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Testing proposal for water vapor transmission rate of waterproof breathable membrane

Feb 17,2024

Source: Link Testing instruments co.,Ltd.

The barrier performance against external water vapor (i.e. moisture barrier) is an important performance indicator for various materials such as building materials. The water vapor transmission rate of the material can be tested and analyzed to prevent and solve problems such as material aging and corrosion caused by water vapor.

Waterproof breathable membrane (also known as Puwei waterproof breathable membrane) is a new type of polymer waterproof material, which is used in different industries. For example, in the construction industry, it is used to prevent moisture and help moisture vapor to be discharged quickly, and to protect and maintain the thermal performance of the structure; the automotive industry It is to provide long-lasting protection for the car lights from the intrusion of external water vapor, dust, oil and other dirt. At the same time, because of its specific and unique ventilation function, it can exchange gases with changes in pressure, thereby reducing the stress on the seal. pressure and extend the service life of auto parts. It can be seen from its application that waterproof and breathable membranes should have high waterproof performance. Therefore, all manufacturing companies should strengthen regular testing of the water vapor transmission rate of waterproof and breathable membranes.

Test methods and instruments

At present, the testing methods for water vapor transmission rate of waterproof and breathable films include weighing method (cup method), electrolysis method, humidity method and infrared method. The method standards that can be referred to are GB 1037-1988 "Plastic Films and Sheets". Water Vapor Permeability Test Method Cup Method", GB/T 21529-2008 "Determination of Water Vapor Transmission Rate of Plastic Films and Sheets - Electrolytic Sensor Method", GB/T 30412-2013 "Water Vapor Transmission Rate of Plastic Films and Sheets" "Humidity Sensor Method for Determination of Water Vapor Transmission Rate", GB/T 26253-2010 "Infrared Detector Method for Determination of Water Vapor Transmittance of Plastic Films and Sheets". This article refers to the standard GB 1037-1988 based on the weighing method.

The testing equipment used in this article is Link Testing LTWTC-203H water vapor transmittance tester.

Test principle: This equipment adopts the testing principle of the weighing method. During the test, the sample is clamped in a moisture-permeable cup. A certain humidity difference is formed on both sides of the sample. Water vapor will change from high humidity to high humidity under the action of the humidity difference. By measuring the change in weight of the moisture-permeable cup over time, parameters such as the water vapor transmittance of the sample can be obtained.

Test samples and test process

Test sample: The sample is a waterproof and breathable membrane provided by a company.

Experimental procedure:

(1) Cut three specimens with a diameter of 74 mm from the surface of the sample.

(2) Clamp the sample pieces into three moisture-permeable cups respectively, then place them on the moisture-permeable cup holders inside the equipment, and close the test chamber door.

(3) Set the sample name, sample thickness, test temperature, test humidity and other parameters, and click the "Start Test" option.

(4) After the test is completed, the instrument automatically calculates and displays the test results.

Test results and analysis

The water vapor transmission rates of the three samples tested this time are: 4307.12 g/(m2·24h), 4382.67 g/(m2·24h), and 4408.86 g/(m2·24h).

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