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NWSP 100.2 Tensile (Trapezoid Tear)

Standard:

NWSP

Method:

NWSP 100.2

Title:

Tearing Strength of Nonwoven Fabrics by the Trapezoid Procedure

Scope

The NWSP 100.2 Tensile properties test method covers the measurement of the tearing strength of nonwoven fabrics by the trapezoid procedure using a recording constant-rate-of-extension (CRE) tensile testing machine.

The CRE-type tensile testing machine has become the preferred test apparatus for determining trapezoid tearing strength. It is recognized that some constant-rate-of-traverse (CRT) tensile testing machines continue to be used. As a consequence, these test instruments may be used when agreed upon between the purchaser and the supplier.

This test method applies to most nonwoven fabrics, treated or untreated, heavily sized, coated or resin-treated. This test method may not be useful for highloft nonwoven fabrics.

Trapezoid tear strength as measured in this test method is the maximum tearing force required to continue or propagate a tear started previously in the specimen. The reported value is not directly related to the force required to initiate or start a tear. This test method provides values in SI units.. The International System of Units (SI units) are the customary metric units used in most of the rest of the world.

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

An outline of an isosceles trapezoid is marked on a rectangular specimen cut for the determination of tearing strength. The specimen is slit at the center of the smallest base of the trapezoid to start the tear. The nonparallel sides of the trapezoid marked on the specimen are clamped in parallel jaws of a tensile testing machine. The separation of the jaws is continuously increased to apply a force to propagate the tear across the specimen. At the same time, the force developed is recorded. The maximum force to continue the tear is calculated from autographic chart recorders, or microprocessor data collection systems.

 

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