• Anaerobic and Cyanoacrylate Adhesives

    Maintenance can be carried out quickly and easily using two types of innovative adhesives. They are Anaerobic Adhesives Sealants and Cyanoacrylate Adhesives. These products also help overcome unforeseen problems during overhaul / breakdown maintenance and are very cost effective. Information on working of these products, their use for different applications (locking, sealing and retaining), method of application and storage instructions are covered in this article.

    Anaerobic Adhesives Sealants

    Anaerobic Adhesives Sealants are a penetrating one-component liquid plastic which has the property of hardening automatically with little shrinkage in joints between closely fitted metal parts to form a strong heat and oil resistant plastic. The catalytic action of the metal surfaces aided by the absence of air, which acts as stabilizer, causes the liquid to harden and form a tough plastic seal / retainer. The product has excellent chemical resistance but is not recommended for exposure to concentrated acids and alkalies. In general these products are suitable for maximum temperature of 150 deg. C. However some grades can withstand higher temperature. Please refer to manufacturer’s recommendation / technical data sheet for their suitability. Varieties of products are available for different applications and in different grades for an application as under.

    Thread Locking

    This variety is useful for all types of metallic fasteners to prevent their loosening due to shock and vibration. It can be used instead of conventional locking mechanisms like lock nut, spring washer, nylok nut (nut with nylon insert), tab washer, split pin, etc. The product also seals threads in addition to locking and prevents thread corrosion. Because of this advantage one could avoid seizing, the problem of removal at a later time.

    Wicking grade of thread locker is designed for locking pre-assembled fasteners (instrumentation screws, set screws, etc.). This grade is also used to seal porosities and hairline cracks in castings and welds. Due to low viscosity, it has the ability to penetrate into tightened threads, porosities and cracks by capillary action. It hardens in to a tough plastic when confined within metallic surfaces.

    Many grades of thread lockers are available for application during assembly. Different grades are made for different locking strengths. Low strength grade is used for low strength metals such as aluminium or brass which could break during disassembly. Very high strength grade is used for heavy duty / permanent application.

    Thread Sealing

    This variety replaces tapes and pastes used on threaded tube / pipe components. Its application prevents damage caused due to over tightening. Liquid also ensures complete contact between threads for a 100 percent seal. Disassembly can be achieved easily with basic tools.

    Fine grade is recommended for fine threaded fittings used in hydraulic and pneumatic installations. Coarse grades are used for coarse metal threads of different sizes. Slow curing grade is recommended where post-assembly adjustment / alignment is required to be carried out.

    Gasketing

    This variety is used instead of pre-formed gasket for flanges, pumps, gear boxes, etc. It fills all voids and thus reduces the need for a fine surface finish and does not require re-tightening. Various grades are available for different application requirement.

    Retaining

    This variety is used to retain / bond non-threaded cylindrical metal components like bearing, gear, coupling, etc. Use of this product reduces the need for close tolerances for assembled parts and hold worn / loose fitting parts (it can replace press fits with slip fits). Many grades are available to suit different requirement (like strength, temperature, gap between components).

    Method of Application

    Clean surfaces with soap, hot water, cleaner / solvent to remove oil, grease, dirt, etc.
    Apply primer on inactive surfaces like aluminium, stainless steel, magnesium, zinc, black oxide, cadmium, titanium, etc.
    Apply primer on all type of surfaces (active and non active) if work is to be carried out at temperature below 5 degree C.
    Apply adhesive sealant to a component and assemble it. During assembly of cylindrical items give slight clockwise and anticlockwise twist to spread the adhesive.
    Application of heat accelerates the curing speed.
    Anaerobic adhesive sealants are non-toxic. A sop and water wash after handling is sufficient.

    Storage

    To obtain the normal shelf life of one year the material should be stored between 5 to 28 deg. C in a cool dry location.

    Disassembly of Adhesive bonds

    Most bonds can be broken apart simply by ordinary tools. Strong bonds can be heated up to 250 deg. C before using mechanical methods.

    Note:
    Henkel Loctite sales two grades of thread locker, one grade of thread sealant, one grade of gasketing and one grade of retaining based on anaerobic technology in semi-solid stick form. It is easy to apply them for overhead application.

