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NWSP 100.1 Tearing Strength

Standard:

NWSP

Method:

NWSP 100.1

Title:

Tearing Strength of Nonwoven Fabrics by Falling-Pendulum (Elmendorf) Apparatus

Scope

The NWSP 100.1 Tearing Strength test covers the measurement of the average force required to propagate a single-rip tear starting from a cut in a nonwoven fabric using a falling-pendulum (Elmendorf) apparatus.

This Elmendorf tearing apparatus is supplied with interchangeable pendulums. This apparatus normally has the capability of determining tearing strength up to 6400 grams-force, for tearing strengths above 6400 grams-force, a high-capacity test instrument is available and is equipped with augmenting weights to increase the capacity.

It is recognized that some of these older test instruments with augmenting weights still continue to be useful standards in the nonwoven industry.

This test method is applicable to most nonwoven fabrics that are treated or untreated, provided the fabric does not tear in the direction crosswise to the direction of the force applied during the test. If the tear does not occur in the direction of the test, the fabric is considered untearable in that direction by this test method.

SI values are regarded as the official standard system of measurement for this standard test method. If other systems of measurement are used in place of SI units (including inch-pound) their values must be reported independently. Systems of measurement must not be combined in any way, but shall be regarded and reported separately.

Principle

The force required to continue a slit previously cut in a nonwoven fabric is determined by measuring the work done in tearing it through a fixed distance. The tester consists of a sector-shaped pendulum carrying a clamp which is in alignment with a fixed clamp when the pendulum is in the raised, starting position with maximum potential energy. The specimen is fastened in the clamps and the tear is started by cutting a slit in the specimen between the clamps. The pendulum is then released and the specimen is torn as the moving jaw moves away from the fixed one. The scale attached to the pendulum is graduated to read the tearing force of the specimen.
Compared to other methods for testing tearing strength this test method has the advantage of simplicity and speed since specimens are cut with a die and results are read directly from the scale on the pendulum. The specimens are relatively small in area, thus require less fabric. The reading obtained is directly proportional to the length of the material torn, therefore, it is essential that the specimen be prepared to the exact size specified. For best results, the recommended capacity of the tester selected is the one where the specimens tear between 20 and 80 % of the full-scale value.

 

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