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Why do glycols reduce formulation viscosity?
Propylene glycol is a known viscosity-decreasing agent, and I imagine all glycols would have this same effect to some extent. Does it have to do with micelle formation?
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5 Replies
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The answer to my old topic about Glycerine may help you.
chemicalmatt said:Glycerine is a polyol just as are diols (propylene glycol), which are all part of the alcohol family. All small-carbon chain alcohols decrease foam and viscosity. PEGs with longer chains do not reduce foam but they will reduce viscosity in most cases. Those hydroxyls act as a tertiary surfactant competing with your longer chain surfactants. David beats Goliath so to speak. -
Thank you @MapX ! So they are in fact competing in micelle formation? Would you see this drop in viscosity if you have polymeric stabilizers/thickeners in the formula
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@evchem2 Small polyols and other hydrophilic small molecules are able to do this because of their difussion abilities (they are very small), and their water solubility.
Polymeric stabilizers behave differently. The ones that are more hydrophilic thend to go where there is water (interphase and other free water zones). Hydrophobically modified ones tend to have their hydrophobic moieties interacting with the oil phase, while the big soluble part of the polymer would be swelling in water. They actually tend to increase viscosity.
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@ketchito thank you, I meant in a system where you were already using polymeric thickeners would you still see the effect from polyols?
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@evchem2 Got it. I think it depends on how much polymeric stabilizers reduce the difussion of polyols to the micelles (amount ant type of your polymer), but I believe the only way is to try.
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