Expandable foam

[Mr Pounder Esquire]

I've never used the stuff. Could this really happen?

[Jonno]

Mr Pounder Esquire scribbled

No. That's all CGI.

[soup]

Yup, mixture consists of two liquids that when combined expand at a ratio of about 50:1 whilst hardening .

A story of its use (perhaps apocryphal).

[Bob Eager]

PLEASE! On uk.d-i-y you must quote the original source (it even mentions it):

[Alan Braggins]

The foam in the GIF isn't a hardening one though:

(And expansion ratios are generally less than 50:1

)

[harry]

The stuff you get in an "aerosol" can is hardened by moisture in the air.

The stuff shown is two component mix. Used to make the stuff blown onto the back of roof slates. Used in boats too.

I think the video is speed up a lot but yes,could happen. Depends on ambient temperature. Ideally the stuff needs to be thoroughly mixed in an exact ratio. Often mixed in a special applicator/nozzle in a continuous procees.

[Martin Brown]

Indeed - it looked more like the concentrated peroxide and potassium iodide reaction although it was actually a bit on the slow side for that. This would also explain the brown colour.

I saw it done recently with highest strength reagents and it projected the jet of toothpaste about 20' into the air. If they were well chilled beforehand that might keep it under control for a short while.

The reaction rapidly reaches boiling point. Indeed the bomabadier beetle uses a variant of this reaction in self defence.

In the early days of polyurethane foam badly mixed batches would sometimes catch fire due to the excellent insualting properties combined with a vigour reaction still occurring internally. Later they added fire retardents which slow down the burn rate at the expense of potentially producing *very* nasty fumes when it does burn.

The other common mistake is to overfill something that is capable of deforming and then watching it buckle outwards or fall apart.

[newshound]

Although it *looked* a bit like polyurethane foam, it wasn't. The bubbles came from hydrogen peroxide, decomposed by a catalyst, the "foam" from the addition of soap or a detergent, the fire from the addition of petrol.