Formula C10H30O5Si5 Appearance Colourless liquid | Density 958 kg/m³ | |
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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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Production
Commercially D5, is produced by cracking polysiloxanes. The silicone polymer equilibrated in the presence of strong base to give the pentamer:
n/5 [(CH3)2SiO]n → n [(CH3)2SiO]5The tetramer octamethylcyclotetrasiloxane is also generated. These two cyclic species are separated from the polymer by distillation.
Environment
D5 and D4 have attracted attention because they are pervasive. Although never reported as being toxic, one report suggests cyclic siloxanes can be detected in some species of aquatic life. However, other scientific reviews have determined that "Siloxane D5 does not pose a danger to the environment."