Difference Analysis of Moisture Barrier Performance of Foamed Sponge Tested by Desiccant Method and Water Method

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Water vapor permeability is an important performance index of the moisture barrier properties of materials. The measurement and research of water vapor permeability is an important link in the application of materials. The principle of cup method is one of the important principles for measuring the water vapor permeability of materials. It is also called the principle of gravimetric method. It calculates the water vapor permeability of materials according to the change of the weight of the test cup. Cup method includes two test methods: desiccant method and water method. This paper comprehensively compares and analyses the similarities and differences between the two methods.

Closed-cell foamed sponge is a kind of foamed sponge which has independent bubbles inside, i.e. there are walls between bubbles, and these bubbles are not connected. This independent bubbles structure and the hydrophobic property of the material itself can effectively prevent water vapor penetration. The good moisture barrier property makes it an ideal sealing material. In this paper, the water vapor permeability of closed-cell foamed was measured by the two methods.

Samples

This paper uses a closed-cell foamed sponge as the test sample.

Standards

This test is performed according to ASTM E96 standard test methods for water vapor transmission of materials

Test instrument

The test instrument used in this study is C360M Water Vapor Transmission Rate Test System, which was independently developed and manufactured by Jinan Labthink Instruments Co., Ltd.

In the desiccant method the test specimen is sealed to the open mouth of a test dish containing a desiccant, and the assembly placed in a controlled environment. Periodic weightings determine the rate of water vapor movement through the specimen into the desiccant.

In the water method, the test cup contains distilled water, and the weightings determine the rate of vapor movement through the specimen form the water to the controlled environment.

Test Procedure

Take 6 specimens with a diameter of 100 mm from the sample, and three specimens were tested by each method.

Desiccant method

(1) Fill a certain amount of desiccant to three test cups, placing the samples in the test cups, inserting the shading mould, and seal the samples with wax. After the sample is sealed, put the test cup onto the cup rack of the equipment and close the test chamber cover.

(2)Set the parameters such as sample name, test temperature, humidity, test method (desiccant method), test mode in the control software of the equipment, and start the test by clicking on the test button. The equipment runs the test according to the set parameters, and the test results are displayed after the test.

Water method

Fill a certain amount of distilled water in the test cups, set the test method to water method, the rest steps are the same as desiccant method

Test results

Take the arithmetic average of the test results of three samples of each test method. The water vapor transmission rate of the samples tested by desiccant method was 2.8064 g/(m2 24h), and that of the samples tested by water method was 3.3916 g/(m²·24h).

Conclusion

The desiccant method and the water method is different in test principles, procedure, test reagents, environment humidity and the direction of water vapor permeation; from the test results, the water vapor permeability of the closed-cell foamed sponge samples tested by the two methods is not the same, it is wise to choose the appropriate test method according to test material in practical application. The test instrument used in this paper can be used for accurate test of two test methods.Labthink Instruments Co., Ltd, is dedicated to providing customers with packaging testing solutions and helping the manufacturers to reach their goals of quality and safety assurance through improvement of packaging testing techniques and development of high-end packaging testing instruments. The newly introduced C series barrier testing systems adopting self-sensing technology revolutionarily improved the testing accuracy, efficiency and automation, realized the paradigm shift of packaging barrier testing instruments. For more information please visit www.labthink.com