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By profchrisreed
#1771443
cockney steve wrote:@profchrisreed Why is it important to let contact-adhesive get touch-dry before bonding?

Shirley, if both surfaces are "wetted" then pressed together, - the solvent will evaporate anyway and a more homogenous layer of adhesive will result, as two dried surfaces will have high spots which give random-point intermittent bonds..


Ah, you find the chink in my glue knowledge! There's apparently something in the chemistry of bonding which requires this.

I said to do it because (a) it's in the instructions, and (b) empirical testing (see later posts) demonstrates it's necessary to get the strongest bond. (b) is also my own experience.
By avtur3
#1771472
profchrisreed wrote:
cockney steve wrote:@profchrisreed Why is it important to let contact-adhesive get touch-dry before bonding?

Shirley, if both surfaces are "wetted" then pressed together, - the solvent will evaporate anyway and a more homogenous layer of adhesive will result, as two dried surfaces will have high spots which give random-point intermittent bonds..


Ah, you find the chink in my glue knowledge! There's apparently something in the chemistry of bonding which requires this.

I said to do it because (a) it's in the instructions, and (b) empirical testing (see later posts) demonstrates it's necessary to get the strongest bond. (b) is also my own experience.


I've asked the question elsewhere before, this is what I was told by an 'old sage' in the car trimming business where contact adhesive is heavily relied on. If the surfaces are not 'dry' then that indicates that the solvent is still present, if the surfaces are brought into contact at this point that restricts the ability of the remaining solvent to evaporate.

Apparently, as the glue is allowed to dry there is a 'sweet spot' on the timeline, that is a time when the glue appears dry (all the solvent has evaporated) but before the adhesive actually dries to the point where it is no longer flexible enough to create a thorough joint. This is the point where any unevenness in the surface of the glue (which there always is) is flexible enough to reshape when the surfaces are brought together and therefore results in the greatest possible area of contact of the adhesive agent without any solvent being present.
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By lobstaboy
#1771475
Loctite 4850

But persevere with the evostick - as said above, proper preparation and cleanliness are essential. Adhesives work at the molecular level - contamination on the surfaces to be joined is a killer.
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By Flying_john
#1771479
At the risk of being accused of thread hijack - a risk I am prepared to take :lol:

For the third time I have to redo the trims around the aeroplane windows. It is leatherette and this is glued to pressed aluminium shaped bits that screw on to cover the fixings for the window plastics.

Every time I have done it, after a few months, it just starts peeling. I believe it is the heat in the aircraft that is causing it. I started with a spray on contact adhesive, then a more expensive hi temperature version. Both failed. I have tried a single piece (there are 3 on each window) with old fashioned brush on evostick still failed, I experiment too with the modern white version of evostic, waste of time and doesn't smell as good.

It has been suggested that I rough up the ally even more and also fold more of the material round to the back, so as we are having the seats redone thought I would try again with the window trims.

Would welcome others advice / experiences.
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By matthew_w100
#1771507
Flying_john wrote:At the risk of being accused of thread hijack - a risk I am prepared to take :lol:


Happy to expand the scope of discussion to all glues :-) I have been convinced for a long time that what is available in DIY stores is only a tame, domestic version of the real glue available to the professional. This was triggered by getting involved in building a Europa and discovering Araldite could be bought in 500g tubes at virtually the same price as B&Q wanted for 25g. And the green jollop for fuzing the fuselage was the stickiest substance I had ever come across. I have never seen my afore mentioned carpet glue available retail, and others have commented on products their cobblers seem to have available. In these days of the internet there must be a good source of this stuff.

And I too would like ideas for attaching trim back to window frames!
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By PeteSpencer
#1771514
kanga wrote:<aviation-ward drift, no use to OP :oops: >

memories of Redux:

https://en.wikipedia.org/wiki/Redux_(adhesive) :)

</>


Redux, which was used to stick Comets together, was often described as the fore-runner of Araldite:

This is not so, they are a different formulation using a different chemical principle, as although both were made by CIBA later CIBA-Geigy at Duxford, Araldite has been around since mid 1940s.

Similarly Evostik, made by Evode Ltd was used by do-it -yerselfer Barry Bucknall on BBC TV in the 60s.

