Product details
| Grade | Loctite 641 |
| Strength | Medium strength |
| Colour | Yellow |
| Family | Retaining compounds |
| Brand | Loctite (Henkel) |
| Stock | Held in Dubai — buy one or bulk |
Pack sizes
Prices on request. Tell us the quantity you need.
Check stockWhat Loctite 641 is for
The serviceable retaining compound. Every other grade in this family is designed to make a joint permanent; 641 is deliberately medium strength at ≥6.5 N/mm², so a bearing retained with it can be pulled off again at the next overhaul without heating the housing to 250°C. Henkel names exactly that application: retention of bearings onto shafts and into housings where disassembly is required for service.
Key features
- Medium strength — designed for parts that come apart again
- ≥6.5 N/mm² compressive shear
- Medium viscosity, 400–800 mPa·s
- Full strength retained in brake fluid and ethanol to 1,000 hours
- 95% retained in unleaded petrol; 90% in motor oil at 125°C
- Cure graphs published on steel, aluminium and zinc dichromate
Typical applications
- Bearings needing removal
- Serviceable assemblies
Technical data
Uncured material
| Technology | Acrylic |
| Chemical type | Methacrylate ester |
| Appearance | Yellow liquid |
| Fluorescence | Negative |
| Components | One component — no mixing |
| Cure | Anaerobic; secondary cure by activator |
| Viscosity, Brookfield RVT 25°C | Spindle 2 at 20 rpm: 400–800 mPa·s |
| Viscosity at 2.5 rpm | 1,215–2,750 mPa·s |
| Viscosity, EN 12092 MV 25°C | 90–180 mPa·s at 277 s⁻¹ |
| Viscosity class | Medium |
| Specific gravity at 25°C | 1.07 |
Strength
Steel pins and collars at 22°C. Cure graphs cover gaps of 0.05, 0.15 and 0.2 mm.
| Compressive shear strength after 24 h (ISO 10123) | ≥6.5 N/mm² (940 psi) |
| Heat ageing data published at | 120°C and 150°C |
| Hot strength plotted to | 150°C |
Chemical resistance
As a percentage of initial strength after ageing.
| Environment | °C | 100 h | 500 h | 1,000 h |
|---|
| Brake fluid | 22 | 100% | 100% | 100% |
| Ethanol | 22 | 100% | 100% | 100% |
| Unleaded petrol | 22 | 100% | 100% | 95% |
| Motor oil (MIL-L-46152) | 125 | 95% | 95% | 90% |
| Water / glycol 50:50 | 87 | 90% | 90% | 90% |
| Acetone | 22 | 100% | 80% | 80% |
Cured material
| Coefficient of thermal expansion (ISO 11359-2) | 80 × 10⁻⁶ K⁻¹ |
| Thermal conductivity (ISO 8302) | 0.1 W/(m·K) |
| Specific heat | 0.3 kJ/(kg·K) |
How to use it
- Clean all surfaces, external and internal, with a Loctite cleaning solvent and allow to dry.
- On inactive metals, or where large gaps are present, use an activator and allow to dry.
- Slip fits: apply around the leading edge of the male part and the inside of the female part, and use a rotating motion during assembly to spread it.
- Press fits: apply thoroughly to both surfaces and assemble at high press-on rates.
- Shrink fits: coat to a smooth even film. Heating the female part — coat the male. Cooling the male part — coat the female. Doing both — apply to the cooled part, and avoid condensation on it.
- Shrink fits: coat the pin, then heat the collar to create enough clearance for free assembly.
- Do not disturb the parts until handling strength is reached.
Handling and storage
- Not recommended for pure oxygen or oxygen-rich systems.
- Not a sealant for chlorine or other strong oxidising materials.
- Not normally recommended on plastics — thermoplastics can stress-crack.
- Disassembly: hand tools first; if needed apply localised heat to about 250°C and take apart while hot. If that temperature is not possible, heat as far as you can and use mechanical aids.
- Store unopened and dry, ideally 8°C to 21°C; outside 8–28°C the properties can be affected.
- Do not return decanted product to the original container.
Choosing a retaining compound
Pick by what happens next. If the joint should never come apart, use 638 (29 N/mm², fills worn gaps) or 603 (thin, for tight fits). If it runs hot, use 620. If it will be serviced — bearings pulled at overhaul — use 641, because a high-strength grade there means heating the housing to 250°C every time.
Always read the current technical and safety data before use —
ask us and we'll send it with your quotation.
