Effect of Recycled Material Content on the Oxygen Barrier Properties of PET Bottles

ABSTRACT: Recycling and reusing waste bottles has become an important measure for environmental protection. Through testing the oxygen permeability of PET plastic bottles with different recycled materials, this paper studies the influence of recycled materials content on the oxygen barrier of the samples, and introduces the test principle, the parameters of C230H oxygen transmission rate test system, the scope of application and the test process, in hope to provide a reference for testing the performance of plastic bottles containing recycled materials.

Keyword: oxygen permeability, oxygen barrier properties, oxygen transmission rate testing system, recycled materials, PET bottles, isobaric method, coulometer method

Significant

Plastic bottles are common packaging containers, which are light and easy to transport. They have been widely used as packaging in food, medicine, health care products, daily chemicals and other industries. In order to reduce the environmental impact of waste plastic bottles, the research and application of waste bottles recycling has gradually come in focus.

PET bottles are widely used plastic bottles. Recycled PET bottles are mostly reclaimed through a certain process to form reclaimed granules for the production of new PET bottles or other plastic products. High oxygen barrier properties is an important index that PET bottles can be used to package oxygen-sensitive products such as fruit juice beverages and dairy products. Therefore, the influence of recycled granules on barrier properties of bottles is an important factor restricting the application scope of PET bottles containing recycled materials.

Figure 1 PET bottles in different shape

Test sample

The oxygen permeability of PET bottles with 25% and 50% recycled materials was tested in this study.

Test standard

The testing principle of oxygen transmission rate of packaging materials includes differential pressure method and coulometer method. This study uses coulometer method to test plastic bottle samples. The testing process is based on the method dedicated in standard GB/T 31354-2014 Determination of Oxygen transmission rate through dry packages- Coulometric sensor.

Test instrument

In this study, C230H oxygen transmission rate test system developed and produced by Jinan Languang Mechanical and Electrical Technology Co., Ltd is used as test instrument.

Figure 2 C230H Oxygen Transmission Rate Test Instrument

Test principle

Coulometer method uses Coulomb sensor as detector. It calculates the oxygen transmission rate of material according to the quantitative relationship between oxygen content and current intensity of sensor in unit time. When testing containers, high purity nitrogen flows inside the container and high purity oxygen flows outside the containers. Oxygen penetrates into the container due to the oxygen concentration difference, and is carried to the sensor by the inner flow of nitrogen for analysis, so as to calculate the parameters of oxygen transmission rate of the sample.

Test process

Because most of the content of PET bottles is liquid, the test conditions of this experiment are set at 23 C and 100% RH.

(1) Seal the two kinds of samples on the container-supporter of the instrument with fast-setting glue to ensure good sealing between the sample and the supporter without leakage.

(2) Container-supporter with sealed samples are connected with the instrument, and the containers and supporter are sealed with sealed bags respectively, and the temperature is controlled by a temperature control cover outside.

(3) Input the sample name, test temperature, humidity and test mode in the control software of the equipment. Click the start button to start the test. The instrument runs according to the set parameters, and the test results are displayed after the test.

Test results

The oxygen transmission rate of PET bottle samples with 25% recycled material was 0.01792 cm3/(pkg day), and the oxygen transmission rate of PET bottle samples with 50% recycled material was 0.01907 cm3/(pkg day).

Conclusion

The results show that the oxygen transmission rates of the two samples are almost the same. The oxygen barrier of PET bottle samples with 25% recycled material content is slightly higher than that of PET bottle samples with 50% recycled material content. In terms of the test process, the instrument is simple to operate, the degree of intelligence is high, the control of the parameters of the test process is accurate and stable, and the test results are accurate and reliable