Ethyl Heptamethyl Trisiloxane (CAS: 17861-60-8), also known as 3-Ethyl Heptamethyl Trisiloxane or Ethyl Trisiloxane, is a remarkable volatile cyclic silicone fluid prized for its unique combination of physical properties and broad applicability. Its molecular structure, featuring both methyl and ethyl groups, delivers an exceptional blend of very low viscosity, low surface tension, and high volatility, making it an invaluable ingredient in formulations ranging from high-end personal care to specialized industrial applications.

Characterized as a colorless, odorless, and transparent liquid, its physical profile is defined by an extremely low viscosity of 1.2 cSt and a density between 0.813–0.818 g/cm³ at 25 °C. This results in unparalleled spreading and wetting characteristics. Its defining feature is its volatility; it evaporates quickly from surfaces without leaving any residue, a crucial attribute for its performance in numerous products.

Within the personal care and cosmetics industry, Ethyl Heptamethyl Trisiloxane is a cornerstone ingredient for enhancing sensory appeal and functionality. It is extensively used in antiperspirants, deodorants, skin lotions, sunscreens, and color cosmetics. Its primary role is to impart an exceptionally light, non-greasy, and silky-smooth skin feel, eliminating any heavy or oily after-effect. Furthermore, it acts as an efficient carrier, enabling the even distribution of active ingredients like sunscreen agents or antiperspirant actives, facilitating the formation of a uniform protective film. Its rapid evaporation helps formulations set quickly, improving performance and durability.

Beyond personal care, this versatile fluid finds a precise role in industrial settings. It is an excellent choice as a heat transfer fluid in closed-system low-temperature oil baths. Its low viscosity, thermal stability, and suitable boiling range allow for efficient and controlled heat exchange in laboratory or industrial processes requiring precise temperature management.

In summary, Ethyl Heptamethyl Trisiloxane is a multifunctional performance fluid whose unique volatile nature delivers enhanced aesthetics in personal care and precise functionality in industrial applications. Its ability to improve product feel and performance ensures its continued importance in innovative formulations across diverse sectors.