Silica dimethyl silylate is a chemical compound, grafted silica material it is a molecule that consists of a silica backbone with dimethyl silylate groups attached. The exact structure can vary depending on the degree of substitution of the dimethyl silylate groups.

Silica Dimethyl Silylate is a modified form of silica primarily used as a thickening, stabilizing, and texture-enhancing agent in cosmetics and personal care products. Silica, a natural mineral, is treated with dimethylsilyl groups to produce a hydrophobic (water-resistant) powder. It is valued for its ability to provide a lightweight, silky feel and is commonly found in products such as powders, foundations, lipsticks, hair products, and creams.

Chemical Composition and Structure
Silica Dimethyl Silylate is chemically modified silica (silicon dioxide, SiO2) treated with dimethylsilane compounds. This process gives the silica hydrophobic properties, improving its ability to disperse in oil-based formulations. The silica structure consists of a three-dimensional network of silicon and oxygen atoms, while the dimethylsilyl groups attached to the surface make the powder water-insoluble and give it a smooth texture.

Physical Properties
Silica Dimethyl Silylate typically appears as a white, lightweight, soft powder that is insoluble in water. It has excellent oil-absorbing properties, making it useful in cosmetic products like mattifying powders and foundations. It is also appreciated for its ability to improve formulation stability and provide a smooth, silky finish on the skin.

Chemical name

[dimethyl-(trimethylsilylamino)silyl]methane;dioxosilane

The name describes the structure of the molecule:

• Silica means silicon dioxide (SiO₂), a common mineral found in sand, quartz and many other types of rock. Silica is known for its absorbing and mattifying properties.
• Dimethyl Silylate refers to a silyl group (a silicon atom bonded to three other groups) in which two of the groups are methyl groups (CH₃) and the third group is a silicate group (SiO₄). These groups are derived from silicon and are used to alter the properties of silica, such as its solubility and its ability to interact with other ingredients.

Production Process
Silica Dimethyl Silylate is produced through a chemical reaction between silica and dimethylsilane, which attaches hydrophobic groups to the silica's surface. This treatment modifies the properties of the silica, transforming it into a powder that disperses easily in oil-based formulations and enhances the texture of final products.

Description of raw materials used in production:

• Dimethylchlorosilane - Dimethylchlorosilane is a chemical compound used as a precursor in the production of silica dimethyl silylate. It is synthesized from chlorosilanes, which are derived from silicon and chlorine.
• Methanol - Methanol, also known as methyl alcohol, is used as a solvent in the production process of silica dimethyl silylate. It is obtained from various sources, including natural gas or biomass.

The synthesis process takes place in different steps:

• Preparation of silica or silicon dioxide: it is derived from natural sources such as sand or quartz. It can also be chemically synthesized, for example, by the reaction of silicon tetrachloride with water.
• Reaction with dimethyl chloro-silicon. Silica is reacted with silicon-containing dimethyl chloroform in the presence of a catalyst. This reaction attaches the dimethyl silyl groups to the surface of the silica particles, forming Silica Dimethyl Silylate.
• Purification. The reaction mixture is then purified to isolate Silica Dimethyl Silylate with processes such as filtration, washing and drying.
• Quality control test. The final product is tested to ensure it meets the required specifications. This may involve testing for purity, particle size and other physical and chemical properties.

It appears in the form of a white powder.

What it is used for and where

Cosmetics

• Anticaking agent. This chemical compound facilitates free flow and prevents aggregation or clumping of substances in a formulation by reducing the tendency of certain particles to stick together.
• Antifoaming agent. The constituent factors for foam stabilisation are the concentration of nanoparticles and hydrophobicity. Foam, even when used in separation operations such as fractionation or flotation, can cause a decrease in density and a deterioration in quality in cosmetic products. The defoaming agent (non-polar oil, silicone oils, hydrophobic solid particles or mixtures of both) is strongly influenced by viscosity and, to an almost directly proportional extent, concentration. However, defoamers can carry an irreversible source of contamination.
• Emulsion stabilizer. Emulsions are thermodynamically unstable. Emulsion stabilisers improve the formation and stability of single and double emulsions. It should be noted that in the structure-function relationship, molar mass plays an important role.
• Skin conditioning agent - Emollient. Emollients have the characteristic of enhancing the skin barrier through a source of exogenous lipids that adhere to the skin, improving barrier properties by filling gaps in intercorneocyte clusters to improve hydration while protecting against inflammation. In practice, they have the ability to create a barrier that prevents transepidermal water loss. Emollients are described as degreasing or refreshing additives that improve the lipid content of the upper layers of the skin by preventing degreasing and drying of the skin. The problem with emollients is that many have a strong lipophilic character and are identified as occlusive ingredients; they are oily and fatty materials that remain on the skin surface and reduce transepidermal water loss. In cosmetics, emollients and moisturisers are often considered synonymous with humectants and occlusives.
• Viscosity control agent. It controls and adapts viscosity to the required level for optimal chemical and physical stability of the product and dosage in gels, suspensions, emulsions, solutions.

