The moisture permeability tester is a professional device used to measure the water vapor transmission rate (WVTR) of textiles, films, non-woven fabrics and other materials. The following are the standard operating procedures and technical points.

I. Equipment structure and principle

Core components

1. Test chamber: sealed chamber with controllable temperature and humidity (usually divided into dry/wet chamber)

2. Weighing system: high-precision balance (0.001g resolution)

3. Temperature control system: PID precise temperature control (range 20-50℃±0.5℃)

4. Humidity system: saturated salt solution or steam generator

5. Data acquisition: automatic recording of mass changes and temperature and humidity

Test principle

Positive cup method (ISO 2528): water vapor permeation from wet chamber to dry chamber

Inverted cup method (ASTM E96): water vapor absorption from dry chamber to wet chamber

Dynamic method (JIS L1099): determination of water vapor carried by airflow

II. Standard operating procedures

1. Sample preparation

Cut a circular sample with a diameter of ≥70mm (no creases/breaks)

If testing multiple layers of materials, stack them according to the actual use direction

Pretreatment: equilibrate at the test temperature and humidity for 24h (GB/T 12704 requirements)

2. Equipment initialization

1. Turn on the constant temperature water bath (set to 23℃ or 38℃)

2. Prepare saturated salt solution:

Dry environment: Mg(NO₃)₂ (RH≈53%)

High humidity environment: K₂SO₄ (RH≈97%)

3. Calibrate the balance (use standard weights)

3. Sample loading and sealing

1. Fix the sample at the mouth of the test cup:

- Positive cup method: add distilled water (liquid surface 3mm away from the sample)

- Inverted cup method: add desiccant (anhydrous CaCl₂)

2. Press with silicone seal to ensure no side leakage

3. Weigh the initial mass (m₀) to an accuracy of 0.001g

4. Test execution

1. Place the test cup in a constant temperature and humidity chamber

2. Set parameters:

Temperature: 23±1℃ or 38±1℃ (select according to the standard)

Air flow rate: 0.5-1.0m/s (dynamic method needs to be set)

Test interval: 1h/time (static method)

3. Start the test, the system automatically records the mass change (m₁, m₂...mₙ)

5. Data processing

Water vapor permeability meter:

WVTR = (Δm×24)/(A×t) Unit: g/(m²·d)

Δm: mass change (g)

A: effective test area (m²)

t: test time (h)

Example:

If the mass decreases by 0.12g within 24h and the test area is 0.00283m², then:

WVTR = (0.12×24)/0.00283 = 1017.7 g/(m²·d)

Email: hello@utstesters.com

Direct: + 86 152 6060 5085

Tel: +86-596-7686689

Web: www.utstesters.com