Description
American Sealants ASI 388 Electronic Grade RTV Silicone is a one-part, neutral cure, moisture-cured sealant that forms a tough, flexible, and durable rubber. Specifically designed for bonding, sealing, encapsulating, and protecting sensitive electronic assemblies, ASI 388 delivers excellent performance in harsh environments.
This electronic-grade silicone offers non-corrosive curing, low odor, superior dielectric strength, and broad adhesion to common substrates. Once cured, it withstands a wide service temperature range from -70°F to 400°F (with intermittent resistance up to 450°F).
Key Features & Benefits
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Non-corrosive, electronic grade RTV silicone
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Excellent electrical insulation properties
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Service temperature range: -70°F to 400°F (intermittent up to 450°F)
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Long-lasting durability with excellent weather, UV, and moisture resistance
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Broad adhesion range to metals, glass, plastics, and more
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Resistant to some chemicals, oils, and environmental stressors
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Non-slump formula suitable for vertical and overhead applications
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VOC compliant (21 g/L, ASTM D2369)
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Meets MIL-46106B Type 1 military specification
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UL Recognized
Common Applications
ASI 388 is used across electronics, industrial, and construction markets:
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Sealing lead wire entries
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Waterproofing sensitive electronic components
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Component mounting and circuit board protection
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Electrical connections and coaxial cable connectors
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Sealing and bonding electronic assemblies
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Encapsulation and coating of PCBs
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Engine components and general industrial sealing
Technical Specifications
| Property | Test Method | Result |
|---|---|---|
| Viscosity | ASI Method | 1,000,000 cps (Spindle 7, 4 rpm) |
| Skin Formation Time | ASI Method | 20 minutes (70°F, 50% RH) |
| Density | ASTM D1475 | 8.7 lbs./gal |
| Hardness | ASTM C661 | 30 Shore A |
| Modulus 100% | ASTM D412 | 0.37 MPa |
| Tensile Strength | ASTM D412 | 300 psi |
| Elongation at Break | ASTM D412 | 600% |
| Service Temperature | ASI Method | -70°F to 400°F (intermittent to 450°F) |
| Dielectric Strength | ASTM D149 | 500 volts/mil |
| Volume Resistivity | ASTM D257 | 3 × 10¹⁵ ohm·cm |
| Dielectric Constant (50Hz) | ASTM D150 | 3 |
| Dissipation Factor (50Hz) | ASTM D250 | 5 × 10⁻³ |
| Cure Rate | ASI Method | 24 hrs (1/8″ bead) |
Compliance & Certifications
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UL Recognized (File No. E209770)
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VOC Compliant (21 g/L ASTM D2369)
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Meets MIL-46106B Type 1 military specification
Compatible Substrates
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Glass, fiberglass, most metals, aluminum, steel
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Porous surfaces, painted surfaces
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Vinyl, PVC, rubber
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Natural & synthetic fibers
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Some plastics (substrates may vary by manufacturer, testing recommended)
Packaging & Ordering Info
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Available in cartridges, 2.8 oz squeeze tubes, pails, and drums
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Colors: clear, white, and black (custom colors available upon request)
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Shelf life: 12 months when stored at 70°F, 50% RH
Contact Chemical Concepts for technical support, substrate testing recommendations, or bulk pricing on ASI 388 Electronic Grade RTV Silicone.
Explore more options in our Silicone & Caulk section, including other neutral cure silicones such as ASI 306 Electronic Grade Self-Leveling Silicone and ASI 335 Neutral Cure RTV Silicone.
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