Styrofoam and Acetone (Video) 1 discussions Acetone breaks the structure of polystyrene in its expanded form, styrofoam. The 'foam' bit goes away. In other words, acetone "dissolves" polystyrene. Also see the video "Pressured Styrofoam" which s.. Tags: styrofoam acetone harry lee leeHSL dissolve polystyrene