Dimethylcyclosiloxane(DMC) [(CH₃)₂ SiO]ₙ , n=3,4,5

What is Dimethylcyclosiloxane  (DMC)

Dimethylcyclosiloxane (DMC) is a mixture of cyclic oligomers consisting of hexamethylcyclotrisiloxane (D3), octamethylcyclotetrasiloxane (D4), decamethylcyclopentasiloxane (D5), and dodecamethylcyclohexasiloxane (D6), with the chemical formula [(CH₃)₂SiO]ₙ (n=3,4,5,6), whose silicon atom is connected to the two methyl groups directly attached. The substance is synthesized by hydrolysis, cracking and distillation using dimethyl dichlorosilane as raw material, and is the core intermediate for industrial preparation of organosilicon materials.

Physical properties, DMC is a colorless transparent oily liquid at room temperature with good fluidity, insoluble in water but soluble in organic solvents such as benzene and ether. Its viscosity range is 1.5~2.5 mm²/s, freezing point is as low as -40℃~-50℃, combustible and chemically stable, but ring-opening polymerization reaction can occur under acidic or alkaline conditions.

In the industrial preparation process, dimethyldichlorosilane is hydrolyzed to generate intermediates, and then the mixed cyclic body is separated by cracking and distillation, and should be protected from light and moisture when stored.

Application of Dimethylcyclosiloxane  (DMC)

In a wide range of applications, DMC is used through ring-opening polymerization to produce silicone rubbers (for seals and insulation), silicone oils (as lubricants, antifoam agents, and cosmetic additives), and silicone resins (for high-temperature coatings and electronic encapsulation). In addition, DMC can be used directly as mold release agents and lubricants in the petrochemical and textile industries, and its component D5 is also used as a volatile carrier in cosmetics.