I tried not to delve to deep into chemistry when discussing this before but acrylic is just another polymer but its high molecular weight means it will surive longer before degrading.

Where the PVC flips may cause chip bleeding within say 12 months, airtites may protect for 10 years. There is another fact to consider. The air-tite is supposedly air-tite but it is neither a vacuum nor contains clean air. Atmospheric conditions could lead to formation of condensation inside. Excessive light will also cause deterioration.

Its fair to say that the harder the polymer, the safer it is. No plastics can be totally free from poly derivatives - they are part of the molecular structure. Mylar is probably the best as its the hardest. The Mylar layer in a cardboard flip is only a few microns thick. Imagine this was an inch thick - you couldnt break it with a sledgehammer.

Museums use Cellulose Tri-acetate. Estimated safe for 100 years in an enclosed environment. Used to be used as the top coat on car bodies.

Finally, some products have chemicals added to make the surface shiny. Beware the more shiny the product is. Mylar, for example, is only transparent when micro thin.