Siwin-9221
Siwin
Siwin-9221
1112-39-6
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Dimethyldimethoxysilane (Siwin-9221) is a difunctional organosilicon compound with the chemical formula C₄H₁₂O₂Si. Registered under CAS No. 1112-39-6, this compound contains both Si-C bonds and Si-O bonds in its molecular structure, with two methyl groups and two methoxy groups attached to the central silicon atom. This combination provides the compound with both chemical stability and reactive versatility.
At room temperature, Siwin-9221 appears as a colorless transparent liquid with a boiling point of 82°C and a molecular weight of 120.22 g/mol. The product is supplied with a minimum purity of 99%, determined by gas chromatography. Its refractive index measures 1.3708.
The difunctional structure of dimethyldimethoxysilane enables it to participate in hydrolysis and condensation reactions while introducing dimethylsiloxy units into silicone polymer chains. Under appropriate conditions, the methoxy groups hydrolyze to form silanol groups, which can further react with other silanol groups or active hydrogen-containing compounds. This reactivity makes Siwin-9221 useful as a building block in silicone polymer synthesis and as a surface treatment agent for inorganic fillers.
Parameter | Value |
Product No. | Siwin-9221 |
Chemical Name | Dimethyldimethoxysilane |
CAS NO. | 1112-39-6 |
Formula | C₄H₁₂O₂Si |
Molecular Weight | 120.22 |
Appearance | Colorless Transparent Liquid |
Boiling Point | 82°C |
Refractive Index (nD²⁵) | 1.3708 |
Purity | ≥99% |
Molecular Structure |  |
Siwin-9221 serves as a modifier for silicone resins, contributing to adjusted performance characteristics and processing behavior. By incorporating dimethylsiloxy units into the resin structure, it can modify flexibility, hardness, and thermal properties of the final resin product. This application serves silicone resin manufacturers formulating products for coatings, adhesives, and electrical insulation applications.
In silicone vulcanizate systems, dimethyldimethoxysilane functions as a structure control agent and chain extender. It helps manage the structuring effect of silica fillers in silicone rubber compounds, improving machining properties and extending the storage time of uncured vulcanizates. Siwin-9221 can serve as a replacement for hydroxyl silicone oil in certain formulations, offering an alternative approach to structure control through alkoxysilane chemistry. This application benefits silicone rubber manufacturers and compounders optimizing processing efficiency and material shelf life.
Dimethyldimethoxysilane is used for surface treatment of fillers in silicone rubber formulations, particularly for fumed silica (white carbon black). The methoxy groups react with hydroxyl groups on the filler surface, while the methyl groups provide a hydrophobic, organophilic coating. This surface modification improves filler dispersion in the silicone matrix and enhances the overall mechanical and processing performance of the resulting composite.
Siwin-9221 can be employed as a co-precursor in the synthesis of macroporous silica aerogels. Its difunctional structure contributes to the formation of flexible silica networks with controlled pore architectures. Silica aerogels produced using dimethyldimethoxysilane can exhibit tailored thermal insulation properties and surface hydrophobicity, relevant to advanced materials and specialty insulation applications.
Siwin-9221 is available in standard industrial packaging. The 210L iron drum contains 180 kg per drum, suitable for regular production consumption. For higher-volume operations, the 1000L IBC container holds 900 kg per unit, reducing material handling and packaging waste.
The product should be stored in tightly sealed containers at room temperature in a dry, shaded location. It is important to avoid contact with alkaline and acidic substances, as these can accelerate hydrolysis and condensation reactions. Storage areas should be situated away from fire sources due to the flammable nature of the product. Proper sealing is essential to prevent moisture ingress, which can lead to premature reaction and viscosity increase.
Siwin-9221 is manufactured under controlled process conditions with systematic quality verification at each production stage. Each batch undergoes gas chromatography analysis to confirm purity levels, along with refractive index measurement and appearance inspection. Production records and batch traceability documentation are maintained to ensure consistency and enable quality verification across production runs.
When stored in original, unopened containers under recommended conditions — sealed, at room temperature, and in a dry environment away from acids and alkalis — dimethyldimethoxysilane typically maintains its specified properties for 12 months from the date of manufacture. Actual shelf life may vary depending on storage conditions and container integrity.
In silicone rubber formulations containing silica fillers, dimethyldimethoxysilane reacts with surface hydroxyl groups on filler particles through its methoxy groups. This surface modification reduces interaction between silica particles and the silicone polymer matrix, mitigating the structuring effect (crepe hardening) that occurs during storage. The result is improved processing behavior and longer storage stability of the uncured compound.
Siwin-9221 should be stored in tightly sealed containers in a cool, dry, well-ventilated area away from direct sunlight. The product must be kept separate from acidic and alkaline materials and away from sources of ignition. Nitrogen blanketing is recommended for partially used containers to prevent moisture contamination.
In certain silicone rubber formulations, dimethyldimethoxysilane can serve as an alternative to hydroxyl silicone oil for structure control. The choice between the two depends on specific formulation requirements, processing conditions, and desired cure characteristics. Formulators should conduct comparative testing to determine the optimal structure control agent for their application.
Handling should take place in well-ventilated facilities with appropriate personal protective equipment, including chemical-resistant gloves, safety goggles, and protective clothing. Avoid inhalation of vapors and prevent contact with skin and eyes. The product is flammable and should be kept away from open flames and ignition sources. Material safety data sheets should be consulted for complete handling and emergency response guidelines before use.
