It's not that simple. If you read the vinylengine topic, you'll see that there are lots of cases when a record kept in an inner poly-lined sleeve, in an outer cardboard sleeve and in an outer PVC sleeve was ruined by the chemical reaction with PVC. I can't even imagine how this reaction may be possible if there are two layers of paper and cardboard between outer PVC and a record, but photos with wavy PVC sleeves (with "waves" in the shape of the record) prove that it's indeed possible. I guess paper and cardboard are porous in their structure, and they aren't strong enough to prevent leakage of PVC molecules. Of course, picture discs are worst in this situation because they aren't usually supplied with protecting cardboard or paper sleeves and directly contact the PVC surface.