Henkel LOCTITE SI 5399 High Temperature Silicone Sealant for Industrial Ovens

LOCTITE SI 5399 High Temperature Silicone Sealant Performance

LOCTITE SI 5399 is primarily used in industrial bonding and sealing, heating engineering, industrial ovens, household electrical appliances, and industrial heating equipment. Under properly validated conditions, it is typically used in applications exposed to temperatures up to 350°C. This high-temperature capability makes the sealant a practical choice for oven doors, stove flues, heating ducts, heat shields, furnace components, electrical heating assemblies, and metal, glass, or ceramic joints located near thermal sources.

The uncured material has a typical specific gravity of 1.04 at 20°C and an extrusion rate of approximately 250 g/min through a 3 mm nozzle at the stated test pressure and temperature. At 23°C and 50% relative humidity, the exposed surface becomes tack-free in approximately five minutes. The cure then progresses inward from the surface, so bead thickness, humidity, temperature, and joint geometry influence the total time required to achieve complete performance.

Flexible Bonding and Electrical Insulation

After one week of curing at 25°C, the silicone provides a typical Shore A hardness of 33, tensile strength of 3.3 N/mm², and elongation at break of approximately 500%. This combination allows the cured bond to accommodate vibration, impact, thermal expansion, and movement between dissimilar substrates without becoming excessively rigid. Typical electrical properties include volume resistivity of 7.3 × 10¹⁵ Ω·cm and dielectric breakdown strength of 23.3 kV/mm, supporting selected electrical insulation and heating-equipment applications.

LOCTITE SI 5399 High Temperature Silicone Sealant can bond and seal many properly prepared metal, glass, ceramic, composite, and compatible elastomer surfaces. Actual adhesion varies with substrate grade, surface treatment, contamination, joint design, service load, and thermal exposure. Representative testing is essential before the product is approved for continuous production or safety-critical equipment.

7 Benefits of LOCTITE SI 5399 High Temperature Silicone Sealant

• High-temperature protection: Suitable for validated applications exposed to temperatures up to 350°C.
• One-component convenience: Requires no measuring, mixing, or separate curing agent.
• Rapid skin formation: Becomes tack-free in approximately five minutes under standard conditions.
• Thixotropic application: Reduces sagging and migration on vertical or shaped surfaces.
• Flexible cured rubber: Helps absorb vibration, shock, and thermal movement.
• Electrical insulation: Provides high volume resistivity and dielectric strength.
• Multi-substrate use: Supports bonding and sealing of metals, glass, ceramics, and compatible materials.

Application, Curing, and Storage Guidance

Clean all bonding surfaces and remove grease, oil, dust, moisture, oxidation, and loose contamination. Apply a continuous bead to one surface and assemble the parts within a few minutes because moisture curing begins immediately after exposure to air. Allow the joint to cure fully before applying heavy service loads; Henkel provides seven days as an example for full curing. Excess uncured material can be removed with a compatible non-polar solvent.

Store unopened containers in a dry location, ideally between 8°C and 21°C. Temperatures below 8°C or above 28°C may adversely affect product properties. Do not use the sealant in pure oxygen, oxygen-rich systems, or with chlorine and other strong oxidizing materials.

Official Resources and Related Silicone Sealants

Review the official LOCTITE SI 5399 technical data sheet for verified performance values, curing information, storage guidance, and safe-use recommendations. Additional product information is available through the official Henkel industrial products portfolio.

Explore our high-temperature silicone sealants for additional heat-resistant bonding and sealing products. You can also browse our industrial RTV silicone sealants for flexible gasketing, equipment sealing, and maintenance applications. Contact our sales team for quotations, package availability, technical documents, bulk quantities, and export support.