Alternative to viscous silicones

Dimethiconol, also referred to as
silicone gum, is a polymer quite similar to dimethicone (but with hydroxyl group). Dimethiconol-based blends are widely used in hair care products to improve the appearance and texture of the hair. They have film forming properties, provide a rich sensoriality and a large variety of benefits to the hair, such as thermal protection or curl definition. However, environmental concerns and sustainability expectations of consumers have been growing a lot the past few years and have led to a technical challenge: how to replace these blends with 100% natural solutions and a better biodegradability while keeping the same performance. 

Developing an alternative

Recently, a new emollient¹ (INCI: C15-19 Alkane – Hydrogenated Polyfarnesene) based on Hydrogenated Polyfarnesene was developed, an innovative molecule highly viscous that offers very interesting properties to replace dimethiconol-based blends. It creates the ideal sustainable and 100% natural alternative to viscous silicones. The carbon footprint of the blend was calculated based on the method IPCC (Intergovernmental Panel on Climate Change) 2007 GWP 100a V1.02 (EcoInvent v2.2 data base) and represented a reduction of 77% of greenhouse gas emission versus classical silicones². Finally, the blend of C15-19 Alkane – Hydrogenated Polyfarnesene is inherently biodegradable while silicones are known to have a poor biodegradability³. Figure 1 shows the comparison of physical properties of C15-19 Alkane – Hydrogenated Polyfarnesene with C15-19 Alkane, dimethicone and dimethicone/dimethiconol blend (DMD). Its viscosity is between dimethicone and DMD whereas its density is lower. Its refractive index is slightly higher, reflecting its higher brightness. 

Filmogen properties

The first step to investigate the performance of the emollient was to understand its mechanism of action. An observation by SEM-FEG (Scanning Electron Microscopy – Field Emission Gun) at x500 and x1500 magnifying was realised to identify whether the product has filmogenic properties like dimethiconol blends. DMD was chosen to be the benchmark.

Both products were applied as a pure raw material on damaged Caucasian hair tresses, from the root to the tip of the hair. Three tresses were used for each assay. The observation was done at room temperature, at 50% of relative humidity and 20 minutes after application of raw material. In figure 2, the three conditions can be observed. On the non-treated hair, the scales are visible. On the tress treated with DMD, the scales are almost not visible anymore and a smooth homogeneous covering film can be observed. On the tress treated with C15-19 Alkane – Hydrogenated Polyfarnesene, a similar result was observed where scales are not visible anymore and a smooth film covers the hair fibre. This observation suggested protective as well as sensory properties leading to further investigation. 

Thermal protective effect

The thermal protective effect was then tested on healthy Caucasian hair exposed to a thermal treatment of 50 runs at 210°C. C15-19 Alkane – Hydrogenated Polyfarnesene was compared again versus DMD. Both were tested purely on the hair tresses. The measured parameter was the integrity of the inner structure of the hair keratin through polarimetric imaging method. The optical device measures the k-index before and after thermal treatment which can be visualised on pictures of hair cross sections. A high k-index 
is represented in red and illustrates a healthy keratin whereas purple represents a low k-index and a very damaged keratin.

In figure 3, the full colour scale and the results can be observed. The non-treated hair exposed to thermal stress has a lower k-index and we can clearly see the induced damages. When the hair is exposed to thermal stress and is treated, either with DMD or C15-19 Alkane – Hydrogenated Polyfarnesene, a significant gain of +38% thermal protective effect against heat damages is observed versus non-treated hair. There are no significant differences between both treatments, meaning that their performance is similar.

The same method was then used to assess the performance of both products in a leave-on hair serum formulation. The first test condition is to treat the hair tress with the placebo serum and to expose it to thermal stress. The second and third conditions are to treat the hair tresses with the placebo formulation containing, in addition, either 3% DMD or 3% C15-19 Alkane – Hydrogenated Polyfarnesene, and to expose them to thermal stress. Results can be observed in figure 4.

The tresses having been treated have a higher k-index and a significant gain of +22% thermal protective effect on the keratin inner structure against heat damages is observed versus placebo. Once again, there
are no significant differences between both treatments, meaning that 
the performance of DMD and C15-19 Alkane - Hydrogenated Polyfarnesene is comparable.  

Sensoriality

To compare the sensoriality performance of DMD and C15-19 Alkane - Hydrogenated Polyfarnesene, a triangle test was performed by an expert panel. The principle of this triangle test is to present in a random arrangement three pre-treated tresses to the panellists. Among these samples, two are identical and the third is different. Subjects are asked to identify the tress that is different from the two others by evaluating different sensory parameters: ease of combing, glossy effect, volume control, gliding effect, greasy sensation, and presence of the product (film deposit, product feel). They can also comment on the sensory of each tress.

The test was realised on damaged Caucasian hair tresses, treated with a rinse-off hair mask containing either 3% DMD or 3% C15-19 Alkane  Hydrogenated Polyfarnesene. No significant difference was observed between the three tresses. DMD and C15-19 Alkane – Hydrogenated Polyfarnesene present therefore a similar sensory profile, based on the studied descriptors.

Volume and curls

Following the good results obtained to previous testings, further investigations were made. The evaluation 
of the volume control and curl definition effect was interesting to perform and gave the opportunity to test the performance of C15-19 Alkane –  Hydrogenated Polyfarnesene on a different hair type.
Indeed, natural Brazilian tresses 
were used and treated with a leave-
on serum. Besides the untreated hair tress, the first test condition was to treat a hair tress with the placebo serum. The second and third conditions were to treat the hair tresses with the placebo formulation containing respectively, in addition, either 3% C15-19 Alkane – Hydrogenated Polyfarnesene or 3% cyclopentasiloxane/dimethiconol (CXD). The formula was applied once on wet hair and the tresses were then dried in a climatic chamber under controlled temperature and humidity conditions at 
20°C and 50% relative humidity during six hours. The evaluation of volume control and curl definition is followed visually at the application of the formula, after four hours and up to six hours.

The non-treated condition came back to its natural look after four hours. A volume control and curl definition effect are observed on the three other conditions after four and six hours. However, the performance is better after four hours for the C15-19 Alkane – Hydrogenated Polyfarnesene treated tress and is even more important and visible after six hours.

Conclusion

Hydrogenated polyfarnesene, combined with C15-19 alkane, is a versatiletexturised ingredient bringing sensoriality and hair care performance thanks to its film forming properties. Its inert and non-polar structure makes it stable and easy to formulate and is compatible with a large variety of oily phases.

It is inherently biodegradable and a relevant 100% bio-based alternative to dimethiconol blends offering the same, and in some cases, even better hair care performance. Further investigations will be made to complete its performance profile, in hair care but also in other applications such as skin care, make-up and sun care.  

References

¹ Emogreen HP 40 (INCI: C15-19 Alkane – Hydrogenated Polyfanesene)

² Greenhouse gas emissions of silicones assessed based on the type of feedstock data coming from available public sources (Global Silicon Council)

³ Chandra, G. (1995). A Review of the Environmental Fate and Effects of Silicone Materials in Textile Applications.