What adhesive - that shrinks when it sets - do you recommend for melamine laminate sheets?

Ah but what glue to stick the magnets in place

Couple of pictures to come of a destructive test, need a mug of tea first

Ha Ha Jason that's the the Question, maybe a bit of double sided adhesive tape or?

Michaelr

As I mentioned the other day a Cyano glue would be up to the job. Easy to run a series of straight beads, a little positioning time, no need for one surface to be porous.I use it quite a bit to stick trims to MFMDF and the odd bit of MFMDF to itself.

So yesterday while the CNC was doing its thing I ripped a couple of 50mm wide strips from an offcut of 18mm MFMDF, ran two beads of mitre adhesive about 300mm long and pushed the two bits together, did not bother to clamp or spray any activator on one surface..

Today I stuck one end in the bench vice and pulled the other, MDF just snapped. Then took a chisel to the joint and did get it apart. Looking at it the melamine film has been ripped off of one board, wider where I pushed the joint together in the middle and just bead width at the ends. I'd say its fit for the job in hand.

If we take the potential need of personal details out of the question I think it fair to say you've now had your money's worth

You asked - To be fair my original question was simply:
"What adhesive that shrinks as it sets would you recommend to bond two large sheets of melamine covered boards (AKA laminate) together?"

And many of us have taken time to provide opinions to that question - most no doubt based on personal experiences - and none of which appears to have given you the answer you seek.

Something tells me that you have not stopped to even consider that possibility so may I offer you one last piece of help.

Listen to all - decide what suits you best - and go and do it. The choice you make is yours alone - if it works it's fine you can congratulate yourself but if it doesn't you can't blame anyone.

Personally speaking I really can't help thinking about Horses and Water

Tug

I spent my working life solving problems on control systems. Gathering information on the precise nature of the fault was an essential start to the process. The more information that is gathered the clearer the problem becomes and the solution will emerge. Once the nature of the problem is identified then testing to eliminate possible causes can take place. I was fortunate that people would feel they could tell me that if they had cocked something up it would stay between us and we could then put it right. Too much information is more useful than too little but your cats name and your inside leg are probably not relevant to this problem. You haves posed some questions that have some very difficult to meet parameters and in real life people accept that an ideal solution may not exist and a work around process may be the best possible outcome. I spent some time on your ruler problem as did a number of others and the result was that not all your requirements could be met but a variety of work arounds were proposed.

Mike

To get clear, I'm sorry if offends anyone that I still have not actually done the bonding, but my 2 sheets are deply buried under projects.

MichaelG - Noted. My main problem is that I would need to go and buy some A0 material and get it cut to size. It would also add unwanted weight onto 2 already slightly heavy boards. I'm assumging honeybomb wont offer enough tentile strength to resist any pre-existing warping. What do you think is the thinnest material (e.g. MDF/plywood) that I could get away with that would absorb enough moisture to allow a wood glue to set?

MichaelR - Magnets won't bond over nice large surface area (to help flatting any warping), will require the melamine to be drilled into. Ultimate flatness is the primary goal here not ease of shifting the A0 MDF sheets.

MichaelR - No, the problem with adhesive tape is that never sets. Over time, any bowing of the material would re-establish itself. Ultimately, I just want to bond melamine to melamine.

So back to my question ideally I really I just want a glue that sets to bond Melamine to melamine.

It would be nice if the glue shrank at least slightly as this would help pull the 2 surfaces together. (In fact best of all would be if the glue shrank to zero thickness and just bondind the two sides together!). But I am happy to drop the shrinking requirement if necessary.

Jason - Much though I hate CA, I concede that CA may well be the best way forward. It would certainly save me the bother of finding and cutting third sheet to fit between other two, that would be required for say wood glue.
Good to see you got a good bond. And hopefully one could still get a good bond right in the middle of a square metre or so (?)

How importantd do you think using thin strips are? And how far apart do you think that they should be?

Thin strips will of course let help let the air out, help get an extremely thin layer of glue... plus in theory even let the additional moisture in the air diffuse back in (eventually).

That said, the problem with strips is that the melamine is such a thin/fragile layer it will need all the help that it can get to fight any bowing after the clamps have been removed. But I think if one ended up with strips of glue over c. 50% of the bonding surface area, that would be fine.

In your model I see that for much of the areas in question you seem to have acheived nice wide bonding strips... but that ends the bonding strips are very narrow. [And FWIW, this is exactly that sort of problem I personally always seem to get with CA!]

Nonetheless, CA may well be the way forwards. But I'll have a think. My boards won't be free to be bonded for at least another week in ay case.

I'm also still tempted by mixing up a load of Epoxy resin - at least I could guarantee it will set! On the down side even though it's so viscous that it would difficult to get it properly thin. So I guess that I would definitely still use strips though to let the air out and minimise the distance the the viscous glue would need to flow to... in order to overcome accidental lumps & bump in the application of the adhesive.

