Responding to consumer demand for renewable-based ingredients, BASF has developed a broad range of light emollients to meet this need, as Yeah-Young Baek, Dr Annette Mehling and Dr Daniela Prinz explain
A dry, light touch and a smooth, non-greasy sensation – consumers are increasingly looking for cosmetic products that deliver pleasant textures and extraordinary sensory experiences.
For a long time, cosmetics manufacturers relied on silicones to meet these expectations. These liquid synthetic materials are cosmetic all-round talents and have been used in personal care products for decades.
Nowadays, consumers' increasing desire for renewable-based and biodegradable ingredients is at odds with silicone use. But while consumers are more disapproving of non-biodegradable ingredients, they do not necessarily want to go without the sensory properties silicones provide.
Manufacturers therefore face the challenge of finding renewable-based ingredients that are as close as possible to silicones' sensorial profiles and on a par with them in terms of their performance, or which even outperform them.
In 2017, more than 3,500 new products that claimed to be 'silicone-free' were launched in Europe alone, according to the Mintel Global New Products Database (GNPD).
That number was up around 35% from the year before, and BASF expects it to rise further in the coming years as a result of increased scrutiny, including by regulators.
With its Cetiol product family, BASF is helping manufacturers create silicone alternative solutions for cosmetics that are highly compatible with commonly used ingredients, and which win over consumers with their silicone-like sensory properties.
While consumers are more disapproving of nonbiodegradable ingredients, they do not necessarily want to go without the sensory properties silicones provide
Cetiol Ultimate (INCI: Undecane and tridecane) is a readily biodegradable, ultra-fast spreading hydrocarbon with volatile properties, and is derived from 100% renewable sources.
Allowing the creation of contemporary, sophisticated textures, the ingredient's performance has been tested in multiple applications, including in a liquid foundation where it enhances colour stability and in a sunscreen oil where it delivers UV filter stability.
Cetiol Ultimate has been compared with cyclomethicone, a silicone agent known for giving skin care products a particularly light and smooth texture.
Figure 1.: Colour stability of Cetiol Ultimate compared with cyclomethicone
To assess the effect of Cetiol Ultimate on colour stability, BASF formulated a foundation containing 10% Cetiol Ultimate and a foundation containing the same amount of cyclomethicone.
The foundations were tested by two panels of 24 female volunteers. One group used the foundation containing Cetiol Ultimate, while the other used the foundation containing cyclomethicone.
The volunteers applied the foundation to their whole face with a sponge. To avoid any falsification of test results, all subjects were instructed not to use any additional topical products one day prior to and during the test period.
The cutaneous colour was measured immediately before (t0 before), immediately after application (t0 after) and after another eight hours (t8), using a MINOLTA CM700-d spectrocolorimeter.
The colour information was then converted into numerical values using the CIE L*a*b* color space model, with L* indicating lightness, a* the red to green value and b* the yellow to blue value.
Overall, the two foundations did not vary significantly (figure 1). The test results summarised by the descriptive statistics method showed that, for parameter b*, the Cetiol Ultimate foundation exhibited somewhat better colour stability eight hours after application.
With respect to the total colour difference (ΔE*), the foundation containing cyclomethicone showed a significant decrease at t8 compared with t0 after, while the silicone alternative did not.
In terms of initial skin sensation, the Cetiol Ultimate formulation delivered a very similar result to the one with cyclomethicone.
The subjects reported that, over time, the foundation formulated with Cetiol Ultimate felt significantly more powdery, while simultaneously exhibiting better coverage. The silicone alternative therefore provides a long lasting natural look.
Figure 2.: Skin sensory profile of Cetiol 4 All compared with cyclomethicone
Sun-savvy consumers diligently apply sun protection products and expect them to feel light and pleasant on their skin. As well as having to meet high consumer demands in terms of sensorial performance, formulators face the technical challenge of avoiding UV filter recrystallisation during product shelf life.
Recrystallisation of UV filters not only reduces the photoprotection afforded by a product; it can also lead to formulation instability.
Cetiol Ultimate's effect on both performance and stability was tested in a study involving two clear anhydrous sun care systems with the same sunscreen formulation base.
In order to achieve the target SPF of 30, a UV filter combination of 3.5% Uvinul T150, 3.5% Tinosorb S and 7.5% Uvinul A Plus was used.
The only difference in the formulations was that one system contained 10% Cetiol Ultimate, and the other 10% cyclomethicone.
The formulation containing Cetiol Ultimate exhibited no UV filter crystals throughout the entire stability test.
By contrast, the one containing cyclomethicone showed a rapid crystallisation of Tinosorb S after just one month of storage under the same conditions.
Therefore, Cetiol Ultimate evidently does not initiate recrystallisation of UV filters, in contrast to volatile silicones.
Figure 3.: Cetiol 4 All: Consumer tests of antiperspirant sticks
In 2016, a new member joined BASF's Cetiol product family: Cetiol 4 All (INCI: Dipropylheptyl carbonate), a light emollient that serves as a base oil for new formulation developments such as face and body care, colour care and antiperspirant sticks.
Cetiol 4 All's advantages over cyclomethicone for antiperspirant sticks were demonstrated in a two-part study.
In the first step, the sensory profiles of the two formulations were measured and compared.
In particular, the silicone alternative stood out for its low level of waxiness and remarkable smoothness just two minutes after application.
The ingredient can also compete with the reference product when it comes to absorption, dryness and tackiness. What's more, Cetiol 4 All leaves significantly less white residue on the skin than the silicone product (figure 2).
In the second part of the study, 75 volunteers evaluated the properties of the two formulations (figure 3).
In all assessed areas, the silicone alternative performed equally well or even better than the silicone. Subjects rated the dry feel of the Cetiol 4 All product better, felt it to be less sticky and preferred it to the reference product overall.
In particular, Cetiol 4 All was rated significantly better with regard to skin irritation. Based on the assessed parameters, it came out on top in the consumer test.
Cetiol Ultimate is 100% derived from renewable feedstocks, readily biodegradable and COSMOSapproved; Cetiol 4 All is moderately biodegradable and complies with the Nordic ecolabel
In addition, in clinical studies conducted to evaluate the deodorant (sniff test) and antiperspirant efficacy, both products exhibited a similar efficacy and performed well.
With Cetiol Ultimate and Cetiol 4 All, BASF offers manufacturers efficient alternatives to silicone oils that do not compromise on efficacy.
Test results show that both ingredients have very similar sensory profiles to silicones in different formulations and can outperform the reference products at the same time.
In terms of sustainability, Cetiol Ultimate offers further benefits. It is 100% derived from renewable feedstocks, readily biodegradable, COSMOS-approved and recommended for use in natural and organic formulations.
Cetiol 4 All is moderately biodegradable and complies with the Nordic ecolabel. With its wide range of applications, it can be used as an alternative to both silicones and mineral oils.
Furthermore, its cost efficiency makes it of particular interest for use in emerging markets.