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Labthink Instruments Co., Ltd.
How to Test Water Vapor Transmission Rate in Films

How to Test Water Vapor Transmission Rate in Films

Product catalog summary

Introduction
Testing the Water Vapor Transmission Rate (WVTR) in films is crucial for determining a material's resistance to water vapor passage. This property is vital in industries like food packaging, pharmaceuticals, textiles, and electronics, where moisture control is essential for product preservation and quality.

Methods for Testing WVTR

Gravimetric Method (ASTM E96, ISO 15106): This traditional method involves measuring the weight change of a sample exposed to a moisture gradient. Key equipment includes a WVTR tester, water-filled containers or desiccants, a precision balance, film samples, and environmental control chambers. The process involves sample preparation, test cell assembly, maintaining environmental conditions, monitoring weight change, and calculating WVTR using a specific formula.
Dynamic (Infrared) Method: This method uses an infrared sensor to measure vapor transmission without direct weighing. It is faster and more automated. Equipment includes a dynamic WVTR tester, film samples, a test chamber, and environmental controls. The process involves sample preparation, test setup, detection, and automatic data recording.
Other Methods: The Electrolytic Method measures conductivity changes in moisture on the film's surface and is used for specialized applications.

Factors Affecting WVTR Testing

Temperature: Higher temperatures generally increase WVTR.
Humidity: Relative humidity on both sides of the film affects results.
Film Thickness: Thicker films may have lower WVTR values.
Film Material: Different materials have varying permeabilities.
Test Duration: Longer durations provide more accurate results.

Applications of WVTR Testing

Packaging Industry: Ensures packaging maintains its moisture barrier.
Textiles: Tests fabrics for waterproof and breathable performance.
Electronics: Evaluates protective films to prevent moisture damage.
Coatings: Tests paints and coatings for moisture protection.

Conclusion
Understanding and measuring WVTR is essential for selecting appropriate materials for specific applications, ensuring product quality and longevity. Labthink offers industry-leading WVTR testers based on Gravimetric, Infrared, and Electrolytic Methods, supporting global permeability testing standards.

Catalog excerpts

How to Test Water Vapor Transmission Rate in Films-1

How to Test Water Vapor Transmission Rate in Films Testing Water Vapor Transmission Rate (WVTR) in films is a critical process for determining how well a material—such as plastic films, packaging materials, or protective coatings—resists the passage of water vapor. This property is essential for industries such as food packaging, pharmaceuticals, textiles, and electronics, where moisture control is vital for product preservation and quality. Here’s a step-by-step guide on how to test Water Vapor Transmission in films: Methods for Testing Water Vapor Transmission in Films The Gravimetric Method and the Infrared Method are the two primary methods used to measure WVTR in films. 1. Gravimetric Method (ASTM E96, ISO 15106) This is the most commonly used and traditional method for measuring water vapor transmission rate, and it involves measuring the weight change of a sample exposed to a moisture gradient. Equipment Needed:  WVTR Tester (Labthink C360M Water Vapor Transmission Rate Tester Gravimetric tester )  Water-filled containers or moisture desiccants (for the moisture source)  Precision balance (accurate to 0.1 mg)  Film samples (usually cut into specific dimensions)  Environmental control (temperature and humidity chamber) Steps: 1. Sample Preparation: o Cut the film sample into a precise size (usually a circular or square shape) according to the test standard. o Clean the film to remove any dust or particles that could affect the test. 2. Assembly of Test Cell: o Place the film sample in a test cell, which typically consists of a dish or cup containing a known amount of water or desiccant. o Seal the edges of the test cell to ensure the film is tightly secured. o The exposed side of the film should be in contact with either a moisture gradient (water) or a desiccant. 3. Environmental Conditions: o The test should be conducted at a controlled temperature (usually 23°C) and humidity (RH) (typically 50%). o Place the test cell in a controlled environment or a clim

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How to Test Water Vapor Transmission Rate in Films-2

maintain these conditions. 4. Monitoring Weight Change: o Over time, water vapor will pass through the film, leading to a change in the weight of the water container or desiccant. o Use a precision balance to weigh the test cell at regular intervals (e.g., every 24 hours). o Record the weight change over time. The larger the weight change, the higher the WVTR. 5. Calculation: o The WVTR is calculated using the following formula: Where: Δm\Delta mΔm = Change in mass (grams) o AAA = Area of the film exposed to water vapor (cm²) o ttt = Time of measurement (hours or days) The result will typically...

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How to Test Water Vapor Transmission Rate in Films-3

The test chamber is equipped with an infrared sensor or similar moisture detection technology. o As water vapor passes through the film, the change in the moisture level on the dry side of the film is detected by the sensor. 4. Data Recording: o The WVTR value is automatically calculated by the system based on the moisture difference over time and the area of the film exposed to the vapor. o 3. Other Methods While the gravimetric and dynamic methods are most common, some specialized applications may use the Electrolytic Method, which measures the conductivity changes in the moisture on the film's...

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How to Test Water Vapor Transmission Rate in Films-4

lines of water vapor transmission rate testers based on Gravimetric Method, Infrared Method and Electrolytic Methods. Our Labthink water vapor permeability testers are recognized as the industry-leading solution for over 30 years and are the basis for many global permeability testing standards such as ASTM E96, ASTM F1249, ISO 10156 and etc. The family of Labthink WVTR analyzers offer a solution for almost any water vapor transmission rate (WVTR) testing need from sheet or barrier films to all types of packages, bottles, cartons, and more.

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