AATCC Test Method 42 (AATCC TM42) is a standard laboratory procedure used to measure the resistance of textile fabrics to the penetration of water by impact. This test is specifically designed to simulate and predict the probable resistance of fabrics to rain penetration, making it invaluable for evaluating materials intended for outdoor and protective wear.
Understanding AATCC TM42: Water Resistance - Impact Penetration Test
This test method is applicable to any textile fabric, regardless of whether it has been treated with a water-resistant or water-repellent finish. It provides a quantifiable measure of how well a fabric can prevent water from passing through it when subjected to the force of simulated rain.
How the Test Works
The AATCC TM42 test involves a precise, standardized procedure to ensure consistent and reliable results:
- Apparatus: The test utilizes an impact penetration tester, which consists of a nozzle that sprays a controlled volume of water from a specific height onto the fabric.
- Specimen Preparation: A conditioned fabric specimen is mounted tautly over a pre-weighed blotter paper. The fabric is positioned at an angle, usually 45 degrees, to simulate the typical angle of rain impact.
- Water Application: A specified volume of water (e.g., 500 mL) is sprayed through the nozzle onto the center of the fabric specimen. The spray occurs under controlled pressure and duration.
- Measurement: After the water spray, the blotter paper positioned beneath the fabric is re-weighed. The increase in the blotter paper's weight indicates the amount of water that has penetrated through the fabric during the test.
- Result: The results are typically reported in grams of water penetrated, with lower values indicating better resistance to water impact.
This method directly assesses the fabric's ability to withstand direct water impingement, which is distinct from simply measuring water repellency (how water beads on the surface).
Key Aspects of AATCC TM42
The table below summarizes the core characteristics and purpose of AATCC TM42:
| Aspect | Description |
|---|---|
| Purpose | Measures resistance of fabrics to water penetration by impact, predicting rain performance. |
| Applicability | Suitable for all textile fabrics, whether finished with water-resistant treatments or not. |
| Methodology | Water sprayed onto taut fabric specimen; penetration measured by weight gain of absorbent blotter paper. |
| Key Output | Quantified in grams of water penetrated, indicating protective capability against water impact. |
| Relevance | Critical for assessing performance in rainwear, outdoor gear, workwear, and protective textiles. |
Importance and Applications
The data derived from AATCC TM42 is vital for various stages of textile production and consumer decision-making:
- Quality Control: Manufacturers use this test to ensure their products meet specific performance standards for water resistance, especially for garments like raincoats, ski jackets, and hiking pants.
- Product Development: It helps engineers and designers select the most appropriate fabrics and finishes for new products where protection against rain or water spray is a key functional requirement.
- Performance Evaluation: The test allows for objective comparison between different fabric constructions or chemical finishes, aiding in the development of more effective water-resistant materials.
- Consumer Information: Results can inform product labeling, providing consumers with clear information about a product's expected performance in wet conditions, thereby building confidence in brands.
For instance, a fabric used in a high-performance rain jacket would be expected to show very low or zero water penetration according to AATCC TM42, indicating excellent protection against rain.
Distinguishing from Related Tests
While AATCC offers several water resistance tests, AATCC TM42 is unique in its focus. For example, AATCC Test Method 22 (Spray Test) primarily measures the surface repellency and wetting resistance of a fabric, indicating how well water beads off. In contrast, AATCC TM42 directly measures the amount of water that penetrates through the fabric under impact, simulating a more aggressive rain event. This distinction is crucial for selecting the appropriate test based on the desired performance characteristic.
AATCC TM42 remains a foundational test for assessing a textile's barrier properties against water penetration under dynamic conditions, providing critical insights into its protective capabilities.
