On 05/02/2013 16:18, Harry Bloomfield wrote:
Brian Gaff used his keyboard to write :
Really, I know some car body filler gets hot as it cures, is this what
you mean.

No, it is the chemical hardener in the filler which attacks the
polystyrene, it basically turns it into slime according to what I have
read. I just needed some advice on whether just keeping the two
separated was enough, or whether one needed to be sealed from the other.

I saw a video of such a repair and they used some substance to seal over
the polystyrene, before applying the filler.


Not quite true. Car body filler is mostly styrene monomer with an inert
filler, the hardner triggers polymerisation to polystyrene. The problem
is that the polystyrene foam insulation is somewhat soluble in the
liquid styrene but this should not cause real problems - particularly
once it is cured.

If you are worried about it getting hot, don't overdose it with the
hardner & it will cure more slowly. It will stick to polystyrene well
as it is all the same thing really but I guess might cause some of the
foam to collapse.

If a cavity forms in the insulation could it be injected with
polyurathane foam?

HTH

Chris K