the mixed surfactants in order to determine their ideal ratio for use.
Agreed witha all above, there should be no problem, but, as pointed out in the previous reply, it is always best to check! Very likely the surfactant mixture may give you an improvement in performance, or possibly you can work with less surfactant loading.
Some more points to consider
especially for surfactants with the lower HLB (actually usually mixtures of different homologes) most of the surfactants will partition into the oil phase. Measured interfacial tension therefore will much depend on ratio of surfactant to oil volume and of course on the time of equilibration and as well were surfactant is added to the oil or to the aqueous phase. The closer the HLB values of the two surfactants the closer will the behaviour to ideal mixing behaviour except if the hydrophobic parts are very dissimilar.
You may also obtain stable o/w emulsions depending on the route and mode of preparation.
HLB's (4 & 1.8) are too low. The mixed surfactants should make w/o emulsion, not o/w.
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