Ethylcellulose oleogels as innovative sunscreen formulas: an exploration using rheology and texture analysis

Ethylcellulose (EC) structures oils into oleogels whose properties depend on the ingredients used. This work aimed to evaluate emollients and the addition of Sorbitan Stearate (SMS) on the physical properties of EC oleogels and their sunscreen application. Oleogels were tested via shear rate sweep and oscillatory stress sweep. Their textural properties were also tested. Stable, shear-thinning oleogels were obtained, where increasing oil mixture complexity resulted in higher viscosity, complex modulus and yield stress. However, EC/SMS oleogels were identical in viscosity, had an increased yield stress and reduced complex modulus and phase angle. UV filters increased yield stress, but the complex modulus remained dependent on SMS. The firmness, spreadability and stickiness of tested oleogels was overall similar. Oil composition affects rheological properties, however, SMS networks appear to dominate over EC networks, as seen by the similar viscosity, yield stress and phase angle among EC/SMS oleogels. The physical properties of EC and EC/SMS oleogels have shown great potential in sunscreen applications. Hansen solubility parameters could predict EC-oil compatibility and the effect of the cooling procedure on physical EC oleogel properties should be explored in future research.