I'm hacking that thread since I have a similar need.
For a high impedance circuit (a charge integrator) which needs to be included into a detector, I need a potting which exhibits the following characteristics :
-Low outgassing
-very high resistivity
-high voltage capable ( 1kV / 1mm)
-moderates cure temperature if applicable
-SMD compliant.
I'm currently using an epoxy bought from RS, but not a big fan : outgasssing is not specified and obviously quiet strong, even after 1 week of cure.
Money is not a major issue : I don't need kilos.
thanks for you help !