Evaporation of xylene (which is a solvent) will leave the polystyrene. I used an other solvent (acetone) to glue compact polystyrene plates together (or ABS more accurately).
The polystyrene left by solvent evaporation will be in an aggregate form that differs from the original material. I expect it to be less dense and be softer. Getting the full strength from a material generally needs lamination, extrusion, injection, isostatic pressing... but this may happen in a later step if you recycle the polystyrene.
Solvents have been proposed again and again to recycle polystyrene foam, getting the compact form.