78 JOURNAL OF COSMETIC SCIENCE
In the next sections, we show approaches to explore natural-based alternatives to the
following silicones:
• Volatile (cyclic) silicones.
• Low molecular weight silicones.
• High molecular weight silicones.
CHALLENGES AND ATTEMPTS IN REPLACING VOLATILE (CYCLIC) SILICONES
The special property of cyclic silicones is their volatility, which makes these silicones feel
extremely light on skin. They are used extensively in leave-on applications ranging from
face care, sun care, color cosmetics, hair care, and particularly often in antiperspirants
and deodorants. Volatile silicones provide a light skin feel that remains after their quick
evaporation. Moreover, they are excellent solvents for all other silicones used in cosmetics.
When replacing volatile silicones in cosmetic formulations, several approaches are
undertaken. Currently, the most common approach is to replace them with hydrocarbons.
Their polarities and viscosities are similar to silicones, and they are available in a large
variety of characteristics. In case high volatility is important, low boiling hydrocarbons like
isododecane or undecane are the preferred choice. The usability of these hydrocarbons as
silicone alternatives was proven for a facial foundation: A tinted day care fluid was formulated
with an ultra-fast-spreading emollient mixture (undecane and tridecane). It was shown
that this formulation could match the properties of the silicone containing formulation
for mechanical smear resistance, rain resistance, gloss kinetics, blemish coverage, and color
homogeneity8. In case more substantivity is required, many other options are available, like
isohexadecane, C15–C19 alkanes, (hemi-)squalane9, or petrolatum liquidum10. These are
only some of the most frequently used examples among an abundance of options available.
Hydrocarbons can be used from fossil and bio-based sources as well11.
Although hydrocarbons offer a large flexibility to the formulator, they still miss some
of the desired sensorial aspects of silicones. Therefore, hydrocarbons can be mixed with
a sensorial agent. In these mixtures, often volatile hydrocarbons are used to mimic the
volatility of silicones, and the sensorial aspect is covered by a non-volatile ester such as
diheptylsuccinate. By adjusting the mixing ratio, the viscosity can be set to similar ranges
as known from dimethicones. Volatile hydrocarbons are also used by silicone polymer
producers when they must replace cyclomethicone solvents for these polymers. In all these
approaches, ingredient suppliers try to match the performance of silicones as closely as
possible to reduce the efforts needed by the formulator.
Additionally, another approach worth mentioning is the replacement of unwanted cyclic
silicones with linear dimethicones. On the one hand, this approach is affecting the full
formulation only to a minor extent, making it easier for formulators, but on the other
hand, it does not eliminate silicones completely and should only be seen as an intermediate
solution.
Beyond this ingredient-driven replacement, one could also revise the formulation from
the beginning to replace silicones. This attempt can be found in formulation areas where
silicones played a major role in the past, like anti-perspirants or deodorants formulations.
In these cases, the simple replacement by another ingredient influences so many aspects
of the formulation that a total revision is needed. For example, ester emollients like
isopropylpalmitate or propylheptylcaprylate, or ether types of molecules like PPG-15

79 Silicone Alternative Solutions in Personal Care
stearyl ether or PPG-14 butyl ether are used together with hydrocarbons, depending on the
most important needs of the formulator (including costs and sensorial aspects).
In hair oil formulations, large quantities (70–95%) of cyclic D5 are used to dissolve high
molecular weight, high-viscous dimethiconol or other silicones. Due to the high volatility
of D5, this is an elegant way to treat the hair with small amounts of these heavier silicones,
avoiding hair that feels and looks greasy. In addition to this, the high molecular weight
silicones act as rheology modifiers, i.e., to thicken the flow behavior of the final product.
Viscous hair oil formulations are needed for consumers to apply the product more easily
and to avoid the aspiration of the hair oil by the consumer. Therefore, to react to the
imminent D5 ban, substituting cyclic silicones requires alternative solutions to dissolve
high molecular weight silicones. Besides very low molecular weight dimethicones, volatile
hydrocarbons (e.g. (iso)dodecane, undecane, tridecane, isohexadecane) can be used as solvents
giving similar properties. Another silicone alternative option is replacing them with lighter
emollients like dicaprylyl carbonate, coco-caprate, or dicaprylyl ether in hair oil sprays.
CHALLENGES AND ATTEMPTS IN REPLACING LOW MOLECULAR WEIGHT
(LINEAR) SILICONES
Dimethicones are utilized in skin care applications for two primary reasons. Firstly, they
serve as conventional emollients that impart the desired sensory profile to the formulation,
resulting in a pleasant, waxy, slippery, and light silicone-like skin feel. In this regard,
lighter dimethicones with viscosities ranging from 1 to 50 cSt are employed as sensory-
inducing emollients, and they are typically incorporated in significant quantities.
The second function of silicones is to act as anti-soaping or anti-whitening agents. Certain
ingredients widely used in cosmetics, such as fatty alcohols or biopolymers, can enhance a
whitening effect when the emulsion is rubbed on the skin due to foaming. This undesired
effect is perceived as unpleasant by consumers. However, by incorporating a small amount of
a silicone into the formulation, the whitening effect can be eliminated. It is important to note
that the quantity required to achieve the anti-whitening or anti-soaping effect is significantly
lower than what would be used with a conventional emollient. Including larger amounts of
heavier dimethicones in skin-care emulsions can result in a greasy and sticky sensory feel.
With growing consumer awareness for sustainability aspects, and brands preparing for
potential regulatory bans on all types of silicones, a dimethicone-free trend is rapidly
gaining momentum. Formulators are faced with the challenging task of finding natural
and high-performing alternatives to dimethicones, often working within tight timeframes.
In the present section, light dimethicones that are commonly used in skincare for their
sensory benefits will be the focus. The initial step in this process involves identifying
natural-based emollients or mixtures that can match the sensory and physicochemical
performance properties of dimethicone at the emollient level. This can be achieved by
combining emollients with different properties, such as varying polarities, spreading
values, viscosity, and sensory characteristics. By doing so, formulators can attain a good
level of flexibility in terms of potential replacements.
However, it is worth noting that the process of selecting the appropriate emollient and
determining the ideal ratio to mimic the performance of dimethicone can be quite daunting.
The intricate nature of this decision-making process adds an additional layer of complexity
to the formulation development journey.