Determination of container oxygen barrier performance using TOY-C1 container/film oxygen permeability tester

The quality of the oxygen barrier performance of the outer packaging directly affects the shelf life of the product. Due to the characteristics of the materials, the oxygen barrier performance of glass bottles and cans is excellent, but the barrier property of plastic containers is not so perfect, so the requirement for standardized testing of their oxygen barrier performance is very urgent. The

development speed of plastic containers in China is very amazing. In the 1980s, the packaging of various carbonated soft drinks, hot-filled beverages, mineral water, edible oil, condiments, wine, jams and other products in the domestic food market was almost all recyclable glass bottles, but now they have been replaced by a wide variety of plastic bottles, two-piece cans, three-piece cans, paper-plastic-aluminum composite flexible packaging and other new materials. In particular, the market demand for PET plastic bottles has grown very fast and now occupies a major share of the domestic beverage packaging market.

The quality of the oxygen barrier performance of the outer packaging directly affects the shelf life of the product. Due to the characteristics of the materials, the oxygen barrier performance of glass bottles and cans is excellent, but the barrier property of plastic containers is not so perfect, so the requirement for standardized testing of their oxygen barrier performance is very urgent.

Traditional solution

The traditional oxygen permeability test method is to make the material into sheets for testing, and then estimate it based on the thickness of the bottle wall and the surface area of ​​the bottle. Since the thickness of the bottle body varies and the material properties change during the production process, manufacturers are skeptical about whether the data from the sheet test can represent the oxygen permeability of the entire container. Industry experts also believe that it is unscientific to use only local oxygen permeability to evaluate the oxygen barrier performance of the entire container.

Limitations of container barrier testing

The characteristics of plastic containers are that they can be made into various shapes according to customer needs, and the wall thickness of the bottle body can also be adjusted. However, these characteristics also bring some difficulties to the container barrier test, which is mainly manifested in:

■ Uncertain container size

With the development of society and the advancement of manufacturing technology, large and small container packaging bottles can be seen everywhere in the market. The size, specifications, volume and surface area of ​​the container are difficult to be consistent, which brings certain difficulties to the container permeability test.
■ Large differences in container mouths

There are many types of containers, and the styles of container mouths are also diverse. Moreover, the shape of the container mouth also shows a trend of change with the development of the market. Because the change of the size and shape of the container mouth significantly affects the fixation and sealing of the container, the connection between the container mouth and the equipment is a major problem in the test process.

■ Connection and sealing between the test chamber and the oxygen permeability tester

Figure 1. The finished sample

There are three main types of test chambers: First, no test chamber is used, and the test can only be carried out in an open state (the oxygen concentration of the test environment is the oxygen concentration of the laboratory environment); second, a transparent plastic bag is used as the test chamber and sealed outside the container sample. This method is difficult to achieve the circulation of oxygen flow, and the oxygen concentration adjustment in the bag is subject to certain restrictions, which can also easily cause the container mouth to be not tightly sealed; third, a special test chamber is made of high-barrier material, which is separated from the container and sealed, with good sealing effect, and oxygen circulation can be achieved.

In addition, the container barrier test has high requirements for the temperature environment of the laboratory. First, it is due to the nature of the sensor, and secondly, the oxygen permeability test itself is greatly affected by the laboratory environment.

The development of foreign container barrier testing

has been discussed by global barrier research institutions and experts on how to solve the problem of container barrier testing. At present, the national standard has no clear provisions on the test standards in this regard. Next, we take the ASTM F 1307-02 standard as an example to look at the current development status of container barrier testing abroad.

ASTM F 1307-02 is a standard test method for testing the oxygen transmission rate of dry packages using a coulometric sensor. Its testing principle is exactly the same as the coulometric film oxygen permeability test. The oxygen transmission rate (O2 GTR) is measured after the sample is fixed on the test device and reaches equilibrium in the test environment. The fixed sample must meet the conditions that the inside of the package is slowly purged by a nitrogen flow and the outside is exposed to an environment with a known oxygen concentration. The preparation method of the package connected to the equipment for testing depends on the shape and type of the package and the test object. [page]

The fixing method shown in Figure 1 is suitable for bottles, thermoformed plastic cups, and barrels. Another fixing method without a transparent outer packaging bag can be used to fix soft bags.

Figure 1 Typical fixing methods for plastic bottles and barrels

A domestic breakthrough in container barrier testing.

The TOY-C1 container/film oxygen permeability tester newly developed by Labthink adopts the electrochemical testing principle and has the dual function of testing the oxygen permeability of films and packaging containers, meeting the requirements of ASTM F 1307, ASTM D 3985 and other standards. The test chamber is made of stainless steel with a high surface finish, which is conducive to sample sealing.

Figure 3 shows a schematic diagram of the sample fixing method of TOY-C1 when conducting a plastic bottle oxygen permeability test.

Figure 3 TOY-C1 packaging container fixing method

Features of TOY-C1 container oxygen permeability test

■ The material used in the oxygen chamber has excellent barrier properties and a large volume. It can meet the test of plastic bottles of 2.5L and below and other packaging containers. The bottle size is required to be less than f120mm and the bottle height is less than 360mm. If the oxygen chamber is not used and open measurement is performed, there is no restriction on the external dimensions of the packaging container.
■ The unique container fixing structure is conducive to a firm seal at the container mouth. The bottle mouth specifications are: the inner diameter is greater than 13mm and the outer diameter is less than 50mm. There are special accessories to support the detection of bags and boxes. There is no need to seal the gas pipeline, and the fixing and replacement of the sample are simple and convenient.
■ The test temperature is the ambient temperature of the laboratory, but the special design of the oxygen chamber is conducive to maintaining the temperature in the test environment.

Outlook

The realization of the oxygen barrier test of the container is of great significance. This not only provides favorable technical support for obtaining scientific container oxygen barrier test data, but also lays a solid foundation for a comprehensive understanding of the barrier performance of the container.