Applications

• Powdered Cosmetics: Silica Dimethyl Silylate is used in face powders, mattifying powders, and powder foundations for its oil-absorbing effect and ability to create a smooth, matte finish on the skin.

• Hair Care Products: Used in hair sprays and mousses, it improves texture and hold, adding volume to the hair without weighing it down.

• Creams and Gels: In lipsticks, creams, and gels, Silica Dimethyl Silylate acts as a stabilizer and thickener, improving the texture and spreadability of the product.

Health and Safety Considerations

Skin Safety
Silica Dimethyl Silylate is generally considered safe for use in cosmetic products. It is well tolerated by the skin and is not known to cause significant irritation or allergic reactions. Being a modified form of silica, it is widely used in cosmetics with minimal risks to skin health.

Allergic Reactions
Allergic reactions to Silica Dimethyl Silylate are rare. However, individuals with extremely sensitive skin should always perform a patch test before using products containing this ingredient.

Toxicity and Carcinogenicity
There is no evidence that Silica Dimethyl Silylate is toxic or carcinogenic. It has been approved for cosmetic use by regulatory bodies such as the Cosmetic Ingredient Review (CIR), which has evaluated its safety when used within recommended concentrations.

Environmental and Safety Considerations
As a derivative of silica, Silica Dimethyl Silylate is considered environmentally friendly and does not pose a significant threat to the environment. However, like all cosmetic ingredients, proper disposal practices should be followed to avoid environmental dispersion.

Regulatory Status
Silica Dimethyl Silylate is approved for use in cosmetic products in many regions, including the European Union and the United States. It is widely used in a variety of cosmetic and personal care formulations due to its functional properties and safety.

Safety

Silica dimethyl silylate is considered a safe ingredient when formulated and supplied in the final product, and is found not to be irritating or sensitizing to the respiratory tract (1)

• Molecular Formula  C₂H₆Cl₂O₂Si₂    
• Molecular Weight  189.14  g/mol
• CAS   68611-44-9
• UNII   EU2PSP0G0W
• EC number   271-893-4
• DTXSID20101306

Synonyms: 

• Dichloro(dimethyl)silane;dioxosilane

References_____________________________________________________________________

(1) Becker LC, Bergfeld WF, Belsito DV, Hill RA, Klaassen CD, Liebler D, Marks JG Jr, Shank RC, Slaga TJ, Snyder PW, Andersen FA. Safety assessment of silylates and surface-modified siloxysilicates. Int J Toxicol. 2013 May-Jun;32(3 Suppl):5S-24S. doi: 10.1177/1091581813486299. PMID: 23696579.

Abstract. The Cosmetic Ingredient Review (CIR) Expert Panel assessed the safety of silica silylate, silica dimethyl silylate, trimethylsiloxysilicate, and trifluoropropyldimethyl/trimethylsiloxysilicate as used in cosmetics. These silylates and surface-modified siloxysilicates function in cosmetics as antifoaming agents, anticaking agents, bulking agents, binders, skin-conditioning agents--emollient, skin-conditioning agents-occlusive, slip modifiers, suspension agents--nonsurfactant, and viscosity increasing agents--nonaqueous. The Expert Panel reviewed the available animal and clinical data as well as information from a previous CIR safety assessment of amorphous silica. The CIR Expert Panel concluded that silica silylate, silica dimethyl silylate, trimethylsiloxysilicate, and trifluoropropyldimethyl/trimethylsiloxysilicate are safe as used when formulated and delivered in the final product not to be irritating or sensitizing to the respiratory tract.