Loctite 242 Blue Medium-Strength Threadlocking Adhesive – 250 mL for Aerospace Fastening

Loctite 242 is the most widely used threadlocking adhesive in aerospace and industrial maintenance, providing medium-strength, vibration-resistant thread locking on metal fasteners while allowing disassembly with standard hand tools when maintenance requires. Its blue color is the universally recognized identifier for medium-strength threadlockers in the Loctite product family, distinguishing it from red high-strength (permanent) and purple low-strength threadlockers.

Applied as a thin liquid to fastener threads before assembly, Loctite 242 fills the microscopic voids between male and female thread surfaces and cures by anaerobic polymerization when oxygen is excluded between the mating metal threads. The cured adhesive film locks the fastener against rotation from vibration and shock loading, preventing the progressive self-loosening that causes fastener-related failures in vibrating machinery and aircraft structures.

The 250 mL bottle provides a large supply for high-consumption MRO operations, aircraft assembly, and maintenance organizations with frequent threadlocking requirements. The bottle’s precision dispensing tip allows accurate application of a controlled volume of adhesive to individual fastener threads without waste.

Technical Information

Loctite 242 is an anaerobic adhesive — it cures only in the absence of oxygen and in the presence of metal ions. When applied to fastener threads and the male-female thread assembly is completed, oxygen is excluded from the thin adhesive film between the mating surfaces. In the presence of the metal ions released from the thread surfaces, the anaerobic polymerization reaction initiates, converting the liquid adhesive to a solid thermoset polymer that fills the thread voids and locks the fastener.

The medium-strength classification of Loctite 242 is defined by the torque required to loosen a fastener assembled with the cured adhesive. Medium strength provides adequate vibration resistance for most aerospace maintenance fastening applications while allowing the fastener to be unscrewed with a standard hand tool when service requires disassembly — unlike high-strength (red) threadlockers that may require heat and impact tools for disassembly.

Cure speed depends on the metal substrate, temperature, and thread gap. Active metals like steel accelerate cure, while passive metals like stainless steel and aluminum cure more slowly. For slow-cure substrates, Loctite Primer N or similar activator primer can be used to accelerate cure to acceptable rates at room temperature.

Why Choose Loctite 242?

• ✅ Aerospace Industry Standard — Most widely used threadlocker in MRO worldwide
• ✅ Medium Strength — Vibration resistant yet hand-tool removable for maintenance
• ✅ Blue Color — Universal identification of medium-strength threadlocker
• ✅ Anaerobic Cure — Cures only in thread voids, not on exposed surfaces
• ✅ 250 mL Economy Size — Economical for high-volume MRO fastening operations

Applications

Loctite 242 is used on aircraft fasteners, panel screws, bracket bolts, accessory mounting hardware, and general industrial threaded fasteners in any application requiring medium-strength vibration-resistant thread locking with maintenance disassembly capability.

Frequently Asked Questions

Q: What strength is Loctite 242?
A: Loctite 242 is a medium-strength threadlocker. It provides strong vibration resistance but can be removed with standard hand tools, unlike high-strength red threadlockers that may require heat for removal.

Q: What is the MPN for Loctite 242 250mL bottle?
A: MPN is 135356.

Q: What is the difference between blue and red Loctite threadlocker?
A: Blue (242) is medium strength — removable with hand tools. Red (271/272) is high strength — typically requires heat for removal. Blue is used for fasteners needing maintenance access; red for permanent critical fasteners.

Q: How is Loctite 242 applied?
A: Apply a drop of Loctite 242 to the leading threads of the male fastener, then assemble. The adhesive cures as oxygen is excluded between the mating thread surfaces. Full cure takes 24 hours at room temperature.

Q: Can Loctite 242 be used on aluminum fasteners?
A: Yes, but aluminum is a passive metal that cures Loctite 242 more slowly than steel. Use Loctite Primer N or equivalent activator primer to accelerate cure on aluminum and other passive metals.