Silicone-treated polyester film

Steven Prins <sprins1102 [at] aol__com> writes

>Sara Moy <moy.sara [at] gmail__com> writes
>
>>Does anyone know if silicon coated polyester (Mylar) has a shelf
>>life?  I have recently encountered some that appears to be degraded.
>>It has a milky, streaky appearance and grimy and tacky feeling. ...
>
> ... beginning about 10-15 years ago it
>started becoming more difficult to find release films that were
>slick and clear, as they seemed always to be in the 1970's and 80's.
>Beginning in the mid-90's, I think, we started getting release film
>that was cloudy/milky in appearance. On some occasions, the release
>agent felt tacky rather than slick. We were informed by the
>resellers that this was OK. And, with the exception of slickness,
>the materials do seem to have normal release properties. But I have
>never been happy with either the milkiness or the tackiness. So I
>hope this thread will result in some new sources for this very
>useful material.

Peter Prins is talking about two different things

   "The milkiness is related to the haze of the PET.  Since he uses
    so little, he will get pot luck and is likely to get a 2% haze
    PET this order and a 15% haze on the next.

    "The tacky vs. slick is related to chemistry--solvent silicones
    are slick and solvent free, UV are tacky.

   "If he wants slick he needs to specify that he wants "tin
    catalyzed solvent silicone coated PET".

   "Mylar is a Dupont trade name--PET is the generic term and short
    for Polyester."

    David Smith
    Loperec Corporation

Peter Mecklenburg
MuseuM Services Corporation


                                  ***
                  Conservation DistList Instance 20:29
                Distributed: Thursday, November 30, 2006
                       Message Id: cdl-20-29-006
                                  ***