Hexamethyldisiloxane is a colorless or light yellow transparent liquid with a melting point of -68.2°C and a boiling point of 100.5°C measured at 1013 hPa. The vapor pressure measured at 20 oC is 44.51 hPa. The water solubility measured at 23 oC is 0.93±0.63 mg/L. The log Kow of HMDS measured at 20 oC is 5.20. The log Koc value estimated using EPISuite v 4.10 ranges from 2.5 (MCI method) to 4.5 (Kow method). Since Episuite does not contain siloxane fragments for log Koc prediction, these values should be treated with caution. The hydrolysis potential of the test substance may have affected the determination of the partition coefficient and water solubility.
Hexamethyldisiloxane is used as a base fluid in various personal care products that require rapid evaporation and high spreadability. After mixing with simethicone, the residence time of silicone on the skin can be adjusted. Unlike other volatile fluids, hexamethyldisiloxane fluid does not cool the skin when it evaporates. Hexamethyldisiloxane is used as a carrier and diluent in the following products: skin cream lotion, bath oil, sunscreen, nail polish, antiperspirant, deodorant, hair spray, and other beauty and hair care products.