Elodie Cuq Arnaud, Alicia Roso
COSCHEM 2022 Virtual Event
Whether they are stiff, textured or curly, thin or thick, blond, red or brown, natural or color-treated, hairstyle is an essential criterion of beauty for everyone. Emollients are widely used in hair care products to improve texture and appearance of the hair. In the emollient category, one of the most employed are silicones. They are appreciated for their efficiency on different types of hair. In return, silicone oils have a low biodegradability profile and could be difficult to wash-off from hair. As sustainability concerns have been rising the last few years, efficient alternatives to silicone oils are highly desirable. The aim of this study was to evaluate the performances on different hair types of a new natural emollient as an alternative to viscous silicones. Film-forming benefits and properties were compared to silicone blends. A new bio-based molecule, hydrogenated polyfarnesene, has presented interesting film-forming and physical properties. Combined with bio-based C15-19 alkane, it creates a natural emollient. Physical properties such as viscosity and refractive index were compared to a blend of dimethicone and dimethiconol. Results showed that the natural emollient had a higher refractive index and a lower viscosity, which suggested a better shiny effect on hair. The film-forming property on hair of the [C15-19 alkane, hydrogenated polyfarnesene] blend was investigated by microscopy (Scanning Electron Microscopy - Field Emission Gun x500 x1500) compared to [dimethicone, dimethiconol] and to untreated hair (ex-vivo test on three bleached caucasian tresses per condition at room temperature, 50% relative humidity, observation 20 minutes after application). The images showed visible scales on the untreated hair. After treatment with the [C15-19 alkane, hydrogenated polyfarnesene] blend a smooth homogeneous covering film was observed, similar to the one observed with the silicone blend. Several benefits were induced by this film-forming property like thermal-protection, frizz-control and curl definition. The protective role of the bio-based emollient on hair was demonstrated by a thermal-protection ex-vivo study on virgin caucasian hair compared to the silicone blend. Treated hair was exposed to thermal stress (50 runs at 210°C). The inner integrity of the hair was evaluated using optical properties of keratin. The k-index which quantifies the optical properties of the keratin was measured before and after the thermal stress (X-polar technology). The untreated hair exposed to thermal stress showed the lower k-index, the organization of the keratin has been modified, indicating damaged hair. On the other hand, the hair treated with [C15-19 alkane, hydrogenated polyfarnesene] and exposed to thermal stress, demonstrated a higher k-index and a significant protective effect against heat damages of +38% versus the untreated hair. No significant differences were observed between silicone blends and the bio-based emollient. The evaluation of the frizz-control and curl definition effect was made on natural Brazilian tresses. 4 conditions were applied. Tress (A) was untreated, tress (B) was treated with a leave-on placebo serum, (C) was treated by a leave-on serum containing 3% of bio-based emollient and (D) was treated with a leave-on serum containing 3% of silicone blend [cyclopentasiloxane/dimethiconol]. The formulas were applied on wet hair. Then, the tresses were dried in a climatic chamber under temperature and humidity controlled conditions (20°C, 50% relative humidity for 6 hours). A better frizz-control and curl definition effect was observed on the [C15-19 alkanes/hydrogenated polyfarnesene] treated tress (C), and even more visible after six hours. [C15-19 alkane, hydrogenated polyfarnesene] blend formulated in a leave-on serum was more efficient than [cyclopentasiloxane/dimethiconol] on frizz-control and curl retention.This work confirmed that the combination of Hydrogenated polyfarnesene and C15-19 alkane constitutes an interesting sustainable ingredient for hair care thanks to its film forming properties. It protects the hair from thermal stress and improves texture and appearance of hair. This natural emollient is able to efficiently create influential hair style for everyone and offers a perfect alternative to dimethiconol blends.
Seppic Research and Innovation, 50 boulevard National, La Garenne Colombes, France