From: Alan \"Uncle Al\" Schwartz <uncleal0@ix.netcom.com>
Newsgroups: sci.chem
Subject: Re: Archival Plastics
Date: 25 Jan 1996 15:08:13 GMT

Mylar is Dacron or PET - poly(ethyleneterephthalate).  There is no 
plasticizer or halogen in Mylar, it is remarkably resistant to UV 
degradation, it is strong and tough, it has a very low gas and water 
vapor permeability, and it heat seals - good stuff!  If you can get a 
grade with added UV absorber such as a  Tinuvin (esp 326, which cuts off 
just into the visible), you will have an extremely capable protective 
film.

Polypropylene is labile toward air oxidation.  It is protected with 
antioxidants, and tends to embrittle with age.

Kapton polyimide is remarkable stuff, and remarkably expensive - over 
kill.  Polycarbonate, polysulfone, PEEK, and thermoplastic polyimides in 
general tend to be UV-sensitive (as is Kevlar).

-- 
Alan "Uncle Al" Schwartz
UncleAl0@ix.netcom.com  ("zero" before "@")
http://vvv.com/adsint/freehand/uncleal/
"Quis custodiet ipsos custodes?"  The Net!

From: glhurst@onr.com (Gerald L. Hurst)
Newsgroups: sci.chem
Subject: Re: Archival Plastics
Date: 26 Jan 1996 06:46:30 GMT

In article <4e86ct$ire@ixnews6.ix.netcom.com>, Alan \"Uncle Al\" Schwartz
<uncleal0@ix.netcom.com> says:

>Mylar is Dacron or PET - poly(ethyleneterephthalate).  There is no 
>plasticizer or halogen in Mylar, it is remarkably resistant to UV 
>degradation, it is strong and tough, it has a very low gas and water 
>vapor permeability, and it heat seals - good stuff! 

"Mylar" is duPont's trade name for THEIR polyester film. Credit
should go to 3-M for this class of product as they were the 
pioneers with Skotch-pak (R). Heat-sealable? My experience is 
that despite the listings in charts of "heat-sealibility" in the 
425-450 degF range for "some" PETs, the material one ends up
using is a laminate or coextrusion with a polyethylene or
blend resin as a heat-seal coat. Again, hats off to 3-M for
this innovation of the sixties.

Jerry (Ico)