Loctite 641 Retaining Compound 10ml

Loctite 641 is a one-component, yellow, medium strength anaerobic retaining compound. It is a methacrylate ester that cures anaerobically, so there is no mixing.

It retains cylindrical fitting parts, especially where the assembly has to be taken apart for service. Where cure is slow or the gap is large, an activator speeds it up.

Where this product is used

• Cylindrical fitting parts that need disassembly for service
• Assemblies where cure is slow or the bond gap is large (activator recommended)
• Parts exposed to motor oil, unleaded petrol, brake fluid or water/glycol
• Assemblies that can be released with localised heat to about 250 °C

Features

• Medium strength, for parts that need disassembly for service
• One component, no mixing
• Yellow liquid; fluorescence negative, so it cannot be checked under UV light
• Anaerobic cure, with activator as the secondary cure
• Retains about 90 % of initial strength after 1,000 hours in motor oil at 125 °C
• Retains 100 % of initial strength after 1,000 hours in brake fluid at 22 °C
• Hot strength tested from 0 to 150 °C; heat ageing tested at 120 and 150 °C

Key specifications

Available sizes

Selecting the right option

Loctite 641 is the medium strength grade, for parts that have to come apart again. For high strength retaining compound see Loctite 680 High Strength Retaining Compound 50ml, or Loctite 648 High Strength, High Temperature Retaining Compound 50ml for a high strength grade that Henkel describes as offering high temperature performance.

Where cure is slow or gaps are large, see Loctite 7471 Primer T Surface Preparation Activator Aerosol 133g and Loctite SF 7649 Activator for Anaerobic Adhesives 133ml.

Using it

Parts should not be disturbed until sufficient handling strength is achieved. Cure speed depends on the materials, the gap and the temperature. The cure-speed graphs, shown for gaps of 0.05, 0.15 and 0.2 mm on steel pins and collars, are in the Henkel data sheet.

Where cure is slow or the gap is large, use Activator SF 7471 or SF 7649.

To disassemble, apply localised heat to about 250 °C and take the parts apart while hot.

Storage and handling

Store unopened in a dry location, optimally between 8 °C and 21 °C. Storage below 8 °C or above 28 °C can adversely affect the properties of the product.

Limits and safety

Not recommended for pure oxygen or oxygen-rich systems, or as a sealant for chlorine or other strong oxidisers. Not recommended on plastics, particularly thermoplastics. Check compatibility with aqueous washing systems.

Frequently asked questions

What strength is Loctite 641?

Medium strength, for parts that need disassembly for service. Compressive shear on steel pins and collars is at least 6.5 N/mm² after 24 hours at 22 °C (ISO 10123).

How do I take apart parts retained with Loctite 641?

Apply localised heat to about 250 °C and disassemble while hot.

Does Loctite 641 resist oil and brake fluid?

Yes. After 1,000 hours it retains about 90 % of its initial strength in motor oil at 125 °C and 100 % in brake fluid at 22 °C.

Can I speed up Loctite 641 with an activator?

Yes. Henkel lists Activator SF 7471 and SF 7649 where cure is slow or gaps are large.

What is the fixture time of Loctite 641?

The Henkel data sheet gives no fixture time. Cure speed depends on the materials, the gap and the temperature, and the cure-speed graphs are in the data sheet.

Can I check Loctite 641 coverage under UV light?

No. Henkel lists it as fluorescence negative.

Related products

See also: Loctite 638 Retaining Compound 50ml, Loctite 680 High Strength Retaining Compound 50ml, Loctite 648 High Strength, High Temperature Retaining Compound 50ml, Loctite 7471 Primer T Surface Preparation Activator Aerosol 133g, Loctite SF 7649 Activator for Anaerobic Adhesives 133ml.