On Wednesday, 13 March 2019 21:15:10 UTC, The Natural Philosopher wrote:
On 13/03/2019 20:49, Mathew Newton wrote:
Just taken delivery of a number of Celotex GA4000 PIR insulation boards and, as shown in the photo below, the 100mm boards in the foreground are extremely wrinkled one foil face, particularly when compared with the completely smooth 30mm and 12mm boards in the background:

http://www.newtonnet.co.uk/permanent/celotex.jpg

The 100mm boards also have an ever so slight bow to them; not enough to cause me an issue but I wondered if the bowing and wrinkles were the result of differential shrinkage within the core?

Any cause for concern?

been left out in the cold thats all.

delta expansion coefficients

Well, if that's so, they will flatten out spontaneously as they equalise.

I have had lots of this insulation and never seen this sort of thing.
I have never seen visible expansion.
I have seen concave edges but not enough to matter.

It's closed cell structure so shouldn't absorb water either.

It may not matter, depending on application and how small you are cutting it up.