Soldoc DPHS: Formulating W/O lotion with a light skin feel

Soldoc DPHS: Formulating W/O lotion with a light skin feel

Introduction

Long term moisturizing effect, long lasting care effect, high protection for external attacks and water repellence are some of the benefits from the water-in-oil (W/O) emulsions. By forming an occlusive layer on the skin, they efficiently reduce the evaporative water loss from the skin, and it makes these types of formulations highly recommended for dry skin, sun care and color cosmetics formulations. However, water-in-oil (W/O) formulations have disadvantages as complex stability and heavy skin feel that are consequences of the high oil content.

The skin feel of W/O emulsions has been described as heavy, oily, sometimes even tacky. The absorption of these classical systems is often slow, and the skin surface appears oily after application.

Emollients with a low viscosity and good spreading properties will improve the spreading and absorption behavior, but it is not sufficient to achieve the desired sensory. Excellent spreading and fresher feeling can only be obtained from low viscosity W/O emulsions.

The branched structure of polyhydoxystearates leads to lower emulsion viscosities compared to molecules with other types of fatty acids. Including multiple polyhydroxystearate moieties in one molecule results in a more stable system.

To illustrate this particular property, a series of experiments has been carried out in which the oil phase content was systematically reduced from 25 wt% to 21 wt%.

It can be clearly seen that the difference is especially pronounced when the oil phase is reduced to 21wt%. Viscosities obtained with the emulsifier PEG-30 dipolyhydroxystearate (Soldoc DPHS) are the lowest viscosities observed in this testing. The reduction of the oil phase content promotes a lighter skin feel, this reduction also impacts in the lower cost of the final formulation keeping the characteristic first feeling of the W/O emulsions.

Graphic 1: Emulsion viscosities depending on the type of emulsifier and on the oil phase content

Viscosity [Pas](Brookfield splindle5/10 rpm);Oil Phase: D5/DEC

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