Molecular structure and high temperature vulcanization (HTV) mechanism of HTV silicone rubber
HTV silicone rubber is based on high molecular weight linear polysiloxane (mainly polydimethylsiloxane – PDMS). Its main chain is composed of silicon oxygen bonds (-Si-O-), which gives the material inherent thermal stability and chemical inertness. The side groups are usually methyl, and phenyl or vinyl groups can also be introduced to adjust specific properties (such as low temperature resistance and vulcanization activity).
High temperature vulcanization process is the key to obtaining the final physical properties of HTV silicone rubber. Commonly used vulcanization systems include:
- Peroxide vulcanization: Organic peroxides are decomposed at high temperatures to generate free radicals, which initiate crosslinking between polymer chains. Suitable for general-purpose products.
- Platinum addition vulcanization: Platinum catalysts catalyze the addition reaction of silicon-hydrogen bonds with vinyl siloxane to form a stable crosslinking network without by-products. Suitable for high-purity, medical grade, food grade and applications with high electrical performance requirements.
Detailed explanation of key performance indicators of HTV silicone rubber
The superior performance of HTV silicone rubber can be quantified through a series of standardized tests:
- Thermal stability and wide temperature range adaptability:
- Operating temperature range: typically -50°C to +250°C (adjustable depending on formulation).
- Hot air aging test (ASTM D573): evaluates performance retention after long-term use at high temperatures.
- Mechanical properties:
- Hardness (Shore A, ASTM D2240): Customizable in the range of 20-90 Shore A.
- Tensile Strength and Elongation at Break (ASTM D412): Characterizes the strength and flexibility of a material.
- Tear Strength (ASTM D624): Measures the ability to resist tearing.
- Compression Set (ASTM D395): Evaluates the ability to maintain sealing properties under pressure.
- Electrical insulation properties:
- Volume resistivity (ASTM D257): > 10^14 Ω·cm.
- Dielectric strength (ASTM D149): Typically > 20 kV/mm.
- Dielectric constant and loss tangent: Stable over a wide frequency range.
- Chemical resistance and biocompatibility:
- Resistant to a wide range of chemicals, oils, and solvents (please refer to the compatibility table for details).
- Specific grades comply with FDA 21 CFR 177.2600 (food contact), USP Class VI (medical grade), LFGB and other certifications.
Precision machining and high-demand applications
HTV silicone rubber can be precisely formed by processes such as compression molding, transfer molding, extrusion and calendaring. Accurate mold design, optimized vulcanization parameters and strict quality control are essential to ensure the performance of the final product. Post-vulcanization treatment is often used to remove low molecular weight by-products and further improve material stability.
Its typical high-demand applications include:
- Aerospace seals and gaskets
- High-voltage cable accessories and insulators
- High-temperature resistant parts of automotive engines and transmission systems
- Medical-grade catheters, implantable components (specific certification required)
- Chemical-resistant seals in semiconductor manufacturing
Conclusion: Key considerations for selecting high-performance HTV silicone rubber
HTV silicone rubber is an ideal material choice for solving challenges in extreme temperature, electrical insulation, chemical compatibility and biological safety. Accurately understanding its performance indicators, differences in vulcanization systems and processing characteristics, and cooperating with suppliers with professional technical capabilities (TNSILICONE) are the basis for achieving high performance and reliability of products.
