low Water vapor transmission rate (MVTR) material 1

[Mike666]

hi,

I need to design a box that should be totally sealed from water and water vapor.

Although i know that the best materials for that purpose is metals
(for example aluminum (MVTR=0.001 g/m^2/day)) it can't be a metal.

The solution I was thinking about was Ceramic ?
Or maybe a plastic with very low MVTR?

What material has the lowest MVTR except metals?
Can I build a composite box from fiberglass (that will give the strength) with a sealing laer made of ceramic material?

thanks

 

[patprimmer]

Glass tends to be pretty low, but I guess it is a ceramic.

Plastics all transmit some water vapour, but co-extruded films with an EvOH barrier layer perform quite well.

As a stand alone plastic PET is quite good.

If a metal layer can be applied to one surface of a film, such as a wine cask bladder, that should give excellent results.



Regards

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[dwightdixon]

You do not need to use very thick aluminum. Maybe you should think about a foil liner or insert molding a plastic box inside or outside a foil liner. There are lots of poucnes made with laminated foil and a plastic inner film which is then heat sealed to form the container.