The ASTM method commonly used for measuring air permeability of fabrics is ASTM D737 - Standard Test Method for Air Permeability of Textile Fabrics. This test method determines the air permeability of a fabric by measuring the rate of airflow through a specified area under a constant pressure differential.
Here is a brief overview of the ASTM D737 test method:
1. Test Apparatus: The apparatus used for this test typically consists of an instrument called a "textile air permeability tester," which comprises a specified test head and associated components.
2. Sample Preparation: Prepare the fabric samples according to specified dimensions, typically using circular samples. The samples should be conditioned under standard testing conditions before the test.
3. Test Procedure: The fabric sample is clamped between the upper and lower test heads of the air permeability tester, creating a circular test area. A constant pressure differential is applied across the fabric, and the rate of airflow passing through the fabric is measured using a calibrated airflow measurement device.
4. Calculation and Reporting: The air permeability value is calculated based on the measured airflow and the fabric test area. Typically, the result is reported in units of cubic feet per minute per square foot (CFM/ft²) or liters per second per square meter (L/s/m²).
It's worth noting that ASTM D737 provides several options for test conditions and procedures, allowing flexibility to accommodate different types of fabrics and testing requirements.
To ensure accurate and consistent results, it's essential to follow the detailed instructions and specifications outlined in the ASTM D737 standard. This method provides a standardized approach to measure and compare the air permeability of textile fabrics.