The Prusa3d knowledge base mentions that acetone will "rejuvenate" PEI in addition to cleaning oil and grease from the surface.
About once a week, or when prints stop sticking, use ACETONE to clean the bed. It removes grease better than IPA or Windex. It also rejuvenates the print surface. However, if you use acetone every day, PEI will become brittle and start cracking.
From a chemical or physical perspective, how does acetone affect the PEI surface?