Mechanical Properties and Friction Dynamics of Organogels Solidified with Rice Paraffin.

Raw materials suitable for a sustainable society have attracted interest in the cosmetics industry. We focused on rice bran as a sustainable material and evaluated the gelation behavior of paraffin extracted from rice bran (rice paraffin) against liquid paraffin, squalane, jojoba oil, and silicone oil. In addition, the frictional properties of the prepared organogel on an artificial skin surface were evaluated using a sinusoidal motion friction evaluation system. Rice paraffin solidified all oils even at the lowest wax concentration of 5 wt%. The hardness and kinetic friction coefficient µ k increased with an increase in the wax composition. The hardness and µ k of organogels solidified with rice paraffin were smaller than those of gels solidified with petroleum-derived paraffin. These differences are caused by the smaller carbon amount of rice paraffin. The friction parameters depended on the type of oil: the µ k of RLG composed of rice and liquid paraffin was greater than that of the other three oils (R, L, and G denote rice paraffin, liquid paraffin, and gel, respectively). These findings promote the development of lipsticks and cleansing gels consisting of sustainable development goal-responsive raw materials.

Friction Dynamics of Organogels on Artificial Skin Surfaces.

Organogels are attractive formulations in cosmetics, food, and pharmaceuticals. They exhibit characteristic frictional and mechanical responses during the collapse of a mesostructure. In this study, the friction dynamics of organogels composed of five different waxes (paraffin wax, microcrystalline wax, ceresin, candelilla wax, and carnauba wax) and liquid paraffin were evaluated using a sinusoidal motion friction evaluation system. All organogels exhibited a velocity dependence of friction coefficient that increased with the acceleration of the contact probe. Depending on the ease of the crystal formation of the waxes in liquid paraffin, hydrocarbon-based waxes formed soft organogels with a low-friction coefficient, whereas ester-based, highly polar waxes formed organogels that were hard and had a high-friction coefficient.