Material Gas Barrier Measurement

The gas permeability test is a standardized laboratory procedure used to quantify how easily a gas, such as oxygen, carbon dioxide, or nitrogen, can pass through a solid material. This measurement is critical for evaluating the barrier properties of materials used in food packaging, pharmaceutical blister packs, and industrial applications. The test determines the Gas Transmission Rate (GTR), which indicates the volume of gas permeating through a unit area of the material over a specific time under set conditions of pressure and temperature. A lower GTR signifies a better barrier, which is essential for protecting sensitive products from degradation. The procedure is typically performed using specialized equipment known as a gas permeability tester, which creates a controlled environment to ensure accurate and repeatable results. This data is indispensable for manufacturers who need to guarantee their packaging will perform as expected throughout the product’s distribution and shelf life.

Gas Transmission Rate Analysis

Gas Transmission Rate (GTR) analysis provides the specific quantitative data resulting from a gas permeability test. It is expressed as the volume of gas that permeates through a unit area of the material per day under a specified pressure differential. This rate is the fundamental metric for comparing the barrier performance of different materials or different batches of the same material. Accurate GTR analysis helps in predicting the shelf life of packaged goods, optimizing packaging thickness, and ensuring compliance with industry standards. The analysis process involves precise control of temperature, humidity, and gas pressure on both sides of the test specimen. We at Labthink provide the instruments and methodologies required for this critical analysis. By understanding the GTR, manufacturers can make evidence-based decisions to improve their products’ quality and safety, ultimately reducing waste and enhancing consumer satisfaction.

Permeation Testing Method Details

Permeation testing involves detailed methodologies to measure gas flow through a material. The most common methods are the differential-pressure method (or manometric method) and the coulometric method (for oxygen transmission rate test). In the differential-pressure method, the test gas is introduced at a higher pressure on one side of the sample, and the pressure increase on the low-pressure side is measured to calculate the transmission rate. The coulometric method, often using a coulometric sensor, measures the oxygen molecules have permeated through the material and reached the sensor. The test sample is mounted as a sealed barrier separating two chambers, and the entire apparatus form a temperature-controlled environment to ensure consistency. The process requires meticulous preparation, including conditioning the sample and calibrating the instrument, to eliminate variables that could affect the result. This rigorous approach ensures that the obtained permeability is a reliable intrinsic property of the material being tested.

Conclusion

We manufacture a series of Gas Permeability Testers that measure the gas transmission rate of materials. Our instruments use methods such as the differential-pressure method and the coulometric sensor method. The testers are designed for various gases, including common, toxic, flammable, or explosive ones, and support ASTM testing standards. Specific models include the VAC-V1 (EX), VAC-V2 (EX), and the C206H Oxygen Transmission Rate Test System, which you can learn more about through our gas permeability analyzer resources.

Most bicycle tires, many motorcycle tires, and many tires for large vehicles such as buses, heavy trucks, and tractors are designed for use with inner tubes. Inner tubes are torus-shaped balloons made from an impermeable material, such as soft, elastic synthetic rubber, to prevent air leakage. The inner tubes are inserted into the tire and inflated to retain air pressure.

Generally speaking, the inner tubes should be of low air permeability so that the air pressure inside can be maintained properly and the tire can keep stable in shape and performance. This article provides a simplified testing procedure for air permeability test of the inner tubes for automotive tires for your reference.

The testing instrument we used is Labthink’s C130H Gas Permeability Tester which adopts differential pressure method. In the tests, the specimen is mounted in a gas transmission cell so as to form a sealed semi-barrier between two chambers. One chamber contains the test gas at a specific high pressure, receives the permeating gas. The gas transmission rate of the test gas can be calculated according to the pressure change of the lower pressure chamber.

The specimens we tested are inner tubes made from butyl rubber, a kind of material that is low in air permeability. Before tests, certain number of specimens should be selected. The specimens should be flat and free of scratches, pinholes or other defects.

When all specimens are prepared, the tests can be performed according to the following procedures.

Step 1: Wipe the dust on the lower pressure chamber off with soft material. Apply a thin layer of vacuum grease on the surface of the lower pressure chamber. Put a piece of filter paper on the lower pressure chamber and then the specimen. The function of the filter paper is to support the specimen and meanwhile prevent the vacuum grease entering the lower pressure chamber.

Step 2: Tighten the test cells. Set test parameters and then start tests.

The tests will be performed automatically and the test results will be given after the tests are finished.

For more details about C130H Gas Permeability Tester, please visit www.labthink.com

About Labthink Instruments Co., Ltd:

Labthink Instruments Co., Ltd is one leading supplier of packaging testing instruments, which is headquartered in Jinan, China and operated in Boston, U.S.A.