Loctite SI 5900 Black RTV Silicone Sealant

LOCTITE® SI 5900 is a commercial-grade, low-strength, moisture-cured thixotropic silicone-based paste engineered primarily for high-reliability flange sealing on rigid assemblies. Formulated to withstand severe joint movement without compromising seal integrity, this single-component RTV silicone requires no mixing and reduces liquid migration immediately following application to the substrate.

Key Features & Industrial Benefits

• High Joint-Movement Tolerance: Explicitly engineered to withstand continuous joint movement and thermal expansion without structural failure.
• Excellent Fluid & Oil Resistance: Ideal for demanding automotive and industrial machinery applications, including oil sumps and timing covers.
• Reduced Product Migration: The thixotropic paste consistency minimizes liquid migration immediately after application, ensuring precise bead placement.
• Pre-Cure Pressure Testing: Capable of withstanding on-line, low-pressure integrity tests carried out before the product begins to cure.
• Certified Compliance: Registered to NSF Category P1 for use as a sealant in and around food processing areas where there is no possibility of direct food contact.

Technical Specifications

• Product Type: Room Temperature Vulcanizing (RTV) Silicone
• Color: Black
• Viscosity: Thixotropic paste
• Tensile Shear Strength: 1.2 N/mm² (determined according to ISO 4587 on Aluminum lapshears at a bond gap of 0.5 mm)
• Skin-Over Time: 15 minutes
• Maximum Gap Fill: Up to 1 mm
• Key Substrates: Metal, Plastic, Glass, and Ceramics
• Cure Speed Condition: Progresses via atmospheric moisture at 23±2 °C, 60±5% RH (Depth of cure depends on temperature and humidity)
• Optimal Storage Conditions: Store unopened in a dry location between 8 °C to 21 °C. Storage below 8 °C or greater than 28 °C can adversely affect product properties.

Application Guidelines

1. Surface Preparation: For maximum engineered performance, ensure all bond surfaces are completely clean and free from grease, oil, or residual contaminants.
2. Dispensing & Assembly: Since moisture curing begins immediately upon atmospheric exposure, parts should be mated within a few minutes after dispensing. 
3. Curing Cycle: Allow the bond line to fully cure before subjecting components to heavy service loads.
4. Cleanup & Safety: Excess uncured silicone material can be easily wiped away using non-polar solvents. Ensure operators are equipped with appropriate PPE before handling; consult the Safety Data Sheet (SDS) for comprehensive precautions.

Usage Restrictions: LOCTITE SI 5900 is not recommended for use in pure oxygen and/or oxygen-rich systems. Do not select this product as a sealant for chlorine or other strong oxidizing materials.

Frequently Asked Questions (FAQ)

Q: What is the maximum gap-filling capability of LOCTITE SI 5900?
A: LOCTITE SI 5900 thixotropic paste is engineered to fill gaps effectively up to a maximum of 1 mm on machined, stamped, or cast mating flanges.

Q: Can LOCTITE SI 5900 undergo pressure testing immediately after application?
A: Yes. LOCTITE SI 5900 is uniquely formulated to withstand on-line, low-pressure quality control tests carried out before the silicone material has fully initiated its moisture cure cycle.

Q: Is LOCTITE SI 5900 NSF certified for food-contact environments?
A: LOCTITE SI 5900 holds an NSF International Category P1 registration. It is certified for commercial use as a sealant in and around food processing areas, provided there is no operational possibility of direct food contact.

Q: How fast does LOCTITE SI 5900 form a skin?
A: This RTV silicone exhibits a rapid skin-over time of approximately 15 minutes under standard atmospheric conditions (23±2 °C, 60±5% RH), meaning components should be mated immediately after dispensing.

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