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Thread-locking products are used when a joint has to be secured against loosening with dynamic load, e.g. vibration. These products also have a sealing function.

Sealing products prevent leakage of different media and can be applied in the thread as well as under head. There is no increase of the breakaway torque.

Clamping products are used for adjusting screws and securing devices. There is no increase of the breakaway torque.
These are different grades of threadlockers; colour refers to different strengths. For example, the purple threadlocker is a low strength, blue is medium and red is high strength; the green threadlocker is a special wicking grade product that allows faster and deeper penetration through the assembled parts.
Generally, anaerobic adhesives are recommended for use on metal surfaces. Some materials are more active than others and depending on the types of materials used the curing may be faster or slower.
An activator achieves two things:

a. Accelerates the cure of the anaerobic adhesives on active materials at lower temperatures or for inactive materials at room or elevated temperature.
b. Cleans the parts to be assembled, replacing the need to use solvents for surface cleaning.
We do not recommend that anaerobic adhesives be used on many types of plastics since the adhesives may cause stress cracking of the soft plastics. However, for some plastics of higher densities such as Acetal (Delrin®) the adhesives can be used without the cracking effect.
Even though these two groups of adhesives appear to be similar, they are designed for specific purposes and applications. The retaining compounds may be used for threadlocking but the threadlockers should not be used to replace retaining compounds.
Again, threadlockers and thread sealants are designed for specific purposes and applications and should not be used interchangeably. A threadlocker adhesive locks and seals the threaded parts with stronger locking/bonding strength and sometimes with friction control.. On the other hand, a pipe sealant seals threaded parts to withstand very high pressure but with lower bonding/locking strength. For locking you need bonding, which is not provided by thread sealants.
An anaerobic gasketing adhesive requires metal contact for curing and attaining the maximum strength. A gasket hinders in the process and so it is never advised to use both. It should be used instead of a gasket as gasket compresses and releases the bolt tension, which in turn causes leakage.
Anaerobic adhesives are not recommended for use in systems that contain pure oxygen or oxygen-rich environment, chlorine or strong oxidizing substances.
Thread coatings for locking and sealing are designed for single use only. Reuse is not reliable and the locking or sealing function is not defined.
There are the following options if reassembly is necessary:
  • a. Use a new, unused pre-applied screw after thoroughly cleaning the mating thread from adhesive residues.
  • b. Clean the thread and the mating thread and reassemble with an anaerobic adhesive. Parts damaged by initial assembly and use must not be reused.
An RTV (Room Temperature Vulcanization) silicone sealant is a sealant that begins to cure immediately upon being exposed to air (specifically the moisture present in the air).
Acetoxy sealants have excellent adhesion to glass or ceramics – typical surfaces in the bathroom or kitchen.
Neutral sealants must be used where metals, plastics or concrete are the substrates to be sealed. They are particularly suitable as non-corrosive sealing solution for connection and expansion joints.
The substrate areas that will be in contact with the sealant must be clean, dry and free of all loose material such as dust, dirt, rust, oil and other contaminants. Non-porous substrates should be cleaned with a solvent and clean, lint-free, cotton cloth. Wipe the surface with a solvent like Acetone or turpentine (do not use an alcohol based solvent as this may effect the curing of the silicone)
Skinning over means that the product has begun to cure and has developed a firm skin on the surface.
Tack-free time is the time taken to reach the point of losing the immediate stickiness.
Acetoxy silicones release acetic acid when curing, whereas neutral curing silicone release methanol when curing. Because neutral cure only releases methanol on curing it is therefore acid-free and does not corrode metallic surfaces as would do an acid curing silicone. Neutral curing silicones are therefore suitable for metallic surfaces such as copper, brass, bronze, zinc, and iron. It is also compatible with alkaline surfaces such as concrete, plaster and brick. Adhesion to plastics is better – e.g. PVC, ABS, polyester, acrylic, polycarbonate. Neither can silicone be over painted, nor are suitable for natural stone due to plasticizer and oil migration from the silicone.
a) All of our standard label materials typically use an acrylic pressure sensitive adhesive. Silicone adhesives are thermally more stable than are acrylic adhesives. Also, silicon perform beyond the range of acrylic adhesives. Silicone adhesives are also more expensive than acrylic adhesives
Not always. Change of Mix ratio may affect the product performance drastically.
Hot melt adhesives do have a shelf life, while the physical appearance may not change appreciably with time, the material gets progressively brittle and lose specific adhesion. Shelf life begins from the date of manufacture and hence the product should be rotated i.e. the material should be used on the first come first consumed basis.
The color of the adhesive is due to the color of the tackifier. Generally the better and stable grades of tackifiers have a lighter color. The light color of un-pigmented adhesive would generally signify a better product.
Being thermoplastic in nature, hot melt adhesives have poor heat resistance. Adhesive bond weakens at elevated temperatures.
Heat resistance of hot melt adhesive is given by Ring&Ball softening point. Higher the softening point, higher is the heat resistance. If the softening point is 'X C', the product is likely to work satisfactory upto a temperature of 'X-20 C'.

Metlok today is a leading manufacturer of Indigenous high technology Adhesive and Sealants. Metlok has been consolidating its position as a technological leader in the Indian market for Bonding and Sealing Solutions.


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