Any spray foam that can expand / cure in a closed bag?

[Home Guy]

I'm trying to apply some expanding foam to the inside of a closed garbage bag that's situated between two surfaces that are about an inch apart. I want the foam to take the shape of the irregular surfaces as it expands and hardens, but I don't want the foam to adhere or bond to these surfaces so I've placed an ordinary plastic garbage bag between them and that's where the foam is being injected.

I'm discovering that the small amount of foam that's leaking out of the fill-holes is expanding and curing nicely, but the foam inside the bag seems to be semi-solid goop. I'm leaving this over night to see if it's any better tommorrow, but I'm thinking I'm going to need a different sort of product other than "Big Stuff" aerosol can gap filler.

I know there's some foam packing material that is isin't particularly messy and I think is applied inside a bag or membrane that conforms to the shape of what-ever is being shipped. Is this stuff available?

Any other ideas?

[Home Guy]

I see that there's 2-part expanding foam that comes in variety of densities, for marine use, hobby, etc.

So you mix 2 parts, and you have maybe 30 seconds or a minute to pour it before it starts to expand.

The stuff you buy in an aerosol can - is that 2 parts (and if so, how do they keep the 2 parts separate)?

[aemeijers]

You are on the right track, but I don't think anybody sells one-use packs of the stuff- it is usually a station on the packing line, fed from tanks. I don't suppose your project is portable enough to carry into one of those shipping places?

[DD_BobK]

Somebody at work just told me about this stuff, I'd never heard of it. Totally new to me.

I always figured that "foamed in place" packing required an expensive setup; tanks, hoses, etc

You might try making your bag "tall" and leaving it open on the top edge. Maybe that allow enough access to atmosphere to cure.

Play around with the volume of foam you squirt in and let it "grow" towards the open edge.

If you get the amount correct you won't get much excess height. The excess can be trimmed off with a utility knife

Seems like the key is using a plastic bag that is not completel sealed. Maybe yours will cure overnight.

HTH

cheers Bob

[Home Guy]

Ivex Flaskpac.

Yea, that's what I was thinking about. I've seen that sort of packaging material at work (we've received stuff that was packed using either exactly that product, or something that worked exactly the same way).

If you notice, that is a 2-part expanding foam product. It's just a self-contained version.

I still wonder how the single-part "foam in a can" works compared to the

2-part stuff.

The foam-in-a-can seems to need exposure to ambient air in order to expand and cure, but the 2-part stuff doesn't.

I don't think I'm going to be able to source any 2-part foam locally. The best shot seems to be a hobby or marine products store. I don't think any of the big-box home improvement stores have this stuff.

I'll probably have to modify my setup so that I can spray the foam-in-a-can with full exposure to ambient air.

[DD_BobK]

The other two links I posted gave experiences about using canned foam sprayed into bags. I have no direct experience but it seemed like the links were applicable esp the Yamaha one.'

cheers Bob

[clare]

Urethane foam requires moisture to set. In a sealed plastic bag there is no moisture, so it never "kicks off" the reaction. You could try misting the inside of the bag lightly with water before injecting the foam.

[gregz]

If your concerned if it will set up inside, try a test. I have added foam to Coleman coolers and the like. I may take a day or two. It sets up internally when you make a ball, so I don't think it need air.

All the small cheap coolers have no insulation in the top. Heat radiates in all directions.

Greg

[jamesgangnc]

US composites sells small quantites of 3 part foam in various densities. The 2lb stuff is porbably good for your project.

[dahailtd]

Or don’t use an airtight bag. Have you considered trying a light linen or cotton based fabric bag?

[Clare Snyder]

Any 2 part urethane foam will cure in an airtight bag as will many soy based foams used for packageing.