There will be migration of additives between any two plastics in intimate contact. That's driven by the concentration gradient. So, from the PP you can expect calcium stearate, antioxidants and any nucleating agent to go into the PVC and conversely plasticizers and stabilizers will migrate from the PVC into the PP. Luckily because the two polymers are quite inert you should not usually find a major problem, only that the lowering of the additive concentration may result in slightly reduced long term thermal stability.
Chris DeArmitt
Plastic & Additives Webinars
Training the Fortune 500 since 2003
