Uv exposure of polyurethane glues does it go deep!

[MikeSharp01]

We are using polyurethane adhesives in various places on our frame, while it is not being used structurally, mostly gap filling / joining insulation boards, I was wondering how it's structure gets damaged by UV exposure. I dimly recall from sleepy materials science lectures about 40 years back that surface changes of plastics resulting from various sources can penetrate beyond the skin although I cannot recall the process. Does this happen in PU adhesives or are the UV degradation effects limited to the outer surface? Any ideas?

Edited August 26, 2019 by MikeSharp01
Typo

[Temp]

I think silicone has better UV resistance than polyurethane...

 

Google found..

 

https://www.directsealants.com/difference-between-silicone-sealant-polyurethane-sealant/

 

"The silica-oxygen (Si-O) bond found in silicone sealants is much more resistant to UV rays than the C-O bond present in polyurethane sealant.The outcome is that silicone sealants are inherently stable and more robust in terms of weatherproofing."

[SteamyTea]

They both discolour.

The best for UV protection should be acrylic, but as they add so much fillers into it, I suspect it is no better than any other.

I am not sure what difference colour will make, reds where always terrible for aging. Black went grey, white went grey, clear went grey, blue went grey, as did yellow and green.

Maybe grey is the best colour.

[MikeSharp01]

1 hour ago, Temp said:

Google found..

 

https://www.directsealants.com/difference-between-silicone-sealant-polyurethane-sealant/

That's an interesting link.