polyurethane foam stuck on painted surface

[dogbural]

Hi,

I have a painted sheet metal, sitting on polyurethane foam.
Ensure the painted surface is fully cured prior to putting on the foam.

However, for some reason when lifting the sheet metal some of foam is stuck and left foam mark on the painted surface.

The sheetmetal is around 1000kg and foam is 1-2cm thick.
The sheetmetal is coated with primer and topcoat.

Also, when I did a quick check using Methylated spirit on the painted surface in contact with foam, the paint came off easily unlike other painted surface not contacted with foam.

Could there be chemical reaction from the foam?

 

[3DDave]

Probably the foaming/blowing agent is the culprit. A double-sided tape or other barrier may be of use or using a different paint system.

 

[TugboatEng]

Polyurethane paint and polyurethane foam? Sure there can be some cross-linking happening if the paint is recently cured. 3Ddave is correct to suggest a double sided tape barrier. There are also some thin single sided FEP tapes that you can apply to the foam to prevent sticking.

 

[dogbural]

Thanks all,

So it could say that the foaming/blowing agent which is formed in the foam can trigger reaction (cross-link).
is there any supporting document that I can read thru on cross-linking between polyurethane materials?

Below is one of barrier I could think of. But this is made of polyethylene. Would it be safe to use on such painted surface?

 

[3DDave]

I would suspect the foaming agent of dissolving the paint. Usually I have seen problems with penetration and damage by plasticizers, but you need more information from your paint supplier and the foam supplier.

 

[TugboatEng]

When you say the paint is fully cured that typically implies full mechanical strength. However, the paint also has a recoat interval, typically 30 days for a polyurethane. During this time the paint still open to cross-linking.

Dissimilar materials are less likely to cross-link. Polyethylene is dissimilar from polyurethane and also has low surface energy which means it doesn't tend to bond to other materials. FEP performs even better.

You can also consider coating the surface with polyvinyl alcohol. This is water soluble and can be washed off after use.

 

[dogbural]

Thanks guys, much appreciated