Dimethicone
[CAS# 9006-65-9]

Identification

• Classification: API >> Digestive system medication >> Acid and gastric mucosal protective drugs
• Name: Dimethicone
• Synonyms: Polydimethylsiloxane trimethylsiloxy-terminated
• Molecular Formula: C₃H₉OSi.(C₂H₆OSi)_n.C₃H₉Si
• CAS Registry Number: 9006-65-9
• EC Number: 618-433-4
• SMILES: [Si](O[Si](C)(C)C)(C)(C)C

Safety Data

• Hazard Symbols: GHS07 Warning
• Risk Statements: H302-H315-H319-H335
• Safety Statements: P261-P280-P301+P312-P302+P352-P305+P351+P338

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Eye irritation	Eye Irrit.	2	H319

Discovery and Applications

Dimethicone, also known as polydimethylsiloxane (PDMS), is a silicon-based polymer composed of repeating units of –Si(CH₃)₂–O–. It is a member of the silicones family, a class of synthetic materials known for their flexibility, chemical stability, and resistance to moisture and temperature extremes. The compound is generally available in a wide range of viscosities, depending on the chain length and degree of polymerization, which determine its behavior in different applications.

The discovery of dimethicone is tied to the broader development of organosilicon chemistry in the early 20th century. Frederic Stanley Kipping conducted foundational research into organosilicon compounds between 1900 and 1940, laying the groundwork for industrial synthesis of silicones. Dimethicone, along with other silicone polymers, was commercially developed during and after World War II, primarily due to increased demand for materials with high thermal stability and electrical insulation properties.

Dimethicone is widely used in the cosmetic and personal care industries. It functions as a skin protectant, emollient, and conditioning agent in a variety of products including lotions, creams, shampoos, conditioners, and makeup. Its water-repellent and smooth texture helps create a barrier on the skin, reducing water loss while allowing breathability. In hair care, dimethicone is known to reduce frizz, impart shine, and improve combability by forming a thin film over the hair shaft.

In dermatology, dimethicone is used in over-the-counter and prescription products to treat dry, itchy, and irritated skin. It is often included in formulations for managing conditions such as eczema and dermatitis due to its barrier-forming and moisturizing properties. It is also a common ingredient in diaper rash creams, where it provides a protective layer against moisture and irritants.

Pharmaceutical applications of dimethicone include its use as an active ingredient in antiflatulent medications. It is used to reduce bloating, discomfort, or pain caused by excessive gas in the stomach and intestines. Dimethicone works by decreasing the surface tension of gas bubbles, allowing them to combine and be expelled more easily. This application is typically seen in chewable tablets and oral suspensions.

Dimethicone also finds utility in the medical device and industrial sectors. Its chemical inertness and lubricating properties make it suitable for use as a release agent in manufacturing, as well as a lubricant in medical equipment such as syringes and catheters. It is used in food processing, particularly in defoaming agents for fermentations and frying oils, where it helps control foam formation without reacting with other substances.

The material is known for its excellent thermal and oxidative stability, allowing it to perform under a wide range of conditions without significant degradation. This has led to its adoption in electronic, automotive, and aerospace industries, where it serves as a component in sealants, greases, and insulating materials.

Safety assessments of dimethicone have demonstrated its low toxicity and good compatibility with human skin. Regulatory bodies in various countries have approved its use in cosmetics, pharmaceuticals, and food-contact applications. It is generally considered non-irritating and non-sensitizing, though accumulation on hair and skin surfaces has led to concerns about product buildup, particularly in personal care formulations with high concentrations.

Dimethicone’s non-water-soluble nature also raises considerations for environmental persistence. While it is not classified as biodegradable, it is not considered acutely toxic to aquatic organisms at levels typically encountered in the environment. Research continues into improving the environmental profile of silicone-based compounds, including dimethicone.

In summary, dimethicone is a widely used organosilicon compound recognized for its hydrophobicity, smooth texture, and chemical stability. It plays a crucial role in cosmetics, pharmaceuticals, medical devices, and industrial processes. Its safety and functional benefits have made it a staple ingredient in many consumer and technical products.

References

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