Two things spring to mind with one for me.
(1) Does this mould have core pullers?
(2) Does this mould have DME heating?
In regard to the first, slow the core pullers down as low as possible, then increase the speed gradually to the point that the crazing around the inserts have disappeared...
I agree with thermcool,
Polyethylene is the choice for this application. The company I work for mould thermal cylinder covers in HDPE for LPG cylinders that get buried underground for a large gas supply company here in Australia. Many of these are used in underground mines, and Hydro power...
Loctite make a ceramic epoxy called Fixmaster Nordbak Brushable ceramic, good for temps to 288 degrees C.
Warning though it is around $500.00 Australian for a 500ml tin.
Here is the link to the product,
http://www.loctite.com.au/int_henkel/loctite_au/index.cfm?&pageid=133&layout=2
I have it wrong, we mould Table Hockey Pucks, 80mm Diameter
and foam filled. I found in our store Friday.
Material is HDPE and wall thickness at a guess is about 4mm.
Weight is 125gms.
Hope that helps.
Sorry for the late reply,
We haven't moulded these in a while, but from what I can remember about the mould - they are about 125mm Dia and 30-40mm thick. Moulded wall thickness is 6-8mm rotational moulded and then foam filled with a cellulose two part high density foam. To be honest I'm not sure...