PEG/PPG-18/18 Dimethicone is a specialized silicone-based emulsifier primarily used to create sophisticated water-in-silicone emulsions. It provides a unique, velvet-like skin feel while stabilizing complex formulas containing both water and oil-soluble components.
- INCI Name:
- PEG/PPG-18/18 Dimethicone
- Chemical/Scientific Name:
- Siloxanes and Silicones, di-Me, 3-hydroxypropyl Me, ethers with polyethylene-polypropylene glycol
- Common Aliases:
- Silicone Glycol Copolymer, Alkyl-Modified Silicone Polyether
| Category: | Emulsifiers |
| Source Origin: | Synthetic |
| Comedogenic Rating: | 0 |
| Primary Industries: | Cosmetics, Sun Care, Hair Care |
| Solubility: | Dispersible in silicones and oils |
At a Glance: Properties & Effects:
| Texture Enhancement: | |
| Formula Stability: | |
| Irritation Risk: | |
| Penetration Enhancement: |
Primary Benefits:
- Facilitates the creation of stable water-in-silicone (W/Si) emulsions.
- Improves spreadability of heavy or high-pigment formulations.
- Provides a non-tacky, silky finish on the skin surface.
- Reduces the surface tension of liquid cosmetic products.
Potential Risks:
- Minimal risk of contact dermatitis in extremely sensitive individuals.
- Accumulation potential in hair if used in high-surfactant cleansing routines.
Biological Action & Cosmetic Profile:
Molecular architecture defines the functionality of this silicone polyether. By grafting hydrophilic polyoxyethylene (PEG) and polyoxypropylene (PPG) chains onto a hydrophobic Dimethicone backbone, chemists create an amphiphilic molecule capable of bridging the gap between incompatible phases. Unlike traditional emulsifiers that often feel heavy or “soapy,” this copolymer maintains the aesthetic lightness of silicones while managing internal water droplets within the formula.
Surface tension reduction is a core mechanical function of this ingredient. Lowering the interfacial tension between Aqua and silicone oils allows for the production of fine, uniform droplets, which results in a smoother application and enhanced shelf stability. When applied to the skin, the Dimethicone portion forms a breathable, non-occlusive film that helps prevent transepidermal water loss without clogging pores.
Formulation versatility is significantly increased through its use in sunscreens and color cosmetics. Because it can stabilize high loads of pigments and physical UV filters like Titanium Dioxide or Zinc Oxide, it prevents the clumping and “whitewash” effect often associated with mineral sun protection. The PPG component specifically aids in pigment wetting, ensuring color remains vibrant and evenly distributed throughout the wear time.
Broader Applications & Origins:
Synthesis of PEG/PPG-18/18 Dimethicone occurs through the hydrosilylation of allyl-started polyethers with hydrogen-containing siloxanes. This manufacturing process allows for precise control over the ratio of PEG to PPG, which dictates the ingredient’s final HLB (Hydrophilic-Lipophilic Balance) and its specific emulsifying power. While primarily recognized for skincare, its film-forming properties are frequently utilized in hair care to provide heat protection and enhance shine without the greasy weight of traditional oils.
Routine Integration:
Synergies:
- Volatile Silicones: Works exceptionally well with Cyclopentasiloxane to create “quick-dry” foundations and serums.
- Humectants: Enhances the delivery feel of Glycerin and Sodium Hyaluronate in cream-gel textures.
- Active Actives: Often used to stabilize sensitive water-soluble actives like Ascorbic Acid within the internal phase of an emulsion.
Conflicts:
- No known chemical conflicts; universally compatible with most cosmetic ingredients.
Clinical Consensus & Safety:
The Cosmetic Ingredient Review (CIR) Expert Panel has evaluated PEG/PPG-18/18 Dimethicone and concluded it is safe for use in the current practices of use and concentration. Clinical data indicates that the large molecular size of this polymer prevents significant percutaneous absorption, limiting any systemic exposure. Research published in dermatological journals supports its non-comedogenic and non-irritating nature, even when used in high concentrations in leave-on products. Although the “PEG” prefix occasionally raises concerns regarding 1,4-dioxane contamination, modern vacuum stripping and purification methods employed by manufacturers ensure levels remain well below regulatory safety limits.
Is PEG/PPG-18/18 Dimethicone a “plastic”?
Technically, it is a liquid silicone polymer, not a solid microplastic. It serves as a fluid conditioning agent and emulsifier rather than a structural plastic bead.
Does it cause breakouts for acne-prone skin?
Because it is a silicone derivative with a high molecular weight, it sits on the surface of the skin and does not penetrate or clog the pores. It is generally considered safe and non-acnegenic.
Why is it used in “waterproof” sunscreens?
The silicone backbone is naturally water-resistant. By acting as the continuous outer phase of an emulsion, it protects the active ingredients from being easily washed away by sweat or water.