LOCTITE 648 is a single-component anaerobic retaining adhesive developed using acrylic technology with urethane methacrylate chemistry. The uncured product appears as a green liquid with low viscosity and exhibits fluorescence under UV light for inspection control. It has a specific gravity of 1.1 at 23°C and a viscosity of 500 mPa·s (cP) measured using Brookfield RVT at 25°C with spindle 2 at 20 rpm, as well as 500 mPa·s (cP) using cone and plate measurement at a shear rate of 129 s⁻¹. The adhesive cures when confined between closely fitting metal surfaces in the absence of air and may be accelerated using compatible activators such as SF 7471™, SF 7649™, or SF 7091™. This retaining compound is engineered for cylindrical fitting parts where bond gaps may approach 0.15 mm and where high strength at room temperature is required. It prevents loosening and leakage caused by vibration and mechanical shock and provides robust curing performance on active metals like mild steel as well as passive substrates including stainless steel and plated surfaces. The product offers high temperature resistance and oil tolerance, accommodating minor surface contamination from cutting oils, lubrication fluids, anti-corrosion oils, and protection fluids. Typical applications include securing gears and sprockets onto gearbox shafts and retaining rotors on electric motor shafts. Curing performance depends on substrate material, bondline gap, temperature, and activator usage. Shear strength development tested at 23°C according to ISO 10123 shows progressive strength build-up on steel, aluminum, and stainless steel surfaces. Smaller bond gaps improve curing efficiency, while higher temperatures such as 40°C accelerate strength development compared to 22°C or 5°C conditions. Activator usage significantly enhances cure speed, particularly on stainless steel components. After curing for 15 minutes at 23°C, LOCTITE 648 achieves a compressive shear strength of 13.5 N/mm² (1,960 psi) on steel pins and collars. After 72 hours at 23°C, compressive shear strength increases to 31 N/mm² (4,480 psi) on steel, 30 N/mm² (4,350 psi) on stainless steel, and 18 N/mm² (2,610 psi) on aluminum. Physical properties after 24 hours at 23°C include a glass transition temperature of 100°C according to ISO 11359-2 and a coefficient of thermal expansion of 93 × 10⁻⁶ K⁻¹ below Tg and 184 × 10⁻⁶ K⁻¹ above Tg. Torque performance evaluated under ISO 10964 demonstrates breakaway torque values of 58 N·m (515 lb·in) for M10 black oxide bolts with mild steel nuts and 32 N·m (285 lb·in) for 3/8 x 16 steel nuts (grade 2) and bolts (grade 5). Prevail torque values are 40 N·m (355 lb·in) for M10 assemblies and 16 N·m (140 lb·in) for 3/8 x 16 assemblies. Breakloose torque for 3/8 x 16 assemblies pre-torqued to 5 N·m measures 29 N·m (255 lb·in), and prevail torque under the same condition also measures 29 N·m (255 lb·in). Environmental resistance testing confirms strong durability after one week of curing at 23°C. The adhesive maintains performance at elevated temperatures up to 200°C in hot strength testing and has been tested down to -75°C (-100°F) for cold strength performance. Heat aging studies at 120°C, 150°C, 180°C, and 200°C demonstrate progressive strength retention over exposure times up to 5000 hours. Chemical and solvent resistance testing at 23°C indicates high retention of initial strength after exposure to motor oil (5W40 synthetic) at 125°C, unleaded petrol, brake fluid, water/glycol 50/50 mixture at 87°C, ethanol, acetone, B100 bio-diesel, and DEF (AdBlue®). On stainless steel assemblies, exposure to sodium hydroxide 20% and phosphoric acid 10% shows controlled strength reduction over time depending on exposure duration. The 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. Prior to application, surfaces should be cleaned with a LOCTITE cleaning solvent and allowed to dry completely. When faster cure speed is required or larger gaps are present, an activator may be applied and allowed to dry before assembly. For slip fitted assemblies, adhesive should be applied around the leading edge of the pin and inside the collar using rotational motion during assembly. For press fitted assemblies, adhesive should be thoroughly applied to both bonding surfaces and assembled using high press-on rates. For shrink fitted assemblies, the adhesive should be coated evenly to produce a smooth film; when heating the hub, coat the pin, and when cooling the pin, coat the hub while avoiding condensation on cooled parts. Components should remain undisturbed until sufficient handling strength is reached. For disassembly, standard hand tools may be used, and if required, localized heating to approximately 250°C can assist removal while hot. Cured adhesive residue may be removed by soaking in LOCTITE solvent combined with mechanical abrasion such as a wire brush. Storage should be in unopened containers in a dry location with optimal storage temperature between 8°C and 21°C. Storage below 8°C or above 28°C may negatively affect product properties, and contaminated material should not be returned to the original container. The technical data provided represent typical values obtained under laboratory conditions of 23°C and 50% relative humidity and are intended as reference information. Users are advised to conduct independent trials to confirm suitability for specific applications and working environments before production use.
