Cyclopentasiloxane

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A lightweight, liquid silicone. Used in moisturizers, conditioners, solvents, and as a delivery agent for other skin-care ingredients.

Cyclopentasiloxane (Wikipedia)
Decamethylcyclopentasiloxane
Skeletal formula of decamethylcyclopentasiloxane
Space-filling model of the decamethylcyclopentasiloxane molecule
Names
IUPAC name
Decamethyl-1,3,5,7,9,2,4,6,8,10-pentaoxapentasilecane
Other names
Cyclopentamethicone

Cyclic dimethylsiloxane pentamer
D5

2,2,4,4,6,6,8,8,10,10-Decamethylcyclopentasiloxane
Identifiers
541-02-6 YesY
1800166
ChemSpider 10451 YesY
EC Number 208-764-9
Jmol 3D image Interactive graph
Interactive graph
MeSH Decamethylcyclopentasiloxane
PubChem 10913
RTECS number GY5945200
UNII 0THT5PCI0R YesY
Properties
C10H30O5Si5
Molar mass 370.77 g·mol−1
Appearance Colourless liquid
Density 0.958 g cm−3
Melting point −47 °C; −53 °F; 226 K
Boiling point 210 °C (410 °F; 483 K)
17.03±0.72 ppb (23 °C)
Vapor pressure 20.4±1.1 Pa (25 °C)
Viscosity 3.74 cP
Hazards
Safety data sheet External MSDS
Irritant Xi
R-phrases R36/37/38
S-phrases S23, S24/25
NFPA 704
Flammability code 2: Must be moderately heated or exposed to relatively high ambient temperature before ignition can occur. Flash point between 38 and 93 °C (100 and 200 °F). E.g., diesel fuelHealth code 1: Exposure would cause irritation but only minor residual injury. E.g., turpentineReactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g., liquid nitrogenSpecial hazards (white): no codeNFPA 704 four-colored diamond
Flash point 73 °C (163 °F; 346 K)
Related compounds
Octamethylcyclotetrasiloxane
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Decamethylcyclopentasiloxane (D5) is an organosilicon compound with the formula [(CH3)2SiO]5. It is a colorless and odorless liquid that is slightly volatile. The compound is classified as a cyclomethicone. Such fluids are commonly used in cosmetics, such as deodorants, sunblocks, hair sprays and skin care products. It is becoming more common in hair conditioners, as it makes the hair easier to brush without breakage. It is also used as part of silicone based personal lubricants. D5 is considered an emollient.

In Canada, among the volume used in consumer products approximately 70% were for antiperspirants and 20% for hair care products.

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