SILICONES
Table 1: Formulations for eyeshadow and liquid foundation. Eyeshadow formulation Ingredient
Vinyldimethicone/dimethicone crosspolymer (and) cyclopentasiloxane Phenyltrimethicone Copper mica Silver mica
Liquid foundation formulation (quick drying, light feel, low cost) Ingredient
Cyclopentasiloxane and PEG/PPG-18/18 dimethicone
Vinyldimethicone/dimethicone crosspolymer (and) cyclopentasiloxane Dimethicone Isotrideceth-5 Water
Cyclopentasiloxane and dimethiconol Sodium chloride Glycerin
Preservative
Titanium dioxide Iron oxides Yellow Iron oxides Black Iron oxides Red
antiperspirants and deodorants and formulations such as sunscreens and colour cosmetics.
%
67.5 22.5 5.0 5.0
%
12.0 3.0
10.0 1.0
60.4 0.5 2.0 3.0 0.1 6.0 1.2 0.3 0.5
Table 2: Silicone crosspolymer properties in relation to their chemical composition. Property
Crosspolymer composition
Thickening agent Ability to swell in silicone fluid (low viscosity linear, cyclosiloxane) Crosspolymer particle
As a downside of the success of crosspolymer development, their use in personal care products may be subject to application patents. This has to be taken into account by the reader.
Antiperspirants
Many antiperspirant formulations are based on cyclopentasiloxane or other cyclomethicones. The typical antiperspirant salts which are added to the cyclomethicone tend to settle which causes problems in the aerosol. Crosspolymers are very suitable thickeners, which also provide a thin, dry, non-tacky film to deliver the antiperspirant salts with reduced whitening. The rheological profile of BRB crosspolymers give superior suspension characteristics as the low shear rheology is high. Also, roll-ons and sticks can be formulated using crosspolymers. In these cases they act as a film former on the skin and can give controlled release of the product. Conventional thickeners, like silica or clays, often lack stability or do not give the right sensory profile. Furthermore, reduced whitening may be obtained by using crosspolymer gels.
Creams and lotions Fluid phase Increased swelling = increased thickening Shear thinning
Reduction in viscosity when shear is applied (e.g. mixing or rubbing out) Silicone polymer chains
Low (entanglement) Shear High (disentanglement)
Low shear (“high viscosity”): •Allowing for easier pick-up •Remains in position after application
High shear (“low viscosity): •Ease of mixing in active ingredients •Ease of product application (e.g. rub-out
Stabilising agent
Compatibility of silicone fluid (which acts as solvent) with various cosmetic ingredients.
Silicone polymer chains
Additives compatible with silicone fluid
In today’s market, consumers require products that are easy to use and effective in small quantities. Novel sensory profiles are essential, so creams that have a distinctive smooth and silky skin feel, and have a non-tacky feel can really stand out from the competition. This is where creams and lotions based on crosspolymers really can give a competitive edge. Furthermore, the crosspolymer film serves as a layer in which fragrances are contained, and where the films acts as a controlled release, providing a long lasting fragrance. Silicone crosspolymers can also offer advantages for sun care products, as they can give products a light and smooth feel, are non-tacky, increase water repellency and have a fast skin absorption. In shaving gels they can give the right feel and lubricity. They also can serve to temporarily fill up wrinkles, thus giving a smoother skin appearance.
Colour cosmetics With the evolution of cosmetic science, colour cosmetics have become increasingly sophisticated. There is a clear need for formulations that offer benefits in addition to colour. Ease of application and longer lasting colour effects have become more important. Furthermore, a non-oily appearance with a pleasant touch, both during and after application, as well as
116 PERSONAL CARE April 2012
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