As well as applying the adhesive in strips, I would of also use a serated glue applicator to help apply the adhesive evenly, as well as to create micro-escape channels for the air to escape locally.

Don

As I said applying the adhesive in long beads(strips) allows any air to escape which may prevent the boards being pressed together if it gets trapped. It is also quite easy to apply an even thickness bead each time, not so easy to spread a thick epoxy or contact adhesives. There is no need to use any form of spreader with the cyano as it is liquid enough to spread under clamping pressure.

I did not clamp the test pieces just gave the middle a push together and left it at that. I would suggest if your boards do have any bow in them you put them convex face to convex face. That way the middle will press itself together when you clamp around the edges. I doubt you have a press so have no way of clamping the middle if you have them concave to concave.

Remember that I also said edges will need to be sealed as that is where moisture will get into the MDF and make it swell.

.

Just forget I mentioned it, Don

MichaelG.

Feels as if Don has fixated on a particular answer and is unable to tune into other ideas! His reasons for rejecting Michael's suggestion show it hasn't been understood, sigh. However, I'll have one last go.

First, a single sheet of anything is bendy. (Try waving a sheet of paper)

Second, doubling the thickness of a sheet by gluing two together is still bendy, despite being twice as heavy:

A much better approach is to increase the effective thickness of the sheet by fitting deep ribs:

It's the increase in depth highlighted in dayglo green that makes the difference. Ribs, or even better a honeycomb, are lighter and stiffer than Don's two boards, use less glue, and there's nothing difficult about the construction.

My images shows nine open longitudinal ribs, which might be overkill, and stiffen end-to-end but not sideways. Michael's honeycomb fixes this, or alternatively a second sheet could be fixed underneath. If the top sheet only is loaded, then the lower sheet can be much lighter than the top - 3mm hardboard would do.

Dave

Well there are difficulties for Don to construct that. He will need to be able to cut parallel strips of for the ribs, he will need to face the outer surfaces and he will need a flat surface to make it on.

Michael's Light weight solid core would be a bit easier but would quite likely need a 8x4 sheet of PU foam or other core material, having to buy two pieces of facing material and not make use of the two sheets of 18mm that he already has. Still needs a flat surface to build it up on and finding a suitable glue. Or you could just go out and buy Egger's Eurolite which has the cardboard honeycomb much like a cheap flat panel door but with Melamine faces but its a big sheet

I would just use Trespa & get on with life. There are a host of varieties & thicknesses. I have a fair quantity of 12mm Th & use it for all manner of things, including worktop for a couple of mobile benches. Main use is for jig making & small plastic parts.Also have made bits for club members yachts out of it.

I have come to my conclusion - in that he has two pieces of unsuitable material and is going (or determined) to try to make something useful from them. It may yet cost more than purchasing something more appropriate, that would easily suffice for the duty required. Four pages of wasted effort from members, later, and he will likely attempt what he thought of in the first place - that of using glue that he already has in dtovk.

.

Nice try, Dave … thanks for the moral support

Just to be clear : The accepted ‘optimum’ is to use a comparatively thin skin on each side of honeycomb, suitable foam, or whatever.

Interior doors, IKEA’s occasional tables, caravans, Aircraft floors, etc. etc. all use “sandwich panels”

The most substantial one we built was a 4 foot square header plate for a shaker … 1” Aluminium alloy plates with four layers of Ciba Geigy ‘F board’ between them, all bonded with Araldite 2002

… Those were the days !!

MichaelG.

.

Edit. __ These products are similar to ‘F Board’ and ‘M Board’

https://www.collinsaerospace.com/what-we-do/Business-Aviation/Cabin/Structures/Honeycomb-Panels/Aerobase

and here is IKEA’s bargain : 

https://www.ikea.com/gb/en/p/lack-side-table-white-30449908/

Edited By Michael Gilligan on 04/04/2022 17:50:43

Hope not, I would make the ribs out of DIY Store Smooth Planed Pine, like wot B&Q sell. This stuff is 18x44mm deep, other sizes available.

Assembly, lay sheet flat on floor and glue thin edge of rib to it. Dowels from rib into the sheet would reduce the strain on the glue. Or instead of dowels: screws, or those rotate in hole cam wotsits that clamp onto a screw-in spigot. as found on self-assembly furniture:

I'd probably just glue the ribs unless the table had to take more than average table weight.

Glued, staple or pin the lower sheet of hardboard, if it's thought worth the bother.

I hope Don has room to lay his sheets flat somewhere, because gluing them without taking on a warp whilst they're leant on a wall or straddling a horse will be difficult.

Dave

Edited By SillyOldDuffer on 04/04/2022 18:33:55

Jason - Yes, like I said, I would definitely use strips.

