Araldite repair failing in dishwasher

[Lobster]

I mended a broken Magimix foodprocessor bowl lid with 2-part Araldite epoxy adhesive a few months ago (I think it was Araldite Rapid?); all has been well until yesterday when I found it in bits again in the dishwasher - the glue was quite flexible and the remnants pulled off quite easily. (I assume that since the repaired bowl must have been through the dishwasher many times sucessfully, the glue must goes rigid again with time.)

Anyway, was quite surprised, as I've put Araldited repairs through the dishwasher countless times over the years with no problems; but I assume it's not an appropriate adhesive to use here.

Any suggestions for a better repair or glue?

The item concerned looks a bit like this: and it's the retaining lug at bottom right which has broken off.

Realistically it needs to be dishwasher-proof; and it has to be able to sustain a fair amount of force.

Thanks David

[Andy Dingley]

Araldite isn't great - other epoxies like West System are much better, as they aren't pre-thickened, so you can mix them up to exactly what you need.

If it's Rapid though, this is well known for not standing up to even boiling water temperatures.

[Jethro_uk]

I bought some epoxy to try and fix a leaky rad (so far it seems to have done the trick). It was Plumbers Mait Quick leak repair putty. It's supposed to be ok at 150 C ....

[The Natural Philosopher]

very bad glue to use for styrene. If there is no gap filling try plastic model plastic cement instead.

I think they also do a sort of body putty for plastic models That could be used to fill gaps

Epoxies typically soften when they get hot and dont in any case adhere very well to styrene. The key to a heatproof epoxy is to stove it hotter then the part will ever get, so I repair china by putting it in the oven while the epoxy sets. THAT then goes brittle hard and clear.

Half the problem is getting exact 50:50 mixes and mixing them totally - heating which renders the epoxy liquid helps mix things much more thoroughly, which is probably why it sets harder.

[The Natural Philosopher]

aren't pre-thickened, so you can mix them up to exactly what you need.

water temperatures.

it will if you heat it to about 140C as it sets.

[The Natural Philosopher]

car body filler is the best cheapest option.

Because its a catalysed reaction, you don't get such severe problems of inadequate mixing that you do with epoxies, so it always sets rock hard. It probably does stick to styrene better as well.

[djornsk]

One method which I have had some success with is welding with a soldering iron which involves stiring up the plastic from both sections in the region of the break, and even transplanting plastic from another part of the item for reinforcement. Though I have never tried it one could perhaps embed wire in the plastic, but not necessarily in this particular repair.

This technique I have found particularly useful in repairing trims in cars where usually there is a side which is not seen with plenty of plastic which can be moved around at the same time achieving a near perfect finish on the visible side.

The motor trade was and no doubt still is a great place to learn how to bodge - ISTR in my first week seeing a Hillman Imp cylinder block repaired with plastic padding by the service manager. It never ceases to amaze me what people can get away with by what I suppose might be called thinking outside the box.

j

[dennis]

Epoxy is catalysed.

[Tim+]

Actually, I suspect that neither is "catalysed" as a true catalyst is not consumed by the process. In car body filler a peroxide supplies oxygen that speeds up the hardening process and in epoxy resins the components chemically combine.

Tim

[The Natural Philosopher]

+1

[Andy Dingley]

Nope. It's a two part mix for a reaction, but that's not the same as being catalysed, and not the same as curing styrene.

[Andy Dingley]

Tried that loads of times as a kid, never got it to work for more than 5 mi= nutes.

However borrowing a trick from car bodyshops, and how they repair bumpers, = then hot-air welding of plastics can work pretty well. Not using a solderin= g _iron_, but rather a hot air gun for surface mount soldering. This seems = to work pretty well on polypropylene and the other unglueable thermoplastic= s. Use an offcut of the same plastic as filler rod.

[Lobster]

No gap filling needed; although there is scope for piling gunk on over the repair to reinforce it. Is model cement really likely to provide a strong enough repair? Or is a different (ie non-Araldite-Rapid) epoxy likely to be better?

Thanks David

[The Natural Philosopher]

if its styrene - and lots of that crappo kitchen gear is - then styrene cement should make it as strong as new.

can either use a pure solvent to weld it or a solvent plus styrene, which is a bit gap filling.

If you have an 'airfix' style model shop nearby get a bit of each and see what works.

[Lobster]

Hmm... same stuff as for solvent-welding waste pipes, which I have sitting on my shelf?

David

[Andrew Gabriel]

then hot-air welding of plastics can work pretty well. Not using a soldering _iron_, but rather a hot air gun for surface mount soldering. This seems to work pretty well on polypropylene and the other unglueable thermoplastics. Use an offcut of the same plastic as filler rod.

I've done it using a gas burner to melt the two surfaces and push them together to fuse.