Can surfactant and defoamer be used at the same time?. Surfactant (an amphiphilic) works based on reducing the surface tension of water binding thru hydrophobic interaction and hydrophilic interaction with water, therefore pulling off things apart and surface tension is reduce cuz water surround the surfactant.
Defoamer is basically a oil. Does using a surfactant along with defoamer affect the surfacatant efficiency? cuz defoamer creates layer on the top gas-water interface meaning surface tesion is high? so surfactant hydrophobic ends surrounds the oil?
Upon agitation there wouldn't be any air pockets? So how does defoamer work?
Hi Xin
As you mentioned surfactant reduces the surface tension of water. As you may observe, there is not air bubbles in pure water but there are more bubbles in soapy water. In fact, soap acts as a surfacatant and reduced the surface tension of water but at the same time, it also causes air bubbles to become more stable.
On the other hand, defoamers or anti-foaming agents are groups of surfactants that not only reduce the surface tension of water, but they also destabilize the air bubbles and foams.
For detailed information, please take a look at the following documents:
http://web.mit.edu/nnf/education/wettability/bubbles.html
Kind Regards,
Navid
Hi Xin
As you mentioned surfactant reduces the surface tension of water. As you may observe, there is not air bubbles in pure water but there are more bubbles in soapy water. In fact, soap acts as a surfacatant and reduced the surface tension of water but at the same time, it also causes air bubbles to become more stable.
On the other hand, defoamers or anti-foaming agents are groups of surfactants that not only reduce the surface tension of water, but they also destabilize the air bubbles and foams.
For detailed information, please take a look at the following documents:
http://web.mit.edu/nnf/education/wettability/bubbles.html
Kind Regards,
Navid
Actually, there are many dissolved air in any liquid. That is how fishes and other underwater species breathe. They have gills to take dissolved oxygen (air) out of water.
Any condition that decreases the solubility of water causes the air to come out. In that case, air is sandwiched between a thin layer of water. Then the matter is whether that air bubble lives or dies!;)
Under normal situation, water molecules at the surface tend to be attracted to the bulk. With surfectant however their tendency to be adhered to each other decreases and that is how air bubbles become stable.
On the other hand, defoamers have positive penetrating and spreading coefficients. That is, they can penetrate into air bubble and spread on its surface and cause the bubble to collapse.
By air you mean to say dissolved oxygen or (N2 + O2 + CO2) cuz we do nitrogen purging to removed dissolved oxygen.
"Any condition that decreases the solubility of water causes the air to come out"
So saturated solution is free from air? and pure water has no decrease in solubility yet there is no air?
And defoamers have the peculiar quality of positive penetration and spreading coefficients which enables them to be classified into a group within surfactants.
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