Specialty Silicone

Konark Silicones

Specialty Silicone

Specialty silicones are engineered to meet the stringent requirements of the aerospace industry, offering properties such as high thermal stability, low outgassing, and resistance to extreme environmental conditions. Leading manufacturers like NuSil, Momentive, and Dow have developed specific silicone products tailored for aerospace applications.

NuSil (Avantor)

NuSil has a long-standing history of providing high-purity silicones for aerospace applications. Notable products include:

SCV-2590: An ultra-low outgassing adhesive designed for sensitive aerospace components.

Silicone Polymers

CV-2500: A low outgassing adhesive suitable for bonding and sealing in spacecraft assemblies.

Silicone Polymers

CV-2948: A thermally conductive material that aids in heat dissipation for electronic components in aerospace systems.

Silicone Polymers

Momentive Performance Materials

Momentive offers a range of silicone products for the aerospace sector, including:

RTV560: A silicone rubber compound known for its high-temperature resistance and low outgassing properties, making it suitable for aerospace sealing and encapsulation.

Momentive

RTV566: Similar to RTV560 but formulated for applications requiring higher durometer hardness.

Momentive

RTV567: A flowable version designed for potting and encapsulating electronic components in aerospace applications.

Momentive

Dow

Dow provides silicone solutions tailored for aerospace needs, such as:

DOWSIL™ 6-1104: A controlled volatility sealant designed for space-grade applications, offering low outgassing and excellent adhesion properties.

Dow

DOWSIL™ 6-1125: Another space-grade silicone sealant known for its low outgassing characteristics and suitability for aerospace sealing applications.

Dow

These specialty silicones are integral to the aerospace industry, ensuring reliability and performance in critical applications such as sealing, bonding, and thermal management.

Low-outgassing silicone is a type of silicone specially formulated to minimize the release of volatile compounds over time, especially under vacuum or high-temperature conditions. Low outgassing is essential in applications where volatile compounds could interfere with sensitive components or environments, such as in space exploration, electronics, optical systems, and cleanroom applications.

Why Low-Outgassing Silicone is Needed

1. Space and Aerospace Applications:

In the vacuum of space, traditional silicone materials can release volatile organic compounds (VOCs) that may condense on critical surfaces, such as lenses, sensors, or mirrors. This outgassing can impair the function of sensitive equipment, degrade optical clarity, or interfere with electronic components.

2. Electronics and Optical Systems:

In enclosed environments with electronics, outgassed compounds can form a thin film on circuit boards, optical lenses, or screens, leading to malfunctions or degradation in performance. Low-outgassing silicones prevent these issues, ensuring reliability and longevity of components.

3. Cleanroom and Medical Applications:

In highly controlled environments, outgassing can introduce contaminants that compromise product quality, particularly in medical devices or sensitive manufacturing processes. Low-outgassing silicones help maintain the purity and cleanliness of these environments.

How Silicone is Made to be Low-Outgassing

Producing low-outgassing silicone involves several key modifications and processing techniques:

1. Formulation Control:

Reducing Volatile Components: Manufacturers carefully select raw materials with inherently low volatility and use higher-purity siloxane polymers with minimal low-molecular-weight fractions.
Modified Cross-Linking Agents: Low-outgassing silicones often use specific cross-linking agents designed to produce fewer volatile by-products. Platinum-catalyzed addition-cure systems (such as vinyl-terminated PDMS) are common in low-outgassing silicones, as they avoid the release of volatile compounds that are typical in peroxide-cured or condensation-cured systems.

2. Post-Curing:

Thermal Treatment: After initial curing, low-outgassing silicones undergo an extended post-cure process, typically at elevated temperatures (often 200°C or higher). This process helps drive off any remaining volatile compounds, reducing the amount of outgassing that occurs over time in the final product.
Vacuum Baking: In some cases, silicones are cured or post-cured under vacuum to further remove any residual volatiles. This is especially important for applications that operate in high vacuum, like space applications.

3. Use of Additives and Stabilizers:

Stabilizers to Suppress Volatiles: Specialized stabilizers can be added to prevent the breakdown of silicone under environmental stresses, minimizing the formation of volatile compounds during use.
Low-Molecular-Weight Siloxane Extraction: In some cases, silicones are subjected to solvent washes or treatments that selectively remove low-molecular-weight siloxane components, further reducing potential outgassing.

4. Quality Control and Testing:

Outgassing Testing: Low-outgassing silicones are rigorously tested to meet outgassing standards, such as those set by NASA or the European Space Agency (ESA). Testing often includes measuring Total Mass Loss (TML) and Collected Volatile Condensable Material (CVCM) to ensure the silicone meets specific low-outgassing criteria.
Certification: Silicones that meet low-outgassing standards are certified for use in vacuum-sensitive or clean environments, ensuring reliability and adherence to industry standards.

Examples of Low-Outgassing Silicone Standards

NASA Outgassing Standard: To be classified as low-outgassing, a material typically must have a TML of less than 1.0% and a CVCM of less than 0.1% when tested in a vacuum environment at elevated temperatures.
MIL-STD and ASTM Standards: The military and other organizations have similar outgassing standards for materials used in high-performance applications.

In summary, low-outgassing silicones are specially formulated and processed to minimize the release of volatile compounds, making them suitable for environments where contamination control is critical. By selecting specific curing agents, performing thermal and vacuum treatments, and adhering to strict testing standards, manufacturers create silicone products that meet the stringent requirements of industries like aerospace, electronics, and medical devices.

Specialty Silicone

Konark Silicones