    Cyanoacrylate Adhesives

    They are single component general purpose adhesives. They are Cyanoacrylate monomers and traces of water on surfaces to be joined initiates polymerization. Water acts as a catalyst in the process. The notable feature of these adhesives is their exceptional speed of cure which is achieved in few seconds. As it polymerizes due to water, relative humidity (RH) in atmosphere is very important. If RH is less than 40 percent, the speed of cure will be slower, and if it is higher than 75 percent, cure will be faster – but with possible reduced bond strength. As curing takes place very fast, special clamps are not required. Only finger pressure is adequate to make strong joints after parts are accurately positioned. They bond variety of materials. Dissimilar parts also can be bonded by them. They are available in different grades based on type of material to be bonded.

    Note:
    These adhesives are not recommended for bonding silicon rubber, Viton and Teflon.

    Method of Application

    Clean both surfaces. A solvent wipe with butyl alcohol, MEK or acetone is considered satisfactory for most surfaces. For aluminium, a dichromate acid etch is recommended.
    Apply thin layer of adhesive on one of the surfaces to be bonded.
    Assemble parts at once ensuring that they are correctly positioned. Apply light contact pressure to prevent movement and minimize the bond gap.
    For Skin protection use nitrile gloves and aprons as necessary. Do not use PVC, nylon or cotton.

    Caution

    Keep away from children.

    Skin contact:

    Bonds skin in seconds and caution in use is advised. Do not pull bonded skin apart. Soak in warm soapy water. Gently peel apart using a blunt instrument. If lips are bonded, apply warm water to the lips and encourage wetting and pressure from saliva in mouth. Peel or roll lips apart.

    Eye contact:

    Immediately flush with plenty of water for at least 15 minutes. Get medical attention. If eyelids are bonded closed, release eyelashes with warm water by covering with a wet pad. Do not force eye open. Cyanoacrylate will bond to eye protein and will cause a lachrymatory effect which will help to debond the adhesive. Keep eye covered until debonding is complete, usually within 1-3 days.

    Storage

    To obtain the normal shelf life of one year the material should be stored upright in a cool dry location at a temperature below 25 deg. C. The time may be extended by storage at temperature approximately between 0 to 5 deg. C. After refrigeration, allow the bonder to reach room temperature prior to application.

    For ready reference important Henkel Loctite products are listed below

     

    Loctite Products and Product No. Application
    Thread Locking  
    290 Wicking thread locker.
    222 Low strength thread locker.
    242 Removable thread locker.
    243 Thread locker for parts contaminated with oil.
    262 High strength thread locker.
    270 High strength thread locker for heavy duty applications.
    272 For high temperature application.
    Thread Sealing  
    542 Fine threaded fittings used in hydraulic and pneumatic.
    565 PST General purpose instant sealer.
    567 PST For temperature up to 200 deg. C.
    577 All types of coarse metal threads (up to 3 inches).
    572 Slow curing for post-assembly adjustment.
    Gasketing  
    574 Fast curing flange sealant.
    510 Gasket eliminator for temperature up to 200 deg. C.
    518 Gasket eliminator.
    573 Flange sealant for slow curing speeds.
    Retaining  
    660 For gaps up to 0.5 mm.
    641 Moderate strength.
    609 Moderate to high strength.
    648 High strength and high temperature up to 175 deg. C.
    638 High strength.
    620 High temperature up to 200 deg. C.
    603 Excellent oil tolerance.
    Semi-solid sticks  
    248 Threadlocker Medium strength.
    268 Threadlocker High strength.
    PST 561 Thread Sealant  
    548 Gasketing  
    668 Retaining  
    General Purpose Bonding
    (Cyanoacrylate Adhesives)     		 
    401 Prism For porous surfaces.
    454 Prism Gel for overhead applications on porous surfaces.
    406 Prism For rubber and plastics. Making O-rings.
    415 Super Bonder Bonding small metal parts.
    495 Super Bonder General purpose application for gaps up to 0.1 mm.
    Additional products  
    7649 General purpose primer N.
    Natural Blue For cleaning and degreasing components.
    Chisel Gasket Remover To remove old gaskets easily.
    Paint Striper To remove paints, varnishes, etc.

     

     

     

    Material Suppliers

     

    Companies selling anaerobic and cyanoacrylate adhesives in India are as under.

    Hankel Loctite had invented anaerobic technology for thread treatment and gasketing in 1950 and they offer good technical support. For more information please visit their website.

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