Silicone Types in Cosmetics
Silicones are among the most versatile functional ingredients in personal care, spanning volatile carriers, occlusive emollients, high-gloss additives, and substantive conditioning agents. The three principal structural families used in cosmetics are cyclic silicones, linear polydimethylsiloxane (PDMS), and phenyl-substituted silicones.
- Cyclic silicones (D4/D5/D6 cyclomethicone): volatile, fast-dry, silky after-feel; D5 (decamethylcyclopentasiloxane) dominant in hair serum and antiperspirant
- Linear dimethicone (PDMS, 5–350 cSt): non-volatile emollient, skin barrier occlusion, smooth spreadability
- Phenyl trimethicone: high RI (1.46), glossy, used in hair shine serums and lip gloss
Each family occupies a distinct functional niche, and formulations often combine two or more types to deliver layered sensory and performance benefits.
Key Performance Properties
| Silicone | Viscosity | Volatility | Primary Use |
|---|---|---|---|
| Cyclomethicone D5 | 3.9 cSt | High (bp 210 °C) | Carrier solvent, antiperspirant |
| Dimethicone 5 cSt | 5 cSt | Low | Light skin feel, foundation |
| Dimethicone 350 cSt | 350 cSt | None | Emollient, barrier cream |
| Phenyl trimethicone | 38 cSt | None | Hair gloss, lip gloss |
| Amodimethicone | — | None | Substantive hair conditioner |
Viscosity is the primary handle for sensory tuning: low-viscosity dimethicones (5–20 cSt) produce a light, spreading feel; high-viscosity grades (200–1000 cSt) add richness and film thickness. Volatile cyclomethicones evaporate after application, leaving no residue — making them ideal carriers in anhydrous sticks, antiperspirant gels, and dry-touch sunscreens.
Formulation Guidelines
Successful incorporation of silicones into cosmetic systems requires attention to emulsification chemistry, loading level, and regulatory status:
- Emulsification: silicone-in-water (S/W) emulsions need specific silicone emulsifiers (cetyl PEG/PPG-10/1 dimethicone, lauryl PEG-9 polydimethylsiloxyethyl dimethicone)
- Loading: 1–5% dimethicone in O/W lotions; 10–30% cyclomethicone in hair serums; 50–80% in dry oils
- Regulatory: D4 restricted in EU rinse-off products (<0.1%); D5 under review; D6 currently permitted
Silicone emulsifiers are polyether-modified silicones that act at the silicone-water interface. Without the correct emulsifier, silicone droplets in S/W systems coalesce rapidly and the emulsion separates on storage. Hydrophilic-lipophilic balance (HLB) of the silicone emulsifier must match the overall emulsion type.
Skin and Hair Benefits
Silicones deliver clinically meaningful performance benefits across both skin-care and hair-care segments:
- Skin: reduces TEWL (trans-epidermal water loss) without pore occlusion; improves slip of sunscreen application; extends SPF performance when blended with UV filters
- Hair: forms non-sticky film on cuticle → smoothness, frizz reduction, heat protection; amino-functional grades (amodimethicone) substantive — deposit preferentially on damaged hair
The non-comedogenic character of dimethicone (even at high viscosity) distinguishes silicone-based barrier films from heavy petrolatum or vegetable-oil occlusives. In sun care, dimethicone blended with organic UV filters improves water resistance and uniform filter distribution, raising measured SPF relative to filter-only systems.
Related Reading
Silicone Oil for Cosmetics · Silicone Oil for Hair Care · D5 Decamethylcyclopentasiloxane