Oxygen transmission rate
Oxygen transmission rate (OTR) testing is performed to measure the speed at which oxygen gas permeates through a material, such as a rigid or flexible plastic film. OTR testing is widely used to assess the barrier properties – or the ability to resist the permeation of oxygen – of different packaging materials, as oxygen is a major cause of spoilage of packaged goods.
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What is OTR and what is it used for?
The oxygen transmission rate is the steady-state rate at which oxygen gas can permeate through a film. OTR is expressed as a mass of oxygen that permeates a given area in one day: g/(m2 x 24h).
OTR tests are commonly used to assess the functionality of packaging materials in the food, cosmetics, and pharmaceutical industries, where oxygen is a major contributor to reactions associated with the spoilage of such products. The analysis results will indicate whether the material can resist the permeation of oxygen well (high barrier properties) or poorly (low barrier properties).
The barrier properties of packaging directly affect the shelf-life of a product. In addition to the barrier effect against oxygen, the packaging's resistance to water should be evaluated. This is done through water vapor transmission rate (WVTR) testing.
OTR testing procedure
Several methods can be applied when determining the transmission rate of a certain gas. Methods that use oxygen detectors are most popular in the examination of food packages, as in that case, low permeability needs to be determined with high sensitivity. The used sensor only detects the molecules of the gas of interest, in which case it does not account for the rest of the atmospheric gases in the surroundings.
When starting the OTR analysis, the temperature and relative humidity (dry, normal, or moist) are chosen based on the predicted storage conditions of the product. Testing condition selection is very important, as the temperature and relative humidity of the environment affect the barrier effect of the material.
One commonly used method of OTR testing is coulometric OTR. In coulometric tests, the material of interest is sealed between two chambers of the OTR machine. One of these chambers contains oxygen and the other one does not. A coulometric sensor measures the oxygen that is transmitted through the barrier film from one chamber to another and thus determines the oxygen transmission rate and permeability of the material.
Suitable sample materials for oxygen transmission rate testing
The oxygen transmission rate can be determined for flexible barrier materials like plastic films and sheeting used in rigid and semi-rigid packaging or industrial applications. Coated films, such as foil or metalized PET, CPP, EVOH, AlOx, or SiOx, are also suitable for OTR analysis. The typical testing area can be chosen to suit the size of the sample, but a minimum sample size of 12 cm x 12 cm is recommended.
Measurlabs offer OTR testing of films and sheeting according to ASTM D3985 (standard conditions) and ASTM F1927 (moist conditions). In addition, OTR tests for finished packages are available. All the analyses can be ordered online. Alternatively, you can contact our experts through the form below to discuss your testing needs in more detail.
Suitable sample matrices
- Packages of for example food, cosmetics and pharmaceuticals
- Rigid and semi-rigid packages
- Plastic films and sheetings
- Coated papers
- Aluminium foils
- Metalized films
- Non-coated films
Ideal uses of OTR testing
- Measuring the barrier properties of packaging materials against oxygen
- Industrial applications
- Product development and quality control
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Frequently asked questions
OTR is most commonly used to determine the barrier properties of packaging materials against oxygen to help estimate their shelf lives. Improvement of product quality and shelf life is possible by optimizing oxygen transmission rates of the packaging materials based on the results of the OTR analysis. Adjusting copolymer ratios, plasticizer content, and polymerization processes with the help of OTR enables efficient product development also in industrial applications.
Relative humidity (RH) can have a big impact on the barrier properties of certain films, which is why OTR measurements are usually done under dry conditions. For example, the oxygen transmission rate of EVOH increases drastically when RH exceeds 75%. The thickness of the film and the temperature of the environment also need to be taken into account because they can affect the results.
The barrier materials used in OTR must often be flexible, rigid, and have a smooth surface.
Flexible barrier materials of rigid packages are suitable for the analysis. Samples can be, for example, plastic films and sheeting, laminates, coated papers, aluminum foils, or metalized films. Samples need to have smooth surfaces to achieve a tight seal between the two chambers of the OTR machine. Testing is also available for finished packages.
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.