Expanding foams

[Fr J Hackett]

Can anyone supply advice or info on the use of expanding foams for use to insulate a coolbox. Specificaly how well do they pour, I need to get it to run / flow into an area that I can't reach. How long does it take to activate and expand and what sort of temperature is it activated at, part of the area is next to the hull so is never likely to be much above 15 C and is quite cold now. Any suppliers to use.

Thanks

 

[Quandary]

There are a variety of foams available based on a foaming expanding liquid, the common builders foam used for sealing construction cavities such as around windows etc is sold in aerosol cans which give the expanded volume on the label, they are injected using a tube supplied usually about 20 cm. long. but this could easily be extended, work back from the furthest reaches of the cavity and let it expand while still fluid ,this stuff has a complex chemical name which I can no longer remember but is marketed by Polycell, etc. It is fine in dryish locations and is very sticky and hard to remove from any surface including upvc and grp. Note the instructions, it is set off by contact with water so you need to spray the area of use before applying.
Polyurethane foam is a higher quality product used as a structural medium in rudders etc . it comes as two pack but may be difficult to place in extended cavities, it is available from any grp supplier such as CFS. For your job I woud use the first type, possibly with an extended squirter tube but I would mask the surrounding area very well first, if it comes out around the surface let it go off and then cut away with a saw. Don't seal the foam in until it starts to set as the expansion force is considerable.
Both these types are readily available general purpose and while insulators are not specifically insulating foams, you could possibly get a specialist product with higher thermal performance from an insulation or ducting specialist.

 

[Quandary]

Regarding the temperature query which I overlooked, the two pack polyurethane is temperature sensitive but above 15C should be fine, this type is good where you want to overlay with polyester or epoxy resin.

 

[Refueler]

Spray expansion foam - we call it Makroflex out here is available in various types for exterior and interior use with varying expansion properties.

But I can vouch that even interior ones do not degrade with water, they discolour but do not fall apart or absorb water.

Main point to watch though is the expansion - it can exert considerable pressure and so needs to be injected carefully.

 

[charles_reed]

Polyurethane foams

all the injectable are water cured and the builders versions are good for insulating areas you can't get into.

The 2-pack version is usually a higher modulus and quicker curing, and doesn't need water to help it cure.

 

[aitchw]

[ QUOTE ]
Main point to watch though is the expansion - it can exert considerable pressure and so needs to be injected carefully.

[/ QUOTE ]


I would add to that caveat the fact that it is best to build it up in stages, letting each batch injected expand fully before adding another one. This not only alleviates the above problem but also the tendency of this foam not to cure properly in the centre of large volumes applied in one go. You can be left with a permanently gooey unexpanded core where it is unable to activate through lack of moisture.

As previously suggested a very light fine spraying of water helps enormously.

I can confirm Refueller's other comments about it's resisitance to taking up water. I have had lumps of it held under water for months as a test and it has been fine when removed.

 

[ningcompoop]

I used both 2-part (pour) and 1-part (spaycan) when refilling a bouyancy compartment on my little boat.
2-part is very messy stuff to use/mix, but it pours and runs well, allows you to do small sections at a time and makes it easier to get into awkward spaces. Reached full expansion in about 5 mins or so. The minimum recomended temp is 10c, (optimum is 20c) otherwise it may not react fully - don't know if you could pre-warm the area with hair-dryer/hot-water bottles, it does exotherm once it starts reacting. Also releases nasty fumes, you'll need ventilation. I ran out before I got finished so I topped it off with polycell expanding foam from a can - fairly easy to use, can be used down to 5c (it says on the can) but you can only get it to where you can squirt the nozzle. Also needs ventilation. The polycell stuff appeared to carry on expanding for quite a few hours after - suprising - beware! Try and work out what volume you need to fill, the canned stuff is very expensive if you have a big space to fill. The canned stuff I just got from the local DIY shed, although if you want to buy in quantity there are sometimes bargains to be had on ebay. The 2-part you'll have to get from a specialist fibreglass supplier - I got mine from CFS, they also have good user info on there site- clicky. They also do sheets/blocks of foam if they would be any use.

 

[andrewbodenham]

Difficult to say without seeing pictures, but it sounds like the 'builders' expanding foam might work well. If you go that route it is well worth investing in a proper dispensing gun (around £15) to use with the 'gun grade' cans of foam widely available from trade suppliers, Screwfix etc. Not only will this work out cheaper than the one-shot DIY cans, but being able to accurately control the flow of material is a real plus.

As others have suggested it's best to build up thick sections in layers of say 20mm. Plastic tubing can be used to extend the gun nozzle to reach inaccessible areas.

Be sure to get a can of 'foam cleaner' (acetone) for cleaning up un-cured foam and equipment - the stuff has a tendancy to get everywhere! And wear gloves!