Might sound like a random question but I seem to remember as a kid that some glues dissolved polystyrene! Need to glue some card to polystyrene to restore an old board game but can’t remember which glues eat polystyrene. Might have been Uhu. Or maybe it was airfix model cement.

Anyway need a strong safe glue!

Or maybe it was airfix model cement.

it would definitely be that was dissolving the polystyrene – airfix models are the polystyrene and the idea of that glue was it dissolved and re-set the plastic when gluing pieces together –

Uhu should be fine – anything non solvent-y should would ok.

Polyeurathene glue (gorilla glue) works really well with polystyrene but foams/ expands as it sets a little so can be messy (and sticks to skin like buggery)

A safer option might well be PVA wood glue, takes a little longer to dry, but any excess can be wiped off with a damp cloth.

Impact adhesive.

I remember a friend repairing his large polystyrene toy glider with it.

Airfix glue/polystyrene cement melts it.

PVA, or maybe wood glue.

Polestyrene cement as used on plastic models and the like will dissolve some poly foams and plastics.

If in doubt try a tiny bit first and observe.

Copydex
glue both sides and use as contact adhesive.
I used to make model airplanes and this was the method for covering the foam wings with Beech veneer.
Quick tip is to add some food colouring to the glue otherwise its invisible.

Copydex.. Or rubber solution glue is a good shout.. Forgot about that!

It’s gloopier than PVA so won’t wick into the polystyrene so much.

http://www.amazon.co.uk/UHU-POR-Styrofoam-adhesive-tube/dp/B000LKOC1M