Adhesives and their applications

[Delta]

Could anyone give me a brief overview of glues such as araldite, RTV, loctite, superglue and dymax.

I'm after typical applications, what they're good for and what they're bad for.

At work RTV is tended to be used for a filler or mechanical glue, loctite is for locking screws and araldite is used on PCB's and keying surfaces.

I'd like to be able to get as much info as possible but the net only offers suppliers not datasheets.

 

[brewnog]

What kind of thing are you after specifically?

If you're searching the internet, you might have more success if you don't use tradenames (for Araldite use epoxy resin, for loctite use cyanoacrylate etc).

Generally, superglues (cyanoacylate) are used where high strength is an issue. They are very quick curing, and are activated (as I recall) by surface moisture. They have very poor properties regarding impact and shock considerations, and do not fill gaps well, - materials to be joined should have a good fit-up. If you ever want to stick your eyes together, cyanoacrylates are the way to go.

Epoxy resins (such as Araldite) are a very broad class of adhesives. Advantages include a high strength, and very low volumetric change during the curing process. One major disadvantage is the high degree of surface preparation which is often required to ensure a good bond. Some formulations have good oil resistant characteristics, some are hard enough to be machined, some are acid or UV resistant. Generally there are two types: single and double part epoxies. The single part epoxies are issued to the application, and are then 'activated' by physical means, - usually temperature or UV, although some work like cyanoacrylates and activate by surface moisture. The double part epoxies require mixing prior to application, - a chemical catalyst promotes the crosslinking reaction. Epoxy resins make reasonably good fillers. Have you seen that "metal putty" stuff? That's a type of epoxy resin, I think.

Loctite, - a trademark for cyanoacrylate, is often used in thread-locking applications because of its high strength, - fasteners are then readily disassembled by applying shock to break the adhesion.

I don't know much about RTV, I'm pretty sure it's elastomer based with special applications in sealing. I'd think there would be different formulations based upon filling characteristics and resistance to particular fluids. Flexibility is almost certainly an issue here too. Silicone sealant seems to be of this type, if you want to make a lot of mess in a very short space of time, silicone sealant is the way to go (providing you can still see...).

I've never heard of Dymax.

 

[Delta]

Thank you very much for your info, its given a great insight and start point, and perhaps a better way of finding them on the net.

I'm actually a quality engineer and need to have an appreciation of different materials, one I'd like to learn more about is adhesives.

With regards to applications I was referring to how they are used not necessarily how they are applied.

As I said, loctite is used for locking screws, we use superglue for lacing knots (thread). RTV we use to fill gaps, such as chips in glass fibre type material and also as potting for connector assemblies, encasing, etc. It's also a favourite to prevent moisture ingress for example as a result of humidity testing or salt fog testing.

Araldite we use to re-adhere pads or IC legs to a PCB. I think its used to hold down wire links also. I was once asked if Dymax could be used instead as it apparently cures quicker, maybe they're the same thing different manufacturer.

I'd have to raid our toxic cupboard to see if any others are used.

Your post highlighted somethings I want to look at, for example, what they are typically used for, cure times, materials used on, strength (malleable?, resistance to shock?), resistive properties (water, oil, electrical)

I'll have a go at those scientific names.

 

[brewnog]

Just to give you an idea just how broad this field is, here's a list of 113 different types of Araldite along with their data sheets! Remember that all these 113 are Araldite, and that's just one of the many trademarked brands available.

http://www.huntsman.com/structural-adhesives/index.cfm?PageID=4316