Oxygen transmission rate

Oxygen transmission rate (OTR) testing describes the speed at which oxygen gas permeates through a material, for example a rigid or flexible plastic film. OTR testing is widely used for measuring the barrier properties, or the ability to resist the permeation of oxygen, of different packaging materials because oxygen is a major cause of food 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 a one-day period: g / (m2⋅24 h).

The analysis results will tell if the material is able to resist the permeation of oxygen well (high barrier properties) or poorly (low barrier properties). OTR tests are commonly used for packaging materials in the food, cosmetics, and pharmaceutical industry because oxygen is one main contributor to reactions associated with spoilage of such products. The barrier effect of the packaging thus directly affects the shelf life of a product. Another test often done in addition to OTR is water vapor transmission rate (WVTR), as water vapor is another main factor related to the shelf-life of products.

OTR testing procedure

Several methods can be applied when determining the transmission rate of a material to a certain gas. Methods that use oxygen detectors are most applied in the examination of food packages, as in that case, a 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 take the rest of the atmospheric gases in the surroundings into account.

When starting the OTR analysis, the temperature and relative humidity (dry, normal, or moist) where the test is performed have to be chosen based on the predicted storage conditions of the product. The selection of the test conditions is very important because the temperature and relative humidity of the environment affects 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 lacks it. 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 OTR test

The oxygen transmission rate can be determined for flexible barrier materials like plastic films and sheetings used in rigid and semi-rigid packaging or in industrial applications. Also coated films such as foil or metalized PET, CPP, EVOH, AlOx, or SiOx are also suitable for OTR analyses. 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.

Suitable sample matrices

  • Packages of for example food, cosmetics and pharmaceuticals
  • Rigid and semi-rigid packages
  • Plastic films and sheetings
  • Laminates
  • 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

What is OTR commonly used for?

OTR is most commonly used for determining the barrier properties of packaging materials for different products against oxygen in order to help estimating their shelf lives. OTR helps to design packaging materials with characteristics optimized for unique demands of a certain product. Improvement of product quality and shelf life is possible by optimizing oxygen transmission rates of the packaging materials based on the results of OTR analysis. Adjusting of copolymer ratios, plasticizer content, and polymerization processes with the help of OTR enables efficient product development also in industrial applications.

What are the limitations of OTR?

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 are also needed to take into account, because they can affect the results for their part.

The barrier materials used in OTR must often be flexible, rigid and have a smooth surface.

What kind of samples can be analysed with OTR?

Flexible barrier materials of rigid packages are suitable for the analysis. Samples can be for example plastic films and sheetings, laminates, coated papers, aluminium foils or metalized films. Samples need to have smooth surfaces in order to achieve a tight seal between the two chambers of the OTR machine.

What is Measurlabs?

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.

How does the service work?

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.

How do I send my samples?

Samples are usually delivered to our laboratory via courier. Contact us for further details before sending samples.