araldite comparisons

[silicono2]

Need a bit if help choosing the best kind of araldite to use! If I'm correct the standard 5-min isn't the strongest. Does it follow the slower drying ones (eg 30 min) set to stronger bonds?

Seb

[The3rd Earl Of Derby]

What are you bonding?

[Ian Stirling]

All else being equal, yes.

Exactly how to get the strongest bond depends on a whole host of factors, surface cleanliness and preparation, materials to be glued, geometry of the gluejoint, flex in materials to be glued, ...

[Nigel Molesworth]

There is almost certainly something better.

[The Medway Handyman]

Generally the longer the setting time the stronger the bond. A single part polyurethane might be easier, like Gorilla Glue.

[Tim Lamb]

You can accelerate Araldite curing time by applying a modest level of heat. What it does to bond strength is beyond my knowledge.

regards

>

[Derek ^]

It weekens it.

IME to more/less what the equivalent "Rapid" would have been. Though you can end up getting bubbles in it.

No good.

DG

[The3rd Earl Of Derby]

Not a good thing to do,given the fact the curing process is at normal tempretures to the instructions

[silicono2]

No specific project in mind, but I often use it to fix shoes--I know you're supposed to use Evo for that but I keep thinking 2-part resins are stronger. The Evo seems to work off after a while, although the

5-min araldite I'm using isn't a lot better. So I was hoping stronger araldite could do the trick.

Seb

[The3rd Earl Of Derby]

Hot gluegun for the soul. ;-) yes,yes I know(sole)

[Nigel Molesworth]

But not flexible. Ask a cobbler what he uses.

[Nigel Molesworth]

When I was a kid, I broke a leg off a table. I mixed up some Cascamite (wonderful stuff), and glued it back together. Only problem, parents coming back in 3 hours.

I put the heating on full, and put every electric fire in my bedroom (which also had the hot water tank in it). I got the temperature above

125 degrees Fahrenheit (50 Celsius) - the greenhouse thermometer ran out at that point.

Glue was set in 2 hours (normally took 24), parents never knew.

[Nick]

I used similar epoxy resins in a job for six years. I discovered that moderate heat helped the epoxy to set better and harder. Heat also helps if you have not got the mixture proportions quite right (which usually happens when mixing a small quantity). The heat was applied by putting the article to be glued in a box containing a light bulb, for a few hours. It is important to heat the article before applying the epoxy. It will tend to get very runny at that stage, so allow for that.

[Nick]

If you can find one locally, visit a stonecutter/mason. The sort of firm that makes stone tops for bathrooms/kitchens etc. I have one as a tenant. They use araldite type stuff for glueing sinks/basins to worktops etc. Certainly smells the same.

2Kgs I think is about a tenner inc. hardener Much too inflexible for shoes unfortunately and where are we to find a cobbler today. I have a couple of tins in my workshop, can send a name or link (if available) should you wish.

Nick

[Ian Stirling]

AIUI. Epoxies are complex beasts. Basically, the faster the epoxy, the more the reaction does not go to completion, but sticks part way there. This means there is less reacted epoxy molecules as a proportion of the whole, and the ends of the molecules which would normally join together instead get immobilised by the molecules that are set around them.

Once it's 'set' (say 10 times the setting time) not much happens. Until you raise it above a certain temperature for the first time. Then the strength drops a bit as the ends of the unbound molecules whip around due to thermal vibrations, and reform so that more of them are joined up. When it cools again, it's stronger - though less flexible than before. Heating again to the same temperature as before does nothing.

Setting at elevated temperatures does nothing bad - apart from losing flexibility.

Then there is the whole issue of differences in the coefficient of expansion of the epoxy and the substrate - if you cure it at elevated temperatures, you're going to lock in some stress, which may weaken the joint.

Then there is heat generated while setting, and the fact that it can get hot enough to damage the setting epoxy.

[Andy Hall]

Presumably using fish glue?

[Nigel Molesworth]

Oh no, not this gag again.

[Matt]

Impressive, but a guy I knew at university managed to roll his mum's mini into a ditch while she was about three days into a fortnights holiday after leaving her previously trustworthy son in sole charge of the family home. He wasn't insured and only had a bike licence. By calling in quite a few favours and using a huge chunk of his grant he reshelled it and it looked as good as new when they came back. He would have got away with it except for one small detail.

Before she went on holiday his mum had caught the headlining with a ring and had torn it slightly. A few weeks later when she booked it in for a service she mentioned the headlining and went out to the car to show the service receptionist the damage. But obviously none was found. She smelt a rat, and when grilled her son lost his nerve and spilled the beans. He went without drink for the best part of the next year and still paying back his huge overdraft years later.

[Chris Bacon]

It's rigid, and the bond will fail quickly. You ought to buy some shoe glue (polteurethane with toluene solvent).

[The Natural Philosopher]

More or less yes.

But epoxies are many and varied, and there is a huge range for industrial uses - essentially you can juggle setting times, brittleness, strength, temperature range etc etc almost ad infinitum.

What you buy in a shed is merely a cheap stripped down version of one of these deemed 'suitable for domestic use' and put in a fancy pack and marked up 30000%.