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Common Plastics #1-#7 Discussion and Question
hchcoin
Posts: 4,825 ✭✭✭✭✭
Here is a basic breakdown of the 7 most common types of plastic and the number associated with each that can be found inside a triangle for recycling purposes. Wondering which of these other than PVC #3 is bad for coin storage? The reason I am asking is I saw someone who was storing 90% in a plastic container similar to the ones used in fishing tackle boxes with polypropylene #5. I am wondering if this is relatively safe for coins because I liked the storage capability. Thanks!
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The real issue is what happens when the plastic begins to depolymerize (decompose), particularly due to prolonged exposure to heat. Decomposition products having a relatively high vapor pressure can be released, and then deposit onto the surfaces of things nearby, like coins, causing chemical reactions in many cases. Anything that could decompose to release an acid should be avoided for long-term storage. PVC is obviously a problem, due to HCl release and subsequent pitting of coin surfaces. Many plastics can decompose to release organic acids, like bisphenol A or phthalic acid, so stay away from these too.
RMR: 'Wer, wenn ich schriee, hörte mich denn aus der Engel Ordnungen?'
CJ: 'No one!' [Ain't no angels in the coin biz]
Thank you. What about the polypropylene? From my limited knowledge of what I learned in chemistry this must be an Alkene. Is this harmful as well? Or is it just less harmful than the PVC?
Sounds like I shouldn't risk putting any silver coins in a Polypropylene #5 container.
Does anyone have any stories of long term storage in plastic fishing containers?
If the coins are 90% 'junk' silver, then it probably won't matter. Coins like this are traded for bullion, rather than numismatic, value. As long as they don't look like they're covered with a film visible to the naked eye, you should be OK.
Whatever you do, try to store them someplace that doesn't get too hot in the summer (e.g., not in an attic).
RMR: 'Wer, wenn ich schriee, hörte mich denn aus der Engel Ordnungen?'
CJ: 'No one!' [Ain't no angels in the coin biz]
Polypropylene is perfectly safe as are most plastics.
What you have to worry about are the additives that are compounded into plastics. For instances, PVC has plasticizers added that make PVC flexible and pliable. The plasticizer slowly leaches out of the PVC causing the problems with which we are all familiar.
Does anyone know what the coin tubes are made of?
The clear tubes are made from acrylic. The square frosty tubes are made from polypropylene.
Thank you!
Plastic everywhere... even slabs
..... 
... Yep, temperature extremes (mainly heat) around plastic is not good.... leaving slabs on your dashboard in Phoenix in the summer can be disastrous (I believe someone had this issue many years ago and posted about it here)... just use common sense storage areas ... low humidity... all will be well... Cheers, RickO
Many of the beautiful OLD coins were stored before plastics and air conditioning...how did they do it ?
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