Cyclopentasiloxane (D5)

CAS Number:

541-02-6

Chemical / IUPAC Name:

Decamethylcyclopentasiloxane

INCI Name:

Cyclopentasiloxane

EC Number:

208-764-9

Molecular Formula:

 C10H30O5Si5

Molecular Weight:

370.77 g/mol

Other Names:

Cyclomethicone D5, D5, Decamethylcyclopentasiloxane, Silicone 245, Cyclic volatile methylsiloxane, 245 Fluid

Common Trade Names:

DC 245 (Dow Corning), XIAMETER PMX-0245 (Dow), KF-995 (Shin-Etsu), SF1202 (Momentive), CM 50 (BRB), Climcol 245

Uses:

Cyclopentasiloxane is a volatile, cyclic silicone fluid. It is widely used in the cosmetics and personal care industry as a base fluid, emollient, and solvent. Its key characteristic is its high volatility, which allows it to evaporate quickly from the skin and hair after application, leaving behind a smooth, silky, non-greasy feel and delivering other active ingredients effectively .

· Skin Care: Used in moisturizers, lotions, sunscreens, and anti-aging creams. It acts as an emollient and spreading agent, providing a smooth, silky feel without greasiness, and enhances the even application of other ingredients .

· Hair Care: Used in shampoos, conditioners, and styling products. It improves wet and dry combing, adds shine and softness, reduces frizz, and provides heat protection by sealing the hair cuticle .

· Makeup & Color Cosmetics: Used in foundations, primers, and make-up removers for its excellent spreading properties and non-greasy feel .

· Deodorants & Antiperspirants: Provides a dry, non-sticky feel upon application .

· Industrial Applications: Used as a dry cleaning solvent, degreaser, and as an intermediate in the production of other silicone polymers .

Origin

Cyclopentasiloxane is a synthetic compound derived from silica (sand). It is manufactured through a hydrolysis and polymerization process of dimethyldichlorosilane, resulting in a cyclic structure with five silicon atoms.

What does Cyclopentasiloxane (D5) do in a formulation?

• Emollient: Provides a smooth, silky, and non-greasy feel on skin and hair .
• Volatile Carrier / Solvent: Evaporates quickly at room temperature, delivering other active ingredients to the skin or hair without leaving an oily residue .
• Spreading Agent: Has low surface tension and high spreadability, allowing formulations to spread evenly and quickly across the skin or hair .
• Hair Conditioning Agent: Improves manageability, reduces friction and tangles, and adds shine and softness to hair .
• Film-Former / Water-Resistance Enhancer: Forms a thin, protective, water-repellent film on the skin, which is particularly beneficial in sunscreens to enhance water resistance .

Safety Profile (Critical):

· General Hazard Classification: Flammable liquid. Flash point is typically between 73°C and 77°C . May be an irritant to eyes and respiratory system .

· Safety Assessment: The Cosmetic Ingredient Review (CIR) has concluded that D5 is safe for use in cosmetics at current practices and concentrations . The Environmental Working Group (EWG) has rated it as safe for use at intended concentrations .

· Environmental Concerns (Critical): D5 has been identified as a Substance of Very High Concern (SVHC) under REACH due to its PBT (Persistent, Bioaccumulative, and Toxic) and vPvB (very Persistent, very Bioaccumulative) properties. It is classified as a long-lasting chemical that can accumulate in organisms and the environment .

· Regulatory Restrictions:

  · European Union: Under the EU Cosmetics Regulation, D5 is restricted to a maximum concentration of 0.1% in rinse-off cosmetic products. A draft amendment has been proposed to extend this restriction to all cosmetic products, including leave-on products .

  · Canada: It is listed as a toxic substance under CEPA and is included in the Cosmetic Ingredient Hotlist .

  · United States: The FDA does not impose specific concentration limits. It is VOC-exempt under the Clean Air Act and CARB regulations .

· Storage: Store in a cool, dry, well-ventilated area away from heat, sparks, and open flames. Keep containers tightly sealed .

Technical profile: