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What's the strongest available fast-setting (2 hour) glue for HIPS styrene/Plasticard?


ship69

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Hello

I am building a model with an pretty strong spring in it, and I am extremely disappointed with Plastic Fusion ! (from Super Glue corp)

On the upside, my Plasticard / HIPS styrene is mechanically stronger that I thought it would be an is fine.

Bonding using EMA Plastic Weld cement is okay, but not brilliant. The problem I have is that any joint is nothing like as strong as the virgin material and thing can always be snapped off again at the original join.

BUT after the rave review in this video by CustomsByZ ("Tutorial: The Basics of Working With Styrene" on YouTube)... I am extremely disappointed with Plastic Fusion from Super Glue corp!

Even waiting a full 24 hour later the joint is just too weak. I have tried thee times now.

- Yes I am mixing it up very thoroughly.
- Yes I am doing so at a reasonable temperature (19deg)

- Yes I am mixing it on card and using a the wooden spatula provided

- Yes I am being careful and think I am getting the proportions about right

- Yes I am working with clean (freshly filed) surfaces.
However the resulting bond is little better than EMA Plastic Weld solvent - which is particularly irritating after all that time spent mixing the glue. Moreover and the setting time is also longer than expected. It says sets in "5-10 minutes" but that's a massive exaggeration, as in 10 minutes it's still pretty gooey and sticky. After 25 minutes it's pretty much a solid, although even after an hour I can still sink a fingernail into it. But either way it never, EVER gets as strong as solid the styrene itself! Not even close.

Although I don't expect them to be as strong as an epoxy resin, I have now order some Tamiya Extra Thin cement and some Mr Cement S to see if either create something stronger than EMA Plastic Weld.

Background

I am layering up my 1mm Plasticard sheets using EMA Plastic Weld produce solids of 3-4mm and I am then joining those solids together at 90 degrees. To get clear, I am looking for joints of high mechanical strength, in order to resist the springs I am working with. The base styrene is strong enough for my purposes, although I had ordered up some ABS in case it wasn't. But I am now concerned that it's harder to glue ABS than styrene so that may prove to be a mistake.
Of course what is so nice is that some sort of bond happens in c.10 seconds, but anyone know how long I should give the styrene to dry in order to achieve say 95% of maximum strength?

Back to epoxies, I don't mind mixing up epoxy glues for say 30 seconds, even 1 minute (if I have to), but I do mind waiting for much longer than say 2 hours or so.

Waiting for glues to dry is a serious problem for me as it interferes with the prototyping process itself.

- What is the strongest glue for styrene that also sets fast - i.e. within 2 to 4 hours?

Many thanks

P.S. I am now wondering if maybe I have a bad batch of Plastic Fusion. What was worrying is that the very first thing to come out of one of the tubes was a transparent oily substance. So this may have been the problem with my first attempt. Fwiw, my attempts have all been using about pea-sized volumes of epoxy glue, and the epoxy looks what I assume is 'normal' (not streaked etc). I cant find any expiry date on the packaging... I got it off an eBay merchant "Motorway Hessle LTD" who have a good rating on eBay (99.8% after 71,162 feedbacks) :^(

The Plastic Fusion glue I bought:
http://www.ebay.co.uk/itm/Super-Glue-Epoxy-10-Minute-Plastic-Fusion-2-Part-Bond-Plastics-Glass-Rubber-/261508621516?

Edited by ship69
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Since writing the above, I have done some further experiments with EMA Plastic Weld.

Plastic Weld being 100% transparent, what I had't realized is that you need good eyes (or reading glasses!) and a bright light to see what's really going on. It turns out that my paint brush is really too small and due to both the absorption by styrene and the rapid rate of evaporation you need to put quite a LOT of the stuff on to get a really strong bond.

And it turns out that if you put quite a lot of Plastic Weld on and let it sink in for a good few second AND if you then squeeze it down hard, although you lose height (due to the squishing of the styrene) which does of course make your model less accurate... you can indeed get a remarkably strong bond.

Unfortunately solvent-melted styrene, even after it has fully 'dried', doesn't ever seem to be get to be quite as strong as virgin styrene, so much original question (above) still stands. And it particularly stands where greater accuracy is required.

With thanks

J

P.S. Btw, does anyone make a coloured version of such cement? As it would be really helpful to be able to more easily see how much cement is going on. Ideally this should be a colour that evaporates off after it sets.


Edited by ship69
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A five minute epoxy might meet your requirements. Devcon is a brand I use and can recommend. Its widely available from places like B & Q. I would mechanically roughen the mating surfaces and like all adhesives is much stronger loaded in shear rather than tension.

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A five minute epoxy might meet your requirements. Devcon is a brand I use and can recommend. Its widely available from places like B & Q. I would mechanically roughen the mating surfaces and like all adhesives is much stronger loaded in shear rather than tension.

Excellent - thanks! Out of interest, how strong do you think the bond can get to be? I mean can it hope to get to be as strong as the base material (styrene in his case) - or will there always be a point of weakness where the glue meets the plastic?

* * *

Meanwhile I am experimenting with various cements: (Mr Cement S, Tamiya Extra Thin and EMA Plastic weld). I have found fine brushes that come in the lids of the former two to be extremely useful. (Why on earth don't EMA do the same thing?). So far I'm not sure how difference there is between them..

Either way I still haven't quite worked out how to get the best possible bonding. Sometimes it does seem to be a very much stronger bond than at other times. I am building up layers of styrene to get the thickness that I need, bonding with cement. Possibly I should allow a slightly longer time for the cement to sink in before matching the 2 surfaces. Where possible crushing together for say 20 seconds with a vice seems to help too.

I've also ordered up some replacement Plastic Fusion from Super Glue corp because I now think my product was off, as it never goes properly yellow (as it does in videos) and it turns out that I can scrape it off with a fingernail!

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I think this will be the likely point of failure

Even with a really good epoxy that is designed for use with plastics ?(!)

P.S. A supplier just recommended a methacrylate glue - how do they compare with epoxy glues?

Any thoughts...

Edited by ship69
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A five minute epoxy might meet your requirements. Devcon is a brand I use and can recommend. Its widely available from places like B & Q. I would mechanically roughen the mating surfaces and like all adhesives is much stronger loaded in shear rather than tension.

I've done a little more research on Devcon's website.

Their "5 Minute epoxy" only works on "fabrics, ceramics, glass, wood, and concrete"

http://www.devcon.com/prodfiles/pdfs/fam_tds_175.pdf

However like Super Glue corp, they also do a "Plastic Welder". Devcon's works on:

> " PVC, fiberglass, ABS, FRT, PBT, PPO, PCBB, Metton®, Lomod®, Valox®, Noryl®, GTX, Minlon®,
> epoxy, RIM urethane, wood, poorly prepared surfaces, and where outdoor weathering or solvent exposure is anticipated"

http://www.devcon.com/prodfiles/pdfs/fam_tds_182.pdf

I can't see (poly)styrene in that list, but ABS is a thermo plastic, and at least has stryrene in it...

Anyhow I've just order some. More later...

Edited by ship69
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Nigel's suggestion of a 5-minute epoxy is a good one, as is the idea of roughening the mating surfaces and making sure they're completely free of oils and other contaminants.

A very good solvent glue for polystyrene is MEK (Methyl Ethyl Ketone). It's very "hot", dissolves polystyrene quickly, then evaporates quickly leaving the plastic fused together. The downsides are that it stinks, is almost certainly very bad for you, and may not be readily available in your part of the world. But if you can get past those problems, it may well do the job for you.

HTH

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Yes, I am trialing Dev' Plastic Welder". Results so far
1. Incredibly hard to work with - tends to squirt out way too much!
2. Sets rather too fast. Starts to thicken within about 4 minutes...
3. Sets hard as a brick within about 30 minutes (much harder than Super Glue corp's Plastic Fusion, 2 samples of which have been utterly hopeless)
I'll need to wait 24 hours to see how strong the bond really is. (I've leaned my lesson on that!)
Meanwhile any idea where I can get some MEK on expedited delivery (to UK mainland)?
I cant find any at either ModelsRgo.co.uk or ScaleModelShop.co.uk ...
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