• Item Name: LOCTITE® SI 5240™
• Manufacturer: Henkel
• Technologies: Alkoxy silicone, one-component, UV/visible light cure with secondary moisture cure
• Color: Clear with yellow to green tint
• Cure Type: UV/Visible light primary cure, moisture secondary cure
• Package Size: Contact Henkel for details
• Shelf Life: Optimal storage 8–21°C; storage below 8°C or above 28°C may affect properties
LOCTITE® SI 5240™ is a one-component alkoxy silicone sealant with thixotropic flow properties. It is initially cured by ultraviolet (UV) and visible light, with a secondary moisture cure for shadowed areas. The product forms a medium-strength, flexible rubber sealant, suitable for applications requiring uniform cavity fill. Biocompatibility testing according to ISO 10993 standards makes it suitable for certain medical device applications.
Bonding
Potting
Coating
Sealing
| Property | Uncured | After Mixing / Cured |
|---|---|---|
| Specific Gravity @ 23°C | 1.06 | – |
| Viscosity, Brookfield RVT, 25°C, mPa·s (cP) | 15,000–35,000 | – |
| Cure Type | UV / Visible light; secondary moisture | Fully cured after 7 days @ 22°C |
| Tack Free Time (Zeta® 7760, 225 mW/cm², s) | 50–55 | – |
| Depth of Cure (Zeta® 7200, 70 mW/cm², mm) | ≥10 | – |
| Shore Hardness, Durometer A | – | ≥40 |
| Elongation at break, ISO 527-3, % | – | 250–450 |
| Tensile Strength, ISO 527-3, N/mm² | – | ≥3 |
| Tensile Modulus at 100% elongation, N/mm² | – | 1 |
| Tear Strength, ISO 34-1, N/mm | – | 12.6 |
| Volume Shrinkage, % | – | 0.8 |
| Coefficient of Thermal Expansion, Pre Tg / Post Tg, K⁻¹ | – | 285×10⁻⁶ / 390×10⁻⁶ |
| Dielectric Breakdown Strength, kV/mm | – | 21 |
| Dielectric Constant / Dissipation Factor | – | 1 kHz: 2.8 / 0.05; 1 MHz: 2.8 / 0.004 |
| Volume Resistivity, Ω·cm | – | 1.2×10¹⁵ |
| Surface Resistivity, Ω | – | 5.15×10¹⁵ |
Notes:
Functional strength develops almost instantly after UV exposure.
Full properties develop over 72 hours.
Moisture cure continues to strengthen shadowed areas.
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