The Lemon Fool

Looking for a cartridge of sealant/adhesive that will set rock hard - looking online, many of them seem to make a virtue of being flexible. Many don't say if they are hard or flexible.

I had thought No More Nails was hard but now their 'All materials' version is 'highly flexible'. any suggestions for one which sets hard please?

Gripfill - https://www.screwfix.com/p/gripfill-adh ... 50ml/10261

MyNameIsUrl wrote:Looking for a cartridge of sealant/adhesive that will set rock hard - looking online, many of them seem to make a virtue of being flexible. Many don't say if they are hard or flexible.

A friend of mine (Anand Jagatia) produced an excellent radio program for the World Service on adhesives. In it they went into adhesion (also down to a molecular level) with various experts. I remember them also saying that for an adhesive to work really well it has to have a certain amount of flexibility so that when the joint is stressed the stress is transferred to the millions of points of adhesion thus spreading the load. They said something like: if it is too hard then either the adhesive fractures or the force gets concentrated at fewer points of adhesion and the thing detaches.

They likened it to a piece of gooey chewing gum on the pavement. It was a balance between flexibility and strength.

I'll see if I can find a link and add it here as I suspect it would be quite interesting even for those not currently gluing anything.

Cheers,
Chris

PS Found it: What makes stuff sticky?

AF62 wrote:Gripfill - https://www.screwfix.com/p/gripfill-adh ... 50ml/10261

Seconded.

It also depends by what the OP means by "rock hard". I'd say Gripfill eventually sets into a material akin to hard plastic, i.e. chips if shocked but remains ever so slightly bendy compared to, say mild steel or concrete.

https://youtube.com/shorts/u7poJywa5z4

Depends why you want it to set “rock hard” though; for e.g. 3d printing or for sticking things together?

Just re-listening to the thing above.

If you have two surfaces that are highly polished and pressed together (especially in space) they stick together because of all the Van der Waals forces. A glue is an intermediary to rid the interface of the gaps and so increasing these attractive forces. It mustn't be brittle and ideally is made of polymer chains that tangle, like hair, so when a force is applied they lock up and distribute the force amongst the atoms on the interfaces.

Fascinating. C.

MyNameIsUrl wrote:Looking for a cartridge of sealant/adhesive that will set rock hard ..

To stick what to what?

V8

csearle wrote:Just re-listening to the thing above.

If you have two surfaces that are highly polished and pressed together (especially in space) they stick together because of all the Van der Waals forces. A glue is an intermediary to rid the interface of the gaps and so increasing these attractive forces. It mustn't be brittle and ideally is made of polymer chains that tangle, like hair, so when a force is applied they lock up and distribute the force amongst the atoms on the interfaces.

Fascinating. C.

Reminds me of what my mate likes to ask about this.

If you make two pieces of the same metal very smooth and put them together, how do the atoms know they are not all part of the same piece of metal? Would one expect them to cold-weld together?

88V8 wrote:

MyNameIsUrl wrote:Looking for a cartridge of sealant/adhesive that will set rock hard ..

To stick what to what?

V8

that remined me of this website: https://www.thistothat.com/ on the subject that's been around since the last millennium

- sd

Mike4 wrote:If you make two pieces of the same metal very smooth and put them together, how do the atoms know they are not all part of the same piece of metal? Would one expect them to cold-weld together?

One of the experts in the episode above said much the same thing. C.

Look also at the epoxy resin crack-sealants. These are used instead of wall plugs when needing to embed large (18M upwards) bolts.