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Dessicant in watertight bag?

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Unless called for by design requirements, the package obsorbs and retains moisture from the air,  not water in its liquid form.

 Water molecules in gaseous/ moisture state do penetrate the envelope, water in its liquid form dosn,t. 

Desicatants may include natural or synthetic in multiple layers to satisfy the requirements. So much depends on what  you got this package out of.

Regards joe

 

 

 

 

 

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2 hours ago, Nucejoe said:

Unless called for by design requirements, the package obsorbs and retains moisture from the air,  not water in its liquid form.

 Water molecules in gaseous/ moisture state do penetrate the envelope, water in its liquid form dosn,t. 

Desicatants may include natural or synthetic in multiple layers to satisfy the requirements. So much depends on what  you got this package out of.

Regards joe

 

Agreed. Also the "plastic"may in fact be a plasticised film with micro perforations, or may even be something as simple as paper coated with carnuba wax or similar (think Smarities or M&Ms), so it may be very hydroscopic.

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I agree with all that but the point that I'm trying to make here is that this bag, used in a vitamins bottle, is clearly made of common packaging plastic, not microperforated paper or cloth as commonly see. It's thick and shiny on both sides, leaves no residue when scratched. It is actually stronger than the one I used for single serving sauces, as it cannot be ripped by hand.

How it can be permeable to air and moisture is a mistery to me. 

DSC_0063.JPG

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It seems to be a common property of polymers. Here's a description of the mechanism:

https://polymerdatabase.com/polymer physics/Permeability.html

So that plastic bag may be permeable to water vapour, and to a lesser extent to liquid water. An important function of the bag is to stop the solid desiccant mixing with your vitamins. Maybe the reason it's so resistant to tearing is because the pellets are harmful if swallowed.

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Thanks. It is amazing to see artificial materials engineered for properties that aren't even apparent. Unless the factory (in Thailand as observers may have noticed) isn't silently cheating everybody, LOL.

Another example is in my new diving snorkel. A (polymer?) membrane under the mouth piece lets water leave, one way. Black magic to me. 

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1 hour ago, Klassiker said:

It seems to be a common property of polymers. Here's a description of the mechanism:

https://polymerdatabase.com/polymer physics/Permeability.html

So that plastic bag may be permeable to water vapour, and to a lesser extent to liquid water. An important function of the bag is to stop the solid desiccant mixing with your vitamins. Maybe the reason it's so resistant to tearing is because the pellets are harmful if swallowed.

Nature produces abundance of edible desiccants for us, No need to consider harmful stuff. Desiccation is not limited to water moisture, however, thence some desiccant may become harmful by contaminants.

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