Test for Undercured Silicone 3

[nlj]

Hello!

I have a part that is made of 7 ply aramid fiber silicone. We are having some burst problems and our supplier believes it is an undercure. (I believe their process is very out of control, but that is another conversation).

I'm trying to determine some testing that can help us confirm whether or not the material in in fact undercured. From most of what I understand if I had a part that had a known good cure I shoud be able to test hardness, elasticity, strength and compare to the suspect parts for undercure.

I also noted that I may visually see bloom on the surface which may imply undercure or overcure

Are there other tests that we would be able to conduct on the parts to confirm or deny the undercure that you are aware of? Or other visual indicators?

Thank you!

 

[GrahamBennett]

Depending on how the aramid textile is made up, it might not be possible to do any physical testing because the fibres would interfer. Cut through the thickest section of the part and look for porosity, which is a sign of severe undercure.

 

[johnnymat]

If you have access to a DSC analytical equipment that woukld give you a definitive answer.
if it is severely undercured the material would feel ike chewing gum and not have the very elastic snap that silicone has.
porosity is a sign of undercure but you also get this if the mould was not filled properly,
you could also check its swell behaviour, A fully crosslinked silicone would give about 5-10% swell in say propanol( overnight at room temp). if it is much more than this say 50 to 100% then pretty good sign that it is not fully crosslinked ( cured )