Loctite 620 Retaining Compound

LOCTITE 620 is an acrylic technology adhesive formulated with methacrylate ester chemistry and supplied as a green liquid with high viscosity characteristics. It is an anaerobic curing product designed for retaining applications and offers medium to high strength performance. The material polymerizes when confined between close fitting metal surfaces in the absence of air and may utilize a secondary cure with activator when faster fixture time is required. The product is specifically developed for bonding cylindrical fitting parts, especially in assemblies where bond gaps can approach 0.2 mm and where maximum strength at room temperature is necessary. It prevents loosening and leakage caused by vibration and mechanical shock while also providing enhanced temperature resistance, making it ideal for higher temperature assemblies such as locating pins in radiator units and bearings in automotive transmissions, along with locking bushings and sleeves into housings and onto shafts. In its uncured state, LOCTITE 620 has a specific gravity of 1.16 at 23 °C. Brookfield viscosity measured using RVT at 25 °C with spindle 5 at 20 rpm is 8,500 mPa·s (cP). According to EN 12092 – MV at 25 °C after 180 seconds, viscosity at a shear rate of 129 s⁻¹ is 1,800 mPa·s (cP). Cure speed depends on substrate type, bondline gap, temperature, and activator usage. Shear strength development tested in accordance with ISO 10123 on steel pins and collars shows variation across substrates such as steel, aluminum, and zinc dichromate. Bond gap conditions of 0.05 mm, 0.15 mm, and 0.2 mm influence curing performance. Temperature conditions of 5 °C, 22 °C, and 40 °C also affect rate of strength build-up. When applied on zinc dichromate steel, use of Activator SF 7471™ or SF 7649™ increases cure speed compared to assemblies without activator. After complete cure, physical properties include a coefficient of thermal expansion of 80 × 10⁻⁶ K⁻¹ measured per ISO 11359-2, thermal conductivity of 0.1 W/(m·K) according to ISO 8302, and specific heat of 0.3 kJ/(kg·K). Elongation at break determined by ISO 37 is less than 1%. Adhesive performance after curing for 24 hours at 23 °C provides compressive shear strength of 17 N/mm² (2,500 psi) on steel pins and collars as per ISO 10123. When cured for 24 hours at 23 °C followed by 24 hours at 177 °C and tested again at 23 °C, compressive shear strength increases to 24 N/mm² (3,500 psi). Environmental resistance evaluation after curing for one week at 23 °C demonstrates reliable hot strength when tested at temperatures up to 250 °C. Heat aging studies performed at 120 °C, 150 °C, and 180 °C show maintained strength levels when tested at 23 °C over exposure periods extending to 5000 hours. Chemical and solvent resistance testing indicates percentage of initial strength retention after aging under specified conditions: motor oil at 125 °C retains 100% after 100, 500, and 1000 hours; unleaded petrol at 22 °C maintains 95% strength; brake fluid at 22 °C retains 100%; water/glycol 50/50 mixture at 87 °C retains 95% after 100 hours and 80% after 500 and 1000 hours; ethanol at 22 °C maintains 100% after 100 and 500 hours and 75% after 1000 hours; acetone at 22 °C retains 95% strength throughout testing intervals. The product is not recommended for use in pure oxygen or oxygen rich systems and should not be used as a sealant for chlorine or other strong oxidizing materials. When surfaces are cleaned using aqueous washing systems, compatibility of the washing solution with the adhesive should be verified as certain aqueous solutions may influence curing and performance. Use on plastics, particularly thermoplastic materials where stress cracking may occur, is generally not advised without compatibility confirmation. For assembly, all internal and external surfaces should be cleaned using a LOCTITE cleaning solvent and allowed to dry completely. To accelerate cure speed or when larger gaps are present, apply activator and allow it to dry prior to adhesive application. For slip fitted assemblies, apply adhesive around the leading edge of the male component and inside the female component while rotating during assembly to ensure proper distribution. For press fitted assemblies, apply adhesive thoroughly to both bond surfaces and assemble at high press-on rates. For shrink fitted assemblies, apply a smooth and even film of adhesive onto the part being assembled; if heating the female part, coat the male part; if cooling the male part, coat the female part; if both heating and cooling are involved, apply adhesive to the cooled component and avoid condensation formation. Parts should remain undisturbed until adequate handling strength has developed. For disassembly, components may be removed using standard hand tools. Applying localized heat to approximately 300 °C facilitates separation while hot; if this temperature cannot be reached, apply the highest possible heat and use mechanical assistance. Cured material can be cleaned by soaking in a LOCTITE solvent followed by mechanical abrasion such as a wire brush. The product should be stored in unopened containers in a dry location. Optimal storage temperature is between 8 °C and 21 °C. Storage below 8 °C or above 28 °C may negatively affect product properties. Material removed from the original container during use may become contaminated and should not be returned. Temperature and humidity reference range is 23 °C / 50% RH = 23 ±2 °C / 50 ±5% RH. Engineering unit conversions include: (°C × 1.8) + 32 = °F; kV/mm × 25.4 = V/mil; mm ÷ 25.4 = inches; µm ÷ 25.4 = mil; N × 0.225 = lb; N/mm × 5.71 = lb/in; N/mm² × 145 = psi; MPa × 145 = psi; N·m × 8.851 = lb·in; N·m × 0.738 = lb·ft; N·mm × 0.142 = oz·in; and mPa·s = cP.