Adhesion to Polyurethane foam

[Mr Efficiency]

Can anyone tell me the adhesion properties of common resins to cured, moulded PU foam, the slick surface, not cut foam. Just a little doubtful that Polyester might stick.

 

[Steve W]

If you are talking about the hard skin of a part molded with an A-B pour foam such as buoyancy foam I would be doubtful that epoxy would stick either without removing the slick skin and even then while either resin would adhere ok the foam would need to be of a reasonable density to have any strength, ie, the foam would fail, not the resin bond. If you just want to bond something to the hard skin without prep a methacrylate adhesive such as plexus would probably work best.

 

[Mr Efficiency]

If you are talking about the hard skin of a part molded with an A-B pour foam such as buoyancy foam I would be doubtful that epoxy would stick either without removing the slick skin and even then while either resin would adhere ok the foam would need to be of a reasonable density to have any strength, ie, the foam would fail, not the resin bond. If you just want to bond something to the hard skin without prep a methacrylate adhesive such as plexus would probably work best.

Thanks, Steve W, the part will be 4lb/cu ft, probably, so not the lowest density, the problem is I can't glass easily inside the mould then pour the foam, as working inside the mould would be too difficult. The mould would be dismantled releasing the cured foam, with a layer of glass then applied to the slick skin. I may experiment on some small samples, seems easy enough to do.

 

[Steve W]

I am familiar with how these foams skin over and it is pretty shiny. As a rule most resins, paints etc don't adhere well to shiny surfaces regardless of what resin type so I would expect you will need to do some prep, it would be nice if you don't need to sand the skin right off, only doing tests will tell.

 

[Mr Efficiency]

I will do some experimenting, including rubbing over with sandpaper, without breaking through into the cellular material underneath.

 

[upchurchmr]

Just remember as was said that the foam has very little strength. Actually the strongest part of that foam block will be the slick/ hard surface.
The bond still does not need to be very strong to do the job.

Are you trying to make structure with foam and 1 ply of glass or will this just be a filler that has good waterproofing?

 

[Steve W]

Want to share what the item is? Have you considered glassing the individual parts of the mold and trimming off the flash before assembling and pouring the foam, you could lay extra laminate after it is de molded if its structural but you would have the best possible bond.

 

[Mr Efficiency]

Want to share what the item is? Have you considered glassing the individual parts of the mold and trimming off the flash before assembling and pouring the foam, you could lay extra laminate after it is de molded if its structural but you would have the best possible bond.

Rather difficult to explain the application(s), but what you suggest there is something I will have to consider. I certainly agree "wet" foam will likely bond better to cured laminate, than the other way round. I'll think some more, and thanks again for the advice.

 

[Mr Efficiency]

Just remember as was said that the foam has very little strength. Actually the strongest part of that foam block will be the slick/ hard surface.
The bond still does not need to be very strong to do the job.

Are you trying to make structure with foam and 1 ply of glass or will this just be a filler that has good waterproofing?

You are right, it would not need to be strong, but being a slick surface it might be little or nothing with polyester. Testing samples is easy enough.

 

[FAST FRED]

If you are building a tank a common method (motorcycle) is to shape a block of foam and use epoxy resin on the outside.

Layer as much glass as is required for proper thickness.

When the gas cap hole is cut in , pour old battery acid in the tank

It will dissolve the interior foam.

What is it that you are trying to create?

 

[Mr Efficiency]

If you are building a tank a common method (motorcycle) is to shape a block of foam and use epoxy resin on the outside.

Layer as much glass as is required for proper thickness.

When the gas cap hole is cut in , pour old battery acid in the tank

It will dissolve the interior foam.

What is it that you are trying to create?

No, not a fuel tank, there is more than one purpose I am thinking of, but one has a bouyancy function mainly, I take it your above example is polystyrene ? I will do some experiments with adhesion to polyurethane "skin".