Meadowfoam seed oil as a natural dispersing agent for colorants in lipstick.

Objective Green and sustainable trends are growing and with that the demand for naturally-derived ingredients is rising. Dispersing agents are essential components of lipsticks due to their ability to wet pigment particles, reduce agglomerates, and prevent re-agglomeration by stabilizing pigment particles. In this study meadowfoam seed oil was evaluated as a pigment dispersing agent for lipsticks and compared to castor oil and octyldodecanol. Methods Dispersions of Red 7 Lake were formulated with 20, 30, and 40% solid content using castor oil, octyldodecanol, or meadowfoam seed oil. Particle size, viscosity, spreadability, wetting, oil absorption, and colour were measured. Four of the nine dispersions were then formulated into lipsticks, including all the 30% pigment dispersions and the 40% dispersion with meadowfoam seed oil. Lipsticks were tested for hardness, pay-off, friction, rheology, colour, and stability for 4 weeks. Results Average particle size was between 6 to 9 µm across the dispersions. The castor oil dispersions were more viscous, stickier, and harder to spread than the other dispersions. The wetting contact angle was very low for all three dispersing agents, indicating that all of the oils wet the pigment well. The lipsticks varied in hardness, as expected, based on differences in the viscosity of the dispersing agents, and oil absorption of the powder. Red 7 Lake absorbed the highest amount of castor oil, which contributed to higher stick hardness. The castor oil lipstick and the meadowfoam seed oil lipstick containing 40% pigment were the hardest and most elastic. The octyldodecanol lipstick was the softest. Friction was the lowest for the meadowfoam seed oil lipstick containing 40% pigment, while pay-off was the highest for the octyldodecanol lipstick. Colour of the lipsticks as a stick and after being spread on paper was very similar. Conculsion While the chemical composition and physicochemical properties of the dispersing agents were different, all three dispersing agents studied formed dispersions and lipsticks with appropriate characteristics. Meadowfoam seed oil's performance was qualitatively and quantitatively similar to castor oil and octyldodecanol. By modifying the amount of pigment and dispersing agent used, lipsticks that have similar characteristics to commercial products can be formulated.