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.
I would just clear coat it.
Tape off everything that you don't want the clear coat on, spray on a coat, let it dry spray on another coat, sand it with some 400 or 600 grit sandpaper, wipe it down, spray on another cover of clear coat.
Might be a bit of a hassle but if you want to make sure that it's not sticky anymore, clear coat is the way to go.