Source: Link Testing Instruments Co.,Ltd.
Sealant is one of the commonly used materials in buildings. It can be used to seal and bond various joints or holes in building parts such as building exterior, interior decoration, window structure, etc. Different building joints have different requirements for sealant performance. For sealants used in building parts such as exterior walls, bathrooms, toilets, kitchens, balconies, floors of floor heating systems, and hollow glass, they should have high waterproof and moisture resistance. The water vapor barrier performance is one of the key factors that determine its waterproof and moisture resistance. For example, the water vapor permeability of sealants used to seal hollow glass is high, and the water vapor in the environment will slowly penetrate into the glass through the sealant, causing condensation or frost inside the hollow glass, affecting its service life. The water vapor permeability of sealants with different base materials is not the same, and the water vapor permeability of the same base material sealants with different fillers is different. Therefore, through the test of the water vapor permeability of sealants, understanding the waterproof and moisture resistance of sealants is the basic requirement for selecting suitable sealants.
Testing Basis and Test Instruments
Currently, the main testing methods for water vapor permeability of materials include cup method, electrolytic sensor method, infrared sensor method and humidity sensor method. This paper uses infrared sensor method to test the water vapor permeability of sealant samples, based on the standard ASTM F1249 "Determination of water vapor permeability of plastic films and sheets - Infrared detector method". This test uses LTWTC-303H water vapor permeability test system as the test equipment, which is independently developed and produced by Link Testing Instruments Co.,Ltd
Test principle: The infrared sensor method calculates the water vapor transmission rate of the sample by testing the attenuation of the light intensity of infrared light when it passes through nitrogen carrying water vapor. During the test, after the sample is clamped in the test chamber of the equipment, the test chamber is divided into an upper and lower test chamber. By filling the upper chamber with high-humidity nitrogen and the lower chamber with low-humidity nitrogen, a certain humidity difference is formed on both sides of the sample. Under the action of the humidity difference, water vapor penetrates from the upper chamber through the sample to the lower chamber and is carried by nitrogen to the infrared sensor for analysis, thereby obtaining the water vapor transmission rate of the sample.
Test sample and test process
Test sample: In this test, a sample sheet made of modified silicone sealant provided by a certain enterprise is used as the test sample. Test process: (1) Sample cutting - Use a sampler to cut 3 samples from the sheet sample made of modified silicone sealant. (2) Conditioning - Place the cut sample in an environment of 23℃ and 50%RH for 4 hours. (3) Test - Clamp the sample on the equipment, set the test parameters, click the test option, start the test, turn on the gas source, and adjust the carrier gas flow. After the test, the equipment displays the test results of the sample.
Test results and analysis
The test values of the three samples in this test were 4.306 g/(m2•24h), 4.213 g/(m2•24h), and 4.257 g/(m2•24h), respectively. The water vapor permeability of the sample was the average of the test results of the three samples, which was 4.259 g/(m2•24h).
The water vapor transmission rate of building sealants is an important indicator for evaluating their moisture-proof performance. This article takes the water vapor transmission rate of a modified silicone sealant sample as an example to introduce the method of using infrared sensor method to test the moisture barrier performance of sealants. The test equipment has a high degree of intelligence, simple operation, high test accuracy and test efficiency, and good repeatability of the test results, which can accurately reflect the barrier performance of the tested sealant to water vapor.
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