Hello,

I'm redesigning the packaging for a pharaceutical product. The current pack is a glass vial with a butyl rubber stopper.

The product is very moisture sensitive and so the moisture protection provided by the rubber stopper is critical. I'm trying to find a a typical value for the moisture vapour transfer rate (MVTR or WVTR) for butyl rubber.

This will allow me to calculate how much moisture will get into the package over its lifetime, and to identify possible alternative materials that could be used to protect the product.

Any resources or info on MVTR values for rubbers would be very helpful.

Best regards,

Barry Lillis.