Water vapor transmission rate
Water vapor transmission rate (WVTR) testing determines how well a material holds moisture, also called the barrier effect. WVTR analyses are important in the product development of materials that must withstand different moisture levels at varying temperatures. Such materials include, for example, food packaging materials, construction materials, and medical equipment.
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Water vapor transmission rate (WVTR) of films and sheeting
Water vapor transmission rate (WVTR) of textiles
Water vapor transmission rate (WVTR) of packages
Water vapor transmission rate (WVTR) of paper or board with the gravimetric dish method
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What is the water vapor transmission rate?
Water vapor transmission rate (WVTR) represents the amount of water vapor that passes through a material or substance over a set period of time. Data received through a WVTR analysis is often presented in g/m2 per day (how much water in weight passes through over a one square meter area in 24 hours).
What is WVTR testing used for?
The water vapor transmission rate is an important variable in materials that are used in wet environments. In food contact materials, an effective moisture barrier is critical to keep the product fresh and prevent it from gathering mold and mildew. Another important variable in food packaging testing is the oxygen transmission rate, which measures the material's barrier effect against oxygen.
A moisture barrier is important in the opposite case as well: when packing liquids, it is important to make sure that the product will not leak through the material, reduce its protective properties, and thus expose the product itself to outer threats. This also applies to products like cosmetics and their packaging solutions.
In construction material applications, WVTR and moisture barriers are important factors in wet rooms and outdoor solutions. For the same reason as in food packaging, keeping moisture out is an important factor in maintaining the quality of buildings and building materials.
How is the water vapor transmission rate measured?
Different materials require different measurement techniques to get the most accurate WVTR results. Materials with weak barriers (that let through a lot of moisture) can be measured with a gravimetric technique, while materials with good barriers (that don't let through a lot of moisture), should be analyzed with humidity sensors or infrared sensors.
It is also important to make the conditions of the analysis similar to the environment where the material will be used. The temperature and carrier gas should be tuned to simulate the intended conditions. Measurlabs' experts always assure that you get your measurements done in the correct conditions so that your test results correspond to the real usage environment of your materials.
Need a WVTR analysis?
Measurlabs offers high-quality WVTR testing services and support from skilled experts whenever needed. We assist in choosing the appropriate testing conditions for the intended use of your material to ensure that the analysis gives you useful insights. Contact us through the form below or by email at firstname.lastname@example.org.
Suitable sample matrices
- Coatings, such as wax, cellulose, polymers
- Plastic films
Typical target materials for WVTR analysis
- Food contact materials
- Packaging materials
- Construction materials
Frequently asked questions
WVTR is commonly used for food contact materials, construction materials and packaging materials, in addition to any other kind of materials that are exposed to moisture or water.
WVTR measurement is carried out at a chosen temperature and moisture. The conditions must be chosen to represent the intended use. The measured surface needs to be free from scratches and other defects, as they allow the gases to pass through. The surfaces need to be smooth so that an effective sealing can be achieved.
WVTR is suitable for different coatings, such as wax, cellulose and polymers, foils, plastic films, and fabrics. Anything from sausage casing to technical sportswear, and more.
Measurlabs offers a variety of laboratory analyses for product developers and quality managers. We perform some of the analyses in our own lab, but mostly we outsource them to carefully selected partner laboratories. This way we can send each sample to the lab that is best suited for the purpose, and offer high-quality analyses with more than a thousand different methods to our clients.
When you contact us through our contact form or by email, one of our specialists will take ownership of your case and answer your query. You get an offer with all the necessary details about the analysis, and can send your samples to the indicated address. We will then take care of sending your samples to the correct laboratories and write a clear report on the results for you.
Samples are usually delivered to our laboratory via courier. Contact us for further details before sending samples.