I insulated the conservatory with bubble polythene over winter. On the doors it had to be held down onto the PVC with sticky tape, either the "invisible" 3M type or masking tape. Exposed to the sun for several months, both types of tape hardened and baked on. The invisible tape could mainly be pulled off, and the remaining sticky residue removed with isopropyl alcohol.
The masking tape was a different matter. It tore rather than be pulled off, and in the end I used an old plastic ice scraper to get off the tape part. It was hard work, and left a very sticky residue on the PVC. The isopropyl alcohol didn't touch it - no effect whatsoever. I had acetone, but couldn't use it as it damages PVC. The only other solvent I had was white spirit. I didn't expect it to damage PVC, and it didn't. It also slowly dissolved the sticky residue, and the PVC is now back to normal.