LOCTITE 242 is a one-component anaerobic acrylic adhesive formulated with dimethacrylate ester chemistry and designed specifically for threadlocking applications. The uncured material appears as a blue liquid and exhibits fluorescence under UV light for inspection purposes. It features medium viscosity with thixotropic behavior, meaning it resists dripping and migration once applied. The product cures when confined between close-fitting metal surfaces in the absence of air and may be used with an activator as a secondary cure system when required. It is classified as a medium strength threadlocker, allowing disassembly with standard hand tools during maintenance or servicing operations.
The product has a specific gravity of 1.1 at 25°C. Brookfield viscosity values measured at 25°C using RVF with spindle 3 at 2 rpm (Helipath) are ≥5,000 mPa·s (cP), and at 20 rpm range from 800 to 1,600 mPa·s (cP). Brookfield RVT measurements at 20 rpm show viscosity values between 900 and 1,400 mPa·s (cP). Lubricity testing according to ASTM D5648 on 3/8 x 16 phosphate and oil steel nuts and bolts with washer indicates a K value range of -10 to 10 percent. The product meets lot testing requirements of Military Specification Mil-S-46163A (regional approval) and is manufactured in North America in accordance with ASTM D5363 lot control requirements.
Cure performance depends on substrate type, temperature, and activator usage. Breakaway strength development tested according to ISO 10964 on M10 steel nuts and bolts shows faster curing on steel and brass compared to stainless steel and zinc dichromate surfaces. Cure speed increases significantly at elevated temperatures such as 40°C compared to 22°C or 4°C. Where cure speed is insufficient or when bonding less active metals, the use of Activator SF 7471™ or SF 7649™ improves performance and accelerates strength development.
After 1 hour at 22°C, breakaway torque values on 3/8 x 16 steel nuts (grade 2) and bolts (grade 5) range from 5.6 to 17 N·m (50 to 150 lb·in), with prevail torque values between 1.7 and 6.8 N·m (15 to 60 lb·in). After 24 hours at 22°C, breakaway torque on 3/8 x 16 steel assemblies increases to 7.9 to 17 N·m (70 to 150 lb·in). For cadmium plated nuts and bolts, breakaway torque ranges from 1.1 to 6.8 N·m (10 to 60 lb·in), and for zinc assemblies from 2.3 to 6.8 N·m (20 to 60 lb·in). On M10 black oxide steel nuts and bolts, breakaway torque ranges from 8 to 19 N·m (71 to 168 lb·in). Prevail torque after 24 hours for 3/8 x 16 steel nuts and bolts ranges from 2.8 to 6.8 N·m (25 to 60 lb·in), while cadmium and zinc assemblies show correspondingly lower values.
Environmental resistance testing conducted after curing for 24 hours at 22°C demonstrates strong retention of strength under various conditions. Hot strength testing shows performance stability at elevated temperatures up to 150°C. Heat aging studies performed at 100°C, 120°C, and 150°C for exposure durations up to 5000 hours indicate gradual strength retention. Chemical resistance evaluation shows 100% strength retention after 1000 hours in motor oil (MIL-L-46152) at 125°C, unleaded gasoline at 22°C, brake fluid at 22°C, and leaded gasoline at 22°C. Ethanol retains approximately 95% strength after 1000 hours, acetone retains 85%, and 1,1,1 trichloroethane retains 90%. In a water/glycol 50/50 mixture at 87°C, strength retention decreases progressively to 70% after 1000 hours. DEF (AdBlue®) exposure at 22°C shows strength retention up to 105% at 100 hours and 95% thereafter.
This product is not recommended for use in pure oxygen or oxygen-rich systems and should not be selected as a sealant for chlorine or strong oxidizing materials. It is generally not recommended for plastics, particularly thermoplastics, where stress cracking may occur. Compatibility testing is advised before use on such substrates.
For assembly, all threaded surfaces should be cleaned using a LOCTITE cleaning solvent and allowed to dry completely. If bonding inactive metals or where faster cure is required, Activator 7471™ or 7649™ should be applied to threads and allowed to dry prior to adhesive application. The product should be shaken thoroughly before use, and care should be taken to avoid contact between the nozzle tip and metal surfaces. For through holes, several drops should be applied to the bolt at the nut engagement area. For blind holes, the product should be applied directly into the internal threads to the bottom of the hole. For sealing applications, a 360° bead should be applied to the leading threads of the male fitting, leaving the first thread free, ensuring complete filling of voids. For larger threads, additional product should be applied to both male and female threads before assembly and tightening.
Disassembly can typically be performed using standard hand tools. In cases of excessive engagement length where removal is difficult, localized heating to approximately 250°C is recommended before disassembling while hot. Cured product residue can be removed using LOCTITE solvent in combination with mechanical abrasion such as wire brushing.
The product should be stored in unopened containers in a dry environment. Optimal storage temperature is between 8°C and 21°C. Storage below 8°C or above 28°C may adversely affect product properties. Contaminated material should not be returned to the original container. The technical data provided represent typical laboratory values and are intended for reference purposes only. Users are advised to conduct their own testing to confirm suitability for specific applications and operating conditions.
