Water vapor transmission rate
Water vapour transmission rate (WVTR) is an analysis technique used for determining how well a material holds moisture, i.e. its barrier effect. WVTR analyses are often an important part of the product development of materials that need to withstand different levels of moisture in varying temperatures. Such materials are for example food packaging materials, construction materials, and medical equipment.
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What is WVTR analysis?
Water vapour transmission rate (WVTR) represents the amount of water vapour that passes through a material or substance over a set period of time. Water vapour transmission rate data 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 analysis used for?
Water vapour transmission rate (WVTR) is an important variable in materials used in wet environments. In food contact materials, an effective moisture barrier is critical to keep the food product fresh and prevent it from mold and mildew. A moisture barrier is important in the opposite way as well: when packing liquids, it is important to make sure that the product will not leak through the material and reduce its protective properties, and thus expose the product itself to outer threats. Same applies to for example cosmetics and their package solutions.
In construction material applications, WVTR and moisture barrier 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 high quality in buildings and building materials.
How do you measure WVTR?
Different materials require different measurement techniques to get the most accurate results. Materials with bad barriers (let through a lot of moisture) can be measured with a gravimetric technique, while materials with good barriers (don't let through a lot of moisture), should be analysed 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.
Suitable sample matrices
- Coatings, such as wax, cellulose, polymers
- Plastic films
Ideal uses of WVTR
- Food contact materials
- Packaging materials
- Construction materials
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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 can 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.
WVTR measurement is an ideal tool for R&D purposes, quality assurance and quality control and when the materials barrier properties need to be measured. Measur offers affordable, high quality WVTR testing with fast turnaround times.