Loctite 515 Flange Sealant

LOCTITE 515 is an anaerobic flange sealant formulated with methacrylate ester acrylic technology. It is supplied as a single component product requiring no mixing before use. The uncured material appears as an opaque dark purple liquid with high viscosity and exhibits fluorescence under ultraviolet light to assist inspection. Curing takes place when the adhesive is confined between close fitting metal surfaces and oxygen is excluded. Once assembled, the product forms a flexible gasket that seals rigid metal flanges and accommodates minor flange movement. It provides immediate resistance to low pressure conditions after assembly and is widely used as a form in place gasket for equipment such as pumps, compressors, thermostats, transmission housings and axle covers.

The product has specific gravity of approximately 1.1 at 25°C. Brookfield viscosity at 25°C ranges from approximately 700,000 to 1,700,000 mPa·s at 0.5 rpm using spindle TB with Helipath, and approximately 150,000 to 375,000 mPa·s at 5 rpm. Flash point information should be referenced from the Safety Data Sheet.

Cure rate depends on substrate type, bond gap, temperature and use of activator. On grit blasted steel, shear strength develops progressively over time, with higher temperatures accelerating cure and lower temperatures slowing it. Controlled bond gaps (0.05 mm to 0.25 mm) influence curing performance. When cure speed is insufficient or larger gaps are present, activators such as SF 7471 or SF 7649 may be applied to improve cure rate.

After curing for one hour at 22°C, compressive shear strength (ISO 10123) is typically at least 5.0 N/mm². After 24 hours at 22°C, similar compressive shear values are maintained. Lap shear strength on grit blasted steel after 24 hours at room temperature is approximately 6.0 N/mm², while tensile strength reaches approximately 14 N/mm². When cured for 24 hours at 90°C, lap shear strength can reach at least 6.9 N/mm².

The cured material has a coefficient of thermal expansion (80 × 10⁻⁶ K⁻¹), thermal conductivity (0.1 W/(m·K)), and specific heat (0.3 kJ/(kg·K)). The product maintains performance over a wide temperature range, including cold strength down to -75°C. Heat aging studies (100°C, 120°C, 150°C) show gradual reduction of strength depending on exposure duration.

Environmental resistance testing indicates strength retention after exposure to motor oil, gasoline, water/glycol mixtures and diesel exhaust fluid. Performance under chemical exposure depends on time and temperature conditions.

For best results, bonding surfaces should be clean and free of grease or contamination. The product is intended for close fitting flanges with gaps up to 0.25 mm. It may be applied manually as a continuous bead or via screen printing. After assembly, flanges should be tightened promptly to prevent shimming. Low pressure testing below 0.05 MPa may be performed immediately after assembly to verify sealing prior to full cure.

The product should be stored in its original unopened container in a dry environment. Recommended storage temperature: 8°C to 21°C. Storage below 8°C or above 28°C may affect product properties. The product is not recommended for use in pure oxygen or oxygen enriched systems and should not be used with strong oxidizing substances. Compatibility should be verified when used with plastics and aqueous cleaning systems.