The Case of the Slumping Polystyrene Foam (Question for the Experts)

Recently, I mounted a few pairs of metal chests of drawers piggyback-style, which entailed drilling some holes. To keep the point of my drill from skittering away, I used a center punch to create a tiny dimple at each of the intended hole locations. Intending to clean the drill and the deburring tool that I’d used on the holes (a hex-shank deburring blade in a hex-shank handle as you can see in the photos below) once I had unpacked the tool-cleaning stuff (WD-40, Fluid Film, etc.), I laid them both — along with the center punch — on a fragment of one of the polystyrene foam sheets in which the metal drawers had been packed for shipment.

Handle of the Gedore 101 turned so that the downward-facing surface that had been in contact with the polystyrene is visible. See the bits of whitish polystyrene clinging to the textured black overmolding? — Handle of the Gedore 101 turned so that the downward-facing surface that had been in contact with the polystyrene is visible. See the bits of whiitsh polystyrene clinging to the textured black overmolding?

Fast-forward a week or so. When I grasped the center punch to lift it off the styrofoam, there was some resistance, as though it had been glued in place. It sort of was. The polystyrene, where it had been in contact with the black overmolding on the handle of the Gedore 101 automatic center punch, had degraded.

The image above shows the center punch (markings are on the butt of the handle, see inset image) and, to its left, a hex-shank handle (a Gedore 676) I’d used to hold the deburring bit with which I tidied up the holes after drilling and before inserting the fasteners. All that the Gedore product listings say about the handles are that they are both 2-component handles, but the black material that I’m assuming was overmolded onto the blue plastic differs slightly between the two. On the center punch, it’s a bit shinier and feels more rigid than on the bit holder. The difference in sheen in these photos is real and not an artifact of the angle of the camera lens.

Some drawer bodies, as delivered, before I bent them into shape.

The small amount of polystyrene adhering to the black material once I’d pried the center punch free were easily removed — scraping with a fingernail was sufficient — and the plastic on the tool was unmarred, but the polystyrene sheet had developed some depressions in the corresponding places and they were deeper than could be explained by the bits that had clung to the center punch’s handle. You can see them in the other photo embedded in this post (the one directly above), which I’ve tweaked to make the concavities more visible.

This is the first time that I’ve seen this sort of behavior from polystyrene foam, but I’m not a materials scientist or packaging engineer. I’m going to try posting a query, accompanied by the second image, to some materials science subreddit or forum and see if I can get a pointer to more information.