Re: Expanding foam and UV

I've heard this said quite a few times, but I'm really not sure. Think about how it's formed - lots of bubbles of propellant expanding away in a PU matrix. I'd say it is largely closed cell, with only a few through paths. Its moisture absorbance is quite low.

Yes, logic suggest this, but embarrassing stories win over logic every time:

Chum decides to make boat dock pontoon out of fibreglass and, to guard against flooding in case of damage, fills it (them actually) with expanding foam. Inevitable damage does occur and pontoon sinks faster than you can say impervious steam liner :-)

I used it as replacement insulation on bottom of a freezer after the initial fibre matting became waterlogged (or rather, ice logged). I also assumed it was closed cell and wouldn't need any further surface sealing, but I was wrong, although it did take about 3 years before it became completely water/ice-logged.

I'd say you can leave a vertical surface exposed to sun and rain for a few months. Eventually you need to fill and seal, having excavated any crumbly stuff.

hahahah. even if it's not true that's hillarious :-)

RT

In article , fred writes

On reflection (this was a while ago), I think it was wave action breaking over the pontoons, rather than damage, that ended up with them waterlogging, but they definitely ended up sinking.

But (back on topic) I agree that short term exposure, of a matter of weeks, will do no harm

I had some filling a rather large hole around pipe - it was left exposed for at least year, when I eventually cut the excess back and mortared over the top it seemed pretty much as sound as it ever had been

It's effectively open cell, just slow. It doesn't matter if it's a "mostly closed" cell foam, if you need it really sealed.

If you use the two-part foams, not the squirty can stuff, there are grades of those that are real closed-cell foams.

It was somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember chris French saying something like:

Ditto. I've left filled holes unpainted for ages and the foam's been fine underneath the dark surface.