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<p>[QUOTE=&quot;desertgem, post: 2396428, member: 15199&quot;]Generally not the plastics themselves, but additives such as plasticizers or adhesives attaching them together. Plastics ( organic polymers generally) are typically very inert to outgassing, but in order to change some such as Polyvinyl Chloride ( PVC_ from a solid, relatively inflexible, opaque material ( plumbing)&nbsp; into flexible, transparent coin holders, etc, a group of chemicals called Phthalate, Adipate and other Polymeric Plasticizers are added. These can gas out and if they condense on coins surface, can in some conditions produce acidic reactions on coin metal, especially copper based. With flexible PVC flips, as much as 30% plasticizer can be initially present and take 20-30 years to outgas. Most of these have left the market place, but some sellers use them as they are softer on a coin until it is someone else&#039;s problem. Hard plastic holders are safe as they do not have the additives. Hard plastic holders do breath as they are affected by changes in atmospheric pressure that acts on the 2 shells. Airtites(tm) of course are not immune from this as they are not air tight.[/QUOTE]</p><p><br /></p>

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