What I was trying to figure out if it was due to silver.
Lots of the mylar has a dusting of silver to a full coat on it.
Silver is an excellent anti-microbial. If that is the reason for it working so good, then maybe you could just get silver doped PET instead.
BoPET (Biaxially-oriented polyethylene terephthalate) is a polyester film made from stretched polyethylene terephthalate (PET) and is used for its high tensile strength, chemical and dimensional stability, transparency, reflectivity, gas and aroma barrier properties and electrical insulation.
A variety of companies manufacture boPET and other polyester films under different brand names. In the UK and US, the most well-known trade names are Mylar, Melinex and Hostaphan.
SNIP
Biaxially oriented PET film can be metallized by vapor deposition of a thin film of evaporated aluminum, gold, or other metal onto it. The result is much less permeable to gases (important in food packaging) and reflects up to 99% of light, including much of the infrared spectrum. For some applications like food packaging, the aluminized boPET film can be laminated with a layer of polyethylene, which provides sealability and improves puncture resistance. The polyethylene side of such a laminate appears dull and the PET side shiny.
Other coatings, such as conductive indium tin oxide (ITO), can be applied to boPET film by sputter deposition
http://en.wikipedia.org/wiki/BoPET