Peter
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By profchrisreed
#1771543
Flying_john wrote:At the risk of being accused of thread hijack - a risk I am prepared to take :lol:

For the third time I have to redo the trims around the aeroplane windows. It is leatherette and this is glued to pressed aluminium shaped bits that screw on to cover the fixings for the window plastics.

Every time I have done it, after a few months, it just starts peeling. I believe it is the heat in the aircraft that is causing it. I started with a spray on contact adhesive, then a more expensive hi temperature version. Both failed. I have tried a single piece (there are 3 on each window) with old fashioned brush on evostick still failed, I experiment too with the modern white version of evostic, waste of time and doesn't smell as good.

It has been suggested that I rough up the ally even more and also fold more of the material round to the back, so as we are having the seats redone thought I would try again with the window trims.

Would welcome others advice / experiences.


Where does the joint fail (ie is the glue residue on the aluminium, the leatherette, or both?

Heat could well be your problem. Most glues soften with heat, and surprisingly little at that. My experience is from making guitars and ukuleles, and on a 30+ degree day just an hour in a hot car can be enough that important parts slide into different positions!

I can only think of three glue types which might stand that heat, though there are probably others.

Superglue (cyanoacrylate or CA). This cures to acrylic plastic, which requires more heat to soften than, say, woodworking glue or epoxy. But it's brittle and a knock or vibration will break the joint.

Hot hide glue, basically boiled up hooves and trimmings, effectively gelatin. This is the traditional instrument glue, and resists dry heat well (damp heat kills it, I believe Mosquitos dissolved in Burma). It will stick to shellac (French polish), which sticks to almost anything. I have both, so I could try it out if I had any leatherette. But hot hide glue is a bit tricky to use.

Resin based glues like Cascamite. But this has been reformulated recently and woodworkers now swear at it, not by it. However, its tougher brother Aerolite might be worth a try. Your friendly aero engineer should have some, and could advise whether it will bond to aluminium. It's expensive if you can't get a few dabs as a favour, and I don't know that it would work.
By profchrisreed
#1771544
Ooh, one more which might be it.

JB weld, an epoxy which claims to stand up to 260 degrees C continuous heat. From motor spares suppliers.

Rough up the aluminium as it makes a mechanical, not chemical/molecular bond.
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By mick w
#1771548
profchrisreed wrote:Ooh, one more which might be it.

JB weld, an epoxy which claims to stand up to 260 degrees C continuous heat. From motor spares suppliers.

Rough up the aluminium as it makes a mechanical, not chemical/molecular bond.


Good for bonding in Bearings & Oil Seals :thumright:
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By rf3flyer
#1771573
profchrisreed wrote:Hot hide glue, basically boiled up hooves and trimmings, effectively gelatin. This is the traditional instrument glue, and resists dry heat well (damp heat kills it, I believe Mosquitos dissolved in Burma).

I'm pretty certain Mosquitos were never glued together with hot hide glue but until the advent of resin glues casein glue was commonplace. And while it's true that in hot, moist tropical climes casein glue (essentially cheese and lime) did soften it was also found in tests that joint failure occurred at pretty much the same load softened of not, the softening allowing some elasticity in the joints much like connective tissue in an animal. Terminal decay of casein smelt of stinky cheese and inclusion of 'smell' was part of the periodic inspection of Horsa gliders in storage awaiting D-Day.
Reference: https://www.waterstones.com/book/the-new-science-of-strong-materials/j-e-gordon/9780140135978

Apologies for thread drift.
Last edited by rf3flyer on Sat May 23, 2020 11:13 am, edited 1 time in total.
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By Bill McCarthy
#1771607
I hear that ether (chloroform) was good for bonding Perspex but getting it ...........?
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By PeteSpencer
#1771615
Bill McCarthy wrote:I hear that ether (chloroform) was good for bonding Perspex but getting it ...........?


Point of order:
Ether, more precisely diethyl ether (C2H5)2O is not chloroform.(CHCl3), which in turn is related to its brother Carbon tetrachloride, (CCl4) all of which long ago used to be freely available upon signature and address.


Peter :|