Mylar is a common trade name for a polyester film made from stretched polyethylene terephthalate. It has multiple industrial applications, but in this context, is used to preserve the shelf life of stored food. It acts as a protective barrier from primarily oxygen and humidity.
Conventional Mylar bags need to be sealed by a heat sealing device whereas zip-lock Mylar bags include a sealing mechanism that can also be heat sealed. Mylar is an extremely strong and effective barrier but can be easily punctured by sharp or pointed objects which is why food grade buckets are also utilized when storing food.
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