{"id":6518,"date":"2017-05-26T08:00:05","date_gmt":"2017-05-26T14:00:05","guid":{"rendered":"https:\/\/www.ulprospector.com\/knowledge\/?p=6518"},"modified":"2022-05-11T09:34:55","modified_gmt":"2022-05-11T15:34:55","slug":"pcc-formulating-clear-oil-water-dispersions","status":"publish","type":"post","link":"https:\/\/ulprospector.ul.com\/6518\/pcc-formulating-clear-oil-water-dispersions\/","title":{"rendered":"Let\u2019s Be Clear: Formulating Clear Oil in Water Dispersions"},"content":{"rendered":"
\"Formulating
Copyright: naphotos \/ 123RF Stock Photo<\/a><\/figcaption><\/figure>\n

Formulating clear oil in water dispersions can be one of the most challenging areas in cosmetic science. It also is an area that has probably had the most interest and follow up questions of any article I have published in the last three years.1<\/sup><\/p>\n

Technically, there are two types of dispersions that are referred to as \u201csolutions\u201d by cosmetic chemists: isotropic and micellular.<\/p>\n

Isotropic solutions<\/strong> are homogeneous mixtures of two or more ingredients in which the particles of the oil or solute are solubilized in a solvent without the use of surfactants.<\/p>\n

Clear micellular solutions<\/strong> are aqueous dispersions which use surfactants and\/or solvents to reduce the oil droplet size to <50 nanometers.<\/p>\n

Micelles are organized structures which surfactants form in water. This point is referred to as the critical micelle concentration or CMC.<\/p>\n

Above the CMC, these structures surround hydrophobic ingredients, like fragrances and oils, and can form clear dispersions if the right surfactant is used at a high enough concentration.<\/p>\n

These emulsions typically have a particle size of approximately 5-10 nanometers and should only be used when emulsifying a highly polar oil phase like a fragrance.<\/p>\n

Micellular dispersions can also be formulated using lower levels of surfactant, if high shear mechanical energy is used to reduce the particle size. However, they normally have a larger particle size.<\/p>\n

Microemulsions are a third type of micellular dispersion that require higher concentrations of surfactant versus typical micellular solutions.2<\/sup><\/p>\n

Microemulsions<\/strong>, unlike typical micellular solutions, are thermodynamically stable dispersions with a particle size of <50 nanometers that instantly form with simple mixing.<\/p>\n

They are low viscosity systems containing an aqueous phase, oil phase, surfactant, and a cosurfactant. The cosurfactant, typically a water insoluble polyol or alkanol, helps reduce the interfacial tension which decreases the size of the dispersed droplets.<\/p>\n

Other ways of formulating clear oil in water emulsions include matching the refractive index of the oil with that of the aqueous phase and molecular encapsulation using cyclodextrin<\/a> (CD). Refractive index matching normally requires an emulsifier and the use of high concentrations of polyol. This only works well with certain types of oils that have a refractive index close to that of water.<\/p>\n

These emulsions also require a thickener to help improve stability since their particle size is typically >100 nanometers. Clear water soluble CD complexes require the use of highly water soluble CD forms like alpha, gamma, or Hydroxypropyl CD and only work for ingredients that will bind inside the donut-like structure. The typical ratio of CD to complexed ingredient is 5-10 parts CD for every 1% complexed ingredient, depending on the type of ingredient used and the molecular weight.<\/p>\n

Key factors influencing emulsion formation\/stability<\/h3>\n