{"id":8357,"date":"2018-06-22T08:00:24","date_gmt":"2018-06-22T14:00:24","guid":{"rendered":"https:\/\/www.ulprospector.com\/knowledge\/?p=8357"},"modified":"2023-08-31T13:53:12","modified_gmt":"2023-08-31T19:53:12","slug":"pcc-oil-in-water-emulsifiers","status":"publish","type":"post","link":"https:\/\/ulprospector.ul.com\/8357\/pcc-oil-in-water-emulsifiers\/","title":{"rendered":"Contemporary Formulation: Oil in Water Emulsifiers"},"content":{"rendered":"
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Copyright: olegdudko \/ 123RF Stock Photo<\/a><\/figcaption><\/figure>\n

Oil in water (o\/w) emulsifiers are among the most common ingredients used in skin care products and serve a multitude of functions in formulations. These include solubilizing oils\/fragrances into water, acting as primary emulsifiers, and as wetting\/dispersing agents. By far their most important role is in helping to emulsify and stabilize oil in water emulsions.<\/p>\n

Emulsifiers are molecules consisting of polar (hydrophilic) and nonpolar (lipophilic) groups that promote and the formation of stable emulsions. Oil in water emulsifiers work by lowering the surface tension of water from 72.8 millinewtons per meter (mN\/m) at 20\u00b0C to that of the oil phase, which typically is between 30-50 mN\/m. The lower the difference in the interfacial tension surface tension between the phases, the easier it is to form the emulsion.<\/p>\n

Emulsifiers must be more soluble in the water than the oil phase in order to form oil in water emulsions. This is referred to as Brancroft\u2019s rule. The exceptions to this rule are oil in water Pickering emulsifiers, which are submicron particles that preferentially disperse in water and absorb at the water-oil interface to stabilize emulsions, even though most don\u2019t reduce surface tension.<\/p>\n

In simple emulsions, finely dispersed droplets of the oil phase are surrounded by an emulsifier layer or interfacial film which helps keep the droplets separated. Emulsifiers are classified as being nonionic (no charge), anionic (negative charge) or cationic (positive charge). They also can be surface tension-reducing nonionic or charged polymers. It is commonplace to use mixtures of emulsifiers to achieve optimal results.<\/p>\n

It\u2019s critical to know the type of oil in water emulsion you want to make when choosing the emulsifier you need to use. Types include microemulsions, nano\/micellular, and lamellar gel network<\/a> (LGN)-based emulsions.<\/p>\n

LGN-based systems are the most common oil in water emulsions used in skin care formulations. LGNs are combinations of low and high hydrophilic-lipophilic balance (HLB) crystalline surfactants that can form lamellar bilayer structures that can swell, thicken, and bind water. These structures have a very low interfacial tension that can effectively emulsify and stabilize oil phases. LGNs need a high HLB surfactant to disperse and swell the low HLB surfactant.<\/p>\n

Ideally both the low and high HLB surfactants should have a melting points of >50\u00b0C to form heat-stable LGNs. The most commonly used low HLB materials include:<\/p>\n