MEW Adhesives

[Colin LLoydParticipant @colinlloyd53450]

I was intrigued by the latest MEW magazine where adhesives were seen as an item that in future would be employed to a greater extent. What adhesives are recommended for bonding metals, are there different adhesives for different metals and what is the current MEW readerships appreciation of metal adhesives?

[Colin LLoydParticipant @colinlloyd53450]

[Roderick JenkinsParticipant @roderickjenkins93242]

I think the MEW readership is pretty conversant with Loctite (other brands are available) type adhesives. These and others are widely used in industry, particularly for joining aluminium and/or composite type materials (racing cars, aeroplanes etc). Home workshops tend to concentrate on using Loctite to replace press fits for retaining things on shafts (They don't trust these new fangled ideas though and usually pin them as well).

The major problem with theses glues is that they are all organic polymers of one sort or another and as such have severe temperature limitations so you need to be careful where they are used in steam or i.c. engines.

Rod

[BazyleParticipant @bazyle]

Will a Locktite joint still hold true in 50 years? Much of our stuff can be longlived.

I remember at work we used to have cameras that took a Polaroid of the oscilloscope screen to past into reports with 'Pritt' adhesive. Trouble was that 3 years down the line if you picked up the report a shower of photos fell out.
Likewise lots of boat modellers using superglue to stick plastic parts find that 3 years later the parts 'ping' off as the glue buids stresses in the plastic I think that suddenly let go.

[Howard LewisParticipant @howardlewis46836]

One of the reasons that adhesives are used, particularly in aircraft, is that the load is not concentrated as it would be with a bolt or rivet, but spread over a larger area, so reducing the level of stress.

Plastic mouldings have stresses "built" into them by virtue of the fact that the material is forced to flow through the mould. Over time these stresses relieve themselves. Temperature can hasten this. A plastic food box will soon distort if regularly washed in hot water, because the heat "encourages" the stress relieving.

Metal castings will stress relieve similarly (In the old days, castings were weathered for a couple of years before machining. Now, if stability is required, the castings are allowed to cool slowly, or reheated and slowly cooled, to stress relieve before machining).

I have used Loctite which was probably twenty years old. (WELL past its shelf life) Several years later, with the anaerobic having been applied over a fairly large area, the joint would NOT break!

So don't be too despondant!

Howard

[Oompa LumpaParticipant @oompalumpa34302]

Posted by Howard Lewis on 31/05/2015 19:08:34:

I have used Loctite which was probably twenty years old. (WELL past its shelf life) Several years later, with the anaerobic having been applied over a fairly large area, the joint would NOT break!

So don't be too despondant!

Howard

I have a largish container of Loctite 626 (might have the wrong number there but definitely 62something) given to me by a friend some twenty years ago and I am still using it. Works just fine. I have of course widened my selection and have about eight different types of Loctite adhesives now all with their own properties.

One adhesive I use regularly and which I think is a little mis-understood is "Tiger Seal". I use this to bond airgun silencers and even in the thirty foot pound guns I have never had a failure. This stuff works great bonding aluminium, carbon fibre and kevlar materials. It is used to bond car panels to the chassis of a number of cars. Great stuff and wouldn't be without it. (Tiger Seal is a Polyurathane adhesive)

graham.

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