Water Vapor Transmission Rate (WVTR) is the rate at which water vapor is transmitted within a material, usually expressed as the amount of water vapor that passes through a material per unit area in a unit time. It is one of the important indicators to measure the permeability of materials to water vapor, depending on the physical and chemical properties of the material, such as the thickness of the material, porosity, structure, temperature, humidity and so on.
Measurement methods and application fields
Measurement method:
cup weighing method: The transmittance is calculated by measuring the difference in water vapor pressure between the two sides of a material over a certain period of time.
infrared method: infrared detection of water vapor through materials.
electrolysis: Measurement of water vapor transmission by electrolytic reaction.
Application field :
packaging industry : Test the water vapor transmission rate of plastic film, paper, composite materials and other packaging materials to evaluate their packaging performance and fresh-keeping effect.
Textile industry : Test the breathability of textiles such as clothing, shoes, tents, raincoats and evaluate their comfort and waterproof properties.
Building materials industry : Test the waterproof and breathable properties of roof waterproof materials, external wall insulation materials, basement waterproof materials and other building materials, and evaluate their moisture-proof, waterproof and breathable properties.
Medical industry : Test the air permeability of medical packaging materials and medical dressings to evaluate their air permeability and water resistance to wounds.
food industry : Test the air permeability of food packaging materials, evaluate its moisture, oxidation and fresh-keeping effect.
A higher water vapor transmittance indicates that the material has a poor barrier to water vapor . Water vapor transmittance refers to the amount of water vapor passing through a material per unit area in a unit time, usually in g/(m²·24h). It reflects the material’s barrier ability to water vapor under certain temperature and humidity conditions. Lower water vapor transmittance means better moisture resistance and more effective protection of contents from moisture.
Food packaging :
The water vapor transmittance directly affects the shelf life and quality of food. High water vapor transmittance will result in dryness of food and affect taste and flavor. Too low permeability may lead to a high humidity environment, easy to breed bacteria and mold, resulting in food spoilage.
Medicinal aluminum-plastic composite film :
The water vapor permeability of pharmaceutical aluminum-plastic composite film is affected by material composition, thickness, additive type and content. The greater the difference between internal and external humidity, the higher the water vapor transmittance. Excessive humidity may lead to hygroscopic expansion of the sample, affecting the accuracy of the test.
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Post time: Oct-21-2024