Yes, the idea of using convex-to-convex to make camping easier, is brilliant thinking. Thank you. And how lucky that I have yet to apply any glue! The only weakness is that I will need to apply multiple clamps all around the edges, but I can probably find some strips of timber/thicker MDF to help spread the load at least a little.

You raise an important worry about CA swelling if it gets too much moisture. TBH, I had slightly forgotten just how much CA adhesive DOES swell over time if moisture ever manages creeps in... e.g. over the years.

How would you recommend I seal the edges? Using some kind of varnish? It slightly worries me just how thin the Melamine layer on MDF sheets is. Maybe moisture will get through it over a few months and my nice strips of CA would eventually product bumps no matter what?

So where did we get to with using a contact adhesive? (e.g. my All Purpose Welder). Thinking it though I guess one problem with contact adhesive is that it's difficult to get on nice and flat in the first place. So lumps & bumps may appear.

With all due respect I really don't want to buy any more panels. If glue fails then yes, but like I say, in the first instance I want to see how far I can get using some sort of adhesive.

Thought: Given how thin the MDF layers are... what about using a thin, solvent-based glue like Collall? (acetone/ethanol solvent) Or E6000 (perchloroethylene I think). Again applied in bead strips. It occurs to me that the melamine layers really are incredibly thin. So maybe after a few hours the enough solvent would work its way through the melamine to cause the glue to set? Particularly if I don't apply too much AND apply it in strips?

Dave - again thank you for your thoughts but I really don't want to spend the time & money to go out buying planks or screws etc. And I definitely don't want the boards to become significantly thicker, as the table top is already slightly too high. And I don't want to lower the table buy cutting the bottom of the legs off (for several reasons).

But you raise a good question as to where to lay the board down WHILE IT SETS. I very much doubt that any of my floors are flat enough. TBH, I had also thought about lying it on a soft bed, while it sets, but obviously I would need to measure what is going on in situ before applying any adhesive. If clamping around the outsides I had thought that I would just have it point vertically upwards...

[General comment: TBH, I am now deeply regretting the fact that I EVER described my application. The problem is that you helpful nice people have come up with all manner of wonderfully creative ideas, but each of which cause unwanted side effects, such significant extra cost (which I can't afford), losing the use one side of melamine to craters & fillings, adding unwanted weight (A0 boards are already hard enough to lift), extra thickness (my table is already slightly too high), paying to buy a different table (but which probably wouldn't fit into my house...)
==> And then everyone gets cross with me for either: not following their personal advice, or for failing to go into the details of exactly why their suggestion wouldn't be suitable for me or for not wanting to engage into a detailed discussion when they challenge my constraints or for not telling them at the start exactly what all my constraints were... or - if all else fails - folks get cross for my not taking action immediately.
So next time, remind me to NOT describe my application.

As that way, we can have a much simpler conversation that just focuses on my question, and do with less opportunity for frustrations & general crossness.]

Donald

Edited By Donald MacDonald 1 on 06/04/2022 01:07:25

I did not say the CA would swell. It is the Cut raw edges of the MDF that can absorb moisture and cause it to swell or at the extremes of heat you mention it could even shrink.

Your easiest way is a few coats of varnish to the cut edges. You could use the iron on pre-glued edging but the varnish will do and you probably have something already, even paint would do.

Chances of the glue lines ghosting through 18mm thick board are zero as is any CA soaking through the Melamine

And then everyone gets cross with me for either: not following their personal advice, or for failing to go into the details of exactly why their suggestion wouldn't be suitable for me or for not wanting to engage into a detailed discussion when they challenge my constraints or for not telling them at the start exactly what all my constraints were... or - if all else fails - folks get cross for my not taking action immediately.
So next time, remind me to NOT describe my application.

Oh I'm not cross with you Donald - just totally exhausted with your manner and your seeming inability to just get on with a simple task. If you can't get two pieces of board together by now it doesn't say much for what you intend to do on top of it. Like I said just get on with it and move on - you might actually enjoy yourself

There is an old joke …

An apocryphal tale with the punchline: “If I were you, I wouldn’t start from here”

… many a true word is spoken in jest.

MichaelG.

That's the key. It's very easy to spend so much time thinking about something and getting advice from experts who have done similar jobs that it becomes an excellent excuse not to do it, while pretending that doing such 'research' is worthwhile. Isn't paralysis by analysis the technical term for this? The polite one anyway...

Complicating jobs by insisting that it's done with some scrap that you've been jealously hoarding for years is very common too.

But then of course there are the old cliches too ...

Leading horses to water etc

None so blind as those who do not want to see.

Etc Etc Etc.

At the last venue for the LOWMEX exhibition there is a slogan written on the wall - "Old proverb" - "Those who say it cannot be done should not interrupt those who are trying to do it".

Me thinks this thread is a perfect example of working in the opposing direction

Tug