ADHESIVE
Silicon Sealent
Silicone sealants are versatile, liquid adhesives that cure into a flexible, rubber-like solid. In industrial settings, they are primarily used for gasketing, sealing joints, and providing a weather-resistant barrier due to their excellent stability across wide temperature ranges.
Key Technical Specifications
The performance of a silicone sealant is defined by its chemical curing system and its physical properties once fully cured.
1. Curing Systems
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Acetoxy Cure: Releases acetic acid (smells like vinegar) as it cures. It is fast-curing and adheres well to glass and non-porous surfaces but can corrode sensitive metals like copper or brass.
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Neutral Cure (Alkoxy or Oxime): Releases a non-acidic byproduct. It is safe for use on metals, plastics, and masonry and offers superior adhesion for industrial piping and electronic housings.
2. Physical Properties
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Temperature Resistance: Standard silicones typically handle -50°C to +200°C. High-temperature versions (often red in color) can withstand up to 300°C+.
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Elongation at Break: This measures flexibility. High-quality industrial silicones often have an elongation of 400% to 600%, allowing them to stretch without tearing.
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Tensile Strength: Typically ranges from 1.5 to 2.5 MPa, providing a durable bond that resists mechanical stress.
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Shore A Hardness: Measures the "stiffness" of the cured rubber. Most sealants fall between 25 and 40 Shore A.
3. Application Performance
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Skin-over Time: The time it takes for the surface to become non-tacky (usually 5–20 minutes).
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Cure Rate: Typically 2mm to 3mm per 24 hours at room temperature and 50% humidity.
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Dielectric Strength: Silicones are excellent insulators, often rated around 15–20 kV/mm, making them ideal for sealing electrical junction boxes.
Comparison of Industrial Sealant Types
Feature | General Purpose Silicone | High-Temp (RTV) Silicone | Neutral Cure Silicone |
|---|---|---|---|
Typical Color | Clear, White, Black | Red, Grey | Clear, Black, Grey |
Temp Range | -50°C to 200°C | -60°C to 315°C | -50°C to 150°C |
Corrosion Risk | High (on metals) | Low | None |
Common Use | Glass, ceramics, DIY | Engine gaskets, ovens | Metal roofs, PVC, Electronics |
Industrial Applications
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Pneumatic Systems: Sealing around manifold housings and port connections where vibration is present.
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Pipe Fitting: Used as a flexible gasket maker for non-pressurized flange connections or as a secondary weather seal.
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Maintenance (RTV): "Room Temperature Vulcanizing" (RTV) silicones are used to create "formed-in-place" gaskets for gearboxes and pumps.
Proper Application Steps
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Clean: Remove all old sealant, oil, and moisture.
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Prime: Some substrates (like certain plastics) require a primer for maximum adhesion.
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Apply: Cut the nozzle at a 45° angle to the desired bead size.
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Tooling: Smooth the bead within the skin-over time to ensure a proper seal against the edges.