Equipment Required for Testing Coated Fabrics and Textiles ASTM D751

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Specification ASTM D751 includes test methods for covering a wide range of mechanical properties of coated fabrics. A coated fabric is a material that has at least one layer of a textile and one layer of a polymeric substance. Examples would be tarps, outdoor clothing, and rain wear. Some of these tests require specialized equipment (hydrostatic resistance, blocking, wicking, impact, etc.), but most of these tests can be performed using a Universal Testing Machine. These tests include:

• Breaking Strength – Procedure A: Grab Test Method
• Breaking Strength – Procedure B: Cut Strip Test Method
• Elongation
• Bursting Strength
• Puncture Resistance
• Tearing Strength – Procedure B: Tongue Tear Method
• Trapezoidal Tear
• Adhesion Coating to Fabrics (only preloading)
• Tack-Tear Resistance
• Seam Strength
• Dead Load Seam Strength
• Crush Resistance

ASTM D751 specifies a testing machine with three main parts:

1. Straining mechanism
2. Clamps for holding specimens
3. Load and elongation recording mechanisms.

ADMET universal testing machines include the straining mechanism (item 1) and built in load and elongation recording mechanisms (Item 3). The clamps (Item #2) are devises that get pinned to the universal testing machine and are designed specifically to hold each of the materials / samples described in each of the various tests listed above. This is a short list of the grips and fixtures required for each of these tests:

• Breaking Strength – Procedure A: Grab Test Method
  • Vise Grips (Top grip mounted on universal joint)
    • Front Jaw Inserts: 25mm tall x 25mm wide
    • Rear Jaw Inserts: 25mm tall x 50mm wide
• Breaking Strength – Procedure B: Cut Strip Test Method
  • Same grips as Procedure A.
• Elongation
  • Test is done at the same time as the breaking strength test so grips are the same.
• Bursting Strength
  • This fixture holds a piece of fabric securely on the top and bottom surface an exposed a circular area of fabric. The other part of the fixture is a polished steel ball that is mounted to the top of the machine which is used to burst the fabric.
• Puncture Resistance
  • This fixture is the same as used for the bursting test but the polished steel ball is replaced with a sharp pointed instrument.
• Tearing Strength – Procedure B: Tongue Tear Method
  • Same vise grips used for the Breaking Strength test but replaced the 25mm x 25mm front jaws with 25mm tall x 50mm wide jaws so you have a set of four 25mm x 50mm jaws.
• Trapezoidal Tear
  • Same vise grips used for the Tearing Strength test
• Adhesion Coating to Fabrics
  • Same vise grips but jaws should be 25mm tall x 75mm wide
• Tack-Tear Resistance
  • This test requires a specialized grip fixture that is used only for this test. It is complicated, and the design can be seen in the specification.
• Seam Strength
  • Same grips as described in Adhesion Coating to Fabrics test
• Dead Load Seam Strength
  • Same vise grips as specified in the other tests
• Crush Resistance
  • This test deflects the material over a button shaped compression platen until the material is crushed or cut. This test requires a unique compression fixture, the exact dimensions of which can be found in the specification.

To summarize, all of these tests can be performed with the following grips / fixtures:

1. Vise grips with 25mm, 50mm, 75mm wide jaw faces
2. Burst fixture with both round and sharp noses.
3. Tack-tear fixture
4. Crush resistance test fixture.

Of course, not all of these are needed if you are only doing a certain test within this specification.

Machine types:

Any ADMET testing machine meets the accuracy requirements listed in the specification. Therefore, you should select the ADMET machine that best matches your maximum load capacity. Our 2000 pound capacity eXpert 2611 is one common choice, and for lower force materials, our 250 pound capacity eXpert 7601 is also commonly used for textile testing.