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Water Vapor Transmission Rate (WVTR)

Controlling moisture migration is crucial to maintaining the taste, texture, and overall quality of packaged food products.  Dairy, meat, seafood, and pet food products require keeping moisture inside a package, while dry products such as gourmet snacks, coffee, grains, dry pet foods, and non-food products require a moisture-free environment to avoid undesirable changes in texture, taste, and microbial stability. 

“Water vapor transmission rate” (WVTR), often referred to as “moisture vapor transfer rate” (MVTR), is the standard indicator of how easily moisture can permeate a packaging film.  Flair provides WVTR values expressed as g/m2 and g/100in2 at 38°C and 98% relative humidity (per ASTM F1249). Increasing WVTR values indicate greater permeability, and lower ability to keep dry products dry, and moist products moist. 

Factors affecting WVTR values include…

  • Thickness
  • Resin Composition
    • Molecular weight distribution
    • Crystallinity/density
    • Chain-length and chain-length distribution
    • Chain orientation
  • Polymer blends
  • Additives
  • Coatings – PVdC, metalizing
  • Processing Parameters – BUR, frost-line height, die gap

When choosing a packaging film, MVTR is often balanced with oxygen transmission rate (OTR) to provide the most appropriate barrier characteristics for a particular product’s needs.


To learn more about optimizing water vapor transmission rates to enhance the quality of your product, or to be sure you’re using the best barrier film for your application, contact Flair today.