Cyclopentasiloxane (D5) CAS 541-02-6

Cyclopentasiloxane (D5) – Volatile Cyclic Silicone for Cosmetics and Personal Care

Basic Information

• CAS Number: 541-02-6

• Molecular Formula: C₁₀H₃₀O₅Si₅

• Molecular Weight: 370.77 g/mol

• INCI Name: Cyclopentasiloxane

• Synonyms: Decamethylcyclopentasiloxane, D5, Cyclopentasiloxane

• Appearance: Clear, colorless, odorless liquid

• Density: ~0.96 g/cm³ (at 20°C)

• Boiling Point: ~210°C

• Flash Point: 78°C (closed cup)

• Viscosity: ~3.5–4.5 cSt (at 25°C)

• Volatility: High (evaporates quickly from skin and hair)

• Solubility: Insoluble in water; miscible with organic solvents and oils

• Storage: Store in tightly sealed containers in a cool, dry place, away from heat and direct sunlight

Overview
Cyclopentasiloxane (commonly referred to as D5) is a low-viscosity, volatile cyclic silicone fluid widely used in cosmetic and personal care formulations. Its unique combination of properties – high volatility, excellent spreadability, low surface tension, and non-greasy feel – makes it an indispensable ingredient in a wide range of products, including deodorants, antiperspirants, creams, serums, sunscreens, hair conditioners, and color cosmetics. It acts as a carrier for active ingredients, improves product application, and imparts a smooth, silky finish without leaving a heavy or sticky residue.

Physicochemical Properties

• Volatile: Evaporates rapidly from the skin and hair surface, leaving no residue.

• Low surface tension: Enhances wetting and spreadability of formulations.

• Non-greasy: Provides a light, silky, and non-oily skin feel.

• Excellent compatibility: Miscible with most oils, esters, and other silicones.

• Thermal stability: Stable under normal processing and storage conditions.

• Non-toxic and non-irritating: Well-tolerated by skin and eyes; suitable for sensitive skin.

• Hydrophobic: Repels water, contributing to water resistance in sunscreens and other products.

Mechanism of Action
In formulations, cyclopentasiloxane acts as a volatile carrier solvent. When applied to the skin or hair, it spreads easily, delivering active ingredients evenly across the surface. It then evaporates at a controlled rate, leaving behind a thin, non-occlusive film of non-volatile ingredients (e.g., emollients, sunscreens, or pigments). This improves product performance while maintaining a light, fresh feel.

Applications

• Deodorants and antiperspirants: Provides a smooth, quick-drying application with a non-sticky finish.

• Skin care: Creams, lotions, serums, and sunscreens – improves spreadability, enhances absorption, and leaves a silky feel.

• Hair care: Conditioners, serums, and styling products – reduces frizz, adds shine, and improves manageability without weighing hair down.

• Color cosmetics: Foundations, primers, and lipsticks – improves pigment dispersion, application, and long-wear properties.

• Other: Used as a carrier for fragrances, active ingredients, and in antiperspirant sticks.

Key Benefits

• Excellent spreadability and lubricity.

• Provides a light, non-greasy, silky skin feel.

• Evaporates quickly without leaving a residue.

• Enhances the delivery of active ingredients.

• Compatible with a wide range of cosmetic ingredients.

• Improves the texture, stability, and performance of formulations.

• Safe for use in leave-on and rinse-off products.

• Non-comedogenic and suitable for sensitive skin.

Recommended Use
Typical usage levels range from 1–50% of the formulation, depending on the desired volatility, spreadability, and sensory properties. For optimal performance, incorporate into the oil phase at room temperature or with gentle heating. Can be combined with other volatile and non-volatile silicones, oils, and emulsifiers for tailored formulations.

Safety and Handling

• Generally recognized as safe for use in cosmetics at recommended concentrations.

• Low irritation potential; well-tolerated by skin and eyes.

• Avoid contact with strong oxidizers.

• Store in a cool, dry place, away from direct sunlight and heat sources.

• Use appropriate personal protective equipment (gloves, safety goggles) when handling.

• Shelf life: typically 24 months under recommended storage conditions.

Quality Assurance
Each batch is tested for purity, viscosity, and residual solvents to ensure consistent quality and compliance with cosmetic standards.