Standard Test Method for Stretch Properties of Knitted Fabrics Having Low Power
5.1 Fabric stretch and fabric growth are useful in selection of fabrics that are required to stretch, but also recover to their original shape.
5.1.1 In apparel, fabric stretch can be caused by a variety of factors. A momentary stress occurs when a fabric is required to accommodate movement, such as sportswear and other loose-fitting apparel (also known as comfort stretch apparel) or external stress such as grabbing and pulling. Additionally, comfort apparel can be subjected to prolonged stress, such as stretching to accommodate positions such as sitting. Another example of prolonged stress occurs when a fabric is required to stretch to accommodate fitting the form of the body, such as swimwear, anchored slacks, and other form-fitting apparel (also known as semi-support apparel).
5.1.2 Fabric growth can also be in response to a variety of stresses. This method evaluates fabric growth due to exposure to prolonged stresses. In form-fitting apparel, fabric growth can apply as garments are worn for a prolonged period of time or under long periods of stress such as sitting. Upon removal of garments or stress, its growth can be seen and evaluated.
5.2 This test method is not recommended for acceptance testing of commercial shipment because the between-laboratory precision is known to be poor.
5.2.1 If there are differences of practical significance between reported test results for two laboratories (or more), comparative tests should be performed to determine if there is a statistical bias between them, using competent statistical assistance. As a minimum, ensure the test samples to be used are as homogeneous as possible, are drawn from the material from which the disparate test results are obtained, and are assigned randomly in equal numbers to each laboratory for testing. The test results from the two laboratories should be compared using a statistical test for unpaired data, at a probability level chosen prior to the testing series. If a bias is found, either its cause must be found and corrected, or future test results for that material must be adjusted in consideration of the known bias.
1.1 This test method covers the measurement of fabrics that exhibit high stretch and good recovery from low tension. Fabric stretch is measured when a known load is applied. Fabric growth is evaluated after a known extension is applied and subsequently removed.
1.2 The procedures for fabric stretch and fabric growth can be used together, or individually.
1.3 While this test method can be used for a knit fabric, fabrics intended for support or other applications are better evaluated using other test methods: D3107, D4964, D6614.
1.4 The values stated in either SI or inch-pound units are to be regarded separately as the standard. Within the text, the inch-pound units are shown in parentheses. The values stated in each system are not exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in nonconformance with the specification.
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.
1.6 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
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