I acquired a ~16 year old laptop. The mat black plastic top (back of the LCD) is sticky. At first I thought the previous owner had stickers on the back that were removed. But that seems like a bad theory now. I rubbed it with a cloth and denatured alcohol and it only got slightly less sticky, but black residue came off on my hands and the cloth. This is apparently not adhesive.. it’s the plastic itself.
What’s my best move? I don’t suppose I can do anything to re-polymerize it. I don’t care about cosmetics.. I just don’t want it to be sticky and marking anything that touches it. One temptation is to put plastic film on it, like cling wrap. But that could just make a bigger mess.
Sounds like those "soft touch" plastic surfaces. I've had a bunch of old plastic things turn sticky that way - it's really hard to get it off but what I do is alternate between isopropyl, WD40 (brushed on with a cotton swab or cotton ball and let it sit for a while to let it break down the sticky before using Clorox or isopropyl to remove the WD40), and Clorox wipes. Eventually the matte finish comes off and you're left with a shiny plastic surface. It just takes a lot of elbow grease, I often give myself finger blisters from scrubbing but it's a relief to get it off.
Edit: also the last time I did this was on some old lighters which had a soft touch plastic which turned sticky, what ended up happening was the WD40 seemed to help soften the sticky stuff which allowed me to push it around by rubbing really firmly in one direction. If you push it towards one spot it'll bunch up like softened sticker goo, then I use Clorox wipes to pinch up the bits of collected goo. It still took a lot of rubbing to get the last sticky stuff off to reveal the shiny plastic underneath but "migrating" the goo into a pile once softened by the WD40 (but degreasing the excess WD40 with the Clorox wipes before rubbing so that your finger doesn't just slip) seemed to be the strategy for my sticky lighters.
Hope that helps you figure out something that works for you
WD-40 sounds like an interesting idea. Most people think of it as an oil, but in fact WD-40 is a cocktail of many different solvents, plus mineral oil, IIUC. It’s indeed more of a cleaning product than a lube.