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Yes, I came here to say something similar but anecdotal. I've seen multiple old electronics items where the plastic parts become sticky and give off smells that remind me a bit of vinegar, vinyl, and horrible pesticides.

I've sometimes wondered if it is just the chemicals breaking down as you describe, or even something like fungal metabolites.

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If it's hard (possibly transparent) plastic and smells like stale puke, that'll be acetate based plastic and there's nothing that can be done. If it's a tacky "grip texture" which has turned into a combo of contact adhesive and staining goop, it's likely to be urethane hydrolysis.

Bad news about the former is it's an autocatalyzing reaction, once it gets going there's no stopping it. The good news about the later is it's relatively easy to scrub off using >95% IPA and a kitchen sponge.

Puke is polybutyrate. Acetate is vinegar.

Ahh good to know, thanks. PBT/PBAT is actually one of the "alloying" additives used to create PLA "Plus/Tough/Meta", as it increases hydrophilicity, deflection temperature, flow and ductility. Hopefully it's used at a low enough ratio that it doesn't get smelly!

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