[eternalsound]

Hello everyone!

For last month I have been struggling to get a stable (without separation) emulsion composed of ester (triacetin) and water. Unfortunately I am not a skilled person in the area so I decided to find some help on the internet. I have been testing different emulsifiers to get water-in-oil emulsion type. The ratio between the ester and water is 20:1, and water phase (about 70% is water) contains protein (about 1%), sodium chloride of 10% and sorbitol of 20%. Does anyone have experience with emulsifying esters and water and could say something about possible methods that I could apply? I tried such nonionic emulsifiers like Tween 80, Span 80 using different concentration, below and above CMC - 1%, 5%, 10%, 15%, several surfactants for textile industry, and I also used the blend system using mixtures Span/Tween 80 to get the wide range of HLB numbers (4.7-15) but to no avail. For agitation, which I know may play a crucial role, I have not exceeded 500 rpm (IKA RW20 overhead stirrer). 

[curiouscat]

Is anything in there shear sensitive? If not try stirring faster. 500 rpm is fairly low as emulsion formation goes.

I've seen some IKA mixers that will emulsify pretty much anything by squeezing it through a tiny rotor-stator gap at huge rpms.

[eternalsound]

Thank you for reply curiouscat!
Yes, there is a enzyme in the water phase, but as far as I know it is quite resistant to the mechanical stress. I have an access to another IKA devices - 18/10 that is able to create 20.000 rmps. The smaller particle size should hinder the coalescence. So far, I have been receiving the separation within few hours after the preparation. Do you think that the extreme mixing would be sufficient in this case? I would rather use the most optimal surfactant than the agitation (the serious problem with bigger volumes after re-scalling the experiment), but it is not that simple. It would be much easier to emulsify 95% of water and 5% of ester than the other way around.

[curiouscat]

I think you have a fairly good shot with the high rpm machine. We had a mixture that wasn't emulsifieng any other way and the IKA mixer worked wonders. I was a bit impressed with that machine.

Though, long term stability I am not sure of. Ours was an application where we only needed the fluids to be emulsified for the duration of a reaction.

Also, there's no harm in using surfactants + mixing. Unless your surfactant is shear sensitive. Can happen with high MW polymers.

[eternalsound]

Thanks again,

Whatever I will try is ok, because luckily it is an educational project that I participate in . I will go for that high-speed shear and I will play around with the surfactants. For water-in-oil emulsion the surfactants having HLB numbers in the range 4-6 are most recommended, however I have noticed, that the increase of concentration of Tween 80, to the certain point (HLB=15) slowed down the phase separation and lowered the volume of water (accumulated at the bottom of the tube).

[curiouscat]

Whatever I will try is ok, because luckily it is an educational project that I participate in . I will go for that high-speed shear and I will play around with the surfactants. For water-in-oil emulsion the surfactants having HLB numbers in the range 4-6 are most recommended, however I have noticed, that the increase of concentration of Tween 80, to the certain point (HLB=15) slowed down the phase separation and lowered the volume of water (accumulated at the bottom of the tube).

I'd be interested in knowing how it turns out. Do keep us posted!