pu-foam which stays elastic?

I have some steel construction, where I need a PU-foam bead of about 2" for insulation against water, to allow adaptation if the steel
extend a little due heat and cold, the foam should stay a little elastic.
Is there a special foam for such purpose, and where could I order it over the net? Or will the standard foam from Loews in the red can with yellow cap also do it?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
Add image file

Polytechforum.com is a website by engineers for engineers. It is not affiliated with any of manufacturers or vendors discussed here. All logos and trade names are the property of their respective owners.