W/O emulsions improved for formulators and consumers

These include oil-in-water (O/W), water-in-oil (W/O), bi-emulsions (W1+W2)/O or (O1+O2)/W, foams and multiple emulsions (W/O/W or O/W/O). In this article, we discuss how Seppic’s latest water-in-oil emulsifier can revive the interest in formulating and using W/O emulsions for different cosmetic applications. Water-in-oil emulsions are known for delivering superior emollience, enhanced drug delivery, superior moisturisation, enhanced skin coverage and water resistancy. Examples of W/O emulsifiers are beeswax, silicone copolyols and ester copolymers. However, both formulators and consumers find some drawbacks in formulating and using W/O emulsions. As it is more difficult to fragment water into fine droplets due to the strong intermolecular cohesion forces between water molecules than oil molecules, more energy is required during the manufacturing process. Also, this type of emulsion is more difficult to stabilise. Salts, glycols, waxes and hydrophobic polymers are commonly used stabilisers. Consumers find W/O emulsions less favourable in terms of sensorial profile. They find them difficult to spread, tacky, and give heavy and oily afterfeel.

Tests

The emulsifying performance of the liquid water-in-oil emulsifier from Seppic, Easynov (INCI name: Octyldodecanol & Octyldodecyl Xyloside & PEG-30 Dipolyhydroxystearate), was evaluated using conventional W/O formulation and four different oils i.e. paraffin oil, C8-C10 triglyceride, C12-15 alkylbenzoate and ethyhexyl palmitate. The emulsions were subjected to stability tests at different storage conditions i.e. room temperature (RT) and 45°C for three months. Results showed that the W/O emulsions using Easynov (now referred to as ‘the new emulsifier’) gave favourable results even after three months at both storage conditions. This is attributed to the synergy between the alkyl polyxyloside (APX) and the polymeric surfactant (Fig. 1). Being a small molecule, APX triggers rapid migration to the interface to facilitate W/O emulsification. The polymeric surfactant with higher molecular weight slowly migrates to the interface which provides excellent stabilisation to the emulsion. As the new emulsifier comes in liquid form, it is possible to formulate a W/O emulsion using cold process. This also allows formulation of modern W/O emulsion with an aqueous phase up to 80% with recommended dosage of 3% to 5%. Texture will be fluid to cream. Please refer to sample formulation 6944A (Table 1).